AP Biology : Understanding Structural Evidence

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding Structural Evidence

The wings of a bird and the wings of a beetle are considered __________.

Possible Answers:

phylogenetic

binomial

homologous

taxonomic

analogous

Correct answer:

analogous

Explanation:

Structures that are similar as a result of convergent evolution are referred to as analogous structures, such as the wings of beetles and birds. These animals do not share a common ancestor, and developed the trait for wings independent of one another. Homologous structures arise when two organisms share a trait due to linkage with a common ancestor. For example, legs of a dog and the legs of a cat are considered homologous.

Phylogeny refers to the evolutionary history of a lineage, and can be used to identify common ancestors. Taxonomy is the naming and classification of organisms. Binomial nomenclature is the scientific name for an organism containing its genus and species.

Example Question #2 : Understanding Structural Evidence

Which of the following statements are true?

I. Analogous structures are structures found in different species that have similar functions resulting from a common ancestor

II. Analogous structures are structures found in different species that have similar functions resulting from natural selection

III. Homologous structures are structures found in different species that have similar anatomical forms, resulting from a common ancestor

IV. Homologous structures are structures found in different species that have similar anatomical forms, resulting from natural selection 

Possible Answers:

I and IV

II and III

III only

II only 

I only

Correct answer:

II and III

Explanation:

Analogous structures are anatomical structures that have similar functions, but arose independently. Due to environmental stresses and natural selection, organisms of different species evolved and adapted independently, resulting in the existence of body parts with similar functions. This refers to convergent evolution. An example of analogous structures are the wings of several different animals. A moth, hummingbird, and a bat are only extremely distantly evolutionarily related, yet they all have wings of some sort, which serve the common purpose of transportation through air. Homologous structures are body parts that are anatomically similar and may share similar anatomical forms, but are not the result of convergent evolution, rather they are the result of divergent evolution. These commonalities within organisms show descent from a common ancestor. An example of homologous structures are the "arms" of three different mammals, a human, a bat, and a whale. Each "arm" has very similar anatomical organization of bones, but is used for very different functions.

Example Question #3 : Understanding Structural Evidence

What is a vestigial trait?

Possible Answers:

A structure that has origins in a common ancestor, but has evolved to perform different functions

A trait that makes an organism better suited to a habitat 

A change to a cell's genome

A structure that has lost its function but has been retained

Correct answer:

A structure that has lost its function but has been retained

Explanation:

A vestigial trait is an attribute that has lost its function but has been retained through evolution. Examples include the formation of goose bumps in humans and pelvic remnants in boas and pythons. A change in the DNA sequence (genome) of a cell is a mutation. A trait that makes an organism better suited for a habitat is an adaption. Structures that arise in organisms that share a common ancestor, but perform different structures are called homologous structures. An example of a homologous structure is the "arm" of a mammal. Mammals have very similar bone and muscle organization in their arms (whales, humans, bats), but the function of each is much different (swimming, grabbing, flying).

Example Question #4 : Understanding Structural Evidence

Which of the following is evidence of a common ancestor?

Possible Answers:

Fossil record

All of these

Morphological similarities

Vestigial characteristics

Correct answer:

All of these

Explanation:

It is believed that all organisms are descended from a common ancestor. Evidence of this includes morphological similarities, vestigial characteristics, and observations made within the fossil record. Recently, phylogenetic trees and cladograms are made using DNA sequence analysis to determine the similarity in the genomes of organisms. 

Example Question #5 : Understanding Structural Evidence

The structures of the front flipper of a whale and the forearm of a wolf have similar bone structure and derive from a common ancestor. This is an example of __________.

Possible Answers:

analogous structures

homologous structures

convergent evolution

the bottleneck effect

Mendel's laws of inheritance

Correct answer:

homologous structures

Explanation:

When parts of an animal serve different functions but have similar placement and bone structure (such as a wolf forearm and a whale flipper) and are derived from a common ancestor, these two structures are homologous. Convergent evolution is a process during which two non-related organisms develop analogous structures that serve the same function but have different structures. The bottleneck effect refers to the decrease in genetic diversity that occurs when a population goes through sudden decline and then expands again. Mendel's laws of inheritance refer to the rules by which different traits, or alleles, are passed on from one generation to the next as discrete units of inheritance called genes.

Example Question #6 : Understanding Structural Evidence

Structures that were once functional in the past but no longer serve a purpose due to evolutionary adaptations and physiological changes are referred to as __________ structures.

Possible Answers:

homologous

None of these

vestigial

similar

analogous

Correct answer:

vestigial

Explanation:

By definition, vestigial structures are structures that are thought to have had a biological function a long time ago but have since lost that function due to evolutionary changes. The human appendix is considered to be an example of a vestigial structure.

Example Question #7 : Understanding Structural Evidence

A human's hand and a cat's paw are considered to be __________ to one another. 

Possible Answers:

vestigial

Allof these

analogous

None of these

homologous

Correct answer:

homologous

Explanation:

Homologous structures show the existence of a shared ancestry through the observation of structural similarities between different species; however, while a human's hand and a cat's paw are structurally similar, they have very different functions.

Example Question #8 : Understanding Structural Evidence

An animal's DNA contains a gene that codes for a protein that produces a compound required for several essential metabolic reactions. Over time, that organism develops a "broken" form of the gene (called a pseudogene) and is no longer able to produce that compound. Why might it be advantageous for the organism to develop this "broken" gene?

Possible Answers:

DNA transcription requires a high amount of ATP, so having "broken" versions of essential gene sequences conserves energy.

Pseudogenes are detected and repaired by DNA polymerase, so organisms that develop them usually show no major advantage or disadvantage.

Pseudogenes are quickly removed from the genome, which makes DNA replication faster.

It is disadvantageous. "Broken" forms of genes are mutations that result in detrimental effects.

The organism's diet may have changed to one that includes that compound as a nutrient, so the organism can conserve energy by no longer producing the compound on its own.

Correct answer:

The organism's diet may have changed to one that includes that compound as a nutrient, so the organism can conserve energy by no longer producing the compound on its own.

Explanation:

When a mutation in a gene prevents it from being read, it may be advantageous if the compound produced by the encoded enzyme can be readily obtained from outside sources, saving energy needed to produce the compound on one's own.

A well-known example of this is the GLO gene for vitamin C production. In fruit-eating animals like bats, guinea pigs, and humans, the gene is still present but has a broken promoter, rendering it nonfunctional.

Example Question #9 : Understanding Structural Evidence

Which of the following is an example of an atavistic trait?

Possible Answers:

The human appendix, which has taken on a modified reduced function from its ancestral form.

Humans often born with the ability to wiggle their ears, resulting from their mammalian ancestors who would orient their ears for better hearing.

Dolphins (very rarely) born with hind flippers, resulting from their four-limbed ancestors.

A crow's ability to recognize human faces, possibly as a result of both species having evolved together.

A rhino's horn, which evolved separately from the horn structures of other animals such as rams or oxen.

Correct answer:

Dolphins (very rarely) born with hind flippers, resulting from their four-limbed ancestors.

Explanation:

An atavistic trait is a rare appearance of an ancestral structure in an evolved organism. Since dolphins evolved from four-legged mammals, a dolphin born with a pair of hind flippers shows is an atavism, an evolutionary throwback.

Ear wiggling is a an example of a vestigial trait. A rhino's horn in relation to a ram's horn represents an analogous vs. homologous structure. Facial recognition in crows is believed to be a product of coevolution.

Example Question #10 : Understanding Structural Evidence

During the 1800’s and 1900’s, a lot changed in evolutionary theory. Which of the following was first theory to be generally accepted by the academic community?

Possible Answers:

The Earth and species change over time

Mutations occur during DNA replication

Genes code for proteins

Uniformitarianism

Correct answer:

The Earth and species change over time

Explanation:

Before any truly accurate scientific work on evolution and inheritance could be done, the academic community had to accept the notion that the Earth and its species change over time. If species were fixed, then genetic variation, natural selection, and evolution could not be plausible. Once the scientific community acknowledged the changes in organisms, they were able to proceed into studies to determine why and how such changes occur.

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