Ch 4 Evolution Flashcards
4 causes of evolution
- Mutations in individual organisms over time
- Migration
- Drift
- Natural selection
Migration
Movement of individuals throughout a population
How drift affects evolution
loss of individuals is random, causing a shift in relative abundance of organisms
How natural selection affects affects evolution
Differential survival and reproduction of individuals due to genetically-based differences in phenotype
The result is a population that contains a greater proportion of organisms better adapted to certain environmental conditions
Example of natural selection
Antibiotic-resistant bacteria
Limits of natural selection
Limited to already existing genetic variations. Also, limited by reproductive capacity of individuals with certain traits, as well as generation time
Example of drift
Certain bugs get stepped on by humans more than other kinds for no particular reason- just due to random chance
Necessary conditions for natural selection to occur
trait variation (difference of phenotypes)
Do individuals evolve over time?
No- populations!
What defines fitness of a species?
Rate of reproductive success
Lithosphere
Contains plates, whose movements alter climate
Artificial selection
Involves human involvement- crossbreeding species to create traits that we deem desireable
