AP Bio Chapter 7- Evolution

Evolution

Genetic change in a population over time

Charles Darwin

The first scientist of propose the theory of evolution (in 1859)

Darwin’s Observations

• similarities in living and fossil organisms

• diversity of life like finches and giant tortoises

Darwin’s Conclusions

• The Earth was old and constantly changing

• Living things evolve over generations

• Living things are related to animals and plants that use to exist and are now extinct

Evidence for Evolution

• Fossils

• Biogeography

• Comparative Anatomy

• Comparative Embryology

• Molecular Biology

Fossils

The preserved remains of a dead organism (show how life as changed over time)

Biogeography

The geographic distribution of species (organisms in different parts of the world are related because they hare common ancestors)

Comparative Anatomy

Anatomical similarities among many species show signs of common descent

Comparative Embryology

Closely related organisms have similar stages in embryonic development

Molecular Biology

The comparison of DNA and amino acid sequences between species (shows how closely related we are)

Homologus Structure

Same structure, different function (shows common ancestry)

Analogus Structure

Same function, different structure (no common ancestry)

Vestigial Structure

A structure that an organism has but does not use

Population

A group of the same organism that can reproduce

Phenotypes

A physical trait that you can see

Natural Selection

Basic mechanism of evolution (survival of the fittest)(phenotypes that are better reproduce more, better genotypes become more common)

Species

A group of populations whose individuals can interbreed and produce fertile offspring

Gene Pool

The total collection of genes in a population at any one time

Microevolution

A change in the relative frequencies of alleles in a gene pool

New Mutations

Constantly being generated in a gene pool (by accident or in result to environmental changes)

Hardy-Weinberg Equilibrium

States that the shuffling of genes during sexual reproduction does not alter the proportion of different alleles in a gene pool

Conditions for Hardy-Weinberg Equilibrium (does not happen in nature)

• Population very large

• Population is isolated

• Mutations do not enter the gene pool

• Mating is random

• All individuals are equal in reproductive success

Hardy-Weinberg Equation

p²+2pq+q²=1

p+q=1

p

Dominant allele

q

Recessive allele

p²

Homozygous dominant allele (AA)

q²

Homozygous recessive (aa) (ALWAYS SOLVE FIRST)

2pq

Heterozygote

Mutation

Random changes in DNA that can create new proteins or new characterstics (changes alleles)

Genetic Drift

A change in allele frequencies due to chance

Bottleneck Effect

A drastic reduction in the size of a population (fire, flood, earthquake)

Founder Effect

When some individuals leave a population and start another one something new (population will be closely related due to lack to genetic diversity)

Gene Flow

New organisms moving in or out of a population (can change a gene pool)

Taxonomy

The naming and classifying of organisms (started by Carl Linaeus)

Taxonomy Levels

Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species

Prezygotic Barriers

Barriers that prevent the sperm from fertilizing the egg

Postzygotic Barriers

Barriers that occur after the sperm has fertilized the egg

Habitat Isolation (Prezygotic)

Organisms are limited to different areas

Temporal Isolation (Prezygotic)

Mating periods change

Behavioral Isolation (Prezygotic)

Behavior of the organism changes

Mechanical Isolation (Prezygotic)

Reproductive structures don’t fit together

Gametic Isolation (Prezygotic)

The egg and sperm are isolated

Reduced Hybrid Viability (Postzygotic)

An organism is born but will die before reproductive age

Reduced Hybrid Fertility (Postzygotic)

The parent organisms cannot reproduce

Hybrid Breakdown (Postzygotic)

Organisms will be sterile

Allopatric Speciation

Species splits into two because of some sort of barrier

Sympatric Speciation

A new species evolves from an existing species while living in the same land

Adaptive Radiation

New organisms form from one original species

Phylogeny

The study of organisms evolved and the relationships between them

Cladograms

Evolutionary relationships based on shared traits

Clodes

Shows the organisms being compared

Nodes

Shows a common ancestor

Derived Characteristics

Shows shared traits