Evolution

142 questions

All types142 Multiple choice76 True / False14 Matching26 Ordering26

Organisms that share a recent common ancestor exhibit a higher degree of similarity in the amino acid sequences of shared proteins such as cytochrome c.

True

False

Show answer & explanation

Answer: True

Answer

The statement is true because species sharing a recent common ancestor have accumulated fewer genetic mutations, maintaining higher similarity in conserved amino acid sequences like cytochrome c.

Comparative biochemistry demonstrates that species with a recent common ancestor share high sequence homology in vital proteins like cytochrome c because minimal time has elapsed for neutral mutations to accumulate.

Step-by-Step Solution

Examine the relationship between evolutionary divergence time and biochemical similarity.

Recent common ancestry corresponds to shorter evolutionary time since divergence.

Fewer generations have elapsed for gene mutations to alter protein structures.

Evaluate cytochrome c as an evolutionary marker.

Cytochrome c is a highly conserved protein across aerobic organisms, making its amino acid sequence similarity directly proportional to evolutionary closeness.

Proteins essential for basic cellular respiration change slowly and accurately reflect lineage relationships.

Key Concept

Comparative Biochemistry in Evolution

Question 2Question →

The table below shows the distribution of three distinct index fossils ( $X$ , $Y$ , and $Z$ ) found within four undisturbed sedimentary rock strata (Layer 1 being the lowermost and oldest, and Layer 4 being the uppermost and youngest):

Rock Layer	Fossils Present
Layer 4 (Top)	Fossil $Z$
Layer 3	Fossil $Y$ , Fossil $Z$
Layer 2	Fossil $X$ , Fossil $Y$
Layer 1 (Bottom)	Fossil $X$

Based on the law of superposition and paleontology principles, which of the following deductions regarding the evolutionary timeline of these organisms is correct?

Fossil

X

represents the oldest ancestral organism, while Fossil

Z

evolved most recently in the geological timeline.

Fossil

Z

is the oldest organism because individuals in upper strata accumulated somatic changes through environmental use and disuse over time.

Fossils

X

and

Z

represent analogous structures that evolved simultaneously within the same geological period.

Fossil

Y

represents a discontinuous genetic variation of Fossil

X

that appeared spontaneously in all rock layers.

Show answer & explanation

Answer: Fossil $X$ represents the oldest ancestral organism, while Fossil $Z$ evolved most recently in the geological timeline.

Answer

Fossil

X

represents the oldest ancestral organism, while Fossil

Z

evolved most recently in the geological timeline.

The law of superposition dictates that in undisturbed sedimentary rock sequences, the deepest layer (Layer 1) is the oldest and the uppermost layer (Layer 4) is the youngest. Because Fossil

X

is found in Layer 1, it represents the earliest organism in the record. Fossil

Z

, occurring in Layer 4, represents the most recently evolved organism.

Step-by-Step Solution

Analyze the rock strata sequence using the Law of Superposition.

Layer 1 (bottom) is the oldest sedimentary deposit, followed by Layer 2, Layer 3, and Layer 4 (top, youngest).

In undisturbed sedimentary rock layers, deeper layers are deposited first and are older than overlying layers.

Map the occurrence of each fossil to its corresponding geological timeframe.

Fossil

X

is present in Layers 1 and 2 (oldest timeframe); Fossil

Y

is present in Layers 2 and 3 (intermediate timeframe); Fossil

Z

is present in Layers 3 and 4 (youngest timeframe).

Fossils preserved in specific strata indicate the geological period during which those organisms lived.

Deduce the relative age and evolutionary succession of the organisms.

The evolutionary chronological order from oldest to newest is Fossil

X

\rightarrow

Fossil

Y

\rightarrow

Fossil

Z

Sequential appearance of index fossils across rock strata reflects the chronological order of biological evolution over time.

Key Concept

Evidence for Evolution: Paleontology and Fossil Records

Estimated Time:2m 0s

Question 3Question →

The flipper of a whale and the wing of a bat possess a similar internal arrangement of bones derived from a common ancestral pentadactyl structure, despite being adapted for different functional roles. Which of the following terms best describes these anatomical features?

Homologous structures

Analogous structures

Vestigial structures

Physiological adaptations

Show answer & explanation

Answer: Homologous structures

Answer

Homologous structures

Homologous structures are anatomical features in different species that share a common fundamental structure and developmental origin because they were inherited from a common ancestor. The pentadactyl limb layout found in whale flippers, bat wings, and human arms is a classic example of homology demonstrating evolutionary divergence.

Step-by-Step Solution

Analyze the anatomical characteristics described in the stem.

The whale flipper and bat wing share a common underlying skeletal plan (pentadactyl limb structure) derived from a common ancestor, but carry out different functions (swimming vs. flying).

Structures with shared evolutionary origin and basic structural framework are classified as homologous.

Distinguish between homologous and analogous structures.

Homology indicates divergent evolution from a common ancestor (same origin, different function), whereas analogy indicates convergent evolution (different origin, similar function).

Understanding structural origins clarifies why pentadactyl limbs in mammals are homologous.

Key Concept

Homologous vs Analogous Anatomical Evidence for Evolution

Question 4Question →

Which of the following statements best describes the primary mechanism proposed by Jean-Baptiste Lamarck to explain evolutionary change in organisms?

Organs that are used extensively become larger and stronger during an organism's lifetime, and these acquired changes are inherited by its offspring.

Organisms with favorable genetic variations are selected by the environment to survive and reproduce.

Random genetic mutations alter the DNA sequence of germ cells, giving rise to novel traits in a single generation.

Overpopulation causes a struggle for limited environmental resources, leading to the survival of the fittest.

Show answer & explanation

Answer: Organs that are used extensively become larger and stronger during an organism's lifetime, and these acquired changes are inherited by its offspring.

Answer

Lamarck proposed that organs developed or altered during an organism's lifetime through use or disuse are directly transmitted to the next generation.

Lamarck's theory of evolution is founded on the concept that an organism can modify its physical structures through frequent use or disuse in response to environmental demands, and that these acquired somatic modifications are passed to its descendants.

Step-by-Step Solution

Identify the core postulates of Lamarckism.

Lamarck's theory relies on two main ideas: (1) Use and disuse of organs causes them to strengthen/grow or shrink/atrophy during an individual's lifetime, and (2) Inheritance of acquired characteristics allows these somatic changes to be passed down.

Understanding Lamarck's specific historical model differentiates it from Darwinism and modern genetic theory.

Evaluate the option that matches Lamarck's mechanism.

The statement regarding organ growth through extensive use and the inheritance of these somatic modifications directly matches Lamarck's theory.

Lamarck believed environmental need drove somatic changes that were subsequently inherited.

Key Concept

Law of Use and Disuse and Inheritance of Acquired Characteristics

Question 5Question →

As vertebrates evolved from aquatic habitats to terrestrial environments, their circulatory systems underwent structural adaptations to increase oxygen delivery efficiency. Which of the following correctly compares the heart chambers of fishes and amphibians?

Fishes possess a two-chambered heart, whereas amphibians possess a three-chambered heart.

Fishes possess a three-chambered heart, whereas amphibians possess a two-chambered heart.

Fishes possess a two-chambered heart, whereas amphibians possess a four-chambered heart.

Fishes possess a single-chambered heart, whereas amphibians possess a four-chambered heart.

Show answer & explanation

Answer: Fishes possess a two-chambered heart, whereas amphibians possess a three-chambered heart.

Answer

Fishes possess a two-chambered heart, whereas amphibians possess a three-chambered heart.

In the evolutionary trend of vertebrate circulatory systems, fishes represent the primitive state with a two-chambered heart (one atrium and one ventricle) that pumps blood through a single circuit. Amphibians represent an intermediate evolutionary stage toward land adaptation, possessing a three-chambered heart (two atria and one ventricle) that supports double circulation.

Step-by-Step Solution

Identify the circulatory structure of fishes

Fishes have a 2-chambered heart consisting of one atrium and one ventricle, operating via single circulation.

Aquatic respiration via gills requires a single circuit pump.

Identify the circulatory structure of amphibians

Amphibians have a 3-chambered heart consisting of two atria and one ventricle, operating via double circulation.

Transition to lungs and skin for gas exchange requires double circulation to separate oxygenated and deoxygenated blood streams into the heart.

Compare the two taxa to determine the correct evolutionary trend

The progression is from a 2-chambered heart in fishes to a 3-chambered heart in amphibians.

Evolutionary complexity increases from lower aquatic vertebrates to higher terrestrial vertebrates.

Key Concept

Evolutionary trends in vertebrate heart chamber complexity

Question 6Question →

Match each anatomical structure on the left with its corresponding category of evolutionary evidence on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct pairings are: Flipper of a whale and wing of a bat matches Homologous structures; Wing of a bird and wing of an insect matches Analogous structures; Pelvic girdle in pythons matches Vestigial organs.

The flipper of a whale and wing of a bat are homologous structures because they share a common pentadactyl bone arrangement derived from a shared ancestor. The wing of a bird and wing of an insect are analogous structures because they evolved independently to perform the same function of flight. The pelvic girdle in pythons is a vestigial organ because it is a reduced structural remnant inherited from ancestral limbed reptiles.

Step-by-Step Solution

Analyze the relationship between the flipper of a whale and the wing of a bat.

They share the same internal skeletal layout (pentadactyl plan) modified for different adaptations.

Structures with a common evolutionary origin and structural plan are classified as homologous structures.

Analyze the relationship between the wing of a bird and the wing of an insect.

They serve the same function (flying) but have completely distinct structural origins (bones vs chitinous membranes).

Structures with similar functions but different evolutionary origins are classified as analogous structures.

Analyze the nature of the pelvic girdle in pythons.

It is a rudimentary, non-functional skeletal structure remaining in limbless snakes.

Degenerate or reduced structures that served a purpose in ancestors are classified as vestigial organs.

Key Concept

Distinction between homologous structures, analogous structures, and vestigial organs in comparative anatomy.

Estimated Time:45s

Question 7Question →

Match each paleontological concept or fossil record discovery listed in Column A with its corresponding geological or evolutionary significance in Column B.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Archaeopteryx lithographica matches with its role as a transitional fossil between reptiles and birds; Index Fossils match with widespread organisms used to correlate relative ages of strata; Potassium-40 decay matches with absolute radiometric dating of ancient rocks; and the Law of Superposition matches with the stratigraphic principle that deeper undisturbed rock layers are older.

Each concept accurately pairs with its definition or significance in evolutionary biology: Archaeopteryx represents transitional link evidence; index fossils pinpoint relative rock layer age due to brief existence and wide distribution; Potassium-40 radioactive decay permits absolute numeric dating of old geological formations; and the Law of Superposition governs relative layer age based on sedimentary deposition.

Step-by-Step Solution

Analyze transitional evolutionary evidence

Identify Archaeopteryx lithographica as the organism demonstrating anatomical traits of both reptiles and birds.

Transitional forms provide direct paleontological proof of gradual macroevolutionary change.

Differentiate stratigraphy methods

Pair Index Fossils with relative rock layer correlation, and Law of Superposition with the rule regarding vertical layer order.

Stratigraphy relies on layer position (Superposition) and biological markers (Index Fossils) to establish relative age timelines.

Identify radiometric absolute dating principles

Associate Potassium-40 decay with numerical absolute dating using half-life decay in ancient mineral rocks.

Radioactive isotopes allow exact chronological age determination unlike relative stratigraphic positioning.

Key Concept

Paleontological Evidence and Stratigraphic Dating Techniques

Question 8Question →

The presence of endemic terrestrial species on oceanic volcanic islands is primarily attributed to vicariance resulting from continental drift, supported by comparative serological tests showing high precipitation cross-reactivity in structural proteins.

True

False

Show answer & explanation

Answer: False

Answer

False

The statement is False because endemic biota on oceanic volcanic islands originate via long-distance dispersal and subsequent adaptive radiation rather than tectonic vicariance. Additionally, comparative serology evaluates soluble serum proteins in blood plasma rather than structural proteins.

Step-by-Step Solution

Analyze the biogeographical mechanism of island colonization.

Oceanic volcanic islands form independently from volcanic hotspot or subduction zone activity in the ocean. They lack prior continental connections, meaning vicariance via continental drift cannot account for their native biota.

Organisms reach oceanic islands via chance long-distance dispersal across oceanic barriers, after which adaptive radiation often occurs.

Examine the biochemical foundation of comparative serology.

Serological testing involves reacting serum antigens from one organism with antibodies produced against serum proteins of another organism. It measures precipitation levels in soluble blood plasma proteins, not structural proteins.

Structural proteins (e.g., collagen, keratin) are insoluble matrix proteins and are not used in standard serological antigen-antibody precipitation assays.

Deduce the truth value of the combined proposition.

Because both the biogeographical mechanism (vicariance on oceanic islands) and the biochemical classification (serological testing of structural proteins) are scientifically inaccurate, the overall statement is false.

A scientific proposition containing false premises regarding both biogeography and comparative biochemistry is false.

Key Concept

Biogeographical Distinction Between Dispersal and Vicariance & Serological Testing in Comparative Biochemistry

Question 9Question →

A paleontologist analyzing a fossilized wood sample recovered from an undisturbed sedimentary rock layer determines that the sample contains $12.5\%$ of its original parent isotope, Carbon-14 ( $^{14}\text{C}$ ). Given that the half-life of $^{14}\text{C}$ is $5,730\text{ years}$ , what is the estimated absolute age of the fossil, and which principle distinguishes this method from relative dating?

17,190\text{ years}

; absolute dating determines numerical age in years using radioactive decay rates, whereas relative dating determines the chronological sequence of rock layers without providing specific ages.

11,460\text{ years}

; absolute dating determines numerical age in years using radioactive decay rates, whereas relative dating measures the ratio of stable isotopes in index fossils.

17,190\text{ years}

; relative dating determines numerical age using index fossils, whereas absolute dating determines the vertical position of sedimentary strata.

22,920\text{ years}

; absolute dating determines the evolutionary order of fossil organisms, whereas relative dating calculates exact half-lives of unstable nuclei.

Show answer & explanation

Answer: $17,190\text{ years}$ ; absolute dating determines numerical age in years using radioactive decay rates, whereas relative dating determines the chronological sequence of rock layers without providing specific ages.

Answer

The estimated absolute age of the fossil is

17,190\text{ years}

. Absolute dating uses decay rates of radioisotopes to calculate specific numerical age, while relative dating determines sequential order of age based on rock strata position.

The option stating

17,190\text{ years}

with absolute dating measuring decay rates and relative dating determining sequential order is correct. The fraction of parent isotope remaining (

12.5\% = (1/2)^3

) indicates that exactly 3 half-lives have elapsed. Multiplying 3 by

5,730\text{ years}

yields

17,190\text{ years}

. Absolute dating uses radioisotope decay rates to estimate precise numerical age, while relative dating relies on stratigraphic principles to establish relative chronological sequence.

Step-by-Step Solution

Determine the number of half-lives that have elapsed from the given percentage of parent isotope.

After 1 half-life:

50\%

; after 2 half-lives:

25\%

; after 3 half-lives:

12.5\%

. Thus,

n = 3

half-lives.

Radioactive decay follows an exponential decay process where the quantity of parent isotope is halved during each constant time interval (half-life).

Calculate the absolute age by multiplying the number of elapsed half-lives by the half-life duration of

^{14}\text{C}

\text{Age} = 3 \times 5,730\text{ years} = 17,190\text{ years}

The total elapsed time is the product of the number of half-lives and the duration of one half-life period.

Distinguish between absolute dating and relative dating principles.

Absolute dating (radiometric decay) gives a specific numerical age in years. Relative dating (law of superposition/index fossils) establishes only chronological order (older vs. younger).

Understanding the fundamental distinction between quantitative radio-isotopic measurements and qualitative stratigraphical comparison is key in paleontological evidence for evolution.

Key Concept

Radiometric Absolute Dating vs. Relative Stratigraphic Dating in Paleontology

Estimated Time:2m 0s

Question 10Question →

Match each piece of biochemical or biogeographical evolutionary evidence on the left with its corresponding evolutionary implication or mechanism on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Cytochrome c sequence homologies match with indicating conservation of essential metabolic proteins from a common ancestor. Disjunct ratite distribution matches with demonstrating vicariance resulting from continental drift. Serological precipitation testing matches with measuring antigenic cross-reactivity for phylogenetic proximity. Adaptive radiation of Galápagos finches matches with illustrating speciation driven by ecological niche diversification.

Each evidence type correctly pairs with its established evolutionary conclusion: Cytochrome c sequence conservation reveals universal metabolic heritage; ratite distribution reflects tectonic vicariance; serological precipitation quantifies serum protein homology; and island finch diversity demonstrates adaptive radiation.

Step-by-Step Solution

Evaluate biochemical evidence from Cytochrome c

Cytochrome c is involved in electron transport; its highly conserved amino acid sequence across unicellular and multicellular organisms provides direct evidence of deep evolutionary homology.

Universal cellular enzymes reflect shared genetic ancestry.

Analyze biogeographical distribution of ratites (rheas, ostriches, emus, cassowaries)

Flightless birds could not have migrated across modern oceans; their presence on South America, Africa, and Australia is attributed to the Mesozoic breakup of Gondwana.

Vicariance through continental drift explains wide spatial separation of closely related terrestrial taxa.

Analyze immunological serological testing

Antisera produced against human serum proteins react most strongly (forming dense precipitate) with chimpanzee serum and progressively weaker with more distantly related mammals.

Precipitate quantity directly correlates with structural homology of serum albumins and globulins.

Examine adaptive radiation in island archipelagos

A single ancestral seed-eating finch colonizing the islands diversified into species specialized for seeds, insects, and nectar.

Geographical isolation combined with natural selection drives morphological divergence into vacant ecological niches.

Key Concept

Evidence for Evolution: Comparative Biochemistry and Biogeography

Question 11Question →

Which biochemical evidence best supports the theory that all living organisms evolved from a shared ancestral origin?

The universal presence of ATP and an identical genetic code across diverse organisms

The acquisition of identical somatic traits by organisms exposed to similar environments

The development of analogous structures with similar functions in unrelated species

The similarity in outer physical appearance caused by protective camouflage in shared habitats

Show answer & explanation

Answer: The universal presence of ATP and an identical genetic code across diverse organisms

Answer

The universal presence of ATP and an identical genetic code across diverse organisms

The universality of fundamental biochemical processes—such as using adenosine triphosphate (ATP) for cellular energy currency and utilizing the same codon system in DNA and RNA to synthesize proteins—provides direct molecular evidence that all living organisms descended from a common ancestor.

Step-by-Step Solution

Identify the biological level being evaluated in the prompt.

The prompt specifically asks for biochemical evidence supporting evolution.

Comparative biochemistry focuses on molecular similarities (DNA, proteins, metabolic pathways) among organisms.

Evaluate the choices to determine which represents molecular/biochemical homology.

The reliance on ATP across all domains of life and the near-universal triplet genetic code indicate that these biochemical systems arose early in life's history and were inherited by all extant species.

Shared complex molecular mechanisms are extremely improbable to have evolved independently in every lineage.

Key Concept

Comparative Biochemistry as Evidence for Evolution

Question 12Question →

In the evolutionary progression of terrestrial plant life, structural adaptations systematically increased in complexity to overcome the challenges of living on land. Which of the following statements correctly identifies a key evolutionary milestone alongside the plant division in which it first arose?

The appearance of true vascular tissues (xylem and phloem) for water and nutrient conduction, first arising in pteridophytes

The development of true vascular bundles and lignified roots, first arising in bryophytes

The production of seeds enclosed within protective ovary walls that mature into fruits, first arising in gymnosperms

The specialization of Malpighian tubules as primary excretory structures for water conservation, first arising in annelids

Show answer & explanation

Answer: The appearance of true vascular tissues (xylem and phloem) for water and nutrient conduction, first arising in pteridophytes

Answer

The appearance of true vascular tissues (xylem and phloem) for water and nutrient conduction first arose in pteridophytes.

The correct choice accurately identifies pteridophytes (ferns) as the first plant group to evolve true vascular tissue (xylem and phloem). This evolutionary milestone distinguished them from non-vascular bryophytes and allowed for tall, upright growth away from water bodies.

Step-by-Step Solution

Analyze the plant evolutionary sequence

Plant evolution proceeded from non-vascular aquatic/moist forms (Thallophytes, Bryophytes) to vascular seedless plants (Pteridophytes) and vascular seed plants (Gymnosperms, Angiosperms).

Tracking major structural transitions establishes when key terrestrial adaptations evolved.

Evaluate vascular tissue origin

Bryophytes lack true xylem and phloem. Pteridophytes are the first vascular plants (tracheophytes) possessing true xylem and phloem.

Vascular tissue provided structural support and long-distance transport needed for terrestrial growth.

Evaluate seed and excretory system statements

Gymnosperms bear naked seeds, not enclosed fruit seeds. Malpighian tubules belong to arthropods, not annelids.

Eliminating erroneous statements identifies the single correct evolutionary pairing.

Key Concept

Evolutionary trends in plant vascularization and organ system adaptations

Estimated Time:1m 30s

Question 13Question →

According to Jean-Baptiste Lamarck's theory of evolution, physical modifications developed by an organism during its lifetime in response to environmental demands are directly transmitted to its offspring. Is this statement true or false?

True

False

Show answer & explanation

Answer: True

Answer

True. Lamarck's theory posits that acquired phenotypic changes gained during an individual's lifetime are passed down to offspring.

The statement accurately reflects Lamarck's hypothesis, which held that environmental conditions trigger specific needs in an organism, prompting structural adaptations through use or disuse that are subsequently inherited by offspring.

Step-by-Step Solution

Analyze the core assertion made in the statement regarding evolutionary change.

The statement asserts that traits acquired during an organism's lifetime due to environmental interaction are inherited by progeny.

Identifying the central claim is necessary to evaluate which historical evolutionary theory it reflects.

Compare the claim against the classic postulates of Jean-Baptiste Lamarck.

Lamarck's theory relies on two primary principles: the law of use and disuse, and the inheritance of acquired traits.

Lamarck explicitly argued that organs change with use/disuse and that these structural alterations are directly transmitted to future generations.

Key Concept

Lamarck's Principle of Inheritance of Acquired Characteristics

Question 14Question →

In an experiment designed to test a fundamental principle of evolution, a scientist cut off the tails of mice for twenty-two consecutive generations. Despite this continuous physical modification, all offspring in the twenty-third generation were born with tails of normal length. Which postulate of Lamarck's theory of evolution was directly disproved by the outcome of this experiment?

Organisms inherit somatic modifications acquired by their parents during their lifetime.

Frequent use of an organ causes it to enlarge, while disuse leads to its degeneration.

New structures arise in organisms in response to specific environmental needs.

Natural selection acts on pre-existing variations to eliminate unfavorable traits.

Show answer & explanation

Answer: Organisms inherit somatic modifications acquired by their parents during their lifetime.

Answer

Organisms inherit somatic modifications acquired by their parents during their lifetime.

August Weismann's experiment directly refuted Jean-Baptiste Lamarck's concept of the inheritance of acquired characteristics. Because surgical removal of tails affects only somatic cells and not germ cells (sperm and egg), the genetic code governing tail development remained unaltered across generations.

Step-by-Step Solution

Analyze the experimental setup and results.

Removing tails surgically for multiple generations represents an acquired somatic change, but offspring continued to inherit normal tails.

Acquired physical changes affect body (somatic) cells rather than germ cells.

Relate the empirical evidence to Lamarckian postulates.

Lamarck asserted that traits acquired during an organism's lifetime could be inherited by subsequent generations.

August Weismann's tail-cutting experiment demonstrated that changes to somatic tissues are not inherited, thus disproving the inheritance of acquired characteristics.

Key Concept

Debunking the Inheritance of Acquired Characteristics (Weismann's Germ Plasm Theory)

Estimated Time:1m 0s

Question 15Question →

In a population of moths inhabiting an industrial region, dark-colored individuals became significantly more common over several generations as pollution darkened the tree trunks. According to Charles Darwin's theory of natural selection, which mechanism best accounts for this change in the population?

Pre-existing dark genetic variations provided a camouflage advantage against predators, resulting in higher survival and reproduction rates for dark moths.

Individual light-colored moths actively developed darker wing pigments during their lifetime to adapt to the soot and passed these acquired traits to their offspring.

Environmental soot directly induced beneficial genetic mutations in all light moths to prevent the species from going extinct.

Light-colored moths stopped using their light wing pigments, causing the light coloration to deteriorate and disappear over generations.

Show answer & explanation

Answer: Pre-existing dark genetic variations provided a camouflage advantage against predators, resulting in higher survival and reproduction rates for dark moths.

Answer

Pre-existing dark genetic variations provided a camouflage advantage against predators, resulting in higher survival and reproduction rates for dark moths.

According to Darwin's theory of natural selection, populations contain natural genetic variations. When the environment changed due to industrial pollution, dark moths gained a camouflage advantage. They were preyed upon less frequently by birds, allowing them to survive and pass their dark-pigment genes to the next generation at higher rates.

Step-by-Step Solution

Identify the foundation of Darwinian evolution.

Natural selection requires inherited genetic variation to already exist within a population prior to environmental change.

Organisms do not generate intentional phenotypic changes within their lifetime to suit new environments.

Analyze the environmental selective pressure.

Soot-covered trees made dark moths less visible to predators compared to light-colored moths.

Selective pressures determine which existing phenotypes offer a survival advantage.

Determine the population-level outcome.

Darker moths survived longer and produced more offspring, increasing the proportion of dark moths in future generations.

Differential survival and reproduction cause advantageous alleles to accumulate in the population over time.

Key Concept

Natural Selection and Differential Reproduction

Estimated Time:1m 0s

Question 16Question →

According to Charles Darwin's theory of natural selection, evolutionary changes occur in a specific logical sequence. Arrange the following processes in the correct chronological order in which natural selection acts upon a biological population.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct logical sequence of natural selection is: Overproduction leading to competition, pre-existing inherited variation, differential survival and reproduction of favored individuals, followed by population adaptation across generations.

Natural selection begins when overproduction of offspring causes competition for limited resources. Pre-existing inherited variations determine which individuals survive environmental pressure. Favorable traits allow greater reproductive success, increasing the trait's frequency in future generations.

Step-by-Step Solution

Identify the initiating condition in Darwin's model.

Overproduction of offspring occurs, leading to environmental resource limitation and competition.

Populations naturally produce excess offspring, creating a struggle for existence.

Determine the substrate upon which selection acts.

Inherited variation must already exist within the population.

Without pre-existing phenotypic variation, differential survival cannot select for specific traits.

Analyze the interaction between variation and environmental pressure.

Individuals with traits favored by the environment survive and reproduce at higher rates.

Differential reproduction ensures favorable alleles are passed to the next generation.

Establish the long-term population outcome.

The frequency of advantageous traits increases in subsequent generations.

Evolution by natural selection is defined as a change in population characteristics over time.

Key Concept

Darwinian Mechanism of Evolutionary Change by Natural Selection

Question 17Question →

A sudden environmental change occurs in a habitat, favoring beetles with darker pigmentation. According to modern evolutionary theory (Neo-Darwinism), which of the following best explains the genetic basis for how this beetle population evolves over successive generations?

Individual beetles acquire darker pigmentation during their lifetime due to environmental stress and pass these somatic changes directly to their offspring.

Pre-existing gene mutations in germ cells provide dark allele variations, increasing in frequency over generations as natural selection favors darker individuals.

The environmental stress converts discontinuous phenotypic variations directly into continuous environmental modifications without altering allele frequencies.

Natural selection creates new analogous structural adaptations within the somatic cells of surviving adults to ensure immediate individual survival.

Show answer & explanation

Answer: Pre-existing gene mutations in germ cells provide dark allele variations, increasing in frequency over generations as natural selection favors darker individuals.

Answer

Pre-existing gene mutations in germ cells provide dark allele variations, increasing in frequency over generations as natural selection favors darker individuals.

Modern evolutionary theory (Neo-Darwinism) explains evolution as a change in allele frequencies within a population over time. Gene mutations in germ cells create heritable variations in the gene pool. When environmental conditions change, individuals carrying advantageous alleles experience greater reproductive success, causing those favorable alleles to become more common in the population over successive generations.

Step-by-Step Solution

Identify the core principle of Modern Evolutionary Theory (Neo-Darwinism).

Neo-Darwinism integrates Mendelian genetics with Darwinian natural selection, emphasizing that evolution is driven by changes in gene/allele frequencies within a population's gene pool.

Evolution occurs at the population level through genetic inheritance, not at the individual level through somatic modifications.

Evaluate the origin and transmission of evolutionary variation.

Random gene mutations occurring in germline cells generate new alleles, creating heritable genetic variation.

Only mutations in germ cells (gametes) are transmissible to offspring, serving as raw material for selection.

Determine the effect of natural selection on allele frequencies.

Individuals possessing favorable alleles (darker pigmentation) have higher differential reproductive success, increasing the dark allele frequency in subsequent generations.

Differential survival and reproduction lead to adaptation over generational time.

Key Concept

Modern Evolutionary Theory (Neo-Darwinism) and Population Genetics

Question 18Question →

Arrange the following stages of allopatric speciation in the correct sequential order from first to last:

Drag items to arrange them in the correct order

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Answer

The correct sequence of allopatric speciation begins with geographic barrier formation, followed by independent genetic divergence in isolation, leading to the development of reproductive isolation mechanisms, and culminating in complete biological speciation upon secondary contact.

Allopatric speciation requires physical geographic isolation to stop gene flow between populations. Over time, independent selective pressures and genetic drift alter gene pools until biological reproductive isolation arises, making interbreeding impossible even if secondary contact occurs.

Step-by-Step Solution

Identify the initial event that begins allopatric speciation.

Physical geographic separation occurs first, which cuts off gene flow between subpopulations.

Allopatric speciation is specifically defined by geographical isolation as its triggering mechanism.

Determine the genetic consequences while populations are geographically isolated.

Subpopulations independently undergo natural selection, mutations, and genetic drift.

Absence of gene flow permits independent changes in allele frequencies across separate environments.

Identify how genetic divergence leads to biological speciation.

Reproductive isolating mechanisms (e.g. mating behavior changes, gamete incompatibility) develop.

Genetic changes eventually affect traits critical for successful mating and fertilization.

Determine the outcome if the geographic barrier is removed.

Secondary contact reveals that the two populations can no longer interbreed to produce viable, fertile offspring.

Biological reproductive isolation confirms that distinct species have formed.

Key Concept

Stages of allopatric speciation and reproductive isolation mechanisms

Estimated Time:1m 30s

Question 19Question →

Match each paleontological evidence or dating principle in Column A with its correct geological or evolutionary significance in Column B.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Archaeopteryx lithographica matches with transitional link features between reptiles and birds; Index fossil matches with relative dating via widespread organisms of short geological lifespan; Law of Superposition matches with deeper layers containing older fossils in undisturbed strata; Radioactive decay half-life matches with absolute numerical dating based on isotopic decay.

Each paleontological term correctly matches its corresponding geological or evolutionary mechanism: Archaeopteryx demonstrates transitional evolution between reptiles and birds, index fossils serve as short-duration marker organisms across strata, the Law of Superposition determines relative age by depth order in undisturbed rocks, and half-life radioactive decay determines absolute numerical chronological age.

Step-by-Step Solution

Identify transitional fossil organisms and their anatomical significance.

Archaeopteryx is paired with the description of a transitional form combining bird and reptile traits.

Transitional forms provide direct structural evidence of evolutionary lineage changes in fossil records.

Differentiate relative dating principles from index fossil applications.

Law of Superposition is linked to relative strata order (older at bottom), whereas Index Fossils are linked to geographically broad, short-lived marker organisms.

Stratigraphy relies on layer placement, while index fossils correlate disparate rock formations globally.

Associate radiometric principles with absolute dating methods.

Radioactive decay half-life matches with absolute numerical dating.

Isotopic breakdown rates supply exact time scales measured in years rather than relative layer order.

Key Concept

Key paleontological concepts including transitional fossils, index fossils, stratigraphy, and radiometric dating techniques.

Question 20Question →

During early embryonic development, human embryos temporarily possess pharyngeal pouches (gill clefts) and a post-anal tail, structural features that are visually similar to those observed in early fish embryos. What is the evolutionary significance of these temporary embryological structures?

They indicate that humans evolved directly from modern species of bony fish in a linear sequence.

They provide evidence that humans and fish share a common ancestor from which shared developmental pathways were inherited.

They represent functional analogous structures essential for gas exchange within the amniotic fluid.

They are somatic adaptations acquired by the embryo in response to the fluid environment of the uterus.

Show answer & explanation

Answer: They provide evidence that humans and fish share a common ancestor from which shared developmental pathways were inherited.

Answer

The presence of pharyngeal pouches and post-anal tails in human embryos indicates that humans and fish share a common ancestor from which these early developmental patterns were inherited.

Comparative embryology demonstrates that vertebrate species undergo similar early stages of embryonic development. The temporary presence of pharyngeal pouches and a post-anal tail in human embryos is a homologous trait resulting from conserved developmental genes inherited from a distant common aquatic ancestor.

Step-by-Step Solution

Analyze the anatomical and embryological evidence described in the stem.

Identified temporary embryonic structures (pharyngeal pouches and post-anal tail) shared across vertebrate embryos.

Comparative embryology studies structural similarities present during early stages of organismal development.

Evaluate the evolutionary relationship established by comparative embryology.

Recognized that shared embryological stages reflect shared genetic blueprints passed down from a common ancestral vertebrate lineage.

Organisms retain conserved developmental genes from common ancestors even if adult structures diverge significantly.

Key Concept

Comparative Embryology as Evidence for Common Ancestry

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