Evolution

Charles Darwin

Natural Selection (survival of the fittest)

Theory of Natural Selection:

1. Genetic Variation exists in members of a population

2. More offspring are born than survive & reproduce

3. Competition exists basic needs

Individuals with adaptive characteristics…

Survive longer & reproduce more than those with less favorable traits

Fitness

How much one contributes to the next generation (more offspring = higher fitness)

Directional Selection

one trait is favored

Stabilizing Selection

Average is best, extremes are selected against: Heterozygous advantage

Disruptive Selection

Both extremes favored, average is worst. Can lead to new species being formed

Divergent Evolution

When on species splits into 2 or more

Artificial Selection

When humans purposely breed organisms to enchanted or remove certain traits

The Fossil Record

Studying relationships between organisms b age, location, and anatomy of fossils

Fossil Dating

Radioactive isotopes decaying at half-life’s (rate), look at the ration of radioactive isotope to product to get the age of the fossil

Index Fossils

Deeper = Older

Comparative Anatomy

Studying similarities in the organism’s structures

Homologous Structures

Similar structures in different animals that arise from a common ancestor

Vestigial Structures

No longer used

Analogous Structures

Similar in function but not evolutionarily related

Convergent Evolution

Similar environmental pressures leading to similar characteristics

Comparative Embryology

Study development of organisms before birth

Comparative Biochemistry

Studying DNA/Amino Acid sequences in different organisms

Harry-Weinberg Law

The alleles in a population make up the “gene pool” of the population. Gene pools described by their gene frequencies

P =

Frequency of dominant allele (how many B are total alleles)

Q =

Frequency of recessive allele (how many b there are)

Formula for Hardy Weinberg Law

P + q = 1

P² =

Frequency of homozygous dominant

2pq =

Frequency of heterozygous

Q² =

Frequency of homozygous recessive

Five Factors that maintain Hardy-Weinberg

1. No mutations

2. No gene flow

3. No random mating

4. No natural selection

5. Large population size

Genetic Driftt

A random process that occurs in small populations

The Founder Effect

Rare alleles have a higher frequency in small pops if a founder carried a rare trait

The Bottleneck Effect

If a disaster occurs, chance determines individuals survival and resulting pop is due to chance not selection

What must two organisms be able to do in order to be declared the same species?

Have fertile offspring.

Prezygotic Isolation

Zygote can’t form.

Geographical Isolation

No contact

Temporal Isolation

Different mating times

Behavioral Isolation

Different courtship rituals

Mechanical Isolation

Can’t physically move to one another

Gametic Isolation

Zygote won’t form

Prezygotic Isolation

Zygote forms but problems arise later

Allopatric speciation

Changes occur while a species is seperated

speciation

Development of a new species

Sympatric Speciation

Change occurs due to mutation while species is still together

Adaptive Radiation

a single species scatters in an area with variety of resources and no competition (EX. Darwin’s finches)

Gradualism

Darwin’s belief change occurs slowly

Punctuated Equilibrium

Species remain the same for a long time and change suddenly

Allometric Growth

Difference in rates of growth of body parts

Homeotic Genes

Genes that make proteins that activate other genes