Introduction to Evolution by Natural Selection

Question 1

What is evolution?

Answer 1

The change in genetic (allelic) frequency within a population over time.

Question 2

What is Natural Selection?

Answer 2

The mechanism for which evolution occurs. Individuals in a population posses traits that are selected for or against. Something in the environment is the selecting agent.

Question 3

What is the importance of variation in natural selection?

Answer 3

Without any variation, there wouldn’t be any traits to select for or against. Thus, future generations would be no different than the current generations.

Variation in a population is needed for natural selection to occur.

Question 4

What is the importance of heritability in natural selection?

Answer 4

If heritable traits weren’t present, what would be the point of the parents surviving certain selective pressures if the offspring cannot inherit the genes that coded for the traits that allowed the parent survive those selective pressures?

Without heritability, natural selection cannot occur and thus Evolution wouldn’t happen.

Question 5

How is differential reproduction important?

Answer 5

Individuals possessing a certain genetic trait will be able to survive longer and produce more breeding offspring, compared to individuals without that certain trait. Thus, the individuals with the trait will pass down more of their genes to the next generation than those without the trait.

Question 6

How is differential survival important?

Answer 6

There needs to be differences in survival up until the reproductive age. Individuals that are able to survive longer (due to the presence of genetic traits that are selected for in the environment), and live up to the reproductive age, will produce more offspring and have a greater chance at passing down favored traits.

Question 7

What is fitness?

Answer 7

The number of viable offspring an individual produced in their lifetime.

Question 8

Explain how a sinus infection and subsequent treatment of it is an example of the theory of evolution by natural selection.

Answer 8

1. There is a population of harmful bacteria in your nasal cavity. Among this population of bacteria is variation in the ability to resist antibiotics.
2. Once the antibiotic is administered, the weakest, least resistant bacteria will die off, while the more resistant bacteria remain. The more resistant bacteria that survived will then be able to reproduce and pass down genes that code for higher levels of antibiotic resistance. There will now be a more resistant population of bacteria in the nasal cavity.
3. If the antibiotic is continued, more of it will be circulating in the body, killing off the slightly more resistant bacteria. However, because of the variation in the new generation of bacteria. There will be individuals that are even more resistant to antibiotics. Those extremely resistant individuals will be able to pass down the genes that code for extreme resistance. But, the population of those resistant bacteria will dwindle over time if the antibiotic is continued.
4. If the antibiotic is stopped before all of the bacteria are properly killed off, then the small population of extremely resistant bacteria will reproduce and pass down those extremely resistant genes to the next generation – resulting in an even more resistant and painful sinus infection.

Question 9

What is an adaptation?

Answer 9

1. A heritable trait that increases the relative fitness of individuals with that trait.
2. A process by which individuals within a population acquire a trait increase their relative fitness.

Question 10

What is genetic homology?

Answer 10

Similar gene sequences between individuals of different species.

Question 11

What is developmental homology?

Answer 11

Similarities in morphology of embryos of different species.

Question 12

What is structural homology?

Answer 12

Similarities in the structure of body parts in different species.

Question 13

How do homologies prove the validity of evolutionary theory?

Answer 13

Homologies prove that many organisms share similar characteristics. Even if the function of those characteristics is slightly different, it is proof that all organisms descended from a common ancestor.

Question 14

How does the Fossil Record prove that evolution occurred?

Answer 14

The fossil record proves that not all species lived together all at the same time, and that extinction of species must have occurred. The fossil record also proves the existence of Transitional Forms, where there is an intermediate state between the current species and the ancestor, which proves that evolution did occur.

Question 15

What are vestigial structures?

Answer 15

Commonly found structures in organisms that serve little-to-no purpose.

Question 16

How do vestigial structures validate evolutionary theory?

Answer 16

It proves that all animals evolved to suit different selective pressures but that they all came from a common ancestor.

Question 17

Explain the misconception that humans evolved from apes.

Answer 17

Humans didn’t evolve from apes. Humans and apes shared a common ancestor at some point. But that common ancestor gave rise to two different lineages.

Question 18

How is variation related to differential survivorship and reproduction?

Answer 18

Variation is the cause of differential survivorship and reproduction. Without variation, there wouldn’t be any differences between individuals in the population, thus they would most likely survive around the same amount of time and reproduce at a similar rate.

Question 19

What is convergent evolution?

Answer 19

Organisms that aren’t related evolve similar features/traits in response to similar selective pressures.

Question 20

Does convergent evolution result in homology?

Answer 20

No, convergent evolution means that the species aren’t closely related. It only deals with responses to selective pressures, not lineage from a common ancestor.