Unit 1, Evolution Flashcards
Meiosis
in gamete cells, four haploid daughter cells
Mitosis
in somatic cells, two identical diploid daughter cells
zygote
1 egg + 1 sperm cell fertilize
mutation
change in nucleotide sequence
chromosome
chain of DNA with stabilizing porteins
random independent assortment
Metaphase 1, chromosomes randomly go to gametes
Charles Darwin
went on 5 year voyage around the world, “evolution is ascent with modification”
Darwinian Evolution
- species accumulate differences
- descendants differ from ancestors
- new species arise from existing ones
natural selection
Mechanism of evolution:
1. individuals have specific inherited characteristics
2. they produce more surviving offspring
3. pop. includes more individuals with inherited traits
4, pop. evolves to better adapt to environment
Lamarck
acquired variation is passed on to descendants
ex: Giraffe’s necks lengthen during individuals lifetime (disproved)
Hardy-Weinberg Principle
- no mutation takes place
- no gene flow is transferring to/from other sources
- random mating is occurring
- population size is very large
- no selection occcurs
homozygous
same alleles
heterozygous
different alleles
dominant allele
Allele that overtakes the other
recessive allele
has to be homozygous recessive for the recessive phenotype to be expressed
codominant
both genes expressed (speckled)
incomplete dominance
trait is “mixed” (R + W = Pink)
phenotype
the way gene is expressed
genotype
the genetic makeup of the gene
nonrandom mating
mating with specific genotypes, shifts genotypic frequency
assortive mating
doesn’t change frequency of individual alleles, Increases proportion of homozygous individuals
disassortive mating
phenotypically different individuals mate, produce excess of heterozygous
founder effect
few individuals from original colony leave and found new population elsewhere
bottleneck effect
drastic reduction in population, and gene pool size
artificial selection
breeder selects for desired characteristics
Fitness
- survival
- how often they mating
- number of surviving offspring
frequency-dependent selection
depends on how frequent a phenotype occurs in a population. (common trait = safe)
positive frequency dependent selection
common phenotypes are favored; variation is eliminated from the population (uncommon trait = safe)
oscillating selection
selection favors one phenotype at a time, shift in population average NOT individuals
heterozygote advantage
keep deleterious alleles in a population, ex: sickle cell anemia
high predation environment
males with drab colors are relatively small, reproduce at younger age
low predation environment
bright coloration, increased spots, successful at defending territories
pleiotrophy
sets limit on how much a phenotype can be altered
absolute dating
age of fossils is estimated by rates of radioactive decay
relative dating
position of the fossil in the sediment
archaeopteryx
oldest known bird fossil
homologous structures
structures with different appearances and functions that are all derived from the same ancestral feature
vestigial structures
have no apparent function, but resemble structures their ancestors posessed
extant
species currently living on Earth
biogeography
study of geographic distribution of organisms
convergent evolution
independent development of similar structures in organisms that aren’t directly related
marsupials
young are born in immature condition and held in pouch until they develop
placentals
young aren’t born until they can safely survive in external environment
speciation
process by which new species arise:
- transformation of one species to another
- by splitting of one ancestral species into another
sympatric speciation
differentiation of populations within a common geographic area into species:
- phenotypically different
- aren’t distinct entities
- utilize different parts of the habitat
population
any group of individuals, usually of a single species occupying a given area at the same time
subspecies
within a single species, individuals in population that occur in different areas may be distinct from one another
geographic isolation
species occur in different areas, separated by river or mountain range
ecological isolation
species in same area, but occupy different habitats
behavioral isolation
species differ in mating rituals
temporal isolation
species reproduce in different seasons/ time of day
mechanical isolation
structural differences prevent mating
prevention of gamete fusion
gametes from the separate species function poorly when they interact
hybrid
post-zygotic, animal is sterile, ex: mule
phermones
chemical signals
reinforcement
incomplete isolating mechanism
introregression
genes jumping from different species
