HiSET Science: Life Science Practice Test — Questions and Answers

Question 1: Which organelle is responsible for producing ATP through cellular respiration in eukaryotic cells?

Nucleus
Ribosome
Mitochondria (Correct answer)
Golgi apparatus

Correct answer: Mitochondria

Mitochondria are the powerhouses of the cell, generating ATP through aerobic cellular respiration via the Krebs cycle and electron transport chain.

Mitochondria carry out aerobic cellular respiration, converting glucose and oxygen into ATP, carbon dioxide, and water. The process includes glycolysis (in the cytoplasm), the Krebs cycle, and the electron transport chain — all within or attached to the mitochondria. Cells with high energy demands, like muscle cells, contain thousands of mitochondria.

Question 2: Which process do plants use to convert light energy into chemical energy stored in glucose?

Cellular respiration
Photosynthesis (Correct answer)
Fermentation
Transpiration

Correct answer: Photosynthesis

Photosynthesis uses light energy, water, and carbon dioxide to produce glucose and oxygen, occurring primarily in chloroplasts.

Photosynthesis occurs in two stages: the light-dependent reactions (in the thylakoids) capture solar energy and produce ATP and NADPH, and the Calvin cycle (in the stroma) uses that energy to fix CO₂ into glucose. The overall equation is: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

Question 3: What is the term for the process by which a cell divides to produce two genetically identical daughter cells?

Meiosis
Mitosis (Correct answer)
Binary fission
Budding

Correct answer: Mitosis

Mitosis is the cell division process in eukaryotes that produces two genetically identical diploid daughter cells, used for growth and tissue repair.

Mitosis proceeds through four phases: prophase, metaphase, anaphase, and telophase, followed by cytokinesis. During mitosis, the duplicated chromosomes are separated equally, giving each daughter cell the same chromosome number as the parent. In contrast, meiosis produces four genetically unique haploid cells used in sexual reproduction.

Question 4: Which type of molecule carries the genetic instructions from the nucleus to the ribosomes?

DNA
tRNA
mRNA (Correct answer)
rRNA

Correct answer: mRNA

Messenger RNA (mRNA) carries the genetic code transcribed from DNA in the nucleus to the ribosomes in the cytoplasm, where it serves as a template for protein synthesis.

During transcription, an mRNA copy of a gene is made from DNA by RNA polymerase. The mRNA then moves out of the nucleus to the ribosome, where translation occurs. Transfer RNA (tRNA) brings amino acids, and ribosomal RNA (rRNA) forms the structural components of the ribosome. Together they translate the mRNA codons into a polypeptide chain.

Question 5: In Mendel's experiments, what term describes a trait that is hidden when a dominant trait is present?

Codominant
Recessive (Correct answer)
Polygenic
Heterozygous

Correct answer: Recessive

A recessive trait is masked when a dominant allele is present. It only shows in an individual who inherits two copies of the recessive allele (homozygous recessive).

Gregor Mendel discovered that traits are controlled by units (now called alleles). A dominant allele (represented by an uppercase letter) masks the expression of a recessive allele (lowercase). A recessive phenotype only appears when both alleles are recessive (e.g., 'aa'). Mendel's Law of Segregation explains how these alleles separate during gamete formation.

Question 6: Which level of biological organization is directly above the organ level?

Tissue
Cell
Organ system (Correct answer)
Organism

Correct answer: Organ system

The organ system level is directly above the organ level. Organs work together in organ systems (e.g., the heart and blood vessels form the cardiovascular system).

The hierarchy of biological organization from smallest to largest is: atom → molecule → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere. Each level builds on the one below, with organs grouped into systems that carry out major physiological functions.

Question 7: What is the primary role of decomposers in an ecosystem?

Producing energy from sunlight
Converting nitrogen gas to ammonia
Breaking down dead organic matter into nutrients (Correct answer)
Consuming living plants

Correct answer: Breaking down dead organic matter into nutrients

Decomposers break down dead organisms and organic waste, recycling nutrients back into the soil and making them available for producers.

Decomposers — mainly fungi and bacteria — perform the critical ecosystem function of nutrient cycling. By breaking down complex organic molecules into simpler inorganic forms (like nitrates, phosphates, and CO₂), they return essential nutrients to the abiotic environment. Without decomposers, dead organic matter would accumulate and nutrients would become unavailable to producers.

Question 8: Which structure controls what enters and exits a cell, maintaining homeostasis?

Cell wall
Cell membrane (Correct answer)
Nucleus
Vacuole

Correct answer: Cell membrane

The cell membrane (plasma membrane) is selectively permeable, regulating the passage of substances into and out of the cell to maintain homeostasis.

The cell membrane consists of a phospholipid bilayer with embedded proteins. It allows small nonpolar molecules (like O₂ and CO₂) to pass freely, while controlling the movement of ions, large molecules, and polar substances through protein channels and carrier proteins. This selective permeability is essential for regulating internal conditions and cellular communication.

Question 9: According to Darwin's theory of natural selection, which individuals in a population are most likely to survive and reproduce?

The largest individuals
Those with traits best suited to the environment (Correct answer)
The oldest individuals
Those that reproduce the most offspring regardless of survival

Correct answer: Those with traits best suited to the environment

Natural selection favors individuals with traits that improve survival and reproduction in a given environment, leading to those traits becoming more common over generations.

Darwin proposed that heritable variation exists within populations. Individuals with traits better adapted to environmental conditions survive longer and produce more offspring. Over many generations, these advantageous traits increase in frequency — this is evolution by natural selection. Key elements are variation, heritability, differential survival, and reproductive success.

Question 10: What type of symbiosis describes a relationship where one organism benefits and the other is neither harmed nor helped?

Mutualism
Parasitism
Commensalism (Correct answer)
Competition

Correct answer: Commensalism

Commensalism is a symbiotic relationship where one organism benefits and the other is unaffected. An example is barnacles living on whales.

In commensalism (+/0), one species derives benefit while the host is unaffected. Classic examples include cattle egrets feeding on insects disturbed by grazing cattle, and epiphytic orchids growing on tree branches for support without harming the tree. Mutualism (+/+) benefits both; parasitism (+/-) benefits one while harming the other.

Question 11: Which base pairs with adenine in a DNA double helix?

Guanine
Cytosine
Uracil
Thymine (Correct answer)

Correct answer: Thymine

In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds, and guanine (G) pairs with cytosine (C) via three hydrogen bonds.

DNA's double helix is stabilized by complementary base pairing following Chargaff's rules: adenine always pairs with thymine (A=T) and guanine always pairs with cytosine (G≡C). In RNA, uracil replaces thymine, so adenine pairs with uracil. These hydrogen bonds, along with the sugar-phosphate backbone, give DNA its stable helical structure.

Question 12: What is the term for an organism's full genetic makeup, including all alleles?

Phenotype
Genotype (Correct answer)
Karyotype
Proteome

Correct answer: Genotype

An organism's genotype is its complete set of genetic instructions (alleles), which determines its inherited traits. The phenotype is the observable expression of those genes.

The genotype includes all the alleles an organism carries, whether or not they are expressed. For example, a pea plant with genotype 'Tt' has one dominant allele for tall (T) and one recessive allele for short (t). Its phenotype would be tall because T is dominant. The genotype, combined with environmental factors, determines the phenotype.

Question 13: In an ecosystem's food chain, organisms that make their own food using sunlight are called:

Primary consumers
Secondary consumers
Producers (Correct answer)
Decomposers

Correct answer: Producers

Producers (autotrophs) make their own food through photosynthesis or chemosynthesis. They are the foundation of every food chain, providing energy for all other organisms.

Producers, or autotrophs, include plants, algae, and some bacteria (like cyanobacteria). They capture energy from sunlight (photosynthesis) or chemical reactions (chemosynthesis) and store it as organic compounds. Primary consumers (herbivores) eat producers; secondary consumers eat primary consumers. Energy flows from producers upward through each trophic level.

Question 14: Which process moves water from soil into a plant's roots by osmosis?

Active transport
Diffusion of solutes
Osmosis driven by a concentration gradient (Correct answer)
Facilitated diffusion via proteins

Correct answer: Osmosis driven by a concentration gradient

Water moves into root cells by osmosis — from an area of high water concentration (the soil) to an area of lower water concentration (the root cells with dissolved solutes).

Root cells contain dissolved minerals and sugars, giving them a lower water potential than the surrounding soil water. Osmosis drives water across the selectively permeable root cell membranes — from the dilute solution in the soil toward the more concentrated solution in the root. This water then moves up the plant through the xylem via transpiration pull and root pressure.

Question 15: What is the function of the large intestine in the human digestive system?

Producing digestive enzymes
Absorbing most nutrients from food
Absorbing water and forming solid waste (Correct answer)
Breaking down proteins into amino acids

Correct answer: Absorbing water and forming solid waste

The large intestine primarily absorbs water and electrolytes from indigestible food matter, forming solid feces for elimination.

By the time food residue reaches the large intestine (colon), most digestion and nutrient absorption have occurred in the small intestine. The large intestine absorbs remaining water, sodium, and other electrolytes, compacting the material into feces. Gut bacteria in the large intestine also synthesize some vitamins (like vitamin K) and aid in fermentation of undigested fibers.

Question 16: Which of the following BEST describes a niche in ecology?

The physical location where an organism lives
The role and position of an organism in its ecosystem (Correct answer)
The total number of species in an ecosystem
The geographic range of a species

Correct answer: The role and position of an organism in its ecosystem

An ecological niche encompasses the role an organism plays in its ecosystem, including its interactions, diet, behavior, and adaptations — not just its location (habitat).

The ecological niche describes how an organism interacts with its biotic and abiotic environment: what it eats, what eats it, when it is active, its temperature tolerances, etc. The competitive exclusion principle states that two species with identical niches cannot coexist stably — one will outcompete the other. Species can coexist by occupying different niches within the same habitat.

Question 17: What happens to energy as it flows from one trophic level to the next in a food chain?

Energy increases at each level
Approximately 90% of energy is lost as heat at each level (Correct answer)
Energy stays the same throughout
Energy doubles at each level

Correct answer: Approximately 90% of energy is lost as heat at each level

About 90% of energy is lost as heat (through metabolism and waste) at each trophic level, meaning only ~10% is available to the next level.

This is described by the 10% rule. For example, if grass (producer) contains 10,000 kcal of energy, the herbivore (primary consumer) that eats the grass can store only about 1,000 kcal, and the carnivore (secondary consumer) only about 100 kcal. This energy loss limits food chains to typically 4–5 trophic levels and explains why large predators are less numerous than their prey.

Question 18: What type of cell division produces gametes (sperm and egg cells) with half the normal chromosome number?

Mitosis
Binary fission
Meiosis (Correct answer)
Cytokinesis

Correct answer: Meiosis

Meiosis reduces the chromosome number by half (from diploid to haploid), producing four genetically unique gametes. When two gametes fuse at fertilization, the diploid number is restored.

Meiosis consists of two rounds of division (Meiosis I and Meiosis II). Meiosis I separates homologous chromosome pairs; Meiosis II separates sister chromatids. Crossing over during Meiosis I increases genetic diversity. The resulting four haploid cells (gametes) each contain one set of chromosomes. In females, one functional egg and polar bodies form; in males, four sperm form.

Question 19: Which of the following is evidence of evolution?

All organisms share the same number of chromosomes
Homologous structures in different species suggest a common ancestor (Correct answer)
All species adapt to their environment within one generation
Mutations always improve an organism's fitness

Correct answer: Homologous structures in different species suggest a common ancestor

Homologous structures — anatomically similar body parts in different species (e.g., the human arm, whale flipper, and bat wing) — suggest descent from a common ancestor and support evolution.

Evidence for evolution includes the fossil record, biogeography, comparative anatomy (homologous and vestigial structures), comparative embryology, and molecular biology (DNA/protein similarities). Homologous structures share the same basic anatomy due to common ancestry, even if they serve different functions. Analogous structures (like a bird wing and insect wing) have similar functions but different origins.

Question 20: What is the role of ribosomes in a cell?

Synthesizing lipids
Producing ATP
Synthesizing proteins (Correct answer)
Storing genetic information

Correct answer: Synthesizing proteins

Ribosomes are the sites of protein synthesis (translation), where the mRNA sequence is decoded to assemble a chain of amino acids into a polypeptide.

Ribosomes are found in both prokaryotic and eukaryotic cells, either free in the cytoplasm or attached to the rough endoplasmic reticulum. During translation, ribosomal subunits clamp onto mRNA and use tRNA molecules (carrying specific amino acids) to read codons three nucleotides at a time, linking amino acids together to form a growing polypeptide chain.

Question 21: Which hormone, produced by the pancreas, signals cells to take up glucose from the blood?

Glucagon
Insulin (Correct answer)
Cortisol
Thyroxine

Correct answer: Insulin

Insulin, secreted by beta cells of the pancreas, facilitates glucose uptake by cells and promotes its storage as glycogen, lowering blood sugar levels.

After a meal, rising blood glucose triggers the pancreas to release insulin. Insulin binds to receptors on cells, activating glucose transporters (GLUTs) that bring glucose inside. Excess glucose is converted to glycogen in the liver and muscle (glycogenesis) or to fat (lipogenesis). In Type 1 diabetes, the immune system destroys insulin-producing cells; in Type 2, cells become insulin-resistant.

Question 22: What is a limiting factor in a population?

A resource or condition that restricts population growth (Correct answer)
The maximum size a population can reach
The rate at which a population reproduces
A predator that controls another species

Correct answer: A resource or condition that restricts population growth

A limiting factor is any resource or environmental condition (such as food, water, space, or disease) that restricts population growth below its theoretical maximum.

Limiting factors can be density-dependent (their effect increases as population density rises, e.g., competition, predation, disease) or density-independent (affect populations regardless of size, e.g., drought, temperature extremes). Together with carrying capacity (K), limiting factors define the upper boundary of sustainable population size in a given environment.

Question 23: Which of the following is an abiotic factor in an ecosystem?

Bacteria
Trees
Temperature (Correct answer)
Insects

Correct answer: Temperature

Abiotic factors are nonliving physical and chemical components of an ecosystem, such as temperature, sunlight, water, pH, and soil composition.

An ecosystem consists of biotic factors (all living organisms) and abiotic factors (nonliving components). Abiotic factors include temperature, light intensity, precipitation, wind, soil type, water availability, salinity, and pH. These physical conditions shape which organisms can survive in a habitat and influence population size, species diversity, and ecosystem productivity.

Question 24: What describes a population bottleneck event?

A gradual increase in population size over many generations
A sudden drastic reduction in population size that reduces genetic diversity (Correct answer)
The maximum stable size of a population in a given environment
Competition between two species for the same resources

Correct answer: A sudden drastic reduction in population size that reduces genetic diversity

A population bottleneck is a sharp reduction in population size due to an environmental event, resulting in reduced genetic variation in the surviving population.

During a bottleneck, most individuals die (due to disaster, disease, habitat loss, etc.), and the survivors pass on a limited gene pool. This can lead to inbreeding and reduced adaptability. The cheetah is a classic example — genetic analysis reveals very low diversity, suggesting a severe ancient bottleneck. The founder effect is related: a few individuals founding a new population with limited alleles.

Question 25: What is the primary function of the nervous system?

To transport oxygen throughout the body
To produce hormones for growth
To detect stimuli and coordinate responses (Correct answer)
To filter waste products from the blood

Correct answer: To detect stimuli and coordinate responses

The nervous system detects internal and external stimuli through sensory neurons, processes information in the brain and spinal cord, and coordinates voluntary and involuntary responses.

The nervous system consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (all other nerves). Sensory neurons carry signals from receptors to the CNS; interneurons process information; motor neurons carry signals to effectors (muscles or glands). The autonomic nervous system controls involuntary functions; the somatic system controls voluntary movement.

Question 26: Which ecological succession type occurs in an area where no life previously existed, such as bare rock after a volcanic eruption?

Secondary succession
Primary succession (Correct answer)
Climax succession
Competitive succession

Correct answer: Primary succession

Primary succession begins on bare, lifeless substrate (like new volcanic rock) where no soil exists, starting with pioneer species like lichens that break down rock into soil.

Primary succession is a slow process that can take thousands of years. Pioneer species (lichens, mosses) break down rock and accumulate organic matter, creating soil. Grasses and shrubs follow, then larger plants, eventually leading to a stable climax community. Secondary succession occurs after a disturbance in an area that already has soil, progressing more quickly because the substrate is already established.

Question 27: What is the central dogma of molecular biology?

Energy flows from producers to consumers
DNA → RNA → Protein (Correct answer)
Proteins fold based on amino acid sequence
Cells arise only from pre-existing cells

Correct answer: DNA → RNA → Protein

The central dogma states that genetic information flows from DNA to RNA (transcription) and from RNA to protein (translation), the fundamental process of gene expression.

Francis Crick proposed the central dogma in 1958. DNA is transcribed into mRNA by RNA polymerase in the nucleus. The mRNA travels to ribosomes where it is translated into a sequence of amino acids, forming a protein. Some exceptions exist (e.g., reverse transcription in retroviruses), but this remains the core framework for understanding how genes are expressed in all cells.

Question 28: Which biome is characterized by permafrost, very low temperatures, and dominated by mosses, lichens, and dwarf shrubs?

Temperate deciduous forest
Tropical rainforest
Tundra (Correct answer)
Taiga (boreal forest)

Correct answer: Tundra

The tundra is characterized by permanently frozen subsoil (permafrost), harsh cold temperatures, and low-growing vegetation like mosses, lichens, and sedges.

The tundra biome exists in the Arctic and on high mountains (alpine tundra). Permafrost prevents deep root growth, limiting vegetation to low-growing plants. Summers are brief but can produce bursts of wildflowers. Animal inhabitants (caribou, arctic foxes, polar bears) have adaptations for extreme cold. The taiga (boreal forest) lies just south of the arctic tundra, featuring coniferous trees and slightly milder conditions.

Question 29: What is the function of guard cells in plant leaves?

Conducting water and minerals upward
Producing glucose during photosynthesis
Regulating the opening and closing of stomata (Correct answer)
Storing starch and nutrients

Correct answer: Regulating the opening and closing of stomata

Guard cells surround each stoma (pore) in a leaf. When guard cells take up water, they swell and open the stoma; when they lose water, they close it, controlling gas exchange and water loss.

Guard cells are specialized cells in the leaf epidermis. In the presence of light and adequate water, guard cells accumulate potassium ions, causing water to enter by osmosis — they become turgid and bow outward, opening the stoma. In drought or darkness, potassium leaves, water follows, and guard cells become flaccid, closing the stoma. This balances photosynthesis needs (CO₂ uptake) against water loss via transpiration.

Question 30: A cross between two parents, each heterozygous for a single trait (Aa × Aa), will produce offspring in what ratio of dominant to recessive phenotype?

1:1
2:1
3:1 (Correct answer)
4:0

Correct answer: 3:1

A monohybrid cross between two heterozygotes (Aa × Aa) produces a 3:1 phenotypic ratio — 3 dominant (AA + Aa) : 1 recessive (aa).

The Punnett square for Aa × Aa yields genotypes: 1 AA : 2 Aa : 1 aa. Since AA and Aa both display the dominant phenotype, three out of four offspring show the dominant trait and one shows the recessive, giving a 3:1 phenotypic ratio. Mendel first described this ratio using pea plants, laying the groundwork for the Law of Segregation.

Question 31: What is the primary difference between aerobic and anaerobic respiration?

Aerobic uses glucose; anaerobic does not
Aerobic requires oxygen and produces more ATP; anaerobic occurs without oxygen and produces less ATP (Correct answer)
Anaerobic requires oxygen; aerobic does not
Both produce the same amount of ATP, but aerobic is slower

Correct answer: Aerobic requires oxygen and produces more ATP; anaerobic occurs without oxygen and produces less ATP

Aerobic respiration uses oxygen and produces up to ~36-38 ATP per glucose; anaerobic respiration occurs without oxygen and yields only 2 ATP per glucose (via glycolysis), producing lactic acid or ethanol as a byproduct.

Aerobic respiration: glucose + O₂ → CO₂ + H₂O + ~36-38 ATP (through glycolysis, Krebs cycle, and oxidative phosphorylation). Anaerobic respiration (fermentation): glucose → 2 pyruvate → 2 ATP + lactic acid (in animals/bacteria) or ethanol + CO₂ (in yeast/plants). Muscles undergoing intense exercise rely on anaerobic respiration when oxygen is insufficient, producing lactic acid and causing fatigue.

Question 32: Which type of mutation involves the addition of one or more base pairs into a DNA sequence?

Deletion
Substitution
Insertion (Correct answer)
Translocation

Correct answer: Insertion

An insertion mutation adds one or more extra nucleotides into a DNA sequence. Like deletions, insertions often cause frameshift mutations that alter all downstream codons.

Insertions add nucleotide(s) into the DNA sequence. If not a multiple of three, this shifts the reading frame of codons downstream — a frameshift mutation — drastically altering the protein produced. Substitutions replace one nucleotide with another and may be silent (no change in amino acid), missense (different amino acid), or nonsense (premature stop codon). Translocations involve segments moving between chromosomes.

Question 33: In photosynthesis, which structure within the chloroplast is where the light-dependent reactions occur?

Stroma
Thylakoid membrane (Correct answer)
Outer membrane
Matrix

Correct answer: Thylakoid membrane

The light-dependent reactions occur on the thylakoid membranes, where chlorophyll and other pigments absorb light energy to produce ATP, NADPH, and oxygen.

Chloroplasts have an outer and inner membrane surrounding the stroma (fluid interior) and thylakoids (membrane-bound sacs stacked into grana). In the thylakoid membranes, photosystems I and II capture light energy, driving the electron transport chain and producing ATP and NADPH, and splitting water (releasing O₂). These products then power the Calvin cycle in the stroma to fix CO₂ into G3P (which forms glucose).

Question 34: Which best describes a keystone species?

The most numerous species in an ecosystem
A species with a disproportionately large effect on its ecosystem relative to its abundance (Correct answer)
A species that was recently introduced to a new ecosystem
Any top predator in a food chain

Correct answer: A species with a disproportionately large effect on its ecosystem relative to its abundance

A keystone species has an outsized impact on ecosystem structure and function relative to its numbers. Removing it causes significant changes to the ecosystem — often collapse.

The sea otter is a classic keystone species: otters eat sea urchins, which eat kelp. Without otters, urchin populations explode and decimate kelp forests, destroying habitat for many species. Keystone species are not always top predators — they can be plants (e.g., fig trees providing fruit for many animals) or even engineers (e.g., beavers creating wetlands). Their effect on biodiversity is far greater than their biomass would suggest.

Question 35: What is the relationship between photosynthesis and cellular respiration in terms of energy and matter?

They are independent processes with no connection
Photosynthesis produces glucose and oxygen that are used in cellular respiration, which produces CO₂ and water used in photosynthesis (Correct answer)
Both processes produce ATP and do not cycle matter
Cellular respiration creates glucose that photosynthesis breaks down

Correct answer: Photosynthesis produces glucose and oxygen that are used in cellular respiration, which produces CO₂ and water used in photosynthesis

Photosynthesis and cellular respiration are complementary cycles: photosynthesis stores energy in glucose and releases O₂; cellular respiration releases that energy as ATP and releases CO₂ and H₂O that photosynthesis uses.

The products of photosynthesis (glucose and O₂) are the reactants of aerobic cellular respiration. The products of respiration (CO₂ and H₂O) are the reactants of photosynthesis. This interdependency creates a continuous cycle of matter and energy in ecosystems. Photosynthesis (endergonic) stores light energy as chemical energy; cellular respiration (exergonic) releases that stored energy as ATP for cellular work.

Question 36: Which domain includes prokaryotic organisms that often live in extreme environments like hot springs and salt lakes?

Eukarya
Bacteria
Archaea (Correct answer)
Fungi

Correct answer: Archaea

Archaea are prokaryotes that often inhabit extreme environments (extremophiles), including hydrothermal vents, highly saline lakes, and highly acidic environments. They differ from Bacteria in membrane chemistry and rRNA sequences.

The three-domain system (Bacteria, Archaea, Eukarya) reflects profound differences at the molecular level. Archaea have unique cell membrane lipids (ether-linked), different RNA polymerases, and some genes more similar to eukaryotes than to bacteria. Many archaea are extremophiles: thermophiles thrive above 80°C; halophiles in high salt; acidophiles in low pH. However, many archaea also live in moderate environments like soil and the human gut.

Question 37: What is the significance of genetic variation within a population?

It decreases the population's ability to survive disease
It increases the population's adaptability to changing environments and survival threats (Correct answer)
It leads to immediate extinction if too high
It only results from random mutations, not sexual reproduction

Correct answer: It increases the population's adaptability to changing environments and survival threats

Genetic variation provides the raw material for natural selection. Populations with more genetic diversity are better able to adapt to environmental changes, diseases, and other challenges.

Genetic variation arises through mutation, sexual recombination (crossing over, independent assortment, random fertilization), and gene flow. A population with high genetic diversity is more likely to contain individuals with traits suited to new threats (e.g., antibiotic-resistant bacteria thrive when others die). Monocultures (very low genetic variation) are vulnerable to single pathogens. Conservation genetics works to maintain diversity in endangered species.

HiSET Science: Life Science Practice Test

Which organelle is responsible for producing ATP through cellular respiration in eukaryotic cells?

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