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Name _______________________ Stream__________
Evolution Mid-unit Test
Open book over the weekend of 12/12-12-13

Using complete sentences compose a complete answer to the following. You may type and print your answers or handwrite on 8.5 by 11 lined paper. Staple this question to your answer sheets. All questions are to be answered.

1. Describe the process of natural selection and how it can lead to the formation of new species

Genetic variation produces differences among the members of a population that are acted upon by natural selection. If two segments of the population are separated in areas that have different environments, and thus different selection pressures, the segments will evolve differently. If the two segments are isolated from each other so that they cannot reproduce3 with one another, then the differences between them will become greater over time. Eventually, the two groups will be different species.

2. Explain how the hypotheses of gradualism and punctuated equilibrium differ

Both gradualism and punctuated equilibrium address the question of how fast does evolution occur? The theory of gradualism proposes that evolution occurs slowly but steadily. According to this theory, tiny changes in a species gradually add up to major changes over very long periods of time. This is how Darwin thought evolution occurred. Stephen Jay Gould and Niles Eldridge developed the theory of punctuated equilibrium, species evolve during short periods of rapid change which are separated by long periods of little or no change. These rapid changes come about because of isolation and new environments. They proposed this theory because of the incomplete fossil records of most species.; often .showing no intermediate forms. Rather then thinking these were missing (yet to be discovered) rapid change would not have any developed.

3. Someone tells you not to worry about air pollution because through natural selection the human species will evolve lungs that can detoxify pollutants. How as a scientist would you reply?

There are a number of issues here. First, the idea presented sounds like Lamarck’s ideas of acquired characteristics…if we need it then we will get it and pass it onto our offspring. It doesn’t work this way. Secondly, given that it is not the above it shows a major misconception of Darwin’s theory of Natural Selection. Only if there is a species variant in some individuals that is resistant to and detoxifies the pollutants AND if those that have this resistance mate AND if it is a genetic trait than it might be possible.. however, the majority of humans would suffer from such pollution and many would die before generations of naturally resistant would evolve. Thirdly, air pollution affects more than just humans…many (even most) other species on our Earth are damaged in some way because of pollution. We are interdependent upon these other species.

4. If an entire population of breeding animals ... such as all chickens in a flock … have no natural variations, will artificial selection produce evolution? Why or why not?

No; to result in evolution , selection must have natural variation on which to operate.

5. What is meant by the term common descent? Explain how data from: 1) fossil record 2) comparative anatomy 3) biochemical studies 4) study of homologous structures support the concept of common descent

The term common descent references the idea that we are all descended from a common ancestor. Fossil evidence supports this because the past traces of organisms show close similarities. Often the layers of sedimentary rock where fossils are found show the sequence of changes made over geologic time. Homologous structures are those that are similar among different species and can be linked to a common ancestor. This is part of the comparative anatomy evidence that points towards a common ancestor.(human, bat, whale, cat, horse, and human forlimbs are examples) Comparative anatomy can also be thought of as comparing the different stages of embryonic development among different species and seeing very common characteristics. Also as a part of comparative anatomy are vestigial structures, those structures that are fully developed and useful in one organism but reduced or not functioning in another (this latter one is called vestigial). Examples are skeletal leg bones in some snakes, showing they had ancestors that did have legs. The biochemical evidence is very strong. Almost all living things use the same basic biochemical molecules..DNA, ATP and amino acids.

6. What is meant by the inheritance of acquired characteristics, a hypothesis that Lamarck used to explain adaptation to the environment?

To explain the process of adaptation to the environment, Lamarck supported the idea of inheritance of acquired characteristics…that the environment can bring about inherited change (the environment can influence those traits that are inheritable. He believed that the increasing complexity of organisms over time was the result of a natural force that was inherent in all living things. This force was a desire for perfection. The prime example is the long neck of the giraffe.

7. Explain how the finches and tortoises that Charles Darwin observed on the Galápagos Islands influenced his thinking.

The islands were characterized by a great diversity of species that had developed different adaptations. Darwin began to think that the varied finch and tortoise species on the islands had evolved from a single finch and single tortoise species from the mainland.

8. Assume that a geographic barrier that results in two very different ecosystems splits a single population. What would likely happen to the two separate populations? Would this process occur more quickly, les quickly, or at the same rate as it would if the two populations lived in similar ecosystems?

The two populations would become different species. Speciation would tend to occur more quickly in two groups in different ecosystems than in similar ecosystems because in different ecosystems, the groups would experience different selection pressures. Those selection pressures would drive the evolution of the two populations in different directions, speeding up the process of speciation.

9. How would you respond to someone who says that he or she doesn’t believe in evolution because it is :just a theory”

I would begin by explaining that science is not a matter of belief it is a matter of evidence to support the ideas that have been developed to explain the world. Theory, as used in science, is as close to fact as science will come given its nature. The word theory is not used in science in a casual way as it is in everyday speech. A statement that is elevated to a theory in science has an abundance of facts to support it..facts that anyone can look at and see. I would also suggest the idea of gravity is a scientific theory. ..I would think here there would be acceptance.

10. Compare and contrast artificial selection and natural selection.

Natural selection is caused by factors in the environment such as light, water, food supply, space, climate, predators, competitors, and parasites, and is undirected. The organisms that are best suited for the environment survive, reproduce, and pass their traits, including those adaptations that improve survival, to their offspring. Artificial selection occurs when humans breed individual animals and plants that have certain desired characteristics, with the goal of obtaining offspring that have these desired characteristics. The traits that are selected may be ones that do not improve a plant’s or animal’s survival in the natural environment.

11. Compare and contrast relative dating and absolute dating.

Fossils found in the layers of sedimentary rocks can be related to the ages of the layers. Because this method only determines if one fossil is younger or older than another, it is called relative dating. Very precise methods that can determine the age of fossils more accurately are. absolute dating. These techniques depend on radioactive isotopes of elements that release energy at a uniform rate and change into a different element. Over time, the ratio of the two elements changes; by measuring the amount of each element in a sample, the length of time since the fossil was formed can be calculated. These methods can date fossils and rocks that formed many millions of years ago.

12. What is a mass extinction? If mass extinctions occur naturally, why is there so much concern about the mass extinction currently in progress?

A mass extinction is the dying out of a large percentage of Earth’s organisms in a short period of time. The mass extinction that is probably going on now is of concern because it is occurring at a fast rate (large numbers of species in a relatively short time), and it is not the product of a natural disaster, such as an asteroid striking Earth, but of human activities.

Last updated  2010/07/14 16:37:31 EDTHits  906