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
5 principles of natural selection
- variation
- trait must be heritable
- more offspring that can survive
- traits that increase fitness are passed down more often
- POPULATIONS CHANGE; not individuals
Hardy Weinberg
- no mutations
- random mating
- no natural selection
- extremely large population size
- no gene flow
Geographical evidence
characteristics of habitat or land loss
Geological evidence
features of Earth overtime (fossils)
Physical evidence
phenotypes/traits of species
Biochemical evidence
chemical composition (molecules – DNA, proteins)
Mathematical evidence
calculations, statistics, models, simulations
Fossils
visual of evolutionary change over time
rate of carbon 14 decay: less carbon = older
Comparative Morphology
analysis of living and extincet structures
Embryotic Homology
similar embryotic development
Vestigial Structures
structures that are conserved even if they are no longer used
Molecular Homology
many species share similar DNA, animo acid sequences
Biogeography
related organisms are different in different places due to evolving in different conditions
ex: finches in Galapagos, Pangea
Genome Changes
antibiotic resistant bacteria, pathogens = new diseases
Synapomorphy
derived characteristics shared by clade members
Derived
similarly inherited from most recent common ancestor
Ancestral
arose prior to the common ancestor
Monophyletic
includes most recent common ancestor and all descendants (grandparents and all grandkids)
Paraphyletic
most recent common ancestor but missing descendants (grandparents and some cousins are missing)
Polyphyletic
no common ancestor but has descendants (grandparents are missing but grandchildren are there)
Allopatric
physical barrier divides a population and is separated (geographic isolation)
- prevents gene flow
- usually caused by natural disaster
Sympatric
new species evolves while still in the same geographical region as ancestral species
- reproductively isolated; when brought back together, and are able to interbreed = they are NOT distinct species
Prezygotic
prevents mating/hinders fertilization
Habitat - Prezygotic
live in different areas/habitats in the same area
Temperal - Prezygotic
mate at different times; time of day/year/season
Behavioral - Prezygotic
different mating rituals
Mechanical - Prezygotic
reproductive anatomy doesn’t fit
Gametic - Prezygotic
proteins on eggs’ surface don’t allow for the egg and sperm to fuse
Postzygotic
prevent hybrid zygote from developing into a fully viable and fertile adult
Reduced viability
impair development/survival
Reduced fertility
hybrid can develop into an adult but is sterile
Hybrid breakdown
1st generation of hybrids survives and reproduces but 2nd generation is sterile
Microevolution
change in allele frequency
ex: genetic drift, natural/sexual selection, gene flow
Macroevolution
large evolutionary patterns
ex: adaptive radiation, mass extinction, stasis
Human causes of extinction
pollution, climate change, poaching, habitat loss/destruction, invasive species
Types of traits
Adaptive: increase chance of survival
Deleterious: decrease chance of survival
both depend on environment
Directional
selecting for 1 EXTREME trait
Stabilizing
select intermediate; AGAINST EXTREME traits
Disruptive
selecting for BOTH EXTREME traits
Sexual selection
chooses mate based on one/more traits; 1 sex has to compete for a mate
- result in traits harmful to an individual; peacock big tail
Early Life
synthesize organic molecules from inorganic molecules with free energy (UV, electric discharge, heat)
RNA World Hypothesis
RNA was the earliest genetic material; created on primitive Earth and could self-replicate without other molecules
Primordial soup: early oceans with inorganic and simple organic molecules; formed with free nucleotides
