Biology 212 Chapter 22; 1-5 Review & Questions

Evidence that species change through time includes data on

(1) Earth's age and the fact of extinction (2) the resemblance of modern to fossil forms in the same area (3) transitional features in fossils (4) the presence of vestigial traits (5) change in contemporary populations.

Apply Darwin's four postulates to a population of mice living on sand dunes in coastal Florida.

(1) Fur color varies within mouse populations. (2) Fur color is heritable. (3) More mice are produced than can survive, and some produce many surviving offspring while others produce few or none. (4) Mice with certain heritable traits, such as the ability to avoid predators by blending in their environment (camouflage), survive and produce more offspring.

The consensus that species are related by common ancestry is supported by data

(1) the geographic proximity of closely related species (2) the existence of genetic, developmental, and structural homologies (3) the contemporary formation of new species from preexisting species

Alleles or traits that increase the reproductive success of an individual are said to increase the individual's fitness

A trait that leads to higher fitness, relative to individuals without the trait, is an adaptation. If a particular allele increases fitness and leads to adaptation, the allele will increase in frequency in the population

When a statistical test was used to compare the results for white models versus brown models, the P value (see BioSkills 3) was 0.01 for each habitat. Does this result increase or decrease your confidence in your take-home message? Explain.

Biologists consider a P value less than 0.05 to be statistically significant, that is, showing a real difference and not just sampling error. Since 0.01 < 0.05, you can be confident that the mice that were camouflaged were attacked less than those that were not.

How can evolutionary fitness be estimated?

Count the number of healthy, fertile offspring produced.

Compare and contrast how evolution by inheritance of acquired characters and the theory of evolution by natural selection would explain the observation of white mice living on light soil and brown mice living on dark soil.

Evolution by inheritance of acquired characteristics predicts that the mice in the different environments needed to change color, so they did so and then passed their traits on to their offspring. The theory of evolution by natural selection is not goal oriented. It predicts that white and brown mice are descendants of an ancestral population that varied in color. The white mice had higher fitness in the beach environment, where they were more likely to escape the notice of predators. Likewise, the brown mice had a higher fitness in the mainland environment.

Both examples demonstrate that evolution can be observed and measured

Evolution by natural selection has been confirmed by a wide variety of studies and is considered to be a central organizing principle of biology

Lamarck proposed a theory of evolution—that species are not static but change through time.

He proposed that evolution occurs by the inheritance of acquired characteristics.

Why don't the biggest and strongest individuals in a population always produce the most offspring?

In some environments, being big and strong lowers fitness.

Why does the presence of extinct forms and transitional features in the fossil record support the pattern component of the theory of evolution by natural selection?

It supports the hypothesis that species change over time.

Some biologists summarize evolution by natural selection with the phrase "mutation proposes, selection disposes." Mutation is a process that creates heritable variation. Explain what the phrase means.

Mutation produces new genetic variations, at random, with no forethought about which variations might prove adaptive in the future. Individuals with mutations that are disadvantageous won't produce many offspring, but individuals with beneficial mutations will produce many offspring. The beneficial mutations will thus increase in frequency through selection.

Evolution is not goal directed and does not lead to perfection

Mutations occur by chance, not because organisms "want" or "need" them to survive. There is no such thing as a higher or lower organism

The average height of humans in industrialized nations has increased steadily for the past 100 years. This trait has clearly changed over time. Most physicians and human geneticists hypothesize that the change is due to better nutrition and a reduced incidence of disease. Has human height evolved?

No, because changes in height due to nutrition and reduced incidence of disease are not heritable.

Natural selection acts on individuals, but evolutionary change occurs in populations

Nonheritable changes that occur in individuals due to acclimatization or acclimation are not adaptations and do not result in evolution

According to data presented in this chapter, which one of the following statements is correct?

Populations—not individuals—change when natural selection occurs.

The researchers placed white and brown mouse models both in abandoned fields, called oldfields, on the mainland (dark soil) and on sand dunes on the islands (light soil) and then measured the percentage of models that were attacked by predators. What is the take-home message of the data? Do the data support or reject the hypothesis that mouse color is adaptive?

The data show that mice that do not match the color of the soil are attacked more often than mice that do match. This supports the hypothesis that fur color is an adaptation in mice, because mice that avoid predators are more likely to survive and produce offspring.

The geneticist James Crow wrote that successful scientific theories have the following characteristics: (1) They explain otherwise puzzling observations (2) they provide connections between otherwise disparate observations (3) they make predictions that can be tested (4) they are heuristic, meaning that they open up new avenues of theory and experimentation. Crow added two other elements of scientific theories that he considered important on a personal, emotional level: (5) They should be elegant, in the sense of being simple and powerful (6) they should have an element of surprise. How well does the theory of evolution by natural selection fulfill these six criteria?

The theory of evolution fits the six criteria as follows. (1) and (2): It provides a common underlying mechanism responsible for puzzling observations such as homology, geographic proximity of similar species, the law of succession in the fossil record, vestigial traits, and extinctions. (3) and (4): It suggests new lines of research to test predictions about the outcome of changing environmental conditions in populations, about the presence of transitional forms in the fossil record, and so on. (5): It is a simple idea that explains the tremendous diversity of living and fossil organisms and why species continue to change today. (6): The realization that all organisms are related by common descent and that none are higher or lower than others was a surprise

A team lead by evolutionary biologist Hopi Hoekstra set out to test the hypothesis that predators are an agent of natural selection on mouse color. They made 250 plasticine models of mice that were alike in every way except that half were painted white and half were painted brown. Suggest one advantage and one disadvantage of using model mice instead of real mice in this experiment.

There are many possible answers. One advantage of models is that all the mice are exactly alike except for color, enabling the control of all variables except the one being studied. Models are also easier to work with than live mice. One disadvantage of using models is that they do not have the same smell and behaviors as real mice.

Darwin developed four postulates that outline the process of evolution by natural selection

These postulates can be summarized by the following statement: Heritable variation leads to differential reproductive success

Darwin and Wallace proposed that evolution occurs by natural selection.

This was the beginning of population thinking, whereby variation among individuals is the key to understanding evolution.

Explain why the overprescription of antibiotics by doctors, or the overuse of everyday soaps containing antibiotics, can be a health risk.

When antibiotics are overused, susceptible bacteria are constantly being killed off, even when an infection is not present. However, any individual bacteria that are resistant to these antibiotics will survive and multiply, reducing the likelihood that antibiotic treatment will be effective in the future.

What is an evolutionary adaptation?

a trait that improves the fitness of its bearer, compared with individuals without the trait

Not all traits are adaptive

and even adaptive traits are limited by fitness trade-offs and genetic, historical, and environmental constraints

True or false? Some traits are considered vestigial because they existed long ago.

false

Traits that are derived from a common ancestor, like the bones of human arms and bird wings, are said to be ______.

homologous

Evidence for evolution is internally consistent

meaning that data from several independent sources are mutually reinforcing

Selection by drugs on the TB bacterium and changes in the size and shape of finch beaks in the Galápagos as a result

of seed availability are well-studied examples of natural selection.

Plato, Aristotle, and several religious texts

present species as unchanging types. This view is called typological thinking.