EVOLUTION

What is Evolution? Change in allele frequencies (the gene pool) over time in a population Biological change on a timescale of generations Individuals change, but only populations evolve

What does evolutionary theory explain? Adaptations Just about any feature on an organism is an adaptation – most of the things you think of By definition: inherited features of organisms that fit life habits, allowing them to survive and reproduce Biodiversity The diversity and number of species on earth All those living things on earth-- the whole “shootmatch”

Natural Selection a.k.a. “survival of the fittest” Broken down into four parts

Natural Selection Individuals in a population vary in their traits Some of these differences are heritable-they can be passed on from parent to offspring.

Natural Selection Many more offspring are produced than can survive only some will survive long enough to reproduce, and some will produce more offspring than others- some will have a suite of traits that are going to allow them to reproduce

Natural Selection Individuals with certain traits are more likely to survive and reproduce. Natural selection occurs when individuals with certain traits produce more offspring than do individuals without those traits

Main Idea: Heritable variation leads to differential reproductive success; this is natural selection Now, rewrite this statement in your own words. Then work on the graphing activity on the back of your notes.

Ways to Create Evolution 1. Genetic drift - genes will vary (so change) in population from generation to generation

Ways to Create Evolution 2. Natural Selection – 3 “modes” (explained soon)

Ways to Create Evolution 3. Gene flow or gene migration – transfer of genes from one population to another (cross breeding)

Ways to Create Evolution 4. Mutation- in genes. This is where new traits come from.

Ways to Create Evolution BONUS WAY (HUMAN CAUSED) -- Non-random mating (like purebred pet breeding)

Natural Selection Selection acts on individuals but populations evolve Process in which more favorable traits survive through time Selection acts on individuals but populations evolve

Modes of Natural Selection

Modes of Natural Selection Directional Diversifying Stabilizing

Why does evolution take so long? Rate of Reproduction Life span # of offspring Growth rate Length of reproduction cycle Number of habitats Size External environmental forces Earthquake, weather, etc.

Rate of Evolution Pressure to change Ability to change – diversity Rate of reproduction – Remember what causes this from your previous notes!

Biological Diversity Diversity is the single most important function of evolution Reasons for diversity Adapt to environmental changes Respond to change Ex: pollution, global warming Live in multiple habitats

Adaptation Natural selection can eventually lead to adaptation Definition – characteristic or trait that improves the survival and reproduction of an individual or population Adaptation is a GENETIC change

Acclimation Definition – Temporarily improving survival and reproductive success Characteristic or trait is NOT GENETIC and cannot be passed on

Types of Adaptation Models of evolution Gradualism – Very slow adaptation Punctuated Equilibrium – Rapid burst of change resulting in new species

Fossils Definition: A remnant or trace of a past organism Many varieties of dating techniques are use to determine when the organisms became fossilized – ex: strata of rock it is found and radioisotope dating Paleontologists are scientists that study fossils

Relationship Types Homologous structures – show a common ancestor Structures are similar, but adapted to the new organism Vestigial structures – structures that are present but have little to no functional value (odd traits link them)

Evolution does not result in perfect organisms Selection edits existing variation (some survive, some don’t) Compromise between adaptations Historical constraints (like earthquakes, volcanoes, etc) Chance (some organisms are simply lucky)