Change & Survive!

Natural selection chapter 22

Natural selection is how species interact with their environment. Those who are successful in their survival and reproduce, pass their genes to future offspring. The theory of natural selection explains how evolution of species occurs.The theory of its action was first fully expounded by Charles Darwin, and it is now regarded as the main process that brings about evolution of species.

There are three kinds of selection:

Directional- one extreme phenotype favored
Disruptive- both extreme phenotypes favored
Stabilizing- the intermediate phenotype favored

In this picture it shows how the brown beetles learned to adapt to their environment and survive. Whereas the green beetles stood out and got wiped out by the birds.

Speciation-chapter 23

In this chapter we learned to apply principle (the hardy Weinberg law) to quantify the changes that occur to populations undergoing small changes at the genetic level. These small changes result in subspecies to new species overtime. We refer to this as microevolution.

Key note:

1) Variation in a

population

2) enviornment "selects" those best fit for survival (adapted)

3)sexual reproduction is essential to ensurethe species overall servival

Types of Evolution:

1) Divergent Evolution

2) Convergent Evolution

Fun Fact:

Wilhelm Weinberg work on the hardy- weinberg principle went unrecongizefor 35 years.

Hybrid Species

The Hardy Weinberg Formula

The hardy Weinberg theory states that the allele frequencies will remain constant generation after generation if five conditions do not occur. All the dominant alleles are assign the letter p and the recessive alleles are assign the letter q. All the alleles for the single gene of interest will total 100% or 1.00 of the population.

There are five conditions that can cause small changes in populations are:

•Mutations- are rare but do introduce new alleles into a population contributing to diversity

•Sexual selection- organism select mates based on certain traits, phenotypes, and behaviors

•Migration- populations are not isolated all the time. Members leave and new enter populations

•Natural selection- some organisms are best suited to environments, these survive and reproduce

•Small population- sometimes these emerge reducing genetic variation and diversity

What does the following formula tell you?

p2+2pq+q2=100% or 1.00

Provides the genotypic frequency for a population

P2 represents the homozygous dominant genotype

Q2 represents the homozygous recessive genotype

2pq represents the heterozygous(carrier)

Q alone is the recessive allele (ovaries/meiosis)