Evolution Continued

1
Evolution Continued

• Chapter 16 pgs 392 415
• Chapter 17 pgs 416 - 445

2
Variation Gene Pools

• Gene Pool- consists of all genes, including all
  the different alleles, present in a population
• Allele- One of a number of different forms of a
  gene
• Relative Frequency- The number of times that the
  allele occurs in a gene pool
• Has nothing to do with the gene being dominant or
  recessive
• Example Mice being black or brown
• Evolution- any change in the relative frequency
  of alleles in a population

3
Genetic Variation

• Recall- Genetics is a game of chance
• Certain Individuals in Small populations pass on
  particular alleles
• Overtime this can cause alleles to appear
  frequent

4
Sources of Genetic Variation

• Mutations -Any change in a sequence of DNA
• Either by mistake in replication OR
  radiation/chemical
• Gene Shuffling- The different combination that
  occur when two organisms mate
• You look like a combination of both parents
• Many different combinations

5
Natural Selection

• Natural selection on single-gene traits can lead
  to changes in allele frequencies and thus
  evolution
• Single-gene trait- A single gene that has two
  alleles (example Different species colors)
• Mice that stand out get eaten faster
• Therefore, Less Likely to survive to reproduce

6
Natural Selection Continued

• Polygenic Traits- Traits controlled by two or
  more genes (example height)
• Directional Selection- Characteristics of one
  species is favored Example Beak Size
• Larger VS Smaller (Food Shortage)
• Stabilizing Selection- Human baby birth weight
• Smaller babies less healthy
• Larger birth problems

7
Testing Natural Selection in Nature

• Variation
• When same species has different anatomical
  features
• Color, size, beaks, total mass
• Example Finches
• Natural Selection
• Rainy Season VS Dry Season
• Rainy Numerous Sources of Food
• Dry Depleted/Scare sources
• These differences create Natural Selection
• Rapid Evolution
• Once differences occur, species can change
  features relatively quickly (Each breeding season
  beaks get bigger

8
Genetic Drift

• In small populations alleles can become more or
  less common
• Controlled by probability
• Occurs when a random change of traits occur over
  time
• Such as animals colonizing a new habitat

9
Genetic Equilibrium

• Hardy-Weinberg Principle
• Allele frequencies stay constant unless one or
  more factors cause frequencies to change
• 5 required conditions
• Random mating
• Very large population
• No immigration/emigration
• No mutations
• No natural selection

10
Process of Speciation

• Isolating mechanisms
• As new species evolve, populations become
  isolated
• Behavioral Isolation
• 2 species capable of mating, but different
  courtship
• Example Different mating songs in birds
• Geographic Isolation
• 2 populations separated by geographic barriers
• Example Squirrels around Grand Canyon
• One side has gray other is black
• Temporal Isolation
• Two or more species breed at different times
• Example Plants releasing pollen on different
  days

11
Ch. 17 History of Life

• Paleontologists
• Scientists who study fossils
• Fossil Record
• Grouping of organisms based on characteristics
• Provides evidence about the history of life on
  Earth
• Shows how different groups have changed over time
• Extinction
• When species die out
• More than 99 of all species are already extinct

12
Patterns of Evolution

• Adaptive Radiation
• Process where species evolve into new and divers
  forms and create new species
• Darwins finches!
• Convergent Evolution
• Occurs when two entirely different, unrelated
  species, develop similar characteristics
• Examples fish, dolphins, sea lions penguins

13
Patterns of Evolution Cont.

• Coevolution
• A process where two species who interact with
  each other evolve together
• Example Flowers Pollinators (bees)
• Punctuated Equilibrium
• Scientists use this to describe patterns of long
  stable periods interrupted by periods of rapid
  change in the fossil record
• Finches moving from island to island
• Trying to fill available niches