Question

1. Describe how new alleles show up in a population.

2. Describe the difference between the term ‘theory’ when it is used in everyday language, and how it is used in scientific context.

3. Explain why mutations do not happen in response to changes in the environment.

4. Traits are not ‘magically’ given to organisms. Explain how the genetic variability in the population can result in a given trait becoming common in that population.

5. Fitness is a difficult concept to grasp when it is used in the context of evolutionary processes. Describe some of the common meanings of the word ‘fitness’ in everyday language and what the term ‘fitness’ means in a biological context.

Answer 1

1.New alleles can be introduced in a population by gene flow, which occurs during breeding between two populations that carry unique alleles.

Genetic variation is caused by:

• mutation
• random mating between organisms
• random fertilization
• crossing over (or recombination) between chromatids of homologous chromosomes during meiosis

Mutations are the ultimate source of variation. Mutation is a sudden and heritable change in an organism. A mutation may produce new allele not present in the population or may change the frequency of existing alleles.

2. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena. If enough evidence accumulates to support a hypothesis, it moves to the next step — known as a theory — in the scientific method and becomes accepted as a valid explanation of a phenomenon.

3. Mutations can occur by the environmental factors. Mutations are genetic changes in an organism. Mutations can occur spontaneously or be induced by environmental factors. Environmental factors that induce mutations are called mutagens. Even though outside factors can cause mutation to occur, what kind of genetic change will occur is random. Genotype-environment interactions - mutations are unconditionally deleterious across alternative environments because they impair an essential function of the organism.

4. Genetic diversity serves as a way for populations to adapt to changing environments. With more variation, it is more likely that some individuals in a population will possess variations of alleles that are suited for the environment. Those individuals are more likely to survive to produce offspring bearing that allele. Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).