Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Class Notes Patterns of Evolution Questions/Main Idea: Name: _______________________________________ Period:_______________________________________ Date: _______________________________________ Notes: • Mechanisms of Change Genetic variation vocabulary • • • • Gene tic drift • • Speciation vocabulary • • • Mechanisms of Speciation - • Geographic isolation Mechanisms of speciation - Reproductive Isolation Summary: • • There are various mechanisms by which evolution can occur: – Genetic Variation, Gene Flow, Genetic Drift, Natural Selection Gene pool → all the alleles of all the genes in a population Gene (allele) frequency → proportion of particular type of alleles in a population Variation has two sources: – mutation → change in DNA that leads to new alleles (harmful or beneficial) – sex (gene shuffling) → meiosis (recombination of alleles during crossing over) and fertilization Gene flow → new alleles (or frequencies) from one population enter another due to migration – e.g., native Americans and “recent” immigrants Genetic drift → random changes in allele frequencies of a gene pool Has a great effect when… – Bottleneck → random event radically decreases population size (and allele frequencies) • e.g., Earthquake in Haiti – Founder effect → a new population started by a small number of individuals (and their allele frequencies) • e.g., American Amish Speciation → splitting of one species into 2 different species Species → a group of organisms that interbreed under natural conditions to produce fertile offspring – Natural conditions: not artificially inseminated or forced into the same location To maintain a population as a single species, genes must freely flow through the entire population Geographic isolation → members of a species are isolated from one another due to a geographic barrier (mountains, rivers). – e.g., a few members of a species leave their original location and are separated from the rest of the species (Darwin's finches) – e.g., barrier develops slowly (formation of Grand Canyon split a population of squirrels into 2 isolated groups that have evolved into separate species, the Kaibab and Albert squirrels) Before mating: – Different breeding times (e.g., trees release pollen at different times) – Different behaviors (e.g., courtship rituals of peacocks) – Mechanical problems (e.g., genitalia doesn’t fit together) After mating: – Hybrids don’t survive – Hybrids are sterile