Biology 104 - Exam 1 Flashcards
biodiversity
how many different organisms are on the planet
evolution
- change overtime, descent with modification
- change in allele frequencies between generations of a given population
microevolution
short-term genetic changes within a population of species
fossils
preserved remnants, impressions in rock of once living organisms
fitness
individual reproductive contribution to the next generation
directional selection
an extreme phenotype is fittest and shifts the phenotype curve
disruptive selection
leads to a balance between 2 or more contrasting phenotypes in a population
stabilizing selection
maintains variation for a particular trait with a narrow range
heterozygote advantage
harmful alleles in one way confer benefit in another
- i.e. heterozygotes for sickle cell are immune to malaria and don’t necessarily have the disease
mutations
- DNA randomly changes to introduce new alleles
- increases genetic diversity
- affect evolution on in subsequent generations that inherit the mutation
genetic drift
- changes in the gene pool due to chance
- rooted in sampling error and has strong affect on small populations
- founder effect & bottleneck effect
founder effect
- founders of a new population
- bring only their alleles => reduces diversity
- entire genotypes eliminated
- rare traits may increase in frequency
bottleneck effect
- population drastically reduced in size
- over hunting, natural disaster, habitat loss
- typically reduces genetic diversity in the surviving population
paleontology
the study of fossils to understand historical ecology, evolution, and human relevance to the past
relative dating
looking at fossils above and below to determine age => estimation
absolute/radiometric dating
- approximates fossils/sediment age using radioactive isotopes
half-life
the time it takes for half the isotope to lose half of it’s mass
biogeography
study of the distributions of species on the planet
homologous structures
structures inherited from a common ancestor
vestigial structures
homologous structure that no longer has a function in a species
analogous structure
structure is alike but there is no common ancestor
- also known as convergent evolution
- selective pressures lead to similar adaptations but not because of commonality
Hardy-Weinburg equilibrium
- no natural selection
- no mutations
- large population
- individuals mate at random
- no immigration OR emmigration
homeotic genes
genes that control development (evo-devo)
- small differences in expression of genes can lead to a new body plan
macroevolution
major changes in the history of life that occur over long periods of time
species
a population or group of populations whose members can interbreed and produce viable offspring
reproductive isolation
leads to speciation, formation of a new species
Issues with Linnaeus’ theory of species
- cannot apply to asexually reproducing organisms
- impossible to assign species names to organisms known only as fossils
- some organisms interbreed in captivity but not in nature
- reproductive isolation is not absolute - interbreeding is still possible despite isolation
prezygotic reproductive barriers
occur before the formation of the zygote
- prevents mating
- prevents fertilization if mating is attempted
- i.e. habitat, temporal, behavioral, mechanic, gametic
postzygotic reproductive barriers
if the zygote is formed:
- failure to develop/reach sexual maturity
- failure to produce gametes
- feeble or sterile offspring
- i.e. hybrid inviability (don’t reach maturity), hybrid infertility (infertile), hybrid breakdown (not able to reproduce)
allopatric speciation
no contact between populations
- physical barrier separates the populations
sympatric speciation
continuous contact between populations
- populations share a habitat but diverge anyway
gradualism
start with a common ancestor and changes slowly appear
punctuated equilibrium
direct, blunt changes in the species
- long periods of limited change interrupted by bouts of rapid change
rapid speciation occurs
- with evolution of key adaptation
- as consequence of widespread extinction event
extinction
species is extinct when all members have died
- failure to adapt to environmental changes
- i.e. habitat, new predator, new disease
background extinction rate
- gradual loss of species to extinction
- 0.1 to 1.0 per year per one million species
impact theory
suggests that meteorites and comets crashed to the Earth and changed the atmosphere/environmental conditions
- i.e. extinction of dinosaurs
plate tectonics
shifting of the continents
human impact
thought to be causing the 6th mass extinction
- losing estimated 20 to 200 per year per one million species
systematics
study of classification
taxonomy
the science of describing, naming and classifying species
- the more features shared by two species, the more taxonomic levels they share
phylogenics
study of evolutionary relationships among species
phylogenic trees
depict evolutionary relationships based on descent from common ancestors
- multiple lines of evidence used to construct the trees
clade
group of organisms consisting of a common ancestor & its descendents
cladogram
type of phylogenic tree
- built using ancestral and derived characters
- makes use of homology
