Praxis Biology: Content Knowledge (5235) Practice Test and Prep

Welcome to the Praxis Biology Content Knowledge study guide, which includes practice questions. We’ll be introducing you to the content categories and key concepts you need to know to pass this exam. This is one of the free resources we provide so you can see the high-level concepts you will find on the Praxis Biology Content Knowledge test to gauge how much you know.

Quick Links to Help You Navigate This Page

• Praxis Biology: Content Knowledge Test Information
• History and Science of Nature
• Molecular and Cellular Biology
• Genetics and Evolution
• Diversity of Life and Organismal Biology
• Ecology: Organisms and Environments
• Science, Technology, and Social Perspectives
• Praxis Biology: Content Knowledge Practice Questions

Praxis Biology Category I: History and Science of Nature

This content category has 21 selected-response questions. These questions account for 14% of the entire exam.

This content category can be neatly divided into 10 sections:

Key Concepts

Germ Theory

Germ theory was first described in the 1500s by an Italian scientist, Girolamo Fracastoro . He proposed that disease is spread by tiny, “seed-like entities.” Most physicians at the time disregarded this statement. Even up until the 1800s, the cause of major diseases or illnesses was not understood. People still widely believed that disease was the cause of internal imbalances (a carryover from medieval times), spiritual punishment, or even “spontaneous generation.”

It was not until Louis Pasteur that people began to accept the germ theory , which states that certain contagious diseases are caused by the invasion of microscopic organisms. Microorganisms that cause disease are called pathogens . Germ theory states that when pathogens invade the body, they grow, reproduce, and make their hosts sick.

Precision versus Accuracy

Precision and accuracy are two ways we can measure the value of our results.

If you take a weight measurement, and you get 5.3kg for your substance, but the actual known weight of that substance is 10kg, then your measurement is not accurate. Your measurement is not close to the known value. Accuracy measures the closeness of a value to a standard or known value.

If you repeat this measurement 10 times, and you get 5.3kg each time, then your measurement is precise . It is still not accurate, but it is precise. Precision refers to the closeness of two (or more) measurements to each other. Precision and accuracy are independent of one another and are used to describe two different relationships between results.

A common analogy for precision and accuracy is to imagine you are shooting a basketball. If you shoot with accuracy , your ball will land in the hoop, or very close to it, each time. “Accuracy” in basketball means you score by landing the ball in the hoop. If you shoot with precision , you may miss the hoop every

time, but the ball consistently hits the same corner of the backboard. This is precise because the ball is ending up in the same location consistently.

Personal Safety Equipment

In the lab, a variety of equipment is available to make sure we stay safe. This is referred to as personal protective equipment (PPE) , and materials are selected to make sure they are compatible with whatever chemical processes are being used.

Goggles or safety glasses are for eye protection. You must use eye protection to shield your eyes from potentially harmful chemicals, wet cultures, infected materials, chemical reactions (explosions), or any type of welding/soldering. Goggles are used when safety glasses will not provide enough protection. Goggles or safety glasses must be worn over prescription glasses, since daily eyewear alone is not sufficient to protect your eyes from harm in the laboratory. You must wear safety glasses at all times in the laboratory; there is not a time when you do not have to wear them.

Face shields are another level of precaution to protect your face from hazardous debris, usually from flying objects, molten metal, chemical gases, radiation, or liquid chemicals (such as acid). Face shields do not replace goggles and must be worn over protective eyewear.

Gloves protect your hands from chemical spills and splashes. They are required at all times when handling chemicals, biologic materials, or radioactive materials. Do not attempt to reuse disposable gloves and do not wear them outside of the lab. You do not need to wear gloves to use computers or open doors but should only wear them while you are working with your experimental materials.

Lab coats must be worn before starting your experiments, so before you handle any chemicals, cultures, or biologic materials. These must cover you to your knees. Lab coats are used to protect your body from accidental spills.

Aprons : Some laboratories will issue aprons instead of lab coats. The purpose of aprons is akin to the lab coat: to protect your body from accidental spills.

Earplugs : These protect your ears from loud sounds or explosions. These are not commonly needed in the lab, but would be used in cases where you are handling materials that could cause dangerous levels of sound.

Biology Praxis Genetics and Evolution

This content category has 30 selected-response questions. These questions account for 20% of the entire exam.

This content category can be neatly divided into 12 sections:

Key Concepts

Mitochondrial Inheritance

Thinking back to the structure of the cell, we know that mitochondria are not only the powerhouses of the cell, but they store important genetic material.

Mitochondrial inheritance occurs when a trait encoded in the mitochondria gets passed down. Because mitochondria are passed into the egg from cells in the ovary, offspring can inherit a genetic condition via the mitochondria. An affected male does not pass his mitochondria down to his offspring, so when we think of mitochondrial inheritance, we know that it always occurs on the maternal (mother) line.

Mitochondrial inheritance can be caused by incorrectly functioning mitochondria, an alteration in the nuclear DNA, or an alteration in the mitochondrial DNA.

Examples of mitochondrial inherited illnesses in humans include mitochondrial myopathy, Kearns-Sayre syndrome, Leigh’s syndrome, and Mitochondrial Depletion syndrome (MDS).

Sickle-Cell Anemia

Sickle-cell anemia is an inherited disorder. People with sickle-cell anemia produce abnormally-shaped red blood cells (shaped like crescents, or sickles), which means the cells can’t transport enough oxygen to the body.

File:Sickle Cell Anemia.png by BruceBlaus is licensed under CC BY-SA 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-sa/4.0/?ref=openverse.

This condition is caused by mutations in the HBB gene and is an inherited autosomal recessive

disorder. That means that a person inherits sickle-cell anemia only when both parents have at least one recessive copy of the gene. You can be a carrier for sickle-cell anemia without showing symptoms, and people who suffer from the disease inherited both recessive copies.

Human Impact on the Extinction of Species

Humans have impacted wildlife diversity in several ways.

Habitat loss

: Habitat loss refers to the destruction or alteration of a natural landscape for human purposes, such as construction. Housing developments, malls, cities, and roads are all examples of how humans have caused habitat loss. Deforestation for logging is another type of habitat loss. This destroys the balance of natural ecosystems.

Amphibians (frogs, toads, and salamanders) are small organisms that are very sensitive to ecosystem changes. Their numbers have declined with habitat loss. Primates are an example of animals displaced by deforestation. When habitats are destroyed, this creates an imbalance in the ecosystem: not only do animals no longer have space to live, but the change in the landscape creates unfair competition, lack of food, or lack of nesting sites.

Water pollution:

People have contributed to pollution through the use of motorized boats (which emit both gas pollution and noise pollution), dumping waste into the waterways (agricultural waste, such as fertilizers, pesticides, or human waste), dumping trash, or oil spills.

Seabirds and marine mammals have been harmed by pollution when infectious diseases get spread into the waterway, they consume pesticides or chemicals, or they become tangled in trash. Oil spills cause massive death and destruction to aquatic life, from birds and mammals down to algae and coral.

In Florida, the manatee population is threatened by humans’ water activity: about 150 manatees die each year from being hit by motorized boats.

Air pollution:

When chemicals saturate the air, that culminates in air pollution. “Chemicals” include smog and smoky byproducts of cars or industrial living. When acidic pollutants combine with water droplets in clouds, this becomes

acid rain. Acid rain damages the environment by killing or harming plants, fish, and wildlife. Acid rain can change the quality and makeup of soils, seep into water systems, and even creep into the airways of animals or humans.

Climate change:

Humans have contributed to climate change by the increased CO2 emissions in the atmosphere. This causes increased global temperature on land and sea. An average increase in global temperature causes polar ice cap melt (which leads to increased sea level rise); warmer, drier weather in temperature regions (contributing to drought and habitat loss); coral bleaching; and extreme weather patterns. All of these cause disruptions in migratory patterns of animals, loss of food sources, loss of habitat, and an inability to cope with new environments.

Disease:

Modern humans are able to travel with ease. This leads to increased transmission of disease, both from person-to-person and person-to-animal. When habitats are introduced to non-native diseases, the animals do not have the built-up immune responses to fight off the diseases. People can spread disease just by travel, but also by traveling with their domestic livestock (dogs or cattle, for example), and this can spread disease.

The introduction of avian malaria, for example, caused a major threat to endemic birds of Hawaii.

Introducing invasive species:

When humans transport new species to an area, this is called introducing an invasive (non-native) species. The introduction of new species disrupts the entire natural ecosystem, causing endemic species to have to compete for food, habitat, and mates.

Popular examples of invasive species are the introduction of the European Starling to America in the 1800s and the introduction of the Bullfrog to Australia in the 1900s. Starlings quickly displaced endemic birds and populated so quickly that today, they are considered a nuisance. Bullfrogs were introduced to Australia for pest control but soon took over entire habitats, threatening several species toward extinction.

And that is some information about the Genetics and Evolution portion of the Paxis Biology Exam.

Praxis Biology Diversity of Life and Organismal Biology

This content category has 30 selected-response questions. These questions account for 20% of the entire exam.

This content category can be neatly divided into 13 sections:

Key Concepts

Binary Fission

Binary fission is a type of asexual reproduction, common among prokaryotes (archaea, bacteria, and protists). In binary fission, a cell duplicates its genetic material (DNA), and then divides, giving rise to two identical cells.

Vascular versus Nonvascular Plants

Vascular plants have vessels to transport water and food throughout the plant. Vascular plants have a phloem (used to transport food) and a xylem (used to transport water). Vascular plants have roots for support and to transport nutrients. Trees, flowering plants, and ferns are all examples of vascular plants.

Nonvascular plants

do not have a vascular system. Nonvascular plants do not have a phloem or a xylem. They are very small and they do not have roots. Instead of roots, nonvascular plants have rhizoids, which are hairs that keep the plant in place. Mosses, liverworts, and hornworts are all types of nonvascular plants.

You can tell if a plant is vascular or nonvascular usually by its location: nonvascular plants are usually found on moist forest floors or on branches of a tree. Remember: nonvascular plants do not have roots, just hairs that help hold it in place. Vascular plants have roots, so flowering plants, trees, and ferns that grow in the soil are examples of vascular plants.

Pollination Strategies

Pollen can be dispersed in several ways.

Wind: Many plants use wind for cross-pollination. These plants usually have flowers that appear in the spring, or seeds that fall and are dispersed by the wind. Grasses, ragweeds, and cereal crops all use wind to help pollinate.

Water: Some plants release seeds or pollen directly into the water. Water-aided pollination occurs in waterweeds and pondweeds.

Insects: Plants rely on the help of insects, such as bees, to pollinate. Plants provide nectar and pollen together as rewards for the insect to visit the flower. When an insect reaches in for the nectar, pollen sticks to its body. The pollen can then come off when the insect visits another flower, allowing for pollination.

Animals: Plants can use the help of larger organisms, like birds or mammals to help pollinate. Animals that consume seeds disperse them later in their scat. In mammals, seeds can stick to an animal’s fur, which is later brushed or rubbed off at another location. Birds that eat nectar from plants transport pollen like bees: when their beaks reach into eat nectar, bits of pollen attach on, and are then transported to the next flower.

And that is some information about the Diversity of Life and Organismal Biology category of the Praxis Biology exam.

Biology Praxis Ecology

This content category has 24 selected-response questions. These questions account for 16% of the entire exam.

This content category can be neatly divided into 12 sections:

Key Concepts

Carrying Capacity

In your house, there is a set amount of space. There are a set number of rooms, bathrooms, walls, and beds. And while you can fill up your fridge to add more food, your fridge can’t hold unlimited food just like your house can’t accommodate an unlimited amount of people. Even if you have people visit, you don’t have thousands of people live there each day, because there just aren’t enough resources for that to happen. In ecology, this is called the carrying capacity of an ecosystem.

Carrying capacity

refers to the maximum population size of the species that can live there sustainably, given the amount of food, water, habitat, and resources needed to survive.

For example, a small population of deer can live in a patch of woods, because they have enough food, water, and shelter to live, grow, and raise baby deer each spring. But the population can’t grow indefinitely: eventually, there is a cap to the number of deer that a forest can support. Too many deer and the forest doesn’t have enough space for shelter. When there are too many deer, they eat away all of the plant species needed to survive, and the forest can’t regenerate plants fast enough to sustain the population. This is the point where the population cannot survive long-term.

Symbiosis

Symbiotic relationships are close relationships between two species. There are three types of symbiotic relationships:

Mutualism: When both partners benefit equally from the relationship. The oxpecker is a type of bird that hangs around rhinos and zebras. The bird eats ticks and parasites from the skin (receives a meal), and the rhino or zebra gets a cleaning (pest control).

Commensalism: One species benefits with the other one is neither helped nor harmed. Barnacles are a type of crustacean that attach themselves to whales. Barnacles can’t move on their own, so they use the whale to move and find food. The whale is not helped or harmed by the presence of a barnacle.

Parasitism: One species (the parasite) nourishes itself off the other species (the host). Here, the host is at a disadvantage. The deer tick is a parasite that attaches itself to a mammal and feeds on its blood. The tick gets food and a host, but the mammal loses blood and nutrients, and it is exposed to the diseases of the tick.

Phosphorus Cycle

Phosphorus

is an essential nutrient for animals and plants alike: it plays an important role in cell development, cell energy (necessary for the ATP process), and DNA. If you don’t have enough phosphorus in your soil, you can have a poor crop yield. The phosphorus cycle refers to how phosphorus moves through sediment, water, soil, and organisms. It is important to consider the phosphorus cycle for agriculture.

• Weathering. Over time, rain and weathering cause rocks to release phosphate ions and minerals. This is then distributed in soils and water.
• Absorption by plants. Plants absorb phosphate salts dissolved in the soil water.
• Absorption by animals. Animals absorb phosphorus by eating plants or other plant-eating animals. Carnivores consume phosphorus by eating herbivores, who consume phosphorus by eating plants.
• Return to the environment by decomposition. When plants and animals die, their bodies decompose. During the decomposition process, organic phosphorus is converted to inorganic phosphorus, which is then recycled to the soil and water.

And that is some information about the ecology portion of the Praxis Biology exam.

Praxis Biology Science, Technology and Social Perspectives

This content category has 15 selected-response questions. These questions account for 10% of the entire exam.

This content category can be neatly divided into 4 sections:

Key Concepts

Endangered Species Act

The Endangered Species Act (ESA) was passed in 1973 as a way to protect endangered or threatened species, as well as their habitats. It contains a list of species that are threatened for extinction and calls for legislative protection. The ESA prohibits the harming (or killing) of endangered species, bans the import/export of endangered species, requires protection for species habitat (land and water), and implements recovery plans for the species.

An estimated 99% of the species protected by the list have been saved by this law. Grizzly bears, humpback whales, and bald eagles are some of the species that have recovered thanks to this act. Its purpose is to protect species from extinction.

Stem Cell Research

Stem cell research (SCR) is the branch of science that focuses on “reprogramming” adult “stem cells” to get them to act like embryonic stem cells. As we develop, cells become specialized. Stem cells are the blank slate of the cell before specialization. As we age, adult stem cells replace cells lost through normal wear-and-tear: stem cells are found throughout our bodies and are an important part of our biology. Stem cell therapy has been used for decades to treat types of blood cancers and replace skin in major burn injuries: stem cells are reprogrammed and replace the normal stem cells in a patient’s body that have been otherwise destroyed. Currently, scientists hope that stem cell research can improve treatment for other chronic diseases, such as heart disease, Alzheimer’s disease, or diabetes.

What makes stem cell research controversial is the use of embryonic stem cells, the type of stem cells derived from a small group of cells in a 5-day embryo. This leads to ethical concerns about destructing possible life or reproductive cloning. There are also concerns about the safety of stem cell therapies as the branch of science continues to evolve.

Soil Erosion

Soil erosion is the wearing away of topsoil. This is a naturally-occurring process that affects all types of landforms. Topsoil can be eroded away or displaced by wind, water, or through farming (tilling). Erosion can reduce a cropland’s productivity, but it also contributes to soil runoff or even flooding or landslides in extreme cases.

Soil erosion can be prevented by planting vegetation. Plants, such as trees or grass cover, establish root systems that help stabilize the soil. This stabilizes the system and prevents risk of flooding or landslides. Plants also prevent wind and water erosion by covering the soil with their roots and acting as a barrier to these natural forces.

Some farmers can also divert flooding by creating a diversion to help with drainage or use erosion control blankets in place of vegetation.

And that’s some basic info about the Praxis Biology exam.

Biology Praxis Practice Questions

Question 1

Which of the following choices best completes the analogy listed below?

Lipids are to storing energy as nucleic acids are to ____.

1. carrying genetic material
2. building and repairing cell parts
3. providing quick energy
4. speeding up chemical reactions

Correct Answer:  1

Explanations:

1. Nucleic acids include DNA and RNA, which carry the cell’s genetic information.
2. Proteins are responsible for building and repairing cell parts.
3. Carbohydrates are responsible for providing quick energy.
4. Enzymes are biological catalysts that speed up chemical reactions.

Question 2

Which of the following is true of the light-dependent and light-independent reactions of photosynthesis?

1. The light-dependent reactions take place in the thylakoid membrane, and the light-independent reactions take place in the stroma.
2. The light-dependent reactions produce some reactants needed for the light-independent reactions, and the light-independent reactions produce some reactants needed for the light-dependent reactions.
3. The light-dependent reactions require energy from the sun, and light-independent reactions do not.
4. All of the above are true.

Correct Answer:  4

Explanations:

1. The photosystems for the light-dependent reactions are located in the thylakoid membrane.
2. The light-dependent reactions produce NADPH and ATP, and the light-independent reactions produce NADP+ and ADP + P.
3. The light-independent reactions, also called the Calvin Cycle, are so named because they do not require solar energy. However, the light-independent reactions do require products made in the light-dependent reactions, so they cannot continue in the dark indefinitely.
4. All the statements are true of the light-dependent and light-independent reactions.

Question 3

Which of the following correctly identifies a major difference between plant and animal cells?

1. Plant cells have a cell wall in addition to a cell membrane, while animal cells only have a cell membrane.
2. Plant cells have a cell wall in place of a cell membrane, while animal cells have a cell membrane.
3. Plant cells have a more rounded shape, and animal cells are more rigid.
4. Plant cells have several smaller vacuoles, while animal cells have a large central vacuole.

Correct Answer:

1

Explanations:

1. Plant cells have a cell wall that surrounds the cell membrane.
2. Plant cells have both a cell wall and a cell membrane.
3. Plant cells are more rigid due to the cell wall, and animal cells have a more rounded shape due to their lack of a cell wall.
4. Plant cells have a large central vacuole to hold waste and water and contribute to turgor pressure.

Question 4

Which of the following choices lists the functions of epithelial cells?

1. hold tissues together, provide insulation and protection
2. provide a barrier, aid in absorption, line internal surfaces
3. move the skeleton, digest food, and pump blood
4. send and receive messages to and from the brain

Correct Answer:  2

Explanations:

1. Connective cells hold tissues together and provide insulation and protection.
2. Epithelial cells can be found in the skin and the lining of internal structures like the esophagus.
3. Muscle cells move the skeleton, help with digesting food, and pump blood.
4. Nerve cells send and receive messages to and from the brain.

Question 5

Which of the following is not an accurate descriptor of vascular plants?

1. Vascular plants contain an internal transport system for water.
2. Vascular plants can control water loss through their leaves.
3. Moss is an example of a vascular plant.
4. Vascular plants contain an internal transport system for food.

Correct Answer:  3

Explanations:

1. Vascular plants have an internal transport system for water.
2. Vascular plants can control water loss through their leaves.
3. Moss is a nonvascular plant.
4. Vascular plants contain an internal transport system for food.

Question 6

Which of the following choices correctly lists the path of blood during pulmonary circulation?

1. right atrium > right ventricle > pulmonary artery > lungs > pulmonary vein > left atrium > left ventricle > aorta
2. aorta > left ventricle > left atrium > pulmonary artery > lungs > pulmonary vein > right ventricle > right atrium
3. aorta > left ventricle > left atrium > pulmonary vein > lungs > pulmonary artery > right ventricle > right atrium
4. right ventricle > right atrium > pulmonary artery > lungs > pulmonary vein > left ventricle > left atrium > aorta

Correct Answer:  1

Explanations:

1. This is the correct pathway of blood during pulmonary circulation.
2. The correct pathway of blood during pulmonary circulation is right atrium > right ventricle > pulmonary artery > lungs > pulmonary vein > left atrium > left ventricle > aorta.
3. The correct pathway of blood during pulmonary circulation is right atrium > right ventricle > pulmonary artery > lungs > pulmonary vein > left atrium > left ventricle > aorta.
4. The correct pathway of blood during pulmonary circulation is right atrium > right ventricle > pulmonary artery > lungs > pulmonary vein > left atrium > left ventricle > aorta.

Question 7

How do the nervous system and endocrine system work together to maintain homeostasis?

1. The endocrine system receives and interprets information, and the nervous system provides the necessary chemicals for the body’s response to the information.
2. The nervous system receives and interprets information, and the endocrine system provides the necessary chemicals for the body’s response to the information.
3. The nervous system provides stabilizing responses in a negative feedback loop, and the endocrine system provides accelerating responses in a positive feedback loop.
4. The nervous system and the endocrine system do not work together to maintain homeostasis.

Correct Answer:

2

Explanations:

1. 1. The nervous system receives and interprets information, and the endocrine system provides the chemicals for the body’s response.
   2. The nervous system governs the body’s response, and the endocrine system helps achieve the response.
   3. The nervous and endocrine systems can each be involved in both negative and positive feedback loops.
   4. The nervous system and endocrine system work closely together to maintain homeostasis.

Question 8

Which of the following statements about membrane transport is true?

1. Facilitated diffusion requires energy to move molecules.
2. Passive transport moves molecules from areas of low concentration to areas of high concentration.
3. Osmosis is the passive transport of only water molecules across a membrane.
4. Active transport uses channel proteins to move molecules across a membrane.

Correct Answer:  3

Explanations:

1. Facilitated diffusion is a type of passive transport, so it does not require energy.
2. Passive transport moves molecules down the concentration gradient, from areas of high concentration to areas of low concentration.
3. Osmosis is a specific type of passive transport and involves the movement of water, not nutrient molecules.
4. Channel proteins are used in facilitated diffusion, which is a type of passive transport.

Question 9

In which of the following phases of the cell cycle does the cell make a complete copy of its DNA?

1. S phase
2. G2 phase
3. prophase
4. cytokinesis

Correct Answer:  1

Explanations:

1. In the S phase or synthesis phase, the cell creates a second complete copy of its DNA.
2. In the G2 phase or second growth phase, the cell continues to grow and replicate organelles needed for cell division.
3. During prophase, the chromosomes condense and a spindle forms.
4. During cytokinesis, the cytoplasm splits and allows the cell to divide into two distinct cells.

Question 10

Which terrestrial biome features the greatest biodiversity?

1. deciduous forests
2. taiga
3. grasslands
4. tropical rainforest

Correct Answer:  4

Explanations:

1. Deciduous forests fluctuate between warm summers and cool winters. They do not have as many different organisms as the tropical rainforests do.
2. Taiga, or boreal forests, are covered with snow for much of the year. The cooler temperatures of this biome do not support a great deal of biodiversity.
3. The grasslands receive only moderate rainfall, not enough to support trees. They do not have a great deal of biodiversity.
4. Tropical rainforests feature the greatest precipitation and experience warm temperatures year-round. This leads to an abundance of biodiversity.

Question 11

Which of the following is an example of thigmotropism in plants?

1. a sunflower turning to face the sun throughout the day
2. a Venus fly trap snapping shut when a fly lands on its sensory hairs
3. Ivy growing up the side of a brick wall
4. a bean plant’s roots growing down, no matter which direction the seed is facing

Correct Answer:  3

Explanations:

1. A sunflower’s behavior is an example of phototropism.
2. A venus fly trap’s behavior is an example of a nastic movement. It differs from thigmotropism because it is a rapid, chemical response to the stimulus, rather than a growth in response to a constant stimulus.
3. Thigmotropism is a growth response to touch.
4. A bean plant’s root behavior is an example of gravitropism or geotropism.

Question 12

Which of the following is a response to an internal stimulus?

1. A cranky toddler asks for a snack.
2. A cat’s eyes dilate in dim light.
3. A dog salivates when it smells a pot roast.
4. A raccoon comes out to eat after the sun sets.

Correct Answer:  1

Explanations:

1. This toddler is responding to an internal hunger or blood sugar stimulus.
2. The dim light is an external stimulus.
3. The smell of the pot roast is an external stimulus.
4. The setting sun is an external stimulus.

Question 13

Which of the following activities contribute to acid rain?

1. agricultural pollution
2. burning of fossil fuels
3. volcanic eruptions
4. All of these contribute to acid rain.

Correct Answer:  4

Explanations:

1. Agricultural pollution leads to the runoff of chemicals into the water supply, which then enters the water cycle and leads to acid rain.
2. Burning fossil fuels releases sulfur dioxide into the air, which combines with water vapor to make sulfuric acid.
3. Volcanic eruptions can emit sulfur gases into the atmosphere, which can combine with water vapor to make sulfuric acid.
4. Agricultural pollution, burning of fossil fuels, and volcanic eruptions can all contribute to the formation of acid rain.

Question 14

The insecticide DDT is harmful to bald eagles. Too much of it causes them to lay eggs with very thin shells. Which of the following processes led to the near destruction of the bald eagle population because of this?

1. algal blooms
2. biomagnification
3. herbicide resistance
4. antibiotic resistance

Correct Answer:  2

Explanations:

1. Algal blooms happen when a limiting resource, like fertilizer, enters an ecosystem in excess and causes an explosion of algae.
2. Biomagnification results when toxins cannot be removed by organisms and those toxins are passed up the food chain in increasing amounts.
3. Herbicide resistance refers to a plant developing a resistance to a previously fatal herbicide.
4. Antibiotic resistance refers to microorganisms developing resistance to a previously fatal antibiotic.

Question 15

Which of the following terms refers to the process of pioneer plants breaking the rock into soil, leading to the growth of small grasses, then small trees, large trees, and finally a variety of plant and animal species?

1. secondary succession
2. climax community
3. tertiary succession
4. primary succession

Correct Answer:  4

Explanations:

1. Secondary succession takes place where there used to be planted.
2. A climax community is the final result of ecological succession, featuring a variety of plant and animal species.
3. Tertiary succession is not a type of ecological succession.
4. Primary succession is typically a slow process and it takes place where no plants previously lived.

Question 16

During which phase of meiosis does crossing-over occur?

1. prophase I
2. prophase II
3. metaphase I
4. telophase II

Correct Answer:  1

Explanations:

1. Chromosome segments experience crossing over and the exchange of genetic information during prophase I.
2. The chromosomes condense and centrosomes duplicate in prophase II.
3. The tetrads, or chromosome pairs, line up in the middle of the cell in metaphase I.
4. New nuclei form with half the DNA of a somatic cell during telophase II.

Question 17

Which of the following correctly identifies a difference between mitosis and meiosis?

1. Mitosis contains two sets of divisions, whereas meiosis contains one set of divisions.
2. Mitosis produces gametes, whereas meiosis produces somatic cells.
3. Mitosis results in two genetically identical daughter cells, whereas meiosis results in four genetically distinct cells.
4. Mitosis occurs in developing cells, whereas meiosis occurs in mature cells.

Correct Answer:  3

Explanations:

1. Mitosis contains one set of divisions, whereas meiosis contains two.
2. Mitosis produces somatic cells, whereas meiosis produces gametes.
3. Mitosis produces diploid cells that are identical to one another. Meiosis produces haploid gametes.
4. Meiosis does not occur in every mature cell.

Question 18

Which of the following is a type of protein around which DNA winds to condense the nucleotides?

1. histone
2. gene
3. chromosome
4. nucleic acid

Correct Answer:  1

Explanations:

1. The winding of DNA around the histone protein forms the chromosome shape.
2. A gene is a segment of DNA that codes for a trait.
3. A chromosome is a long, organized strand of DNA.
4. A nucleic acid, like DNA or RNA, holds an organism’s genetic information.

Question 19

In which direction is the complementary RNA strand built during elongation?

1. RNA is always added from the 5’ end towards the 3’ end.
2. RNA is always added from the 3’ end towards the 5’ end.
3. RNA can be built in either direction.
4. RNA is not built as a complementary strand.

Correct Answer:  2

Explanations:

1. RNA is added to the complementary DNA strand from the 3’ end towards the 5’ end.
2. RNA is added to the complementary DNA strand from the 3’ end towards the 5’ end.
3. RNA can only be added to the DNA strand from the 3’ end towards the 5’ end.
4. RNA is built as a complementary strand to a DNA template strand.

Question 20

Which of the following statements is true about the universal genetic code?

1. The same codons code for the same amino acids in all living things.
2. All living things have the same number of genes.
3. DNA is located in the nucleus in all living things.
4. Offspring are genetically identical to their parents across all living species.

Correct Answer:  1

Explanations:

1. The universality genetic code means that the same codons code for the same amino acids in all living things. The order and sequence will vary between species, however.
2. Not all living things have the same number of genes. For example, humans have about 10,000 more genes than fruit flies have.
3. Not all living things contain a nucleus. Prokaryotes do not have a nucleus, but they do have DNA.
4. Organisms that reproduce sexually have offspring that are genetically different from both parents.

Question 21

In pea plants, round seeds are dominant over wrinkled seeds, and yellow seeds are dominant over green seeds. A pea plant who is heterozygous for both seed shape and color is crossed with another pea plant who is also heterozygous for both traits.

What phenotypic ratio can be expected in the offspring?

1. 9 round and green : 3 round and yellow : 3 wrinkled and green: 1 wrinkled and yellow
2. 9 round and yellow : 3 wrinkled and green : 3 wrinkled and yellow : 3 round and green
3. 9 wrinkled and green : 3 round and green : 3 wrinkled and yellow: 1 round and yellow
4. 9 round and yellow : 3 round and green : 3 wrinkled and yellow: 1 wrinkled and green

Correct Answer:  4

Explanations:

1. The correct phenotypic ratio expected in the offspring is 9 round and yellow : 3 round and green : 3 wrinkled and yellow: 1 wrinkled and green.
2. The correct phenotypic ratio expected in the offspring is 9 round and yellow : 3 round and green : 3 wrinkled and yellow: 1 wrinkled and green.
3. The correct phenotypic ratio expected in the offspring is 9 round and yellow : 3 round and green : 3 wrinkled and yellow: 1 wrinkled and green.
4. The phenotypic ratio in the offspring is 9 dominant for both traits : 3 dominant for trait one, recessive for trait two : 3 recessive for trait one, dominant for trait two: 1 recessive for both traits.

Question 22

Which of the following examples does not show an animal’s changing behavior increasing its fitness?

1. Prairie dogs have developed a complex “language” to warn the colony of potential danger.
2. The quokka, a small marsupial, is increasingly threatened by predators, so its habitat range has decreased over time.
3. Wolves have more success hunting in packs, so lone wolves become less and less common over time
4. Raccoons are more likely to find food and less likely to be attacked at night, so they have become nocturnal.

Correct Answer:  2

Explanations:

1. The ability to warn one another of danger has helped the prairie dog survive.
2. The quokka has been unable to adapt to the increased predation, so its numbers have declined. It has not increased its fitness for its environment.
3. An increased ability to catch prey means the wolf pack has increased fitness.
4. Developing nocturnal behavior in response to threats has increased the raccoons’ fitness for its environment.

Question 23

During meiosis, nondisjunction can keep chromosomes from separating. Which mutation is caused by this mistake?

1. trisomy
2. substitution mutation
3. deletion mutation
4. addition mutation

Correct Answer:  1

Explanations:

1. A trisomy is an extra copy of a chromosome. This happens when the chromosomes fail to separate during meiosis.
2. A substitution mutation occurs when a nucleotide is replaced with a different nucleotide. It may or may not result in the same amino acid.
3. A deletion mutation occurs when a nucleotide is deleted from the sequence. This results in a change to the sequence of amino acids.
4. An addition mutation occurs when a nucleotide is added to the sequence. This results in a change to the sequence of amino acids.

Question 24

Which of the following is an example of genetically modified organisms?

1. rice, which has a gene inserted to produce beta carotene
2. corn, which has a gene that makes it resistant to certain pests
3. cows with human genes that cause them to produce milk identical to human breast milk
4. All of these are examples of genetically modified organisms.

Correct Answer:  4

Explanations:

1. Inserting a gene into rice is a form of genetic modification.
2. Inserting a gene into corn is a form of genetic modification.
3. Inserting a human gene into cows is a form of genetic modification.
4. Genetic modification involves inserting a gene that wasn’t previously present into an organism to achieve a goal or characteristic.

Question 25

Which of the following scenarios is an example of sympatric isolation?

1. Kaibab and Albert squirrels have become permanently separated by the Grand Canyon. They passed down different traits and over time, became two different species.
2. The finches on the Galapagos Islands have developed different beak shapes based on the seeds found on the islands.
3. One population of apple maggot flies only mate on the leaves of apple trees, and another population only mates on the leaves of hawthorn trees. Over time, the two populations are unable to interbreed.
4. A dam is built that prevents fish from upriver from mating with fish from downriver. Eventually, the two populations of fish are no longer able to interbreed.

Correct Answer:  3

Explanations:

1. Geographic separation as described here is a type of allopatric isolation.
2. Geographic separation as described here is a type of allopatric isolation.
3. Reproductive isolation is a type of sympatric isolation.
4. Geographic separation as described here is a type of allopatric isolation.