AP BIO UNIT 12

Microevolution

Small allele frequency changes in 1 population

When does microevolution occur

When variation is present

Ways to measure Genetic variation

average hetrozygosity- % herto loci

Nucleotide diversity- compare DNA sequences

Microevolution mutations

point mutations

chromosomal alterations (change in # of chromosomes)

Create new genes (translocation)

sequence of genes changes (inversions)

Duplications

Hardy weinberg eq

p- frequency of 1 allele

q- frequency of 1 allele

p+q=1

p²- P of individual with p trait

q²- P of individual with q trait

2pq- P of heterozygosity

5 conditions for HW EQ

No mutations

Random mating

No natural selection

No genetic drift (large pop size)

No gene flow (no migration)

Natural selection

differential success in survival and reproduction due to differing traits

Genetic drift

Change event that change allele frequencies

Alters small pops

Founder effect

few individuals become isolated and repopulate with a new allele distribution- bottleneck effect

less genetic variation

Gene flow

movement of genes in and out of pop- nearby pops can become more similar

Relative fitness

measure of genetic contribution to gene pool

Directional selection

1 extreme

Disruptive selection

both extremes

stabilizing selection

averaging phenotype - less variation

Intrasexual selection

same sex compete with each other

Intersexual selection

Females choose males or other way around

Sexual dimorphism

each gender has different traits

Diploidy

genetic variation hidden from selection by heterozygosity

Balancing selection

Maintains 2 morphs in pop through hetero advantage

Frequency dependent selection

when phenotype becomes too abundant, it becomes unfavorable

Neutral variation

nucleotide differences don’t affect much

Evolution

descendants of ancestral species have big changes

Struggle for existence

Results from overproduction where individuals have to compete to survive.

Transitional fossil

fossil that occurs between 2 important end stages of evolution

Homology

similarity from common ancestors

Vestigial Structures

remnants from ancestors

Convergent evolution

no common ancestors but similar features

Analogous structures

results from convergent evolution. no common ancestors

Endemic species

only found in one place on earth

Ways to track shared homology

shared DNA/proteins

Similar molecular homology- similar ATP production systems

Molecular clocks and evolutionary relationships- differences in DNA sequence

Speciation

Formation of new species caused by diversity

Macroevolution

Creation of a new species

Species

can interbreed and produce viable, fertile offspring

Reproductive isolation

factors that allow for speciation

Habitat isolation

Prezygotic barrier, occupy different areas

Temporal isolation

Prezygotic barrier, breed at different times

Behavioral isolation

Prezygotic barrier, different courtship rituals

Mechanical barriers

Prezygotic barrier, parts don’t fit

Gametic isolation

Prezygotic barrier, sperm can’t fertilize eggs

Postzygotic barriers

Reduced hybrid vitality, die easily

Why might a hybrid not be able to live well?

Parents have different chromosome number

Too many recessive alleles in both parents

Limitations of Species concept

Doesn’t apply to:

fossils (too old)

Asexual organisms (self reproduce)

can’t apply when gene flow is present

Morphological Species concept

body shape distinguishes

Ecological Species Concept

Defined by niche

Phylogenetic Species Concept

defined by smallest group that shares common ancestor

Allopathic speciation

Gene flow interrupted by geographic isolation

Sympatric Speciation

speciation that occurs when pops live in similar areas

Mechanisms of sympatric speciation

polyploidy- errors in cell division, extra chromosomes

sexual selection- only breed with certain colors/shapes

habitat differentiation- live in slightly different habitats, use different resources

Allopolyploidy

2 species have different number of chromosomes- causes problems

Autopolyploidy

1 species has a problem with chromosome duplication- causes problems

How to determine fossil age

Relative age- based on position in rock

Absolute age- based on radioactive dating

Mass extinction

5 have occurred

over 50% of species must be wiped out

Divergent Evolution

Common ancestor, related but became very different in appearance

Adaptive radiation

group of organisms forms many new species to fill niche

King philip came over for green soup

Kingdom phylum class order family genus species

Kingdoms of life

Plantae animalia fungi protista eubacteria archaebacteria

Domains of life

Bacteria Eukarya Archaea

Species epithet

similar sounding scientific name doesn’t = similar species

Systematics

classifying organisms based on phylogeny- cladogram

Clade vs taxon

clade- ancestor +all descendants

taxon- group of organisms/individuals