ET 4/20

Which statement BEST explains why natural selection acts on an organism’s phenotype rather than on its genotype?

• More than one phenotype can result from the same genotype.

• More than one genotype can result in the same phenotype.

• Both homozygous genotypes result in the same phenotype

• Only heterozygous phenotypes result from the same genotype.

Which statement is MOST likely the explanation of why certain animals are able to adapt to changing environments?

• Some species have a greater variation in their genetic makeup.

• Some species have mostly dominant genes.

• Some species have unlimited habitats.

• Some species react by mutating.

Look at the phylogenetic tree above.

Which hypothetical organism is the most recent common ancestor for Organisms A and G?

• 1

• 2

• 3

• 4

When do mutations help make an ecosystem more sustainable?

• when mutations decrease the number of individuals in an ecosystem

• when mutations increase the number of individuals in an ecosystem

• when mutations decrease the number of species in an ecosystem

• when mutations increase the number of species in an ecosystem

• A

• B

• C

• D

Researchers have discovered that the ear bones of mammals are homologous to some bones in fish jaws. Which claim is BEST supported by this fact?

• Fish do not require a sense of sound.

• Fish and mammals have a distant common ancestor.

• Selection pressures have acted over time on mammals but not fish

• Selection pressures have promoted similar evolution in fish and mammals.

A cow and a frog have similar bone structures in their forelimbs. Both have phalanges and radius, ulna, and humerus bones. However, the cow and frog are animals with very different life cycles from each other. Which MOST likely describes why the body structures of these animals are so similar?

• Both have undergone similar mutations.

• Both descended from a common ancestor

• Both reacted similarly to environmental pressures

• Both spread out from the same geographical region.

Scientists study similarities between groups of organisms to determine how they may have changed over time. All of the following are used as evidence for the similarities between the two organisms shown above EXCEPT

• early development

• body structure

• habitat

• DNA

The forelimb of the monkey, bat, penguin, and alligator look very different on the outside, but their skeletal structures are similar. This evidence suggests that these animals

• may have evolved from a common ancestor.

• all reproduce in a similar fashion

• live in similar environments.

• should all be able to fly someday.

Horses have one of the most complete fossil records of any living organism. Some species of horses are shown, along with an approximate time of when they lived. It is hypothesized that all these horses are closely related to each other.

Which is the BEST conclusion that can be made about these horses over time?

• Beneficial gene mutations resulted in physical changes to the horses.

• Dietary changes caused the physical appearance of the horses to change.

• The environments in which the horses have lived have remained unchanged

• Horses began to change in response to changes to other organisms in their ecosystems.