Natural Selection and Patterns of Evolution Worksheet

Complete the worksheet writing 100- to 200-word short answers for each question. Format your references consistent with APA guidelines.

1. What is the direct evidence in support of the theory of natural selection? Include at least four examples. Paleontology shows us that organisms have changed gradually over time, as reflected in the fossil record. Biogeography shows us how new species only arise near very similar species. Similar species share a common time and place. Developmental biology shows us that an organism builds on ancestral features as it develops from a single cell. Genetics shows us that we can group species by similarity of genes.

2. Humans shape their environment in ways that other organisms cannot. Are humans subject to the same pressures of natural selection as other organisms? Why? Humans, just as all other organisms are subject to natural selection pressures. The fact is that over a period of time, unavoidable gene pool changes occur in all species. It is estimated that ever since humans branched away from chimpanzees, they have been experiencing 4.2 amino acid changing mutations on average per generation (Gould, S.J. 2002). Through a mechanism called genetic drift, gene frequencies change over a period of time, and it’s very occurrence is a phenomenon that cannot be denied. Random events cause an increase or decrease in a certain gene, occasionally resulting in gene fixation or extinction. Humans are subject to such accepted Biological phenomenon just as all other species. The ability of humans to impact their environment does not mean that they have a realistic sense of control over it, nor does it in any way prevent the occurrence of mutations in them, so the pressures of natural selection still apply to them in the varied environments that they live across the world.

3. Provide an example of convergent and divergent evolution, adaptive radiation, and co-evolution. Then, choose one of the examples you provided. What implications might this example have for future humans? Convergent evolution: Two different species adapt similarly when they share similar niches. Australia has several examples. Tasmanian tigers are very similar to wolves or dogs. The marsupial lion had many features similar to cats they even had a saber toothed version of a marsupial similar to saber toothed cats. Divergent evolution: When species separate into dissimilar niches, they evolve quite differently. The formation of limbs in early amphibians compared to their fish ancestors is an example.

Adaptive radiation: When a species spreads in to different niches it forms multiple species. A classic example is the Darwin’s finch. The common ancestor split into several species as it occupied the various niches. Coevolution is where two species evolved together. Many species of plants produce flowers that only bats can fertilize. The bats evolved to take advantage of the flowers and the flowers rewarded the bats with nectar and flowering at night. Coevolution of humans and cows: The cows allowed us to exploit land that wasn’t suitable to crops. They greatly increase our food supply. Perhaps in the future we will use them in many different ways. The way they convert cellulose to sugar in the guts with microbes could lead to the easy conversion of grass into alcohol to power our cars (Cook, H., & Bestman, H. D. (2000).

4. How does a new species evolve from a pre-existing species? Include a brief analysis of the factors affecting speciation. Separate groups of organisms belonging to the same species may adapt in different ways to better exploit diverse environments or resources. They also may evolve varied characteristics for attracting mates. That is, different groups evolve in different directions. Over time, these groups or populations may become so different that they can no longer breed together–separate species are formed. Factors can be mutations in the DNA of a certain group for instance also environment could be a big factor. For example when small populations of organisms become isolated in a new environment. This differs from allopatric speciation in that the isolated populations are numerically much smaller than the parental population.( Dobzhansky, T. G. 1982).

References

Dobzhansky, T. G. (1982). Genetics and the Origin of Species: Columbia University Press.

Gould, S. J. (2002). The Structure of Evolutionary Theory: Belknap Press.

Cook, H., & Bestman, H. D. (2000). A Persistent View: Lamarckian Thought in Early Evolutionary Theories and in Modern Biology. Perspectives on Science and Christian Faith, 52, 86-97.