UNIT 7.7 to 7.13 - AP BIOLOGY

ap biology

morphological homologies

modified traits shared among different species

homologous structures (morphological homologies)

variations in a structure that was present in a common ancestor

vestigial structures (morphological homologies)

 reduced features that serve little or no purpose for the organism

analogous structures (morphological homologies)

distantly related/unrelated organisms have similar traits

evidence of common ancestry of all eukaryotes

membrane-bound organelles, linear chromosomes, introns

RNA World Hypothesis

RNA could have been the earliest genetic molecule

early Earth atmospheric conditions were ideal for forming monomers for life

there was a presence of free energy and an absence of atmospheric oxygen (O₂)

phylogentic trees and cladograms

diagrams that show evolutionary relationships among species.

phylogentic trees and cladograms constructed based off of the

morphological similarities from living/fossil species. DNA and protein sequence similarities (more accurate)

out-group

the species that is least closely related to the remainder of the organisms

node

where the two lines meet, representing the most recent common ancestor

root

represents the common ancestor of all species

speciation

creation of new species

allopatric speciation

evolution of a new species due to geographical isolation of the same species (ex: geographical barriers, like a river). no gene flow, and separation may expose populations to different selective pressures

sympatric speciation

evolution of a new species due to reproductive isolation from a surviving ancestral population. can result from genetic mutations (polyploidy)

divergent evolution

occurs when adaptations to new habitats result in phenotypic diversification, with the possibility of rapid speciation rates

reproductive isolation

prevents gene flow between populations

PREzygotic barriers (Hard To Be My Guest)

prevent production of a fertilized egg. habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gamete isolation.

habitat isolation (PREzygotic barrier)

where species have different habitats and rarely come in contact

temporal isolation (PREzygotic barrier)

where species breed during different times of day, seasons or years

behavioral isolation (PREzygotic barrier)

where species have different courtship behaviors

mechanical isolation (PREzygotic barrier)

where reproductive structural differences prevent successful mating and reproduction

gamete isolation (PREzygotic barrier)

where sperm of one species may not be able to fertilize the eggs of another species (sperm and egg cant fuse)

POSTzygotic barriers

prevent a zygote from developing into a viable, fertile offspring

punctuated equilibrium

evolution that occurs rapidly after a long period of stasis (period of little to no change)

gradualism

evolution that occurs slowly over a LONG TIME. ecological conditions change gradually too

extinction

the disappearance of a species. can occur on a large scale at one time. species diversity decreases severely.

an ecosystem’s diversity can be determined

by extinction and speciation rates. high species biodiversity = high speciation levels, low extinction levels

extinction provides newly available niches

 the role an organism plays within its environment (producer, decomposer, scavenger, etc.)

extinction leaves an open niche for another species to occupy

leads to rapid speciation rates and adaptive radiation