Chapter 1
Based on your knowledge of adaptation, what is a plausible order for the following items to occur when a population undergoes selection?
1. The availability of food becomes limited due to overpopulation or environmental change. 2. Only individuals that have advantageous traits are able to survive. 3. Parents pass the traits that allow them to survive on to their offspring. 4. The number of individuals in the population with advantageous traits grows.
When natural selection takes place, it changes the observed range of behavior or morphology of all individuals in a population. True or False?
False "Natural selection does not change all instances of a trait in a population. If it did, no variation would be left and future adaptations could not occur. Natural selection results in a change in the distribution of values of a trait in a population."
The average morphology (size, shape, and composition) of individuals in a population always changes rapidly when that population invades a new habitat. True or False?
False "When a population invades a new habitat, the average morphology of individuals can change at variable rates. The rate of change is determined by the directional pull of selection pressures."
During the late 1970s, environmental change caused flux in the quantities of the different sizes and hardnesses of seeds available to finches in the Galápagos. Given what you know about natural selection, match each period of environmental change to the average beak depth you would expect to find in the finch populations (Shallow, Medium, or Deep Beak Depth).
*1976-ish: Shallow Beak Depth* "During this period, many small and easy to crush seeds were available. Finches with small beak depth could easily access these seeds. There was no pressure selecting for a deeper beak depth." *1977-ish: Medium Beak Depth* "A serious drought took place during this period. Small, soft seeds became scarce and large, hard to crush seeds were the only ones available. Finches with small beaks began to die off. Because selection happens gradually, the average beak depth was medium." *1978-ish: Deep Beak Depth* "The drought subsided during this period. However, finches with deep beaks were able to survive and reproduce with a greater frequency during the drought. Because offspring share the traits of their parents, the average beak depth became deep."
Which of the following statements regarding the life experiences that led Darwin to his theory of adaptation are accurate? Charles Darwin's ideas were not widely accepted during his lifetime. Charles Darwin spent years on a mapping voyage through South America. Charles Darwin was boor to a poor family and was familiar with the social struggle for existence. Charles Darwin finished schooling to become a medical doctor.
*Correct:* Charles Darwin spent years on a mapping voyage through South America. "It is unlikely that Darwin would have generated his theory of natural selection by adaptation without the experiences he gained from his time on the HMS Beagle. This voyage was extremely influential because it allowed him to observe variation in living and fossil animals." Charles Darwin's ideas were not widely accepted during his lifetime. "Darwin's ideas were rejected by most scientists at the time and were even viewed by the general public as being an act against the church. In fact, it took Darwin over two decades to publically present his theory because he knew that it would be ridiculed." *NOT CORRECT:* Charles Darwin finished schooling to become a medical doctor. "At his father's request, Darwin did start schooling to become a medical doctor. However, he was not very good at medical studies and failed out. His failure at medical school is one of the reasons Darwin was free to pursue a career as a naturalist." Charles Darwin was boor to a poor family and was familiar with the social struggle for existence. "Darwin was actually born to a very prosperous family. This is why he had the freedom to take a voyage on the HMS Beagle."
Peter and Rosemary Grant conducted a landmark study of the ecology and evolution of the medium ground finch Geospiza fortis in the Galápagos. Place in order the changes that they witnessed during their time there.
1. Rains were not very good. 2. Plants produced fewer seeds than normal. 3. Some finches began to die. 4. The distribution of specific characteristics began to change within the population.
Scientists can use Darwin's theory of adaptation by natural selection to predict the adaptations that an organism will experience next. True or False?
False "While many adaptations seem to arise repeatedly in evolution, the actual evolutionary scenario in the future of a given population is not predictable. Adaptations do not only move in a single direction. Scientists have a hard time predicting environmental changes, let alone how organisms will adapt to them."
What is the term that demographers use for the ability to produce offspring?
Fecundity "Fecundity is an important word to know when describing which individuals will be competitive enough to pass their traits to the next generation."
Fill in the blanks using the given words. Natural selection often results in changes in behavior or morphology that increase the reproductive success of _____ even if those changes decrease the reproductive success of _____. groups / individuals
Natural selection often results in changes in behavior or morphology that increase the reproductive success of *individuals* even if those changes decrease the reproductive success of *groups*.
Which of the following statements regarding the role of individuals within a population are correct? Individuals in a population do not compete with one another but with other populations. Not all individuals in a population survive to reproductive age. What is best for the individual is best for the population or species. When selection occurs, all individuals in a given population end up with exactly the same characteristics. Individuals produce as many offspring as possible.
*Correct:* Not all individuals in a population survive to reproductive age. "Selection cannot happen at the level of the group or population because the individuals within a group are constantly in competition with one another for survival." Individuals produce as many offspring as possible. "This is because they are driven to meet their own evolutionary interests (survival of offspring) over the evolutionary interests of the group or population." *NOT CORRECT:* Individuals in a population do not compete with one another but with other populations. "Because resources are finite, individuals within the same population (who share the same geographic space) compete more with each other than they do with other populations." What is best for the individual is best for the population or species. "This is not always the case. When competition is high, individuals often engage in behaviors that are detrimental for the group." When selection occurs, all individuals in a given population end up with exactly the same characteristics. "Selection can only occur because individuals have different characteristics that are advantageous in different environmental scenarios."
Identify the reasons why Peter and Rosemary Grant's study of the medium ground finch on the island of Daphne Major was so remarkable. The Grants discovered a new species of finch. The Grants documented the finches' adaptation to the changes in their environment. The Grants were able to directly show how Darwin's postulates led to evolutionary change. The Grants disproved a major part of Darwin's theory of evolution.
*Correct:* The Grants documented the finches' adaptation to the changes in their environment. "A two-year drought starting in 1976 allowed the Grants to study adaptation in real time." The Grants were able to directly show how Darwin's postulates led to evolutionary change. "The Grants took measurements of all of the birds on the island. When a catastrophic event occurred on the island, they were able to document the birds' responses, particularly in terms of changes in the populations' beak depths." *INCORRECT:* The Grants discovered a new species of finch. "The Grants studied the medium ground finch, which Darwin had observed in the 1800s." The Grants disproved a major part of Darwin's theory of evolution. "The Grants' study supported Darwin's theory."
Based on your knowledge of the environments where fish and humans live, match the adaptive responses in eye structure to the correct organism (fish or human). Lens collects light equally throughout. Lens is flat Lens is spherical Lens has a high capacity to gather already bent light. Lens has a very high light gathering power. Lens can gather light in a 180* visual field.
*Fish:* Lens has a very high light gathering power. "The lens in a fish eye is adapted to take in as much light as possible. Since light is not bent when it passes from water into the cornea, a fish eye lens does not require a special adaptation to account for bent light." Lens can gather light in a 180* visual field. "The lens of a fish eye increases smoothly from the surface of the lens to the center. This allows the lens to take in and refract light from a full 180° visual field." Lens is spherical "Because light does not bend when it passes from water into the cornea, it can pass through a spherical surface. Such a surface is optimal for gathering as much light as possible." *Human:* Lens has a high capacity to gather already bent light. "The lens in a human eye is adapted to take in light that is already bent. It had to adapt to do so because light becomes bent when it passes between the air in a terrestrial environment and the cornea." Lens collects light equally throughout. "Even though the lens in a human eye cannot have a spherical structure (gather light in a 180° visual field), it is adapted to take in as much bent light as possible by collecting it evenly throughout." Lens is flat "The lens in a human eye is shaped like a squashed football so that it can take in as much bent light as possible."
Which of the following ideas were widely accepted before Charles Darwin and which were a unique contribution by Charles Darwin? Small evolutionary changes accumulate to make large ones. Organisms can pass changes on to their offspring. Environmental pressures cause organisms to change. Major evolutionary change happens slowly. Variation is what allows organisms to change over time.
*Widely Accepted Before Charles Darwin:* Environmental pressures cause organisms to change. "Many naturalists noted the relationship between morphological form and the environment before Charles Darwin did." Organisms can pass changes on to their offspring. "Inheritance, or the idea that change can be passed on from parent to offspring, was known to animal breeders before Darwin was born." *Unique Contribution by Charles Darwin:* Small evolutionary changes accumulate to make large ones. "At the time that Charles Darwin presented his ideas, most people believed that evolutionary change happened in large jumps." Variation is what allows organisms to change over time. "At the time that Charles Darwin presented his ideas, most people believed that variation was not important." Major evolutionary change happens slowly. "At the time that Charles Darwin presented his ideas, most people believed that evolutionary change happened rapidly."
What is it called when two or more organisms that are not related to one another exhibit similar complex adaptations?
Convergence "Convergence provides us with evidence that similar selection pressures can generate similar complex adaptations. If such an adaptation arises twice (without common ancestry), it cannot be a coincidence!"
Match the examples of variation to the correct category of variation (continuous or discontinuous): Achondroplasia Human hair color Human height Human blood groups Albinism Human skin color
Continuous: Human Height "As mentioned in the chapter, there are no distinct categories for human height. Humans grade smoothly from short to tall. The only exception is when genetic circumstances like achondroplasia are present." Human Hair Color "There are no distinct categories for human hair color. Human hair grades smoothly across varying shades." Human Skin Color "There are no distinct categories for human skin color. Human skin grades smoothly from light to dark." Discontinuous: Achondroplasia "As mentioned in the chapter, this is the condition that causes affected individuals to be much shorter than other people, have proportionately shorter arms and legs, and bear a variety of other distinctive features. You either have this condition or you do not." Human Blood Groups "Humans belong to very specific blood groups (A, B, AB, or O). There is no continuous gradation between them" Albinism "Albinism is a rare disorder caused by a lack of pigment that either an individual has or does not have."
Match the following newly selected changes in behavior or morphology to the level that would benefit from them (individual or group population). Cannibalism High Fecundity Rates Larger Body Size to Attract Mates Thicker Hair to Survive Cold Sharper Canines to Defend Food Resources
Individual: - High Fecundity Rates - Cannibalism - Sharper Canines to Defend Food Resources - Larger Body Size to Attract Mates - Thicker Hair to Survive Cold Group or Population:
Place the evolution of the human eye in order.
Page 20 of the textbook (Figure 1.22)
Given what you know about stabilizing selection, match each beak depth distribution to when it occurred in the stabilizing selection event.
Page 9 of the textbook (Figure 1.9) (Basically, open bars are before selection and shaded bars are after selection...) "After stabilizing selection acted on the finch population, more individuals had average sized beaks. Furthermore, the number of individuals with extreme beak sizes (very shallow or very deep) dropped off.Good job! The selection event caused the distribution to shift towards an average beak size."
Which of the following statements regarding the rate at which natural selection produces adaptations are true? Barring unusual circumstances, most new species do not arise in a short period (for example, 30 to 46 years). Significant adaptations, such as a change in beak size or body weight, can occur over remarkably short periods of time (for example, 30 to 46 years). All significant adaptations, such as a change in beak size or body weight, take millions of years to occur. Incremental adaptions can take millions of years to occur.
Significant adaptations, such as a change in beak size or body weight, can occur over remarkably short periods of time (for example, 30 to 46 years). "If the selection pressure is strong enough, then even significant adaptations can occur quickly." Barring unusual circumstances, most new species do not arise in a short period (for example, 30 to 46 years). Incremental adaptions can take millions of years to occur.
Darwin observed the domestication of pigeons as an evolutionary phenomenon. Identify the statements that are true about the pigeons depicted in the images. They are an example of artificial selection. They are different breeds in the same species. They are an example of rapid evolution. They naturally evolved in different directions owing to environmental conditions.
They are an example of artificial selection. "In the nineteenth century, pigeon breeding was a popular hobby. Humans bred rock pigeons for particular traits, such as certain markings or showy feathers." They are different breeds in the same species. "All of the birds in the images are different breeds of the rock pigeon, shown in (d), illustrating the large range of variation that can be contained within a single species." They are an example of rapid evolution. "Humans created many different forms of pigeons in just a couple hundred years. In the perspective of geological time, this is a very short amount of time." NOT: They naturally evolved in different directions owing to environmental conditions. because "These pigeons are the result of directed breeding."
What state does a population reach when the average value of an adaptive trait no longer changes? a. Stabilizing Selection b. Equilibrium c. Fixation d. Selection
b. Equilibrium
