Unit 8 Evolution

For finches on the Galapagos, a significant change in beak size can be observed across years with plentiful rainfall or intense drought. How can the changes in finch beak size be attributed to evolution?

• Finches on the island are domesticated and are artificially selected for beak size.

• Finches on the island reproduce with finches from nearby islands that have larger beaks, resulting in changing beak sizes over time.

• Finches on the island without well suited beak sizes change their diet to induce and enhance growth of their beaks.

• Finches on the island with better-adapted beak sizes have increased survival.

Answer explanation

Finches on the island with better-adapted beak sizes have increased survival. The beak sizes are genetically controlled and therefore are an inherited trait. The range of phenotypes in beak size allows for some members of the population to have increased access to food, which increases their survival. This, in turn, increases their likelihood of passing that trait on to their offspring.

The bottleneck effect is used to describe an event where a population decreases. One example involves the northern elephant seal. They have a reduced genetic variation due to a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000, but they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted. Which phrase best explains this change in gene frequency?

• natural selection

• gene flow

• genetic drift

• speciation

Answer explanation

The process of changing gene frequency over time is known as genetic drift. The reduction of the population of seals allowed genetic drift to occur.

The diagram shows a portion of the fossil record. Select ALL of the statements that are supported by the record.

• Life moved to land in layer 6.

• Shelled organisms existed before fish.

• Fish were the first life forms.

• Layer 5. is older than layer 2.

• The oldest life existed in water.

Answer explanation

Statements supported by the fossil record:The oldest life existed in water. Shelled organisms existed before fish.Layer 2 is older than layer 5. The oldest layers are the lowest layers. There is no evidence in this record of life moving to land and fish only appeared first in layer 3, meaning they were not the first life forms recorded here.

Examine the homologous structures shown here. If a DNA analysis was used as an additional piece of evidence for evolution, what would the analysis show? Select ALL that apply.

• Their nucleotide sequences would have much similarity.

• The chromosome number would be the same for all species.

• They are equally related to each other through evolution.

• They would code for similar amino acid sequences.

• Their DNA sequences would be identical.

Answer explanation

The similarity would be evident through DNA comparisons, but no two organisms have identical DNA, even ones in the same species, so their differences would be evident. Since they have similar DNA sequences, they will code for similar amino acid sequences as well.

A student is given four components of evolution, shown in the four boxes here. Which statements can be formed using the terminology shown here to accurately describe the evolution within a species? Select ALL that apply.

• Individuals have different genetics, leading to the evolution of populations.

• Populations are able to undergo evolution to create changes to the individual's genetics.

• Individuals with adaptations are based on genetics, allowing for populations to undergo evolution.

• Individuals undergo evolution depending on the genetics of the population.

• Populations have individuals with changing genetics that lead to evolution.

Answer explanation

The key feature here is that individuals cannot evolve, only populations evolve. Individuals are either adapted or poorly adapted in their environment. This is how evolution by means of natural selection occurs.

In what instances might punctuated equilibrium occur?

• when the environment is generally stable

• when the environment is rapidly changing

• when the environment is unusually humid

• when the environment experiences gradual change overlong periods of time

Answer explanation

Punctuated equilibrium asserts that evolution occurs in short bursts followed long periods of equilibrium.  Generally, punctuated equilibrium will occur when the environment is rapidly changing. The driving force of evolution in this case is some sort of change in the environment that necessitates a need for quick change.

Many of the proteins produced by humans have identical or nearly identical counterparts in chimpanzees. For example, the hemoglobin in your blood is about 99% similar to chimp hemoglobin. This suggests that humans and chimps share a common ancestor, from which both species evolved via ____________.

• convergence

• determination

• coevolution

• divergence

Answer explanation

While humans and chimps remain very similar in some ways, the differences that exist between them have arisen over time due to different adaptations to differing conditions.

The diagram shows the embryo development of four vertebrates and suggests all of the following EXCEPT

• there are very few differences in the early development of any vertebrates.

• common features (gills and segments) in the embryos of all vertebrates.

• there are no similarities in the embryos of all four groups.

• common ancestry of vertebrates.

Answer explanation

The chart DOES show that there are common developmental milestones, and therefore relatedness, in all vertebrates. The chart does not suggest that there are significant differences between the four embryos.

Consider the graphic of the divergence of one founder species into many additional bird species. This speciation resulted in

• the survival of mutated individuals within the original population.

• biodiversity due to anatomy and available food resources.

• convergent evolution that resulted in a variety of lineages.

• extinction of individuals in the population who died due to starvation.

Answer explanation

This divergence, a type of adaptive radiation, resulted in biodiversity due to anatomy and available food resources. There was variation in the original population. Environmental and geographic stresses allowed certain variations on beak type to survive. Eventually, the differences lead to speciation.

What makes the evolution of species possible?

• mutation and natural selection

• homology and adaptation

• mutation and fossil evidence

• comparative anatomy and homologous structures

Answer explanation

mutation and natural selection--Through mutation, some offspring are born slightly different than their parents, and through natural selection, if the mutation proves to be an advantage in the current environment, then the organism will survive and reproduce passing the mutation along to future offspring. Over time, species change through random genetic mutations which lead to adaptations by means of natural selection.