Thursday, February 24, 2011

Blog #4

Blog # 4 Describe the three types of selection: directional, stabilizing and disruptive and give an example of each in your own words

  Direction is choosing one thing only. The trait favors one that it likes. So it is kind of like its personally choosing the trait

  Stabilizing -When selective pressures select against the two extremes of a trait, the population experiences stabilizing selection. For example, plant height might be acted on by stabilizing selection. A plant that is too short may not be able to compete with other plants for sunlight. However, extremely tall plants may be more susceptible to wind damage. Combined, these two selection pressures select to maintain plants of medium height. The number of plants of medium height will increase while the numbers of short and tall plants will decrease.

  Disruptive selection pressures act against individuals in the middle of the trait distribution. The result is a bimodal, or two-peaked, curve in which the two extremes of the curve create their own smaller curves. For example, imagine a plant of extremely variable height that is pollinated by three different pollinators, one that was attracted to short plants, another that preferred plants of medium height and a third that visited only the tallest plants. If the pollinator that preferred plants of medium height disappeared from an area, medium height plants would be selected against and the population would tend toward both short and tall, but not medium height plants. Such a population, in which multiple distinct forms or morphs exist is said to be polymorphic. 


Thursday, February 17, 2011

Blog 2

Blog # 2 Why is fossil record hard to interpret?

 With the fossils we have nowadays, it is still unsafe to call what happend to the reptile or mammal. With only a little trace, we could only think that much. Rocks have a little information of what happend millions of years ago. It is possible to guess the right information about the rock. But we would not be so sure even when we come to a conclusion.

Blog 3

Blog #3 Explain what microevolution is? What are the three ways that variation occurs?

Microevolution is a change in gene frequency within a population. This change is due to four different processes: mutation, selection, gene flow and genetic rift. For example, as the bird species live for many generations, evolution would start to take effects. The DNA is altered and it is some-what rare to have a  mutation. Basically, genes would cross thus creating something additional.

Thursday, February 3, 2011

Blog #1 semester 2

Why is evolution a theory and not a law?


  Many people beleive it is fake and many people beleive it is real, but theres no way to prove that evoloution is real. There has been many debate with religon as well. You see we dont have hardcore proof that we evoloutionized from monkeys or sea fish. So we will never no until something big happends.