Evidence of Evolution Practice Questions

Correct answer: The forelimbs of a man and the flippers of a whale

Homologous organs share a common embryonic origin and basic anatomical structure, indicating common ancestry. The forelimbs of humans and whales have the same pentadactyl bone arrangement despite serving different functions like grasping and swimming.

Correct answer: Their ancestors had functional versions of these structures

Vestigial organs are reduced, non-functional remnants of structures that were functional in ancestors. Their presence provides evidence of descent with modification from ancestors who required those structures for survival.

Correct answer: Cytochrome c

Cytochrome c is a highly conserved protein found in the mitochondria of almost all eukaryotes. Because it changes very slowly over time, the number of amino acid differences serves as a 'molecular clock' to estimate when two species diverged.

Correct answer: Convergent evolution

Convergent evolution occurs when unrelated species independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. Analogous structures perform the same function but have different anatomical origins.

Correct answer: Archaeopteryx

Archaeopteryx displays a mix of reptilian features (teeth, long bony tail) and avian features (feathers, wishbone). It serves as critical fossil evidence showing the transition from theropod dinosaurs to modern birds.

Correct answer: Ernst Haeckel

Haeckel's Biogenetic Law suggested that the embryonic development (ontogeny) of an individual repeats the evolutionary history (phylogeny) of its species. While the literal interpretation is largely discredited, embryology remains a vital tool for showing common ancestry.

Correct answer: Reappearance of a lost ancestral trait

Atavism is the occasional occurrence of an ancestral trait that was lost generations ago, such as a human born with a small external tail. This occurs when dormant genes from an ancestor are unexpectedly expressed.

Correct answer: The distribution of Marsupials in Australia

The isolation of Australia led to the independent evolution of marsupials, which occupy niches held by placental mammals elsewhere. This geographical distribution shows that evolution is influenced by both common descent and physical isolation.

Correct answer: It demonstrates a clear evolutionary trend of increasing body size and limb specialization

The horse lineage is one of the most complete fossil records available. It documents gradual changes in tooth structure for grazing and the reduction of toes to a single hoof for faster running on open plains.

Correct answer: Use the exact same set of twenty amino acids to build all their proteins

The near-universality of the genetic code and the use of the same 20 amino acids across all domains of life is powerful evidence for a single common ancestor. It suggests the basic biochemical 'machinery' of life was established very early in history.

Correct answer: Adaptive radiation

Adaptive radiation is the process in which a single ancestral species evolves into a variety of forms that occupy different ecological niches. The finches diversified primarily through changes in beak shape to exploit various food sources.

Correct answer: Homology

Homology is the study of structures that are similar due to shared ancestry. It represents divergent evolution, where a common underlying plan is modified for different ecological roles.

Correct answer: Mesozoic

The Mesozoic era is characterized by the dominance of dinosaurs and other large reptiles. It consists of the Triassic, Jurassic, and Cretaceous periods before the mass extinction event 66 million years ago.

Correct answer: Peripatus

Peripatus (the velvet worm) exhibits annelid-like features like a thin cuticle and segmentally arranged nephridia, alongside arthropod-like features like tracheae and claws. It provides clues about the transition between these two phyla.

Correct answer: Sedimentary

Sedimentary rocks form from the accumulation of minerals and organic particles over time. The gentle pressure and lack of extreme heat allow the remains of organisms to be preserved as fossils within the layers (strata).

Correct answer: Nictitating membrane, a remnant third eyelid (plica semilunaris)

The plica semilunaris in the corner of the human eye is a remnant of the nictitating membrane (third eyelid) found in many vertebrates like birds and reptiles. It no longer serves its original protective function in humans.

Correct answer: A non-functional DNA sequence that closely resembles a working gene

Pseudogenes are 'genomic fossils'—sequences that have accumulated mutations and lost their protein-coding ability. The sharing of specific pseudogenes between species is strong evidence of common ancestry.

Correct answer: Biogeography

Biogeography examines how geographical barriers like oceans and mountains influence the evolution and distribution of species. It explains why similar environments in different parts of the world often have very different flora and fauna.

Correct answer: The approximate time since two species shared a common ancestor

The molecular clock relies on the observation that genetic mutations accumulate at a relatively constant rate over time. By comparing the DNA differences between two species, scientists can back-calculate when their lineages diverged.

Correct answer: Dense hair on the body of a newborn (Lanugo)

While some body hair is normal, the excessive development of hair (hypertrichosis) or the presence of a functional tail are considered atavistic because they represent the full expression of traits typically suppressed in modern humans.