Natural Selection and Evolution

A small number of lizards from a mainland population have been deposited on four isolated islands because of the effects of a rare strong storm.

Which of the following best predicts the outcome of these lizards reproducing for many generations on the islands?

• Courtship rituals specific to each island lizard species prevent the lizards from interbreeding.

• Speciation results from bottleneck events that happened before the ancestral species reached the islands.

• The different species that currently exist are the result of hybridization between lizards from different islands.

• The isolation prevents gene flow; thus, the lizards on different islands experience prezygotic isolation.

Scientists want to determine whether the rapid economic growth in China between 1950 and 2000 caused a mass extinction of animal species during that time period. A mass extinction event is considered to occur when the rate of species extinction far exceeds the background extinction rate. The scientists collected data on the number of extinctions of selected vertebrate species in China between 1950 and 2000, as shown in Table 1. Extinction rates were ascertained by measuring the average percent of species lost (PSL).

Which of the following is the null hypothesis most relevant for evaluating the data in Table 1 ?

• There is no significant difference between the extinction rate of animals between 1950 and 2000 in China and the background extinction rate.

• There is no significant difference between the extinction rates of mammals, birds, amphibians, and reptiles in China.

• There is a significant difference between the extinction rate for mammals in China and the background extinction rate for mammals.

• Because of climate change, habitat loss, pollution, and excessive exploitation of resources, China experienced a mass extinction event between 1950 and 2000.

Finch beak depth was measured before and after a severe drought in 1977. The averaged results are shown in Figure 1. After the drought, there were fewer seeds available for the finches to eat and the seeds that did remain were larger and harder to crack open. Researchers claim that when large, hard seeds are the predominate food source, the average beak depth of these finches tends to increase in subsequent generations.

Using the evidence provided, which of the following best justifies the researchers' claim?

• Finch beak depth increased after the drought because the overall numbers of finches decreased, reducing competition for resources.

• Finch beak depth increased as a consequence of selective pressure after the drought because the remaining seeds were larger and harder.

• Finch beak depth increased after the drought due to intraspecific competition since finches with deeper beaks attract more mates.

• Finch beak depth increased after the drought due to increased predation since finches with deeper beaks can fight off predators more effectively.

Five new species of bacteria were discovered in Antarctic ice core samples. The nucleotide (base) sequences of rRNA subunits were determined for the new species. The table below shows the number of nucleotide differences between the species.

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By discharging electric sparks into a laboratory chamber atmosphere that consisted of water vapor, hydrogen gas, methane, and ammonia, Stanley Miller obtained data that showed that a number of organic molecules, including many amino acids, could be synthesized. Miller was attempting to model early Earth conditions as understood in the 1950s. The results of Miller’s experiments best support which of the following hypotheses?

• The molecules essential to life today did not exist at the time Earth was first formed.

• The molecules essential to life today could not have been carried to the primordial Earth by a comet or meteorite.

• The molecules essential to life today could have formed under early Earth conditions.

• The molecules essential to life today were initially self-replicating proteins that were synthesized approximately four billion years ago.

What is natural selection?

• The process by which certain traits or characteristics become more or less common in a population over time, based on their ability to survive and reproduce in a given environment.

• The process by which organisms intentionally change their traits to better survive in their environment.

• The process by which species evolve into new species.

• The process by which individuals adapt to their environment over time.

Give an example of natural selection in action.

• Development of flight in birds

• Formation of mountains through tectonic activity

• Evolution of antibiotic resistance in bacteria

• Photosynthesis in plants

What is adaptation?

• The process of ignoring new conditions or changes in the environment.

• The process of avoiding new conditions or changes in the environment.

• The process of adjusting to new conditions or changes in the environment.

• The process of staying the same despite changes in the environment.

Explain how adaptations are related to natural selection.

• Adaptations are traits or characteristics that are determined by chance. Natural selection is the process by which individuals with the most offspring survive.

• Adaptations are traits or characteristics that help an organism survive and reproduce in its environment. Natural selection is the process by which individuals with advantageous adaptations are more likely to survive and pass on their genes to the next generation.

• Adaptations are traits or characteristics that are acquired during an organism's lifetime. Natural selection is the process by which individuals with the most offspring survive.

• Adaptations are traits or characteristics that are only found in humans. Natural selection is the process by which individuals with the most offspring survive.

What is population genetics?

• The study of genetic variation within families.

• The study of genetic variation within individuals.

• The study of genetic variation within and between populations.

• The study of genetic variation within species.