EVOLUTION & SPECIATION

VOCABULARY REVIEW• EVOLUTION – CHANGE OVER TIME

• NATURAL SELECTION INDIVIDUALS BETTER ADAPTED TO THE ENVIRONMENT ARE ABLE TO SURVIVE & REPRODUCE– A.K.A. “SURVIVAL OF THE FITTEST”

NEW VOCABULARY

• POPULATION GROUP OF INDIVIDUALS OF SAME SPECIES THAT INTERBREED

• GENE POOL COMMON GROUP OF ALL GENES PRESENT IN A POPULATION

Gene PoolCombined

genetic information of all members

Allele frequency is # of times alleles occur

Variation in Populations2 processes

can lead to this:

Mutations -change in DNA sequence

Gene Shuffling –

from sexual reproduction

•Genetic Drift = changes to allele frequency as a result of chance

•Bottleneck effect = dramatic reduction in population size usually resulting in significant genetic drift

Genetic Drift changes populations…….• Random change in allele

frequency causes an allele to become common

• Founder Effect: - Genetic Drift that occurs when individuals from a large population leave to establish a new population

- Allele frequencies of the new population will not be the same as those of the original

• Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)

• Nonrandom mating: inbreeding and assortive mating (both shift frequencies of different genotypes)

• Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment

Sexual selection• Sexual

dimorphism: secondary sex characteristic distinction

• Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism

Evolution of Populations

Occurs when there is a change in relative frequency of alleles

Generation 1: 1.00 not resistant0.00 resistant

Resistance to antibacterial soap

How natural selection works

Resistance to antibacterial soapGeneration 1: 1.00 not resistant

0.00 resistant

How natural selection works

Resistance to antibacterial soap

mutation!

Generation 1: 1.00 not resistant0.00 resistant

Generation 2: 0.96 not resistant0.04 resistant

How natural selection works

Resistance to antibacterial soapGeneration 1: 1.00 not resistant

0.00 resistant

Generation 2: 0.96 not resistant0.04 resistant

Generation 3: 0.76 not resistant0.24 resistant

How natural selection works

Resistance to antibacterial soapGeneration 1: 1.00 not resistant

0.00 resistant

Generation 2: 0.96 not resistant0.04 resistant

Generation 3: 0.76 not resistant0.24 resistant

Generation 4: 0.12 not resistant0.88 resistant

How natural selection works

Natural Selection on Polygenic Traits

• Shifts to middle range

• Shifts to 2 extremes

• Shifts to 1 extreme

SPECIATION• THE FORMATION OF NEW

SPECIES

• AS NEW SPECIES EVOLVE, POPULATIONS BECOME REPRODUCTIVELY ISOLATED

• REPRODUCTIVE ISOLATION – MEMEBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.

These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.

SPECIATION IN DARWIN’S

FINCHES• SPECIATION IN THE GALAPAGOS

FINCHES OCCURRED BY:

- FOUNDING OF A NEW POPULATION,

- GEOGRAPHIC ISOLATION which led to -- REPRODUCTIVE ISOLATION and

CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.

Evidence of Evolution1. Fossil Record

2. Geographic Distribution of Living Species

3. Homologous Body structures

4. Similarities in Embryology

Evidence of Evolution

Fossil Record provides evidence that living things have evolved

Fossils show the history of life on earth and how different groups of organisms have changed over time