Lecture #30: POPULATION & EVOLUTION Ms. Day Honors Biology http://glencoe.mheducation.com/sites/9834092339/student_view0/chapter20/animation_-_mechanisms_of_evolution.html

Population & Evolution Group of the same species living in the same place at the same time that can interbred Species: a group of populations whose individuals can to interbreed and produce living offspring that can reproduce themselves Gene pool: ALL of the genes (alleles) in a population at any one time

“Individuals are selected, but populations evolve.” Populations = smallest unit of evolution

Causes of Microevolution A change in the gene pool of a population over many generations There are 5 reasons why populations can evolve.

How can this happen? Genetic Drift #1: Small Populations How can this happen? Genetic Drift Genetic drift: changes in the gene pool of a SMALL population due to chance (reduces genetic variability) http://highered.mcgraw-hill.com/sites/0072835125/student_view0/animations.html# 2nd to last video

Genetic Drift Example #1 Bottleneck Effect Caused by a natural disaster Leaves surviving population with less genetic variation than original population

Ex: NORTHERN ELEPHANT SEAL

Genetic Drift Example #2 Founder Effect: a result of colonization by a few individuals from a parent population finding a new place to live http://nortonbooks.com/college/biology/animations/ch16a01.htm http://bcs.whfreeman.com/thelifewire/content/chp24/2402002.html

Cause #2: Migration of Alleles Gene Flow: alleles/genes migrate (move) between populations (reduces differences between populations)

Cause #3: Mutations a change in an organism’s DNA original source of genetic variation (raw material for natural selection) Mutations can immediately lead to NEW variation in a population

Cause #4: “Picky” Mating Nonrandom mating “picky” mating Unequal chances of each egg getting fertilized Assortative mating - choosing individuals more like self

Sexual Selection results in sexual dimorphism differences between the sexes in secondary sexual characteristics

Cause #5: Natural Selection Different survival and reproductive success due to variation https://highered.mheducation.com/sites/9834092339/student_view0/chapter20/animation_-_mechanisms_of_evolution.html

LIGHT/DARK ROCK HABITAT MEDIUM COLOR ROCK HABITAT