Ch 11. Species and Races Flashcards
species
group whose members have the greatest resemblance. each has 2 part name
2 part name of species
1st: indicates genus, a broader group
2nd: specific to species within genus
biological species
consistent definition to determine differences between species
reproductively isolated
can interbreed and produce fertile offspring, but cant reproduce with other species
gene pool
sum total of all alleles within a species. makes an impermeable container for gene pool. change in frequency can only happen within a species
prefertilization barriers
failure to mate/produce an embryo
spatial isolation
prefert. different species dont come in contact
behavioral isolation
prefert. ritual mating behaviors differ
mechanical isolation
prefert. incompatible sex organs
temporal isolation
prefert. timing of readiness to reproduce is diferent
gamete incompatibility
prefert. proteins on egg that allow sperm to bind dont work for another species
postfertilization barriers
fertilization occurs, but hybrid cant reproduce
hybrid inviability
postfert. zygote cant complete development because genetic instructions incomplete
hybrid sterility
postfert. hybrid cant produce offspring because chromosome number is odd. (mule)
speciation
evolution of species from an ancestral form. isolated population diverge in traits. divergance can lead to reproductive isolationa nd formation of a new species. 3 steps necessary
3 necessary steps for speciation
- isolation of gene polls of subgroups/populations of the species
- evolutionary changes in gene pools of 1 or both of isolated population
- evolution of reproductive isolation between population, preventing future gene flow
founder hypothesis
diversity of unique species on oceanic islands and isolated bogs, caves, and lakes resulted from colonization by 1 species that rapidly speciated, taking advantage of many different resources. allopatric or sympatric.
allopatric
isolation due to geographic barrier
sympatric
separation of gene pool even when near each other
polyploidy
process of chromosome duplication. if occurs in hybrid, fertility may be possible again. mostly in plant and some insects and frogs.
instantaneous speciation
hybrids from polyploidy may produce offspring and are immediately creating a new species (can’t reproduce with parental species) due to genetic incompatability (polyploidy creates double the genes as the parents)
gradualism
speciation occurring over millions of years with tiny changes accumulating
punctuated equilibrium
dramatic changes in few thousand years, followed by many thousands or millions of years of little changes
biological race
populations of a single species that have diverged. little gene flow between them, evolutionary changes differ between populations
geneological species concept
species is smallest group of reproductively compatible organisms containing all known descendants of a common ancestor. emphasizes unique evolutionary lineages, increasing number of identifiable species
human races
white, black, pacific islander, asian, australian, aborigine, and native american. physical differences used to define are skin color, hair texture, eye, skull, and nose shape
morphological species concept
individuals of same species look alike (similar morphology). correlated with isolation of gene pools. mostly used by paleontologists
out-of-africa concept
homio sapiens evolved once in africa from homo erectus. most supportive data
multiregional hypothesis
homo sapiens evolved throughout range of homo erectus
hybridization-and-assimilation hypothesis
homo sapiens evolved out of africa and migrated and hybridized with homo erectus in different areas of globe
allel frequency
trait in one population is more common than in the other. result of evolution.
2 traits of isolated race
- unique alleles specific to race
2. differences in allele frequency for some genes relative to other races
hardy-weinberg theorem
allele frequency remains stable in large populations that randomly mate and experience no migration or natural selection. forms basis of modern science of population genetics. describes relationship between allele frequency and genotype frequency for a gene with 2 alleles in a stable population.
hardy- weinberg cont.
frequency is written ‘p’ and ‘q’. each gamete carries one copy of each gene (frequency of gametes=frequency of alleles). assume every member has equal chance of mating with any member of opposite sex (like lottery drawing). drawn like punnet square, including frequency. equation: (pxp)+2pq+(qxq)=1
HW#1: p=80% dominant(A) q=20% recessive(a). what are the frequencies?
anser: AA=0.64, Aa=0.32. aa=0.04 0.64+0.32+0.04=1
work: pxp+2pq+qxq
0. 8x0.8+2(0.8x0.2)+0.2x0.2
human race
NOT biological groups. no race-specific alleles. (sickle cell not a black disease, cystic fibrosis not a white disease). hypothesis that human races represent independant evolutionary groups isn’t supported by observations.
why is human race not a true race?
morphological characteristics (skin, hair, eye shape, etc) used to classify race are determined by multiple genes, therefore those genes should be specific to certain gene pools. no clear boundaries for gene pool. ‘mixing’ for thousands of years. races fail to meet criteria for identifying populations as isolated from each other
why do human groups differ?
natural selection. ex1: sickle cell anemia is an adaptation that increases fitness in malaria prone areas ex2: nose shape is adaptation to climate. long and narrow for dry climates, short and wide for tropical climates
convergent evolution
traits shared by unrelated populations due to similarities in environments. cause of skin color (exposure to UV light)
Dark skin and UV light
absorbs less UV light. UV interferes with storing folate which inturn causes birth defects, and low sperm production
light skin and UV light
allows for more vit D absorption from sun in darker environments
genetic drift
change in allele frequency due to chance. 3 types, founder effect, bottleneck population, and small populations
founder effect
genetic drift. small population of larger population leave and establish new population. small populations gene pool is poor reflection of larger gene pool. genetic diseases is more common due to small gene pool with some individuals carrying recessive genes in high frequency
sampling error
small population gives poor reflection of larger populations gene pool
bottleneck population
genetic drift. dramatic, short lived reduction in population size (i.e. natural disaster). new population differs in gene frequency because survivors have ‘sampling error’ and gene pool isnt exact match as before
small populations
genetic drift. allele frequency more apt to change in chance events. frequency may substantially change after a few generations. can lead to extinction in plants and animals.
sexual selection
trait that influences the likelihood of mating
assortive mating
choosing a mate based on attractive traits. exaggerates physical differences between populations
race in human society
social structure in humans, no biological meaning
racism
idea that some groups of people are naturally superior that others
