Question

Please answer the following questions! 1) Define the four forces of evolution, making sure to highlight how they lead to change in a population. 2) Do you think sexual selection should be considered a fifth force of evolution? Why or why not. 3) Define cline and describe one example of a cline (this can be from the course material, or from outside sources, Explain how the trait is distributed and how it relates to the environment. 4) You have just discovered a new population of extant (currently living) giraffes! What kind of information would you need to determine whether or not they are a new species as defined by the 1) biological species concept, 2) ecological species concept, and 3) morphological species concept? Now pretend they are fossil giraffes. What are some of the complications surrounding the definition of a paleo-species?

Answer 1

There are four forces of evolution: mutation, gene flow, genetic drift, and natural selection.

1) Mutation: is a random heritable change in a gene or chromosome, resulting from additions, deletions, or substitutions of nitrogen bases in the DNA sequence. Mutations create variations in gene pool of a population which accumulate over time giving rise to evolution of traits.

2)Gene flow: Gene flow, also called gene migration is the introduction of genetic material (by interbreeding) from one population of a species to another. If the rate of migration is high, this can have a significant effect on allele frequencies of the population.

3)Genetic drift : is a mechanism of evolution in which allele frequencies of a population change over generations due to chance .Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations.Genetic drift may result in the loss of some alleles (including beneficial ones) and the fixation, or rise to 100%, percent frequency, of other alleles.

4) Natural selection :is the process by which some organisms have a greater chance of surviving and reproducing than others due to features that are better adapted to the environment. As a result, those advantageous features are passed on at a higher frequency than less advantageous traits. Natural selection can cause change in allele frequencies, with fitness-increasing alleles becoming more common in the population.Natural selection can fix or eliminate genetic traits in a population, thereby changing the genetic makeup over time.