June 2024 Living Environment Regents — Answer Key & Worked Solutions

Every question from the June 2024 Living Environment Regents exam, with the correct answer and a full step-by-step solution. Check your work, learn the method, then convert your raw score.

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These are real questions from the June 2024 Living Environment New York State Regents examination, published by NYSED. Worked solutions are written by RegentsLab.

Question 1 · 2 pts

In an animal cell, all of the organelles work together to carry out

(A) photosynthesis
(B) diffusion
(C) metabolic processes ✓
(D) information storage

Worked solution

$\text{Organelles (mitochondria, ribosomes, etc.) each perform specialized jobs}$

$\text{Together these jobs make up the cell's overall metabolism}$

Answer: metabolic processes

Organelles each carry out specific sub-tasks, but collectively their coordinated activity constitutes the cell's metabolic processes (energy release, synthesis, etc.).

Question 2 · 2 pts

A colony of 47,000 quaking aspen trees, all connected by one root system, is considered to be Earth's most massive organism. When the trees are stressed, shoots are sent out from the roots and develop into new trees. Every new tree in this colony would contain

(A) the same genetic information, because it is produced asexually ✓
(B) the same genetic information, because it is produced sexually
(C) less genetic material, since it is produced from root cells
(D) a different combination of genes, since it is produced from various roots

Worked solution

$\text{New shoots arise by mitosis from root tissue, not fertilization}$

$\text{Asexual reproduction produces genetically identical offspring (clones)}$

Answer: the same genetic information, because it is produced asexually

Because the new trees sprout asexually from the shared root system via mitosis, they are genetic clones of the parent, all carrying identical DNA.

Question 3 · 2 pts

Scientists have found that different tissues in the prostate gland, a male reproductive organ, respond to different hormones. The tissues in the center area of the gland respond to testosterone and the tissues in the outer area of the gland respond to estrogen. The cells that make up these two regions of the prostate are different in that

(A) cells in the center area produce more estrogen than cells in the outer area
(B) cells in the outer area have many testosterone receptors
(C) they contain different receptors on their cell membranes ✓
(D) they contain different DNA sequences for the production of hormones

Worked solution

$\text{All cells in the body share the same DNA}$

$\text{Differential hormone response comes from differing surface receptors, not differing DNA}$

Answer: they contain different receptors on their cell membranes

Since all cells share identical DNA, differing responses to testosterone versus estrogen must come from the different receptor proteins present on each region's cell membranes.

Question 4 · 2 pts

Energy transfers in a natural ecosystem are represented in the diagram below, showing arrows of energy flow from Grasses to Rabbits, Beetles, Slugs, and Mice; from those to Small birds, Badgers, and Hedgehogs; and ultimately up to Hawks and Foxes. Which statement about this ecosystem is correct?

(A) A reduction in the number of species present would most likely upset the stability of this ecosystem. ✓
(B) This ecosystem would not be affected if decomposers did not perform their function.
(C) This ecosystem lacks producer organisms.
(D) There are most likely more foxes than rabbits in this ecosystem.

Worked solution

$\text{Greater species diversity provides multiple energy pathways}$

$\text{Losing species removes pathways and destabilizes the food web}$

Answer: A reduction in the number of species present would most likely upset the stability of this ecosystem.

A diverse food web with many interconnected species is more stable; removing species eliminates energy pathways and destabilizes the ecosystem.

Question 5 · 2 pts

The process of differentiation occurs when

(A) two different cells, a sperm cell and an egg cell, combine to produce a zygote
(B) different zygotes are formed each time that an egg and sperm unite
(C) different kinds of cells and tissues form during embryonic development ✓
(D) two different sexes are present among the offspring, after sexual reproduction

Worked solution

$\text{A single zygote divides by mitosis}$

$\text{Genes turn on/off differently in different cells, producing specialized cell types and tissues}$

Answer: different kinds of cells and tissues form during embryonic development

Differentiation is the process by which genetically identical embryonic cells become specialized into different cell and tissue types.

Question 6 · 2 pts

Which two human systems work together to provide glucose for the cells of the body?

(A) nervous and reproductive systems
(B) nervous and respiratory systems
(C) circulatory and digestive systems ✓
(D) circulatory and respiratory systems

Worked solution

$\text{Digestive system breaks food into glucose}$

$\text{Circulatory system transports glucose to body cells}$

Answer: circulatory and digestive systems

The digestive system breaks food down into glucose, which the circulatory system then transports throughout the body to cells.

Question 7 · 2 pts

The chart below includes structures found in a multicellular organism. Which row contains the structures that would be most numerous?

(A) organs
(B) tissues
(C) organelles ✓
(D) cells

Worked solution

$\text{Each cell contains many organelles, so organelles far outnumber the cells}$

$\text{Hierarchy: organelles} > \text{cells} > \text{tissues} > \text{organs, so organelles are the most numerous}$

Answer: Organelles

Every cell in a multicellular organism contains many organelles, such as mitochondria and ribosomes, so organelles far outnumber the cells themselves. Since many cells make up each tissue and many tissues make up each organ, the structures become less numerous moving up the hierarchy from organelles to cells to tissues to organs, making organelles the most numerous row in the chart.

Question 8 · 2 pts

Dioxin, a toxin associated with waste incineration and some plastics, has been found to directly disrupt normal gamete production in human females. Dioxin most likely affects the

(A) testes and progesterone production
(B) ovaries and estrogen production ✓
(C) DNA in the nuclei of sperm cells
(D) pancreas and insulin production

Worked solution

$\text{Female gamete production occurs in the ovaries}$

$\text{Ovaries also produce estrogen, so disrupting gamete production affects estrogen output}$

Answer: ovaries and estrogen production

Since the question specifies disruption of gamete production in females, the affected organ must be the ovaries, which also produce estrogen.

Question 9 · 2 pts

A gene present only in a single plant species was found to regulate protein content. This gene could increase the protein content of other food crops in the developing world. The most likely method that scientists would use to incorporate this gene into a variety of food crops is

(A) genetic engineering ✓
(B) selective breeding
(C) sexual reproduction between the plants with this gene and those without it
(D) deletion of the genes that limit protein production from each individual food crop plant

Worked solution

$\text{The gene exists in only one species, so normal breeding cannot transfer it between species}$

$\text{Genetic engineering directly inserts a gene from one species into another's DNA}$

Answer: genetic engineering

Because the gene is unique to a single species, it can only be moved into unrelated crop species directly through genetic engineering, not through breeding.

Question 10 · 2 pts

A decrease in predators within an ecosystem would lead to an increase in herbivores. The increase in herbivores would cause a decrease in

(A) decomposers
(B) prey
(C) consumers
(D) producers ✓

Worked solution

$\text{More herbivores} \Rightarrow \text{more grazing pressure on plants}$

$\text{Increased consumption of producers reduces their population}$

Answer: producers

With more herbivores feeding on plants, the population of producers (plants) would decrease due to increased grazing pressure.

Question 11 · 2 pts

The lioness (female lion) and cub shown in the photograph have similar characteristics. In order for some of the genetic information in the lioness to be present in the cub, the genetic information from the mother must have been

(A) copied and present in the egg cell of the lioness ✓
(B) combined with genetic information from another lioness
(C) contained in half of the DNA found in the sperm cells of the father
(D) able to make enzymes to produce all of the carbohydrates found in the mother

Worked solution

$\text{The mother's genetic information must be packaged into her gamete (egg) to be inherited}$

$\text{The egg's DNA combines with sperm DNA at fertilization to form the cub's genome}$

Answer: copied and present in the egg cell of the lioness

For the mother's genes to appear in the cub, her genetic material must have first been copied into the egg cell she contributed at fertilization.

Question 12 · 2 pts

Which statement best describes a critical function of the placenta?

(A) Meiosis occurs in the placenta, allowing for the development and release of eggs.
(B) Blood from the mother and fetus mixes at the placenta, providing nutrients and oxygen.
(C) The placenta filters out all harmful toxins and chemicals from the mother's blood, so that they cannot reach the fetus.
(D) The exchange of oxygen and carbon dioxide occurs between the mother and developing fetus across the placenta. ✓

Worked solution

$\text{Maternal and fetal blood do not actually mix}$

$\text{Gases, nutrients, and wastes diffuse across the placental membrane between separate blood supplies}$

Answer: The exchange of oxygen and carbon dioxide occurs between the mother and developing fetus across the placenta.

The placenta allows diffusion of gases like oxygen and carbon dioxide (and nutrients/wastes) between separate maternal and fetal blood supplies without the bloods mixing.

Question 13 · 2 pts

Organisms maintain internal stability in a changing environment. To do this, they make a series of adjustments. The process of making these continual adjustments is referred to as

(A) cellular respiration
(B) active transport
(C) natural selection
(D) dynamic equilibrium ✓

Worked solution

$\text{Homeostasis is maintained through ongoing, continual adjustments}$

$\text{This continual adjustment process is called dynamic equilibrium}$

Answer: dynamic equilibrium

Dynamic equilibrium describes the continual, active process by which organisms maintain internal stability despite a changing environment.

Question 14 · 2 pts

A species of octopus lives in the depths of the ocean where oxygen levels are low. These octopuses have specific proteins in their blood that allow for more efficient oxygen transport than in those that live in surface waters. Which statement best explains the presence of these proteins in the octopuses living deep in the ocean?

(A) Migration to warmer and shallower ocean water favored the formation of the specific proteins.
(B) Octopuses that had the specific proteins were able to survive and reproduce in the deep water environment and passed the trait on to future generations. ✓
(C) When some octopuses migrated to a deeper environment, they needed to produce new proteins so that their blood could carry more oxygen.
(D) Mutations occurred in the body cells of the octopuses, which resulted in the specific proteins being produced and passed on to their offspring.

Worked solution

$\text{Random genetic variation already existed in the population}$

$\text{Individuals with the favorable protein variant survived/reproduced better (natural selection)}$

$\text{The trait was passed to offspring, becoming common in the population}$

Answer: Octopuses that had the specific proteins were able to survive and reproduce in the deep water environment and passed the trait on to future generations.

This is natural selection: individuals with a pre-existing favorable variant survived and reproduced more successfully in the low-oxygen environment, passing the trait to offspring.

Question 15 · 2 pts

Tissue engineering is being developed as a technology that would use laboratory-grown tissues to replace diseased or damaged human body parts, such as hearts and kidneys. In order to build these new body parts, scientists would start by

(A) assembling molecules directly into tissues that can make body systems
(B) making organelles and using the organelles to develop organs
(C) engineering body systems in order to develop organelles for transplant
(D) growing cells to develop tissues and then growing these tissues to form an organ ✓

Worked solution

$\text{Levels of organization: cells} \to \text{tissues} \to \text{organs}$

$\text{Tissue engineering follows this order, building up from individual cells}$

Answer: growing cells to develop tissues and then growing these tissues to form an organ

Following the levels of biological organization, engineered organs must be built starting from cells, which form tissues, which then form the organ.

Question 16 · 2 pts

People with cystic fibrosis have decreased levels of some digestive enzymes in their small intestines. It is essential that they take enzyme supplements in order to prevent malnutrition. These enzymes are an important part of the digestive process because they

(A) break down foods so that nutrients can be absorbed and used ✓
(B) contain vitamins and other nutrients necessary for a healthy diet
(C) allow the person to synthesize large, inorganic nutrient molecules
(D) are the building blocks of carbohydrates and other nutrient molecules

Worked solution

$\text{Digestive enzymes catalyze the breakdown of large food molecules into smaller absorbable ones}$

$\text{Without enzymes, nutrients cannot be broken down, absorbed, or used, leading to malnutrition}$

Answer: break down foods so that nutrients can be absorbed and used

Digestive enzymes chemically break down large food molecules into smaller units that can be absorbed into the blood and used by the body.

Question 17 · 2 pts

A reproductive cycle is illustrated in the diagram: Growth stages -> Adults, with process 2 leading from Adults to Sperm/Eggs, process 1 also near Adults to Sperm/Eggs, process 3 from Sperm and Eggs to Zygotes, and Zygotes back to Growth stages. Which statement about this reproductive cycle is correct?

(A) Mutations that occur during processes 1 and 2 will not be passed on to offspring.
(B) Exact copies of the parents are produced, which leads to a stable population.
(C) Sorting and recombining of genes occurs, which leads to new genetic combinations. ✓
(D) The three processes result in offspring with half as much genetic information as the adults.

Worked solution

$\text{Processes 1 and 2 represent meiosis, producing sperm and eggs with unique gene combinations}$

$\text{Process 3 represents fertilization, combining sperm and egg DNA into a zygote}$

Answer: Sorting and recombining of genes occurs, which leads to new genetic combinations.

Meiosis (processes 1 and 2) shuffles and recombines genes into gametes, and fertilization (process 3) combines them, producing offspring with new genetic combinations.

Question 18 · 2 pts

Kidney-transplant surgery places a healthy kidney from one person into the body of another. The body will often produce substances that work against this transplanted organ. The system most directly involved in attacking the transplanted kidney is the

(A) excretory system
(B) nervous system
(C) circulatory system
(D) immune system ✓

Worked solution

$\text{The transplanted kidney contains foreign antigens (different DNA/proteins)}$

$\text{The immune system recognizes foreign antigens and produces antibodies/attacks the organ (rejection)}$

Answer: immune system

The immune system recognizes the transplanted kidney's cells as foreign due to differing surface antigens and mounts an immune response against it, causing rejection.

Question 19 · 2 pts

An energy pyramid for a forest ecosystem has four levels (A-D from bottom to top): Level A (bottom), B, C, and D (top). Which numbered column in the chart below contains four terms that correctly identify the most likely types of organisms found at each of the four levels in the pyramid? | Pyramid Level | Column (1) | Column (2) | Column (3) | Column (4) | | --- | --- | --- | --- | --- | | D (top) | carnivores | carnivores | heterotrophs | producers | | C | heterotrophs | carnivores | autotrophs | carnivores | | B | producers | herbivores | herbivores | herbivores | | A (bottom) | herbivores | producers | producers | heterotrophs |

(A) Column (1)
(B) Column (2) ✓
(C) Column (3)
(D) Column (4)

Worked solution

$\text{Bottom of pyramid (A) must be producers, the largest energy base}$

$\text{Level B (herbivores) eat producers; level C and D (carnivores) are consumers of consumers}$

$\text{Only Column (2): A=producers, B=herbivores, C=carnivores, D=carnivores fits this order}$

Answer: Column (2)

An energy pyramid must have producers at the base, herbivores next, then carnivores, matching only Column (2): A=producers, B=herbivores, C=carnivores, D=carnivores.

Question 20 · 2 pts

The diagram below shows information about human body temperature regulation: Normal body temperature (36-38 degrees C) leads to Body temperature gets too low, which leads to Blood vessels in skin constrict, reducing heat loss, and Muscles begin shivering, generating heat, which leads to Body temperature increases, and this loops back to Normal body temperature. These events can be best described as an example of

(A) a feedback mechanism that maintains homeostasis ✓
(B) a cycle that regulates cellular communication
(C) an immune system response to increasing heart rate
(D) a body system regulating hormone production

Worked solution

$\text{A drop in body temperature triggers responses (vasoconstriction, shivering)}$

$\text{These responses restore temperature to normal, completing a feedback loop that maintains homeostasis}$

Answer: a feedback mechanism that maintains homeostasis

The diagram shows a feedback loop, low temperature triggers responses that raise it back to normal, which is a classic homeostatic feedback mechanism.

Question 21 · 2 pts

The World Wildlife Federation's recent report indicated that there has been a 60% decline in the size of monitored wildlife populations in just over 40 years. The most likely factor contributing to this decline was

(A) animals reproducing successfully
(B) the destruction of many natural habitats ✓
(C) passing environmental protection laws
(D) the introduction of native species into habitats

Worked solution

$\text{Habitat loss reduces resources and living space available to wildlife}$

$\text{This is the leading cause of biodiversity/population decline worldwide}$

Answer: the destruction of many natural habitats

Habitat destruction (deforestation, development, etc.) is the leading driver of global wildlife population decline, unlike the other listed options which would help or not affect populations negatively.

Question 22 · 2 pts

An Adirondack Mountain ecosystem, the Northern Boreal Forest (Taiga), is shown, containing organisms such as moose, timber wolf, red squirrel, snowshoe hare, lynx, mink, various birds, and conifer trees (larch, fir, spruce, cedar). An abiotic factor in this ecosystem is the

(A) pH of the soil where the trees grow ✓
(B) number of deer of reproductive age
(C) different species of grass present
(D) balance between predators and prey

Worked solution

$\text{Abiotic factors are nonliving components of an ecosystem}$

$\text{Soil pH is a nonliving chemical property; the other choices all describe living organisms/populations}$

Answer: pH of the soil where the trees grow

Abiotic factors are nonliving parts of the environment; soil pH is nonliving, while the other choices describe populations of living organisms.

Question 23 · 2 pts

A partial food chain is represented below. Grasses $\rightarrow$ Field mice $\rightarrow$ Owls A student observed owls hunting mice in a field. Some chemicals from the waste products of the owls were made available to be absorbed by the roots of the grasses due to the action of

(A) autotrophs
(B) carnivores
(C) herbivores
(D) decomposers ✓

Worked solution

$\text{Owl waste contains complex organic compounds}$

$\text{Decomposers break these down into simple inorganic nutrients}$

$\text{These nutrients (e.g. nitrogen compounds) are absorbed by grass roots}$

Answer: decomposers

Decomposers recycle nutrients locked in waste and dead organic matter back into forms (like minerals) that plant roots can absorb, completing the cycle of matter.

Question 24 · 2 pts

Which two terms are opposite processes?

(A) autotrophic nutrition and photosynthesis
(B) asexual reproduction and cloning
(C) digestion and synthesis ✓
(D) natural selection and evolution

Worked solution

$\text{Digestion breaks large molecules into smaller subunits}$

$\text{Synthesis builds larger molecules from smaller subunits}$

$\text{These are opposite (reverse) biochemical processes}$

Answer: digestion and synthesis

Digestion is a catabolic (breaking down) process while synthesis is an anabolic (building up) process, making them functional opposites, unlike the other listed pairs which are near-synonymous or unrelated in that way.

Question 25 · 2 pts

Which human activity would most likely deplete finite resources?

(A) recycling of aluminum and paper
(B) protection of wildlife habitats
(C) uncontrolled population growth ✓
(D) regulations that reduce industrial pollution

Worked solution

$\text{More people demand more energy, water, land, and raw materials}$

$\text{Finite (non-renewable) resources are consumed faster than they can be replaced}$

Answer: uncontrolled population growth

Unchecked population growth increases demand on limited resources such as fossil fuels and minerals, accelerating their depletion, while the other choices describe conservation practices.

Question 26 · 2 pts

Macaques are a species of monkey. They normally reproduce sexually, but, in January 2018, scientists cloned two baby macaques from a single body cell. These monkeys are genetically

(A) identical to each other, but different from the donor of the body cell
(B) different from each other, but identical to the donor of the body cell
(C) identical to each other and to the donor of the body cell ✓
(D) different from each other and from the donor of the body cell

Worked solution

$\text{Cloning copies the full DNA of a single donor body cell}$

$\text{No genetic recombination occurs, so all resulting individuals share identical DNA}$

Answer: identical to each other and to the donor of the body cell

Because cloning is asexual and derives every offspring from the same original nucleus, the clones and the donor all carry identical genetic information.

Question 27 · 2 pts

Which event would most likely be the immediate result of significantly lowering the oxygen concentration in a freshwater lake?

(A) a decrease in the number of fish ✓
(B) an increase in the number of plants
(C) an increase in biodiversity
(D) a decrease in water temperature

Worked solution

$\text{Fish require dissolved oxygen for aerobic respiration}$

$\text{Low oxygen causes suffocation and death of oxygen-dependent fish}$

Answer: a decrease in the number of fish

Fish and other aerobic organisms depend on dissolved oxygen; a sharp drop in oxygen level directly causes fish die-offs before other ecosystem changes occur.

Question 28 · 2 pts

Scientists have modified papayas to be resistant to the papaya ringspot virus and to decrease the time that it takes for them to ripen. These modifications

(A) may cause papayas to ripen too slowly, causing loss of revenue
(B) are passed to any organism that eats them, making the organism resistant to the virus
(C) are an example of using agricultural technologies to increase farm yields ✓
(D) could spread ringspot virus throughout the entire ecosystem

Worked solution

$\text{Genetic modification for disease resistance and faster ripening reduces crop loss}$

$\text{This raises the amount of usable, marketable produce, i.e. increases yield}$

Answer: are an example of using agricultural technologies to increase farm yields

Genetically engineering crops for virus resistance and faster ripening is a direct application of biotechnology to boost agricultural productivity.

Question 29 · 2 pts

Vaccinated individuals are protected from disease because their bodies have been stimulated to

(A) produce antibodies against specific pathogens ✓
(B) synthesize antigens against harmful microbes
(C) make fewer white blood cells during infection
(D) manufacture more enzymes to react to microbes

Worked solution

$\text{Vaccine introduces a weakened/inactive antigen}$

$\text{Immune system responds by producing specific antibodies and memory cells}$

Answer: produce antibodies against specific pathogens

Vaccines work by triggering the immune system to manufacture antibodies specific to a pathogen's antigens, providing future protection.

Question 30 · 2 pts

A species of predatory wasp is introduced to control an insect pest. A possible negative consequence of this action is that the new predatory wasp may

(A) limit the population of the insect pest
(B) prey on beneficial insects ✓
(C) disrupt mineral availability in the ecosystem
(D) cause an increase in pesticide-resistant plants

Worked solution

$\text{Introduced predators are not limited only to the target pest}$

$\text{They may also consume other, non-target (beneficial) insect species}$

Answer: prey on beneficial insects

A classic risk of biological control is that the introduced predator becomes invasive and preys on non-target, beneficial insects, disrupting the ecosystem.

Question 31 · 2 pts

Base your answer on the following information: Industrialization has contributed to unsafe levels of mercury compounds building up in aquatic ecosystems, including in the tissues of many predatory fish species. As a result, many people have concerns about eating any seafood. The mercury, at relatively high levels, can be especially harmful during development of a fetus and of young children. It can also affect adult health in various ways. However, seafood is also an important part of a healthy diet. The omega-3 fats in seafood are essential to the proper functioning of the circulatory system. They are also important for optimal development of a baby's brain and nervous system. Mercury Levels in Various Fish or Seafood Types (ppm/oz.): Swordfish 0.995, King mackerel 0.73, Cod 0.11, Trout 0.07, Halibut 0.024, Tilapia 0.013, Shrimp 0.009 Based on the information given, which statement concerning the eating of fish and seafood is most accurate?

(A) People should avoid eating seafood because the negative effects of the mercury in seafood are far worse than any benefits that eating seafood may provide. Even shrimp and tilapia contain high levels of mercury.
(B) The normal development of a baby's nervous system requires that the mother be more concerned with eating enough seafood and less concerned with the side effects of higher levels of mercury on the child.
(C) Eating certain selected species of seafood can provide health benefits without the negative effects of high mercury intake. ✓
(D) It is important that pregnant women eat a regular diet of seafood, including swordfish, halibut, and cod.

Worked solution

$\text{Low-mercury seafood (shrimp 0.009, tilapia 0.013, halibut 0.024 ppm/oz.) still provides omega-3 fats}$

$\text{Choosing these species avoids the high mercury levels of swordfish (0.995) or king mackerel (0.73)}$

Answer: Eating certain selected species of seafood can provide health benefits without the negative effects of high mercury intake.

The data table shows a wide range of mercury content, so choosing low-mercury species lets people gain seafood's health benefits while minimizing mercury exposure risk.

Question 32 · 2 pts

Which statement is best supported by the information provided about the levels of mercury present in seafood?

(A) Human activities do not affect mercury levels in fish species.
(B) Future generations can be affected by choices made by past and present generations. ✓
(C) Fish that consume plants have the highest levels of mercury compounds.
(D) If people stop eating fish, then the mercury levels in fish will decrease.

Worked solution

$\text{Industrialization (a past/present human choice) caused mercury buildup}$

$\text{This affects fetal/child development in future generations}$

Answer: Future generations can be affected by choices made by past and present generations.

The passage links industrial activity (a choice of past and present generations) directly to health risks for developing fetuses and children, i.e. future generations.

Question 33 · 2 pts

Grasshopper mice feed on bark scorpions, but, unlike other mice, grasshopper mice are unaffected by the painful venom of the scorpion. Scientists have determined that these mice have one amino acid difference in their pain receptors, which causes the receptor to function differently and prevents feeling the pain associated with the scorpion venom. This change in protein function was originally caused by a change in

(A) molecular bases located in the nucleus ✓
(B) fat molecules in the cell membrane
(C) the amino acids in the DNA
(D) the genes located in the protein

Worked solution

$\text{A DNA base-sequence mutation occurs in the nucleus}$

$\text{Altered DNA base sequence} \rightarrow \text{altered mRNA codon} \rightarrow \text{different amino acid in the receptor protein}$

Answer: molecular bases located in the nucleus

Protein changes ultimately trace back to a change (mutation) in the sequence of nitrogenous bases in the DNA within the nucleus, which alters the amino acid sequence produced.

Question 34 · 2 pts

Certain organisms living deep in the ocean can obtain energy from inorganic compounds that flow out of volcanic vents. They can use this energy to synthesize energy-rich organic compounds. Which row in the chart below correctly pairs an organism that performs a similar function in land environments with the process involved? Row 1: small mammal, respiration Row 2: grasses, photosynthesis Row 3: small mammal, photosynthesis Row 4: grasses, respiration

(A) Row 1
(B) Row 2 ✓
(C) Row 3
(D) Row 4

Worked solution

$\text{Vent organisms use chemosynthesis (inorganic energy} \rightarrow \text{organic compounds)}$

$\text{The land equivalent function is photosynthesis, performed by producers such as grasses}$

Answer: Row 2: grasses, photosynthesis

Both chemosynthesis and photosynthesis convert an external energy source into stored energy in organic compounds; grasses (autotrophic producers) are the land analog, using photosynthesis.

Question 35 · 2 pts

Scientists are concerned about the decreasing numbers in the populations of Atlantic salmon along the east coast of North America due to overfishing and changes in their breeding environments. Some businesses have developed farm-raised populations of certain varieties of salmon. Large, farm-raised populations have a limited genetic diversity as compared to wild-caught salmon. Which row in the chart below correctly pairs possible effects of fish farming? Row 1: Negative Effect - Loss of biodiversity among farmed fish; Positive Effect - Increased sales of fish, a food source Row 2: Negative Effect - Increased sales of fish, a food source; Positive Effect - Limited genetic diversity in salmon population Row 3: Negative Effect - Loss of biodiversity in wild fish; Positive Effect - Decreased population size Row 4: Negative Effect - Increased biodiversity; Positive Effect - Increased population size

(A) Row 1 ✓
(B) Row 2
(C) Row 3
(D) Row 4

Worked solution

$\text{Farming reduces genetic diversity in the farmed population (negative)}$

$\text{Farming increases available fish supply and market sales (positive)}$

Answer: Row 1

Row 1 correctly identifies a true negative consequence (loss of biodiversity among farmed fish due to limited breeding stock) paired with a true positive consequence (more fish available for sale as food).

Question 36 · 2 pts

DNA studies have shown that bears and raccoons evolved from a common ancestor about 50 million years ago. Giant pandas evolved from a more recent ancestor that was related to bears. The red panda evolved from a more recent ancestor that was related to raccoons. Which evolutionary tree best represents these sequences of events?

(A) Tree 1: a shared base splitting into a raccoon/red panda branch and a giant panda/bear branch ✓
(B) Tree 2: bear branching first, then splitting into red panda, giant panda, and raccoon
(C) Tree 3: raccoon branching first, then splitting into bear, red panda, and giant panda
(D) Tree 4: a shared base splitting into a giant panda/raccoon branch and a red panda/bear branch

Worked solution

$\text{Bears and raccoons share a distant common ancestor (base of tree)}$

$\text{Giant panda branches from the more recent bear lineage}$

$\text{Red panda branches from the more recent raccoon lineage}$

Answer: Tree 1

The correct tree must group giant panda with bear (closer common ancestor) and red panda with raccoon (closer common ancestor), both stemming from one shared, older ancestor, which matches Tree 1.

Question 37 · 2 pts

Researchers studying water fleas (tiny organisms that live in fresh water) have noticed that the appearance of the water flea follows a pattern, as seen in the table below. The Effect of Predator Type on Water Flea Appearance: three columns show water flea body shape/armor under No predator, Stickleback fish, and Backswimmer bug conditions (images show differing spine/helmet armor). If all three water fleas are genetically identical, which statement best explains why the three water fleas have different appearances?

(A) Random alterations of genes occur in water fleas when they eat different foods.
(B) Predators in the water flea's environment cause mutations in the water flea.
(C) Genes are not involved in the appearance of these water fleas.
(D) Water flea gene expression can be influenced by the type of predator present in their environment. ✓

Worked solution

$\text{Genetically identical organisms} \Rightarrow \text{differences are not due to different DNA}$

$\text{Environmental cues (predator presence) alter which genes are expressed}$

Answer: Water flea gene expression can be influenced by the type of predator present in their environment.

Since the water fleas share identical DNA, the differing armored appearances must result from differential gene expression triggered by environmental (predator) cues, not from mutation or altered DNA.

Question 38 · 2 pts

Base your answer on the following information: It was widely accepted that humans inherit their mitochondria only from their mothers. In 2002, an individual suffering from fatigue and muscle pain was found to have a mutation in his mitochondrial DNA. DNA sequencing of family members revealed that he had inherited the mutated mitochondria from his father. Since 2002, evidence of additional cases of children inheriting mitochondrial mutations from their fathers has been found. The discovery that humans can inherit mitochondria from their fathers illustrates the concept that

(A) inquiry does not judge the reliability of sources
(B) experiments without controls are not valid
(C) scientific explanations are tentative and subject to change ✓
(D) advancements in technology usually make scientific theories invalid

Worked solution

$\text{Old accepted idea: mitochondria inherited only maternally}$

$\text{New DNA sequencing evidence overturned/revised this accepted explanation}$

Answer: scientific explanations are tentative and subject to change

This case shows that widely accepted scientific ideas can be revised when new evidence emerges, reflecting the tentative, evidence-based nature of science.

Question 39 · 2 pts

Base your answer on the same information as question 38 regarding a mutation in mitochondrial DNA inherited from a father. The most likely explanation for why children who inherited mutated mitochondria suffer fatigue and muscle pain is that their mitochondria fail to

(A) provide the antigens needed to fight the mutated DNA
(B) regulate the transport of nutrients to the muscle cells
(C) synthesize the starch needed by the muscles
(D) release enough energy for cells to function properly ✓

Worked solution

$\text{Mitochondria perform cellular respiration to produce ATP}$

$\text{Mutated mitochondrial DNA} \Rightarrow \text{impaired respiration} \Rightarrow \text{insufficient ATP/energy for muscle cell function}$

Answer: release enough energy for cells to function properly

Mitochondria are the primary site of energy (ATP) production; a mutation disrupting their function reduces the energy available to muscle cells, causing fatigue and pain.

Question 40 · 2 pts

Base your answers on the following information: Burmese pythons are an invasive species in the Everglades National Park. In 2010, there was a rare hard freeze, which residents hoped would eliminate these pests that were originally from very warm areas in Asia. Roughly 40% to 90% of the pythons were killed by the freeze event. Since not all of the pythons were killed during the freeze event, the members of the current large python population in the Everglades might differ from the members of the python population from before 2010. Which statement best describes a likely cause for the changes that might exist in the present python population?

(A) The python species needed cold-tolerant genes, and they appeared in 2010 by rapid mutation.
(B) The freeze event served as a selecting agent, and a higher percentage of the pythons existing today are cold-tolerant. ✓
(C) Many individual pythons were unable to reproduce during the freeze event and did not pass on their cold-tolerant genes.
(D) There was no actual change in the population, and if a similar freeze event occurred again, 40-90% of the snakes would die.

Worked solution

$\text{Pre-existing genetic variation included some cold-tolerant individuals}$

$\text{Freeze killed less cold-tolerant pythons (selecting agent)}$

$\text{Survivors (more cold-tolerant) reproduced, raising the trait's frequency}$

Answer: The freeze event served as a selecting agent, and a higher percentage of the pythons existing today are cold-tolerant.

This is natural selection: the freeze acted as an environmental selecting agent that removed less cold-tolerant individuals, shifting the surviving population toward greater cold tolerance.

Question 41 · 2 pts

Pythons in their native habitat often eat a large animal and then do not feed again for weeks. In the Florida Everglades, food sources are often small mammals and birds. The current large python population in Florida can be described as a species that

(A) will quickly die out because there are no appropriate food sources in their environment
(B) will develop new digestive organs as needed to succeed in the Florida Everglades
(C) has expanded only because small animals reproduce so quickly that they provide an unlimited food source
(D) has already successfully adapted to an unfamiliar environment through natural selection ✓

Worked solution

$\text{Existing variation in feeding behavior/physiology allowed some pythons to exploit smaller, more available prey}$

$\text{These individuals survived and reproduced, establishing a thriving invasive population}$

Answer: has already successfully adapted to an unfamiliar environment through natural selection

The large, established python population in an unfamiliar habitat shows successful adaptation through natural selection, not organisms deliberately developing new organs or an infinite food supply.

Question 42 · 2 pts

Base your answers on the following information: Fishers are mammals that prefer to live in forested areas. The fisher feeds on acorns, berries, and apples, as well as on smaller mammals and birds. They are one of the few organisms that are successful in killing and eating porcupines. Porcupines are large rodents that have sharp spines, or quills, that cover most of their body. The fisher has no natural enemies. Most fisher deaths are due to automobiles and trapping. The population has also been negatively affected by logging and road-building. Recently, new regulations have been adopted that affect the trapping of fishers. Which action would probably result in an increase in the fisher population?

(A) removing all regulations regarding fisher trapping
(B) increasing the area where fisher trapping is allowed
(C) changing the fisher trapping season from 46 to 30 days ✓
(D) decreasing the cost of the permit needed for fisher trapping

Worked solution

$\text{Shortening the legal trapping season reduces the number of fishers killed by trapping}$

$\text{Fewer deaths} \Rightarrow \text{population increase}$

Answer: changing the fisher trapping season from 46 to 30 days

Since trapping is a major cause of fisher deaths, shortening the trapping season is the only listed option that reduces trapping pressure and would allow the population to grow.

Question 43 · 2 pts

Humans have negatively affected the ecosystem that fishers occupy. An altered or changed ecosystem can

(A) never recover or become stable again
(B) usually recover gradually to a point of long-term stability ✓
(C) never recover unless there is a decrease in biodiversity
(D) usually recover quickly into the same ecosystem as it was previously

Worked solution

$\text{Ecosystems undergo ecological succession after disturbance}$

$\text{Over time, they reach a new, relatively stable state (not necessarily identical to the original)}$

Answer: usually recover gradually to a point of long-term stability

Disturbed ecosystems generally do not recover instantly or return to an identical prior state, but through succession they gradually move toward a new long-term stable condition.

Question 44 · 1 pt · constructed response

Base your answer on the information below and on your knowledge of biology. Monarch Butterfly Parasites: Monarch butterflies are in trouble. Their populations have been declining quickly in recent years due to several factors, including habitat loss, climate change, and infection by parasites. To investigate ways to reduce this decline, some scientists studied a parasite that often infects and weakens monarch larvae (caterpillars). The larvae ingest parasite spores as they feed on milkweed plants. Once in the intestinal tract of the caterpillar, some of the spores can infect the cells of the intestine and reproduce. The scientists collected samples of the parasite from four areas of North America where monarchs live. They found four different variations in the parasites. Scientists cloned each of the four variations of parasites in order to have enough to test with the monarch larvae. Monarch larvae feed exclusively on milkweed plants. Two types of milkweed monarchs feed on are swamp milkweed (SM) and tropical milkweed (TM). Both kinds of plants contain chemicals known as cardenolides, but tropical milkweed has higher levels of these chemicals. These chemicals are absorbed into the tissues of the larvae as they feed on milkweed. The cardenolides give the larvae some resistance to infection by the parasites. The scientists conducted experiments to determine how the harm caused by these parasites may be affected by the amounts of cardenolides in the two kinds of milkweed. The monarch larvae were divided into groups. Each of the groups was fed one of the two types of milkweed and then exposed to one of the four parasite clones: E-1, E-11, F-3, or F-13. The overall purpose of the testing was to determine whether it was the type of parasite clone or the type of plant that the larvae were fed that would have the greatest effect on the percent of caterpillars that became infected. The data table below shows the results obtained by the scientists. Infections Based on Type of Food Plant and Parasite Clone: Parasite Clone E-1: Percent infected on Tropical Milkweed (TM) = 83, Percent infected on Swamp Milkweed (SM) = 100 Parasite Clone E-11: TM = 88, SM = 92 Parasite Clone F-3: TM = 75, SM = 100 Parasite Clone F-13: TM = 86, SM = 100 Directions (44-45): Using the information in the data table, construct a bar graph on the grid provided. 44 Mark an appropriate scale on the axis labeled 'Percent of Monarch Larvae Infected.'

Model answer: An appropriate scale numbers the vertical axis from 0 to 100 in equal increments (for example, by 10s: 0, 10, 20, 30, ... 100), using consistent, evenly spaced gridlines so that every data value (75 to 100) can be plotted accurately and the full range of the given data fits on the grid.

Worked solution

$\text{Data range: minimum } = 75,\ \text{maximum } = 100$

$\text{Choose a starting value of } 0 \text{ and an ending value that meets/exceeds } 100$

$\text{Divide axis into equal intervals, e.g. } 0,10,20,\dots,100$

$\text{Label each gridline with its numeric value, spaced evenly}$

Answer: An appropriate scale numbers the vertical axis from 0 to 100 in equal increments (for example, by 10s: 0, 10, 20, 30, ... 100), using consistent, evenly spaced gridlines so that every data value (75 to 100) can be plotted accurately and the full range of the given data fits on the grid.

A correct scale must start at zero (or a low value), use equal, evenly spaced numeric intervals (such as increments of 10), and extend high enough to include the maximum data value of 100, so that all percentages in the table can be plotted precisely on the grid.

Question 45 · 1 pt · constructed response

Base your answer on the following information. Monarch Butterfly Parasites: Monarch butterflies are in trouble! Their populations have been declining quickly in recent years due to several factors, including habitat loss, climate change, and infection by parasites. To investigate ways to reduce this decline, some scientists studied a parasite that often infects and weakens monarch larvae (caterpillars). The larvae ingest parasite spores as they feed on milkweed plants. Once in the intestinal tract of the caterpillar, some of the spores can infect the cells of the intestine and reproduce. The scientists collected samples of the parasite from four areas of North America where monarchs live. They found four different variations in the parasites. Scientists cloned each of the four variations of parasites in order to have enough to test with the monarch larvae. Monarch larvae feed exclusively on milkweed plants. Two types of milkweed monarchs feed on are swamp milkweed (SM) and tropical milkweed (TM). Both kinds of plants contain chemicals known as cardenolides, but tropical milkweed has higher levels of these chemicals. These chemicals are absorbed into the tissues of the larvae as they feed on milkweed. The cardenolides give the larvae some resistance to infection by the parasites. The scientists conducted experiments to determine how the harm caused by these parasites may be affected by the amounts of cardenolides in the two kinds of milkweed. The monarch larvae were divided into groups. Each of the groups was fed one of the two types of milkweed and then exposed to one of the four parasite clones: E-1, E-11, F-3, or F-13. The overall purpose of the testing was to determine whether it was the type of parasite clone or the type of plant that the larvae were fed that would have the greatest effect on the percent of caterpillars that became infected. The data table below shows the results obtained by the scientists. Infections Based on Type of Food Plant and Parasite Clone | Parasite Clone | Percent of Larvae Feeding on Tropical Milkweed (TM) that Became Infected | Percent of Larvae Feeding on Swamp Milkweed (SM) that Became Infected | | --- | --- | --- | | E-1 | 83 | 100 | | E-11 | 88 | 92 | | F-3 | 75 | 100 | | F-13 | 86 | 100 | Construct a bar graph following the directions below. - Construct vertical bars in the area provided on the grid to represent the results for each parasite clone for the larvae that were fed tropical milkweed (TM) in the areas marked TM. Shade the TM bars in black. - Construct vertical bars in the area provided on the grid to represent the results for each parasite clone for the larvae that were fed swamp milkweed (SM) in the areas marked SM. Shade the SM bars with diagonal lines.

Model answer: Bar graph with 8 bars (TM and SM for each of clones E-1, E-11, F-3, F-13): E-1 TM=83, E-1 SM=100; E-11 TM=88, E-11 SM=92; F-3 TM=75, F-3 SM=100; F-13 TM=86, F-13 SM=100. Bars must accurately reflect these heights on a scale marked on the y-axis, with TM bars shaded solid black and SM bars shaded with diagonal lines.

Worked solution

$\text{E-1: TM }=83,\ \text{SM }=100$

$\text{E-11: TM }=88,\ \text{SM }=92$

$\text{F-3: TM }=75,\ \text{SM }=100$

$\text{F-13: TM }=86,\ \text{SM }=100$

Answer: Bar graph with 8 bars (TM and SM for each of clones E-1, E-11, F-3, F-13): E-1 TM=83, E-1 SM=100; E-11 TM=88, E-11 SM=92; F-3 TM=75, F-3 SM=100; F-13 TM=86, F-13 SM=100. Bars must accurately reflect these heights on a scale marked on the y-axis, with TM bars shaded solid black and SM bars shaded with diagonal lines.

Each data table value is plotted as a vertical bar of matching height above its labeled clone/plant-type position, using the shading key given (solid black for TM, diagonal lines for SM).

Question 46 · 1 pt · constructed response

State whether the types of milkweed that the larvae were fed made a difference in whether or not the larvae became infected. Support your answer.

Model answer: Yes, the type of milkweed made a difference; larvae fed swamp milkweed had a higher percent infected (92-100%) than larvae fed tropical milkweed (75-88%) for every parasite clone tested.

Worked solution

$\text{Compare SM vs TM infection percent for each clone}$

$\text{SM percentages (92-100) consistently exceed TM percentages (75-88)}$

Answer: Yes, the type of milkweed made a difference; larvae fed swamp milkweed had a higher percent infected (92-100%) than larvae fed tropical milkweed (75-88%) for every parasite clone tested.

Because tropical milkweed contains higher levels of cardenolides, larvae feeding on it were more resistant to infection, so the type of milkweed did affect infection rate.

Question 47 · 2 pts

Which row in the chart below correctly identifies the average percent of infection of the larvae that ate tropical milkweed and the average percent of infection of the larvae that ate swamp milkweed?

(A) 75 (TM), 92 (SM)
(B) 88 (TM), 100 (SM)
(C) 83 (TM), 98 (SM) ✓
(D) 98 (TM), 83 (SM)

Worked solution

$\text{TM average} = \frac{83+88+75+86}{4} = \frac{332}{4} = 83$

$\text{SM average} = \frac{100+92+100+100}{4} = \frac{392}{4} = 98$

Answer: Row (3): 83, 98

Averaging the four TM values gives 83 percent and averaging the four SM values gives 98 percent, matching row 3.

Question 48 · 1 pt · constructed response

Describe how the results of the experiment might have been different if very few spores of parasite clone F-13 were placed on the milkweed leaves, compared with the number of spores placed on leaves for the other three clones.

Model answer: The percent of larvae infected by clone F-13 would likely have been lower than shown, because fewer spores means fewer larvae would have ingested enough spores to become infected.

Worked solution

$\text{Fewer spores available} \Rightarrow \text{lower probability of larvae ingesting spores}$

$\text{Lower exposure} \Rightarrow \text{lower percent infected for F-13 compared with the other clones}$

Answer: The percent of larvae infected by clone F-13 would likely have been lower than shown, because fewer spores means fewer larvae would have ingested enough spores to become infected.

Reducing the dose (number of spores) of clone F-13 would reduce the larvae's exposure to the parasite, likely resulting in a lower infection rate for F-13 than reported.

Question 49 · 2 pts

Base your answer on the following information. Frogsicles: Frozen but Still Alive: The wood frog has the amazing ability to survive winter in a frozen state. Ice crystals touching the frog can trigger the freezing of its body fluids. Most of the water moves out of their cells and into body cavities, where it turns into solid ice. Their cells are protected from dehydration and frostbite by the antifreezing effect of their cells absorbing extremely high concentrations of sugar. When these frogs freeze, they stop breathing, their heart stops beating, and they enter a state of dormancy that can last several months. In spring, the frogs thaw, and the excess sugar moves out of their cells. The frogs resume normal activities in less than 24 hours. A wood frog's body systems' responses to ice crystals touching it in winter and to the conditions in the spring can best be explained by

(A) the differentiation of mature body cells during development
(B) a response of their cells to changing environmental conditions ✓
(C) the enzymatic breakdown of water as the frog freezes
(D) a response of the immune system to excess sugar levels

Worked solution

$\text{Freezing temperatures} \rightarrow \text{cells move water out and absorb sugar}$

$\text{Warming temperatures} \rightarrow \text{cells release excess sugar and resume function}$

Answer: a response of their cells to changing environmental conditions

The frog's cells actively adjust their internal chemistry (moving water out, absorbing sugar, then reversing this) in direct response to changing external temperature, maintaining homeostasis.

Question 50 · 2 pts

Which scientific question could lead to an investigation to help determine the stimulus that causes wood frogs to thaw in the spring?

(A) Do the frogs thaw if the air temperature remains below freezing all winter?
(B) Does the changing length of daylight or warming cause the frogs to thaw? ✓
(C) Do the frogs get hungry when they are frozen?
(D) Does the weight of the frog change after they freeze?

Worked solution

$\text{A valid stimulus-testing question must propose a testable environmental trigger (photoperiod or temperature)}$

Answer: Does the changing length of daylight or warming cause the frogs to thaw?

This is the only choice that proposes testable environmental stimuli (daylight length or warming temperature) that could plausibly trigger thawing, making it a valid investigable scientific question.

Question 51 · 1 pt · constructed response

Identify one structure present in the cells of these frogs that plays a role in the rapid removal of water and the absorption of high concentrations of sugar. Justify your answer.

Frogsicles: Frozen but Still Alive: The wood frog has the amazing ability to survive winter in a frozen state. Ice crystals touching the frog can trigger the freezing of its body fluids. Most of the water moves out of their cells and into body cavities, where it turns into solid ice. Their cells are protected from dehydration and frostbite by the antifreezing effect of their cells absorbing extremely high concentrations of sugar. When these frogs freeze, they stop breathing, their heart stops beating, and they enter a state of dormancy that can last several months. In spring, the frogs thaw, and the excess sugar moves out of their cells. The frogs resume normal activities in less than 24 hours.

Model answer: The cell membrane; it regulates (controls) the movement of substances such as water and sugar into and out of the cell.

Worked solution

$\text{Cell membrane controls diffusion/transport of water and dissolved sugar across the cell boundary}$

Answer: The cell membrane; it regulates (controls) the movement of substances such as water and sugar into and out of the cell.

The cell membrane is the structure responsible for selectively allowing water to leave and sugar to enter the cell, which is exactly what happens as the wood frog freezes and thaws.

Question 52 · 1 pt · constructed response

A cellular process that produces sex cells in fruit flies is represented in the diagram below: a cell with 8 chromosomes divides into two cells, and each of those two cells divides again into two more cells, producing four total sex cells. Based on the information in the diagram, how many chromosomes will be present in each of the sex cells of the fruit fly? _____ chromosomes

Model answer: 4 chromosomes

Worked solution

$\text{Starting cell} = 8 \text{ chromosomes}$

$\text{Meiosis: two divisions halve chromosome number}$

$8 \div 2 = 4 \text{ chromosomes in each sex cell}$

Answer: 4 chromosomes

This diagram represents meiosis, which reduces the chromosome number by half, so each sex cell produced from an 8-chromosome cell contains 4 chromosomes.

Question 53 · 1 pt · constructed response

The model below represents the reproductive system of human females. It shows two fallopian tubes with fringed ends leading to a pair of round structures labeled A on each side, and a single structure labeled B located where the two sides of the uterus join near its base, above the cervix/vaginal canal. Describe the roles of structures A and B in the production of offspring. A: _____ B: _____

Model answer: A (ovaries): produce and release egg cells (ova) for fertilization. B (uterus): is where a fertilized egg implants and the embryo/fetus develops until birth.

Worked solution

$A = \text{ovary} \rightarrow \text{produces eggs (ova) via meiosis and releases them during ovulation}$

$B = \text{uterus} \rightarrow \text{site of implantation and development of the embryo/fetus}$

Answer: A (ovaries): produce and release egg cells (ova) for fertilization. B (uterus): is where a fertilized egg implants and the embryo/fetus develops until birth.

The paired round structures (A) are the ovaries, which generate and release eggs, while the central structure (B) is the uterus, which houses and nourishes the developing embryo after fertilization.

Question 54 · 1 pt · constructed response

Base your answer on the following information. A student placed four different test tubes in a water bath at 37°C, human body temperature. The contents of the test tubes are listed below. Two of them contain a human enzyme. Test Tube 1: ground meat, water, protein-digesting enzyme Test Tube 2: bread, water, starch-digesting enzyme Test Tube 3: ground meat, water Test Tube 4: bread, water After 15 minutes, the student tested the contents of each tube for the presence of both amino acids and glucose. He obtained the results shown in the table below. Describe the results that the student would most likely obtain if he ran the same experiment again but placed the test tubes in a hot water bath at 65°C for 15 minutes. Justify your answer.

Model answer: Test tube 1 would test negative for amino acids and test tube 2 would test negative for glucose, because the high temperature (65°C) would denature the protein-digesting and starch-digesting enzymes, preventing them from breaking down the meat or bread.

Worked solution

$65^{\circ}\text{C} \gg 37^{\circ}\text{C (optimal human enzyme temperature)}$

$\text{High heat denatures enzyme shape/active site}$

$\text{Denatured enzyme cannot catalyze breakdown of protein or starch} \Rightarrow \text{no amino acids or glucose produced}$

Answer: Test tube 1 would test negative for amino acids and test tube 2 would test negative for glucose, because the high temperature (65°C) would denature the protein-digesting and starch-digesting enzymes, preventing them from breaking down the meat or bread.

Human enzymes function best near body temperature; at 65 degrees Celsius they denature and lose their functional shape, so no digestion products (amino acids or glucose) would form in tubes 1 and 2.

Question 55 · 1 pt · constructed response

Identify the purpose of Test Tubes 3 and 4 in this experiment. Justify your answer.

Model answer: Test tubes 3 and 4 are the controls; they show that the food alone (without enzyme) does not break down into amino acids or glucose, confirming that the positive results in tubes 1 and 2 were due to the enzymes, not some other factor.

Worked solution

$\text{Tube 3/4 lack enzyme} \Rightarrow \text{isolate the effect of the enzyme as the variable being tested}$

$\text{Both tested negative for amino acids/glucose, confirming enzyme was needed for digestion}$

Answer: Test tubes 3 and 4 are the controls; they show that the food alone (without enzyme) does not break down into amino acids or glucose, confirming that the positive results in tubes 1 and 2 were due to the enzymes, not some other factor.

Tubes 3 and 4 serve as experimental controls, demonstrating that digestion (production of amino acids/glucose) does not occur without the addition of the digestive enzyme.

Question 56 · 1 pt · constructed response

Base your answer on the following information. The process of photosynthesis is responsible for providing the energy necessary to sustain most ecosystems on Earth. The flow of energy in an ecosystem is represented in the diagram below as an energy pyramid with, from bottom to top, Level A, Level B, Level C, and Level D. Identify the source of energy for an ecosystem and describe how it is transferred from one level in the system to the next.

Model answer: The sun is the source of energy. Energy is transferred from one level to the next when organisms at one trophic level are consumed (eaten) by organisms at the next level, transferring the chemical energy stored in food/organic molecules.

Worked solution

$\text{Sun} \rightarrow \text{producers (Level A) via photosynthesis, storing energy in organic molecules}$

$\text{Producers} \rightarrow \text{consumers (Levels B, C, D) via feeding/predation}$

Answer: The sun is the source of energy. Energy is transferred from one level to the next when organisms at one trophic level are consumed (eaten) by organisms at the next level, transferring the chemical energy stored in food/organic molecules.

Solar energy captured by producers through photosynthesis is passed up the pyramid as each level is consumed by the next, transferring chemical energy stored in food.

Question 57 · 1 pt · constructed response

The chart below is a summary of the net number of atoms in the molecules used and produced during the process of photosynthesis. | Type of Atom | Number of Atoms in the Molecules Used for Photosynthesis | Number of Atoms in the Molecules Produced by Photosynthesis | | --- | --- | --- | | Carbon (C) | 6 | 6 | | Hydrogen (H) | 12 | 12 | | Oxygen (O) | 18 | 18 | A student claimed that there is no gain or loss of matter during photosynthesis. Provide evidence from the data to support this claim.

Model answer: The number of atoms of each element used equals the number produced (6 carbon, 12 hydrogen, and 18 oxygen atoms on both sides), showing that matter is conserved, not created or destroyed, during photosynthesis.

Worked solution

$\text{Carbon: } 6 \text{ used} = 6 \text{ produced}$

$\text{Hydrogen: } 12 \text{ used} = 12 \text{ produced}$

$\text{Oxygen: } 18 \text{ used} = 18 \text{ produced}$

Answer: The number of atoms of each element used equals the number produced (6 carbon, 12 hydrogen, and 18 oxygen atoms on both sides), showing that matter is conserved, not created or destroyed, during photosynthesis.

Because the counts of each atom type are identical on the input and output sides of the reaction, the data show that photosynthesis conserves matter (atoms are rearranged into new molecules, not gained or lost).

Question 58 · 1 pt · constructed response

Base your answer on the following information. Hudson River Zebra Mussels: Researchers have been monitoring the effects of zebra mussels in the Hudson River. Zebra mussels are small, aquatic, clam-like animals that arrived in the United States in cargo ships traveling from Europe to the Great Lakes in the 1980s. Since waterways connect the Great Lakes to the Hudson River, zebra mussels had spread to the Hudson River by 1991. Zebra mussels can produce a million eggs per year, and the larvae drift before attaching to hard surfaces. Mussels feed by filtering water through their gills and straining out algae, called phytoplankton, and microscopic animals. By the end of 1992, without a predator, the zebra mussels outweighed all other consumers in the river. They filtered a volume of water equal to all of the water in the river every one to four days during the summer, removing food and dissolved oxygen. Zebra mussels caused problems by clogging water pipes and damaging boats, docks, buoys, and other structures. State one reason that the zebra mussels could successfully spread throughout the rivers and lakes in the U.S.

Model answer: Zebra mussels produce huge numbers of eggs/larvae (up to a million per year) each year, and the free-drifting larvae are easily carried by connected waterways (and ships) to new locations, with no natural predators to limit their spread.

Worked solution

$\text{High reproductive rate (millions of eggs/year)} + \text{drifting larvae} + \text{connected waterways} + \text{no predators} \Rightarrow \text{rapid spread}$

Answer: Zebra mussels produce huge numbers of eggs/larvae (up to a million per year) each year, and the free-drifting larvae are easily carried by connected waterways (and ships) to new locations, with no natural predators to limit their spread.

The combination of an enormous reproductive output, free-drifting larvae that travel via connected waterways, and the absence of natural predators allowed zebra mussels to colonize new water bodies rapidly.

Question 59 · 1 pt · constructed response

A student made a claim that once zebra mussels were established in the Hudson River, the zebra mussel population would affect the food webs by reducing the food available for native consumer populations. Explain how the data in Graph 1 could be used to support the student's claim. (Graph 1, described: 'Phytoplankton and Zebra Mussels (ZM) in the Hudson River,' 1987-2009, shows Zebra Mussel Density (per m2) on the left y-axis and Phytoplankton Chlorophyll (micrograms/liter) on the right y-axis, plotted by year on the x-axis.)

Model answer: Graph 1 shows that as zebra mussel density increased (starting around 1992), phytoplankton chlorophyll levels decreased, indicating the mussels were filtering out and consuming the phytoplankton, reducing the food (phytoplankton) available for native consumers that also rely on phytoplankton.

Worked solution

$\text{Zebra mussel density} \uparrow \Rightarrow \text{phytoplankton (chlorophyll) levels} \downarrow$

$\text{Inverse relationship supports reduced food availability for native consumers}$

Answer: Graph 1 shows that as zebra mussel density increased (starting around 1992), phytoplankton chlorophyll levels decreased, indicating the mussels were filtering out and consuming the phytoplankton, reducing the food (phytoplankton) available for native consumers that also rely on phytoplankton.

The inverse pattern between rising zebra mussel density and falling phytoplankton levels in Graph 1 provides direct evidence that zebra mussels were depleting the food source (phytoplankton) needed by native consumers.

Question 60 · 1 pt · constructed response

Other than reducing the food available for native populations, state one negative consequence of failing to keep zebra mussels out of the Great Lakes.

Model answer: Zebra mussels clog water intake pipes and damage boats, docks, and buoys, causing economic/infrastructure damage.

Worked solution

$\text{Zebra mussels attach to hard surfaces in large numbers} \Rightarrow \text{clog pipes, damage structures}$

Answer: Zebra mussels clog water intake pipes and damage boats, docks, and buoys, causing economic/infrastructure damage.

As described in the passage, zebra mussels attach to and clog water pipes and damage boats, docks, and buoys, representing a significant economic and infrastructure cost.

Question 61 · 1 pt · constructed response

The graph below shows changes in two mussel populations in the Hudson River (Graph 2: 'Zebra Mussels (ZM) and Native Mussels (NM) in the Hudson River,' 1991-2009, with ZM Density per m2 on the left axis and NM Density per m2 on the right axis, plotted by year). The native mussels and zebra mussels have similar ecological roles. State one reason for the pattern represented by the data in Graph 2.

Model answer: Because the two mussel species occupy the same niche and compete for the same limited resources (food and space), the native mussel population declined as the zebra mussel population increased, an example of competitive exclusion.

Worked solution

$\text{Same niche} \Rightarrow \text{interspecific competition for resources}$

$\text{Zebra mussel density} \uparrow \Rightarrow \text{native mussel density} \downarrow \text{ (competitive exclusion)}$

Answer: Because the two mussel species occupy the same niche and compete for the same limited resources (food and space), the native mussel population declined as the zebra mussel population increased, an example of competitive exclusion.

Since the two species share the same ecological role/niche, they compete directly for resources; the graph's inverse pattern reflects the zebra mussels outcompeting the native mussels.

Question 62 · 1 pt · constructed response

Base your answer on the following information. Mimicry in Snakes: Mimicry is an evolved resemblance between two species. The harmless scarlet king snake mimics the Eastern coral snake. The king snake has evolved red, yellow, and black bands that make it look very similar to the venomous coral snake. In some areas, both snakes are found together and consume some of the same organisms for food. Explain how mimicry is a benefit to the king snake species.

Model answer: By resembling the venomous coral snake, predators that have learned to avoid the coral snake's coloring also avoid the harmless king snake, reducing predation on king snakes and increasing their chances of survival and reproduction.

Worked solution

$\text{Predators avoid coral snake pattern (learned/instinctive avoidance of venomous prey)}$

$\text{King snake resembles that pattern} \Rightarrow \text{predators avoid king snake too} \Rightarrow \text{increased survival}$

Answer: By resembling the venomous coral snake, predators that have learned to avoid the coral snake's coloring also avoid the harmless king snake, reducing predation on king snakes and increasing their chances of survival and reproduction.

Mimicking the warning coloration of the venomous coral snake tricks predators into avoiding the harmless king snake as well, increasing its survival rate and reproductive success.

Question 63 · 1 pt · constructed response

Predict how the population size of king snakes might change over time without coral snakes in the area where they live. Justify your answer.

Model answer: The king snake population would likely decrease, because without coral snakes present, predators would no longer learn to avoid the red-yellow-black banding pattern, so king snakes would lose the protective benefit of mimicry and be preyed upon more often.

Worked solution

$\text{No coral snakes} \Rightarrow \text{predators do not learn/reinforce avoidance of the banded pattern}$

$\text{Loss of mimicry advantage} \Rightarrow \text{increased predation on king snakes} \Rightarrow \text{population decreases}$

Answer: The king snake population would likely decrease, because without coral snakes present, predators would no longer learn to avoid the red-yellow-black banding pattern, so king snakes would lose the protective benefit of mimicry and be preyed upon more often.

The mimicry benefit depends on predators associating the color pattern with danger from real coral snakes; without coral snakes to reinforce that avoidance, king snakes would face more predation and their population would likely decline.

Question 64 · 1 pt · constructed response

Base your answer on the following information. Predators in the Adirondacks: To help keep the number of deer in check, an environmental group proposes the reintroduction of large predators, such as mountain lions, into the Adirondacks. Coyotes are a main predator of deer, especially the sick and young ones. Opponents of the proposal believe that the Adirondack deer population has been regulated by coyotes, hunting, bad winters, and land development projects. They also question the ability of the mountain lions to survive in the current Adirondack environment. Describe one possible result of reintroducing mountain lions into the Adirondacks.

Model answer: The deer population could decrease as mountain lions prey on them (increased predation pressure), helping to control deer numbers; alternatively, mountain lions could compete with coyotes for the same food source.

Worked solution

$\text{Adding a new predator} \Rightarrow \text{increased predation on deer, and/or competition with coyotes for prey}$

Answer: The deer population could decrease as mountain lions prey on them (increased predation pressure), helping to control deer numbers; alternatively, mountain lions could compete with coyotes for the same food source.

Introducing a new predator would add predation pressure on the deer population, potentially reducing deer numbers, while also creating competition between mountain lions and coyotes for the same prey.

Question 65 · 1 pt · constructed response

Explain how land development projects could reduce the deer population in the Adirondacks.

Model answer: Land development destroys or fragments deer habitat, reducing the amount of food, shelter, and space available, which lowers the carrying capacity of the environment and results in fewer deer being able to survive.

Worked solution

$\text{Development} \Rightarrow \text{loss of habitat/food/shelter} \Rightarrow \text{lower carrying capacity} \Rightarrow \text{smaller deer population}$

Answer: Land development destroys or fragments deer habitat, reducing the amount of food, shelter, and space available, which lowers the carrying capacity of the environment and results in fewer deer being able to survive.

By removing forest and natural habitat, land development reduces the food and shelter resources available to deer, lowering the carrying capacity of the area and thus the size of the population it can support.

Question 66 · 1 pt · constructed response

Base your answer on the following information. Biologics: The newest drugs to treat deadly illnesses like cancer, autoimmune diseases, and heart disease are called biologics. Biologics are drugs that mimic naturally occurring proteins. These biologics are injected into patients. Doctors recently noticed that these drugs do not work for some patients. They developed the model below to explain why the drugs are ineffective in as many as 50% of patients. The model shows: (1) Dendritic cells digest biologics and present small pieces to other immune cells, starting a search-and-destroy reaction, activating a quiescent T cell into a helper T cell, which activates a B cell; (2) The activated B cell produces antidrug antibodies that home in on the drug molecules, marking them for destruction. Based on the information in the model, explain why the biologic drugs are ineffective for some people.

Model answer: Because the biologic drug is a protein, the immune system recognizes it as a foreign antigen; dendritic cells present it to T cells, which activate B cells to produce antidrug antibodies that bind to and mark the drug molecules for destruction before they can act, making the drug ineffective.

Worked solution

$\text{Dendritic cell digests biologic} \rightarrow \text{presents antigen to T cells}$

$\text{Helper T cell activates B cell} \rightarrow \text{B cell produces antidrug antibodies}$

$\text{Antibodies bind/mark drug} \rightarrow \text{drug destroyed before it can function}$

Answer: Because the biologic drug is a protein, the immune system recognizes it as a foreign antigen; dendritic cells present it to T cells, which activate B cells to produce antidrug antibodies that bind to and mark the drug molecules for destruction before they can act, making the drug ineffective.

The patient's immune system treats the biologic drug like any foreign protein, mounting an immune response (via dendritic cells, T cells, and B cells) that produces antibodies which neutralize the drug before it can have its therapeutic effect.

Question 67 · 1 pt · constructed response

Base your answers to questions 66 through 68 on the information below and on your knowledge of biology. Biologics The newest drugs to treat deadly illnesses like cancer, autoimmune diseases, and heart disease are called biologics. Biologics are drugs that mimic naturally occurring proteins. These biologics are injected into patients. Doctors recently noticed that these drugs do not work for some patients. They developed the model below to explain why the drugs are ineffective in as many as 50% of patients. 67 Explain why biologic drugs may be more effective in patients diagnosed with AIDS.

Model answer: Because AIDS destroys helper T cells, patients with AIDS have a weakened immune system and cannot mount a normal search-and-destroy (antibody) response against the biologic drug, so fewer antidrug antibodies are made and the drug is not marked for destruction, allowing it to remain active longer.

Worked solution

$\text{AIDS (HIV) destroys helper T cells}$

$\text{Fewer helper T cells} \Rightarrow \text{fewer activated B cells}$

$\text{Fewer antidrug antibodies produced} \Rightarrow \text{biologic drug is not destroyed}$

Answer: Because AIDS destroys helper T cells, patients with AIDS have a weakened immune system and cannot mount a normal search-and-destroy (antibody) response against the biologic drug, so fewer antidrug antibodies are made and the drug is not marked for destruction, allowing it to remain active longer.

The model shows that helper T cells trigger B cells to make antidrug antibodies that destroy the biologic. Since HIV/AIDS depletes helper T cells, this immune response is weakened, so the biologic drug survives longer and works better.

Question 68 · 1 pt · constructed response

In order to make the biologic drugs more effective, doctors experimented with coating the biologic drugs with a synthetic vaccine particle (SVP). This SVP changes the way that the immune system responds to the drug particle by blocking the production of antidrug antibodies. 68 Explain why a person would still have immunity to other pathogens after being exposed to these SVPs.

Model answer: The SVP only blocks the specific immune response (antibody production) directed at the biologic drug; it does not affect the rest of the immune system, so the person's other immune cells and antibodies against different pathogens are unaffected and continue to function normally.

Worked solution

$\text{SVP blocks antidrug antibody production only}$

$\text{Other T and B cells specific to other pathogens are not affected}$

$\Rightarrow \text{general immunity to other pathogens is preserved}$

Answer: The SVP only blocks the specific immune response (antibody production) directed at the biologic drug; it does not affect the rest of the immune system, so the person's other immune cells and antibodies against different pathogens are unaffected and continue to function normally.

Because the SVP's suppression is specific to the antidrug antibody response, the immune system's ability to recognize and respond to unrelated pathogens (via different specific antibodies/memory cells) remains intact.

Question 69 · 1 pt · constructed response

Base your answers to questions 69 through 71 on the information below and on your knowledge of biology. Plants Rebound in the Chesapeake Bay Chesapeake Bay vegetation, including sea grass and freshwater plants, is an important part of the area's coastal ecosystem. These areas act as nurseries that shelter young fish and invertebrates, clean the water, and stabilize shorelines by preventing erosion. In the 1950s, the human population greatly increased in the Bay area. As the growth continued, cities and farms were releasing large amounts of nitrogen compounds and other nutrients into the water. These nutrients had a very positive effect on the growth of small microscopic organisms, such as algae and plankton, in the Bay. As the algae continued to grow near the surface, the growth of more complex plants living deeper in the Bay decreased. In the 1980s, state and federal regulations were passed that limited the amount of nutrients that could be present in the runoff from farms and wastewater treatment plants. As a result, underwater plants are now growing again in the Bay, and there has been a large decrease in the amount of nitrogen compounds present in the water. 69 State one possible reason why the rapid growth of algae in the Bay resulted in a decline in the number of complex underwater plants.

Model answer: The dense algae growing near the surface blocked sunlight from reaching the deeper-growing complex plants, so those plants could not carry out enough photosynthesis to survive and grow.

Worked solution

$\text{Algae overgrowth near surface} \Rightarrow \text{blocks sunlight penetration}$

$\text{Deeper plants receive less light} \Rightarrow \text{reduced photosynthesis}$

$\Rightarrow \text{decline in complex underwater plants}$

Answer: The dense algae growing near the surface blocked sunlight from reaching the deeper-growing complex plants, so those plants could not carry out enough photosynthesis to survive and grow.

Algae blooms shade out light needed by submerged aquatic vegetation, reducing their photosynthetic rate and survival.

Question 70 · 1 pt · constructed response

Explain one specific way in which the change from more complex plants to more algae could disrupt food webs in the Bay region.

Model answer: Organisms (such as young fish and invertebrates) that depend on complex plants for food or shelter/nurseries would lose their habitat and food source, causing their populations to decline, which would reduce food availability for the consumers that feed on them.

Worked solution

$\text{Loss of complex plants} \Rightarrow \text{loss of nursery habitat/food for fish, invertebrates}$

$\Rightarrow \text{decline in populations dependent on those plants}$

$\Rightarrow \text{disruption spreads through consumers in the food web}$

Answer: Organisms (such as young fish and invertebrates) that depend on complex plants for food or shelter/nurseries would lose their habitat and food source, causing their populations to decline, which would reduce food availability for the consumers that feed on them.

Complex plants serve as nurseries and food sources; replacing them with algae removes this niche/resource, disrupting the organisms and levels of the food web that depended on it.

Question 71 · 1 pt · constructed response

In order to determine which nutrient had the greatest effect on the overgrowth of the algae, several types of data were collected. Identify one type of evidence that researchers would look for to support the conclusion that nitrogen compounds were responsible for the algae growth.

Model answer: Evidence that as nitrogen levels in the runoff/water decreased (after the 1980s regulations), algae growth also decreased (a correlation between nitrogen concentration and algae/plankton population over time).

Worked solution

$\text{Measure nitrogen concentration in water over time}$

$\text{Measure algae abundance over the same time period}$

$\text{Show a correlation: nitrogen} \downarrow \Rightarrow \text{algae} \downarrow$

Answer: Evidence that as nitrogen levels in the runoff/water decreased (after the 1980s regulations), algae growth also decreased (a correlation between nitrogen concentration and algae/plankton population over time).

A valid piece of supporting evidence would be a documented correlation between decreasing nitrogen levels and decreasing algae growth over the same time period, especially after regulations reduced nutrient runoff.

Question 72 · 1 pt · constructed response

Mosquitoes are insects whose bite can cause discomfort and disease in humans. In an attempt to control mosquito populations, scientists have used radiation to prevent the males from producing functional sperm. 72 Explain how the mosquito population can be controlled as a result of this procedure.

Model answer: Sterile males mate with females but cannot fertilize their eggs, so the females produce no offspring (or the eggs do not develop), causing the mosquito population size to decrease over time.

Worked solution

$\text{Radiation} \Rightarrow \text{males produce nonfunctional sperm}$

$\text{Sterile males mate with females} \Rightarrow \text{no fertilization/no viable offspring}$

$\Rightarrow \text{fewer new mosquitoes are born, population decreases}$

Answer: Sterile males mate with females but cannot fertilize their eggs, so the females produce no offspring (or the eggs do not develop), causing the mosquito population size to decrease over time.

Because fertilization requires functional sperm, mating with sterilized males fails to produce offspring, reducing reproduction rate and lowering the population over generations.

Question 73 · 2 pts

After exercising outside on a cold day, a student noticed that his fingers were not as cold as when he started. One possible explanation for this phenomenon would be that exercising

(A) causes more sweat to be produced, which cools the body
(B) increases the blood circulation, causing body parts to feel warmer ✓
(C) increases the breathing rate to remove waste products
(D) decreases the amount of energy needed, so the fingers feel warmer

Worked solution

$\text{Exercise} \Rightarrow \text{increased heart rate/circulation}$

$\text{More warm blood flow to extremities} \Rightarrow \text{fingers feel warmer}$

Answer: (2) increases the blood circulation, causing body parts to feel warmer

Exercise increases heart rate and blood flow throughout the body, delivering more warm blood to the extremities such as the fingers, making them feel warmer despite the cold.

Question 74 · 2 pts

The diagram below represents changes in some red onion cells being observed with a compound microscope after a particular solution was added. Which statement best explains the changes observed?

(A) Distilled water was added to the slide and diffusion caused water to move out of the onion cells.
(B) Salt solution was added to the slide and active transport caused water to move out of the onion cells.
(C) Distilled water was added to the slide and active transport caused water to move out of the onion cells.
(D) Salt solution was added to the slide and diffusion caused water to move out of the onion cells. ✓

Worked solution

$\text{Cells shrink away from cell wall} \Rightarrow \text{water left the cells (plasmolysis)}$

$\text{Hypertonic (salt) solution} \Rightarrow \text{water moves out by diffusion (osmosis)}$

Answer: (4) Salt solution was added to the slide and diffusion caused water to move out of the onion cells.

The shrinking of the cell contents away from the cell wall indicates water left the cells (plasmolysis), which occurs when a hypertonic salt solution is applied and water moves out by diffusion (osmosis), not active transport.

Question 75 · 2 pts

A homeowner observed different types of birds feeding at bird feeders filled with an assortment of food. 75 Competition arises most often when two birds have similar

(A) enzymes
(B) niches ✓
(C) habitats
(D) ecosystems

Worked solution

$\text{Competition occurs when organisms compete for the same resources/role}$

$\text{Niche = an organism's role, including its resource use}$

Answer: (2) niches

A niche describes an organism's specific role and resource use in the environment; two species with overlapping niches compete for the same limited resources, such as the same food.

Question 76 · 2 pts

Base your answers to questions 76 and 77 on the information below and on your knowledge of biology. To demonstrate some of the steps involved in the analysis of DNA, a student was given two paper strips with single-stranded DNA sequences recorded on them. The two strips are illustrated below. Strip 1: TTA[CCGG]ATTACCCGATTA[CCGG]ATAATCT[CCGG]ATATCCGTT Strip 2: TTAGGCTTAAGCT[TAAT]GGCC[TAAT]AGT[TAAT]ACGGT[TAAT]ACAT The student cut between the C and G in each of the shaded CCGG sequences in strip 1 and between the As in the shaded TAAT sequences in strip 2. Both sets of DNA fragments were arranged on a paper model of a gel. 76 The results of this type of DNA analysis are often used to help determine

(A) if two organisms contain the same carbohydrate molecule
(B) the number of DNA molecules in an organism
(C) if the DNA codes for the synthesis of fat molecules in all cells of an organism
(D) the evolutionary relationship between two organisms from different species ✓

Worked solution

$\text{Restriction enzymes cut DNA at specific sequences}$

$\text{Resulting fragment patterns (gel electrophoresis) can be compared between species}$

$\text{Similar patterns} \Rightarrow \text{closer evolutionary relationship}$

Answer: (4) the evolutionary relationship between two organisms from different species

Gel electrophoresis of restriction-enzyme-cut DNA fragments is commonly used to compare DNA sequence similarity between organisms, which helps determine how closely related different species are evolutionarily.

Question 77 · 1 pt · constructed response

Identify the specific type of molecules performing the action of cutting the DNA samples.

To demonstrate some of the steps involved in the analysis of DNA, a student was given two paper strips with single-stranded DNA sequences recorded on them. The two strips are illustrated below. Strip 1: TTA[CCGG]ATTACCCGATTA[CCGG]ATAATCT[CCGG]ATATCCGTT Strip 2: TTAGGCTTAAGCT[TAAT]GGCC[TAAT]AGT[TAAT]ACGGT[TAAT]ACAT The student cut between the C and G in each of the shaded CCGG sequences in strip 1 and between the As in the shaded TAAT sequences in strip 2. Both sets of DNA fragments were arranged on a paper model of a gel.

Model answer: Restriction enzymes (restriction endonucleases).

Worked solution

$\text{DNA cutting at specific sequences is performed by restriction enzymes}$

Answer: Restriction enzymes (restriction endonucleases).

Restriction enzymes (endonucleases) recognize specific DNA sequences and cut the DNA at those sites, which is exactly what is modeled by cutting the paper strips at the CCGG/TAAT sequences.

Question 78 · 1 pt · constructed response

In the Making Connections lab, for trial 1, students squeezed a clothespin as many times as they could in a minute. State one specific biological reason why their muscle cells "got tired" during the second trial.

Model answer: The muscle cells built up lactic acid (from anaerobic respiration) because they were not receiving enough oxygen fast enough to keep up with the demand of repeated contractions, causing fatigue.

Worked solution

$\text{Rapid muscle contraction} \Rightarrow \text{oxygen demand exceeds oxygen supply}$

$\text{Cells switch to anaerobic respiration} \Rightarrow \text{lactic acid builds up}$

$\Rightarrow \text{muscle fatigue (cells "got tired")}$

Answer: The muscle cells built up lactic acid (from anaerobic respiration) because they were not receiving enough oxygen fast enough to keep up with the demand of repeated contractions, causing fatigue.

When muscle cells cannot get enough oxygen to sustain aerobic respiration during repeated fast contractions, they perform anaerobic respiration, producing lactic acid, which causes the sensation of fatigue.

Question 79 · 1 pt · constructed response

Base your answers to questions 79 and 80 on the information below and on your knowledge of biology. An experiment was conducted to measure the effect of exercise on pulse rate for a group of high school students. The table below shows the results. 79 Explain why the resting pulse rates for these students were not all the same.

Model answer: Individual students differ genetically and in physical fitness level (e.g., level of physical conditioning, body size, health), so their baseline (resting) heart rates naturally vary from person to person.

Worked solution

$\text{Genetic variation and differences in fitness level between individuals}$

$\Rightarrow \text{different resting metabolic/heart rates}$

Answer: Individual students differ genetically and in physical fitness level (e.g., level of physical conditioning, body size, health), so their baseline (resting) heart rates naturally vary from person to person.

Because each student is a genetically unique individual with different levels of physical fitness, body size, and health, their resting pulse rates naturally differ.

Question 80 · 1 pt · constructed response

Explain how the increased pulse rate as a result of exercising helps the body maintain homeostasis.

Model answer: A faster pulse rate pumps blood more quickly, delivering more oxygen and glucose to the working muscle cells and removing carbon dioxide and other wastes faster, meeting the increased metabolic demand of exercise and keeping internal conditions stable.

Worked solution

$\text{Exercise increases cellular respiration demand in muscle cells}$

$\text{Increased pulse rate} \Rightarrow \text{faster delivery of O}_2\text{/glucose, faster removal of CO}_2\text{/wastes}$

$\Rightarrow \text{internal balance (homeostasis) is maintained during increased activity}$

Answer: A faster pulse rate pumps blood more quickly, delivering more oxygen and glucose to the working muscle cells and removing carbon dioxide and other wastes faster, meeting the increased metabolic demand of exercise and keeping internal conditions stable.

The increased pulse rate speeds up circulation, ensuring cells get the extra oxygen and nutrients they need during exercise and that wastes are removed quickly, keeping the internal environment stable despite the increased demand.

Question 81 · 2 pts

Note: The answer to question 81 should be recorded on your separate answer sheet. Shown below are two tools that students used as models of finch beaks during the Beaks of Finches lab investigation. 81 Which important concept of natural selection do these model beaks represent?

(A) dynamic equilibrium
(B) limiting factor
(C) environment
(D) variation ✓

Worked solution

$\text{Different tool shapes (tweezers vs. clothespin)} \Rightarrow \text{model different beak shapes}$

$\text{Different beak shapes represent natural variation within a population}$

Answer: (4) variation

The two different tools represent different beak shapes that could exist within a finch population, modeling the natural variation among individuals that natural selection acts upon.

Question 82 · 2 pts

Base your answers to questions 82 and 83 on the diagram below and on your knowledge of biology. The diagram shows the changes in distribution of certain molecules inside and outside of an artificial cell over a period of time. Note: The answer to question 82 should be recorded on your separate answer sheet. 82 The change in the distribution of oxygen molecules was most likely due to

(A) membrane receptors
(B) active transport
(C) synthesis
(D) diffusion ✓

Worked solution

$\text{Oxygen moves from area of higher concentration to lower concentration}$

$\text{Even distribution reached without energy input} \Rightarrow \text{diffusion}$

Answer: (4) diffusion

Oxygen molecules moved from a region of higher concentration to lower concentration until evenly distributed, which is the definition of diffusion, a passive process that requires no energy.

Question 83 · 1 pt · constructed response

State one possible reason why the proteins did not move out of the cell.

Model answer: The protein molecules were too large to pass through the pores/spaces of the cell membrane (or there were no carrier/channel proteins available to transport them out).

Worked solution

$\text{Protein molecules are large macromolecules}$

$\text{Cell membrane is selectively permeable} \Rightarrow \text{blocks large molecules like proteins from passively crossing}$

Answer: The protein molecules were too large to pass through the pores/spaces of the cell membrane (or there were no carrier/channel proteins available to transport them out).

Because the cell membrane is selectively permeable, large protein molecules cannot simply diffuse across it like smaller molecules (such as water or oxygen) can, so they remain trapped inside.

Question 84 · 1 pt · constructed response

Other than beak adaptations, identify one characteristic that would help finches on an island compete successfully, and explain specifically why that characteristic would make them successful.

Model answer: Example: Stronger or larger wings would help a finch fly farther/faster to reach more feeding areas or escape predators, increasing its chances of survival and reproduction compared to finches without this trait.

Worked solution

$\text{Identify a non-beak trait, e.g., wing strength, coloration/camouflage, or claw shape}$

$\text{Explain specifically how that trait improves survival/resource access/reproduction}$

Answer: Example: Stronger or larger wings would help a finch fly farther/faster to reach more feeding areas or escape predators, increasing its chances of survival and reproduction compared to finches without this trait.

Any specific, plausible adaptive trait (such as stronger wings for flight efficiency, camouflage coloration to avoid predators, or sharper claws for perching/climbing) can be credited as long as a clear, specific reason is given for how it improves the finch's ability to compete for resources and survive.

Question 85 · 1 pt · constructed response

During a hurricane, a large raft made up of tree trunks, branches, and other vegetation was washed off the coast of an island. A few days later, this raft washed up on the shore of a new island a few miles away. Along with the vegetation present in the raft, there were about a dozen lizards that were native to the original island, but their species was not living on the new island. A similar species of lizard did live there and had for many years. Once the lizards arrived at the new island, they found food and other resources that they needed to survive. Describe one specific way that the newly arriving lizards might affect the population of lizards already present on the new island.

Model answer: The newly arrived lizards would compete with the native lizard species for the same limited food and resources, which could cause the native lizard population to decrease (or be forced to shift its niche) due to increased competition.

Worked solution

$\text{Two lizard species now share the same habitat/resources}$

$\text{Competition for the same food/resources} \Rightarrow \text{one or both populations affected}$

$\Rightarrow \text{likely decline in the native lizard population}$

Answer: The newly arrived lizards would compete with the native lizard species for the same limited food and resources, which could cause the native lizard population to decrease (or be forced to shift its niche) due to increased competition.

Because the newly arrived lizards occupy a similar niche to the native lizards, they will compete for the same limited resources, which would most likely reduce the size of the native lizard population over time.

June 2024 Living Environment Regents — Answer Key & Worked Solutions

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