Unit 7 - Natural Selection Flashcards
Evolution
change in the genetic makeup of a POPULATION OVER TIME
Natural Selection
process which individuals that have certain traits tend to SURVIVE AND REPRODUCE at high rates than others due to traits
Phenotypic variation
can decrease/increase fitness
DNA sequence doesn’t matter
Selective Pressures
changes in the environment
Heritable traits
from PARENT TO OFFSPRING
- sexual reproduction (crossing over, independent assortment, random fertilization)
- random mutations
- adaptations to environment
Ways to increase fitness
- more offspring = more survive
- successful competition for resources = increase change of survival and reproduction
Fitness
reproductive success = evolutionary fitness
more changes in the environment will lead to more evolution/adaptation
Artificial selection
selective breeding by humans to encourage a desirable trait
can increase OR decrease genetic diversity
Population
a group of individuals that are the same species, live in the same area, and interbreed to produce FERTILE offspring
Gene pool
population’s genetic makeup
all copies of every type of allele
Fixed allele
1 allele present for a particular locus (where on a chromosome a specific gene is); an allele that is the only variant that exists for that gene in a population
Genetic drift
CHANCE event that cause a change in allelic frequency from one generation to the next
How does genetic drift affect a population?
- most affects small population
- increased mortality and decreased reproduction (from natural disaster)
- loss of genetic variation
- harmful alleles become fixed
does NOT produce adaptations (random event!!)
Bottleneck
large population is significantly reduced by a non-selective disaster
ex: fire, famine, etc
Founder
a few individuals isolate and establish a new population with a different gene pool; lose genetic diversity
Gene Flow
transfer of alleles in/out of a population; migration
Convergent evolution
similar traits but unrelated lineage due to similar selective pressures/niches
Analogous structure
pairs with CONVERGENT EVOLUTION
similar structure/function with different ancestors
penguins, sharks, dolphins: light color bellies but only because they adapt that way to the environment
Divergent
accumulation of differences in groups (due to DIFFERENT ENVIRONMENTAL PRESSURES) that leads to speciation (formation of NEW SPECIEIS)
Homologous Structures
pairs with DIVERGENT EVOLUTION
common ancestor/blueprint but evolves into different structures with different functions
humans, bats, cats: same bone structures in arms with fingers due to common ancestor but now has different functions
Coevolution
2 interdependent (dependent upon one another) species influence each other’s morphology
ex: prey/predator, plant/pollinator
Adaptive Radiation
ancestral species develop into different species and fills in different environmental niches
modifies homologous structures and is due to ecological opportunity
Gradualism
evolutionary chang is slow; small genetic change favored by natural selection
Punctuated
periods of stasis (no change) to rapid development (punctuated)
What increases chance of survival?
increased variation will help populations survive in changing environmental conditions
increased variation will mean more chances for an individual to have a favorable trait
Phenotypic advantage
fitness advantage in an individual
Selective pressures
biotic/abiotic factors that influence survivability
- availability of resources
- predators
- disease
- climate
Environmental factors
trait previously suited may no longer be suited after changed environment