*III. The Red Queen Effect- "The Evolutionary Arms Race"
          Predators and prey, competitors and the Environment are constantly driving the evolution of its/their "partners". Perfection is impossible.
IV. Adaptations are Compromises- most adaptations will be good and bad. Giraffes neck, seals (bad on land, good in water), etc.
V. Genetic Limitations- DNA can only take a population so far. It can only use the alleles that are present now.
VI. 99% Extinction
VII. Not all evolution is adaptive- 5 forces
      Only Natural Selection is adaptive
     

Does evolution always make a population better? Can it ever acheive perfection?

Does evolution always make a population better? Can it ever achieve perfection?

NO! Evidence:

• Sexual Selection - Finding and attracting a mate takes precedence over their survival. For example: Peacocks,  Elk
• Fecundity>Longevity -Passing down genes has more effect on evolution than living a long life. For example: Salmon. Born in a sterile environment then move and become "eating machines". They produce enough fat to travel back to where they were born. When traveling back upstream they stop eating because they HAVE to die for their species. Their bodies produce nutrients for the food that the babies can live on for a short period of time.

IV. Gene Flow- Migration
     A. Immigration- movement into a population (adds alleles)
     B. Emigration- movement out of a population (subtracts alleles)
V. Non-Random Mating
     A. Inbreeding- tendency to mate with an individual more closely related. Increases p^2 and q^2 (AA&aa) and decreases 2pq (Aa)
     B. Outbreeding- tendency to mate with an individual less closely related.
     C. Assortative Mating- tendency to mate with one's own morph."look" >q^2 <p^2+2pq

      

5 Forces Continued

II Mutation- point mutations will add "new" alleles to a population. Insignificant in the short term. The #1 most important in the long term.
III. Natural Selection- an allele, or genotype, is favored by the environment.
    3 basic types:
               A. Directional- when one "extreme" is forced over the other. Example: a giraffes neck
               B. Stability - the average is favored over extremes. Example: deer population: bucks with big         antlers are killed in hunting season and small bucks don't breed, so the antler size left are the middle size. this is BAD. Humans are predators
               C. Disruptive: when the average is selected out of the population: GOOD. also known as frequency dependent selection: individual with the more common traits are selected out of the population. Example: Trout eat the flies that are most common. Animal are predators

5 Forces that Disrupt the H/W Equilibrium:

-Remember, a population will remain unchanged unless an outside force acts on them.

Tongue rolling

 -2003
TR = .75 A_
NTR = .25 aa

-2013
TR = .80 A_
NTR = .20 aa

What force changed this? Was it just chance?

I. Genetic Drift - allele/gene frequencies change by chance in a population.
This is more likely to happen in a SMALL population. There are 2 events
that will promote genetic drift:
A. The Founder Effect - when a small number of individuals migrate away and become genetically isolated. A small amount of individuals have many descendants. ex. Amish
B. Population  Bottleneck - when a large population is reduced down to very small size. ex. Blackfooted ferret, cheetah
  

How is genetic variation preserved and potentially even promoted in a population?

I. Diploidy - For every gene there are (at least) two copies because almost every species on the earth currently is sexually reproducing. What does this do for us?
     A. Allows recessives to exist. (Example: white skin. Dark skin is very common among people along the equator. This prevents skin cancer from the sun but when our ancestors moved out of Africa, we developed light skin because we didn't have to worry about skin cancer as much and light skin allows us to absorb the sun and make our own Vitamin D.)
     B. Allows codominance. (Example: African people want to be heterozygous for Sickle Cell Anemia because the recessive protects against Malaria. This could not happen without Diploidy.)

II. Meiosis
     A. Crossing Over - It is the number 1 factor for genetic variation in gametes.
     B. Independent Assortment - the number 2 factor for genetic variation - two chromosomes separating do not affect each other (flipping two coins). This exponentially magnifies the variation from crossing over.

III. Sexual Reproduction
     A. Two parents' genetic info is randomly passed to offspring. (You are not the same as your siblings.)
     B. Mechanisms that promote outbreeding. (the opposite of inbreeding - we think marrying our cousins is gross and flowering plants promote outbreeding because they attract pollenators.)

IV. Clines - Happens when a population's genetics change from one side of its range to another.

V. Ecotype - genetic variation types of the same species because they live in different ecosystems.

II. Darwin's Theory
A. All populations are genetically variable.  "New" variations can suddenly appear within a population.  These variations can be passed to the offspring.
B. (Thomas Malthus)  All populations will eventually reach a size where "more offspring are born, than can survive to breeding age."
C. A competition will occur between individuals for limited resources.
D. The environment selects those individuals best adapted to survive and pass on their genes. Natural Selection.