Bio Exam 3

• phenotypic variation must exist
• phenotypic variation results in different reproductive success
• variation must be genetically inherited (phenotype linked to genotype)

• disruptive selection
• directional selection
• stabilizing selection

• fossil record
• molecular record
• homology
• divergent evolution
• vestigial structures
• development

species- group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups

• when individuals cannot produce fertile offspring     
• 2 types     
• 1) prezygotic     
• 2) postzygotic

• prevents the formation of zygots
• ex. ecological isolation; behavioral isolation; temporal isolation; mechanical isolation

• hybrids fail to develop or cannot become established in nature
• ex. leopard frogs

the formation of two descendant species from one ancestral species

it cannot unless gene flow is zero or very near zero

• 1- population is large
• 2- random mating occurs
• 3- no mutation takes place
• 4- no migration
• 5- no selection occurs

• change through time
• decent with modification
• change in gene frequencies through time

• mutation
• gene flow
• nonrandom mating
• genetic drift 
• selection

• ultimate source of variation 1-10 times per 100,000 cell divisions
• natural selection does not affect mutation rate

• the movement of alleles from one population to another
• low levels of gene flow homogenize allele frequencies among populations

certain genotypes are more likely to mate than others

• mating with relatives increases homozygosity
• doesn't change allele frequency

• opposite of inbreeding increases proportion of heterozygosity
• doesn't change allele frequency

• random changes by chance (most frequency in small populations)
• leads to a loss of alleles in isolated populations
• 2 types: founder effect; bottleneck effect

• the result of differential fitness
• artificial vs. natural

• continental drift
• glacier expansion and retreat
• stream course change
• colonization of remote areas
• -often combined with genetic drift
• mountain upwelling

when populations are geographically separated

• when populations are together
• much less common

• many plants readily hybridize
• -usually are infertile
• -polyploidy can lead to fertility (it is estimated that 80% of grass species are polypoid species)
• ex. Tragopogon (goat's beard)

the study of relationships among organisms and between organisms and their environment

a group of individuals from the same species that share the same habitat, share the same resources, and potentially interbreed

the measurement and statistical study of characteristics of populations

• size
• density
• dispersion
• age structure
• sex ratio
• natality and mortality

• total number of individuals
• if population size is constant, then: b+i=d+e
• b=births
• i=immigration
• d=deaths
• e=emigration

number of individuals per unit area

• how the individuals are spaced
• 3 types: random, uniform, clumped

the relative number of individuals in each cohort

birth rate

• each individual has a total reproductive value 
• TRV= CRV+RRV where CRV is current reproductive value and RRV is residual reproductive value