Biology help please?

Question

1. How does geographic reproduction affect speciation?

2. How does the fossil evidence support evolutionary theory?

3. How does infection (?) protect an individual from infectious disease? (It doesn't seem to make sense to me how an infection can protect someone from infectious diseases. Unless it was meant to say 'vaccination')

4. Why may an individual with a compromised immune system be unable to fight off and survive infections by microorganisms that are usually benign?

Help is appreciated.

Answer 1

1. Geographic "isolation" may lead to speciation because populations that are separated geographically do not interbreed and share any differences that arise. If the differences accumulate over time, the populations may become so different that they cannot interbreed any more. At this point, the populations have become different species.

2. Fossil evidence shows changes in organisms over time -- that's evolution.

3. Infection causes the body to assemble defenses against that infectious agent. The person won't be susceptible to that disease in the future.

4. A compromised immune system will not respond effectively against infectious agents. So infections that would usually be fought by someone's intact immune system can cause serious illness in someone with a compromised immune system.

Answer 2

1. Geographic reproduction affects the formation of species if isolated subgroups reproduce only with themselves. For example, if a species of birds is present across a large land mass and also an island. The birds on the island are more likely to breed with the other birds on the island. This isolation can cause the random mutations that accrue to amplify. Eventually this may cause an entirely new species to form.

2. Fossils show that change occur ed over time. This is weak because the fossil record actually seems to show "stepped" evolution, NOT gradual evolution, however.

3. Infection causes an individuals immune system to be on alert and to strengthen. It also makes the individual produce antibodies to the specific ethological agent that infected it, so it becomes immune. (how often can you get chicken Pox?)

4. A person having AIDS can easily die from infections that would ordinarily not kill a healthy person because the immune system, the body's defense, has been directly attacked. This is like a nation trying to defend itself without its soldiers.