Exam 1 Flashcards
Homologous species
indicative of evolution from a common ancestor.
analogous species
Evolve to look & function the same through convergent evolution.
convergent evolution
same solution to similar selection pressures.
rudimentary structures
unused, left over from the previous ancestry
comparative embryology
evolution of development, similarities in embryos
conserved molecular characteristics
dna, rna, proteins, specific enzymes & enzyme pathways
evolution
change/time in allele frequency of a population
Darwin & Wallace independently concluded evolution in…
1859
natural selection
non-random, unequal reproductive success (reproduction of the fittest)
Darwin’s observations:
- organisms have the capacity to produce exponential population growth
- populations tend to remain stable ( w fluctuation) not exponential
- resources are limited
- some variation is heritable
- better adapted individuals leave more offspring
Earth’s operating conditions
- sunlight
- water
- gravity
- limits & boundaries
- dynamic equilibrium
- cyclic processes
adaption
trait that increases the fitness of an individual
evolutionary fitness
relative contribution of an individual in a population to the next generation (reproductive output)
r selected
lots of offspring with low investment and low survival rates
k selected
few offspring with high investment & high survival rates
directional selection
selection against 1 extreme, shifting toward the other extreme. Graph just slides down
diversifying selection
shift away from intermediate to both extremes. Graph turns into an M shape (could lead to speciation)
Stabilizing selection
selection against both extremes. Graph narrows.
sexual selection
natural selection that results in adaptions that directly influence reproductive success.
Inter-sexual = between sexes
Intra - sexual = with in sexes
Genetic Drift
variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.
GD: bottle neck effect
Catastrophic reduction in population. Original population -> chance survivors -> new population
GD: founder effect
a few individuals from a population start a new population with a different allele frequency than the original population
Gene flow
immigration/migration of individuals between populations that result in change in population allele frequencies.
- more gene flow between 2 populations makes them more similar
- less gene flow means they’re more diverged
- not totally random
mutations
random change to DNA
- introduce new alleles to a population
- adds diversity
- natural selection acts on mutations to eliminate mal-adaptive options
non- evolving population
- very large population size (no genetic drift)
- no gene flow (no immigration/migration)
- no mutations
- no selection, all individuals are equal in reproductive success
Hardy- Weinburg Theorum
there is no evolutionary change just via reproduction…a force must ensure that at least 1 of 5 parameters must be broken for evolution to occur
Species
based on the ability to interbreed. If interbreeding is possible then speciation is not complete.
- biological species concept is based on infertility rather than physical similarity
Prezygotic barriers
- before zygote = a fertilized egg
- behavioral isolation (mating dance0
- mechanical isolation (bees only being able to pollinate flowers shaped a certain way)
- gametic isolation (surface proteins on the gametes are incompatible)
Postzygotic barriers
- hybrid inviability = they die before they fully develop
- hybrid sterility = they’re not able to produce viable gametes & reproduce
- hybrid breakdown = fizzling out after a couple generations
Genetic isolation can lead to new species
it is the blocking connection between populations
genetic divergence can lead to new species
it is becoming incompatible genetically
macroevolution
mutation, gene flow, genetic drift, natural selection, + 3.8 billion years
LUCA
last universal common ancestor
allopatric speciation
geographic separation, scale and type of movements, migration, & dispersal can be key factors
Example: pollen blown by wind, ground squirrels on either side of the grand canyon, adaptive radiation
adaptive radiation
divergent evolution compares and contrast with convergent evolution
convergent evolution
creating analogous structures through similar selection pressures (often founder effect involved)
sympatric speciation
by autopolyploidy in plants causes instant new species
autopolyploidy
self-duplication of chromosome numbers
- plants tolerate extra chromosome sets, flexibility & plants can self pollinate
ecological isolation
through behavioral/geographical
allopolyploidy
hybridization with meiotic nondisjunction (no separation of homologous chromosomes) + self fertilization
