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According to "evo-devo" thinking, an organism's body form can be substantially changed

through mutations or changes in the expression of one or a few genes that regulate developmen

In the axolotl, development is altered. Adult axolotls retain features (external gills and aquatic life) that were juvenile in its ancestors, a phenomenon known as


The example of ocean and lake stickleback fishes indicates that morphology can be altered

by altering the expression of a developmental gene in some parts of the body but not others.

The feathers of Archaeopteryx may have been used for flight. However, it's likely that their original function was for


Anti-evolutionary thinkers sometimes argue that natural selection could not produce a complex structure like the vertebrate eye. They claim that all of the parts of the eye must have arisen at once, asking why natural selection would favor the development of part of an eye that is not yet capable of forming a focused image. Which of the following statements is consistent with a survey of eye structure in the molluscs?

There are many intermediate stages of eye complexity that fulfill different adaptive functions

Feathers are an example of an ________; they originally evolved ________.

exaptation . . . for some other function and only later became adapted for fligh

Over a span of several thousand years, a number of species show adaptations to climate change: drier, warmer conditions select for succulent vegetation and deep taproots in plants, burrowing in mammals and amphibians, and other similar adaptive changes. What will happen if the climate shifts in the opposite direction and becomes progressively wetter and cooler?

Different adaptive trends will probably be favored in the new climatic environment

Structures that evolved from the same structure in a common ancestor are


The process through which species not closely related may come to resemble one another if they live in a similar environment is known as

convergent evolution

Cave-dwelling catfish and cave-dwelling salamanders share striking similarities: both organisms lack pigmentation and their eyes are reduced or absent. The most recent common ancestor to these organisms had normal pigmentation and fully developed eyes. The similarities between cave catfish and cave salamanders are an example of

analogy (convergent evolution)

The similarities in function of hummingbird wings and the wings of a butterfly reflect

analogy but not homology

Ever since Darwin, systematics has tried to

classify species in groups that reflect evolutionary relationships

Which of the following options lists taxonomic categories in the correct order from most specific to most general?

genus, family, order, class, phylum

________ and ________ mean the same thing

Clade . . . monophyletic taxon

In mammals, the presence of four limbs is ________ and hair is ________.

a shared ancestral character . . . a shared derived character unique to mammals

A systematist includes a lizard in a phylogenetic analysis of relationships among bird families. In this analysis, the lizard would be treated as

the outgroup

In accordance with the principle of parsimony, scientists prefer

phylogenetic trees that minimize the number of evolutionary changes

How can a phylogenetic tree be used to make predictions?

Features shared between two groups are likely to have been present in their common ancestor

Molecular data can be used to assess relationships among the major groups of living organisms whose common ancestors lived millions or billions of years ago. Similar techniques can be used to assess relationships among populations within a species. How can molecular techniques be useful for such varied comparisons?

Faster-evolving gene sequences provide better data for comparisons among close relatives, whereas very slowly evolving sequences work best for distantly related taxa

You compare homologous nucleotide sequences between several pairs of species with known divergence times. A pair of species that diverged 1 million years ago has two nucleotide differences, a pair that diverged 2 million years ago has four nucleotide differences, and a pair that diverged 3 million years ago has six nucleotide differences. You have sequence data for another pair of species where the divergence time is unknown. There are five nucleotide differences between them. Based on your clock, when did their line of ancestry diverge?

2.5 million years ago

In the three-domain system, the eukaryotes are represented

only within the domain Eukarya

The three-domain system

subdivides the prokaryotes into two different domains

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