Evolution 4 Flashcards
Large population
The effect of chance on allele frequencies is thereby greatly reduced
Random mating
Individuals show no mating preference for a particular phenotype
No net mutation
No alteration in DNA sequence of a alleles
No gene flow
No immigration or emigration
No natural selection
All genotypes have an equal chance of surviving and reproducing
Sympatric
Don’t need geographic barrier
reproductive isolation occur
2 sympatric
hybridization and polyploidan population
hybrid
two different individuals mate and produce fertile offspring
examples of hybrids
Red wolf
Skua
Red wolf
60 left
Small natural population
Carolina’s
result of mating between wolf and coyote
Polyploidan population
Entire set of chromosome fail to segregate in meiosis abc result in diploid gamete
diploid gametes
double set of chromosome
example of polyploidan population
Rodent in Argentina
common in amphibians, plants (majority)
strawberries kiwis dandelions
premating or prezygotic
prevent mating prevent mating or fertilization between species
- speices psecific mating calls
- species specific mating rituals
- species specific pheromones (scent)
- gamete incompatibility (sperm and egg can’t fertilized)
- physical parts don’t fit
- species specific mating seasons (related to timing, TEMPORAL)
zygote
fertilized egg
types of reproduction isolating mechansim
premating and post mating
hybrid morality
hybrids are born but die early
ex: ensatina (salamander)
REDUCED HYBRID VARIABILITY
reproductive barrier
a biological feature of the organism that prevents individuals of closely related species from interbreeding when their ranges over lap
-hybrid sterility
mules, can’t have fertile offspring)
REDUCED HYBRID FERTILITY
postzygotic barrier
operate after hybrid zygotes are formed
temporal isolation
when species breed at different times
-ex: eastern and weatern spotted skunks breed at different times of year
SPECIES SPECIFIC MATING SEASONS
habtitat isolation
two species live in same general area but not in same kinds of places
-ex: thamnophis (species of garter snakes, one lives in water and land)
behavioral isolation
or:
little or no sexual attraction between males and females
-ex: fireflies of various species siganlt to feamle of their kind by blinking their lights in a patricular rhytmes, then feamles flash back and atrract males
SPECIES SPECIFIC MATING CALLS, RITUALS AND PHEROMENS
mechanical siolation
female and male sex organs are not compatible
PHYSICAL TRAITS DON’T FIT
gametic isolation
male and female from two different spices may copulate but the gametes do not united to form a zygote
-ex: male and female urchins release eggs and sperm into sea but fertilization occurs only if species specific molecules on surfaces of egg and sperm attach to each other
GAMETE INCOMPABILITY
hybrid breakdown
first generation of hybrid offpsiring are viable and fertile but when these hybridsmate with one another or with either parent species the offspring are feeble or sterile
reproductive isolation
prevents gene flow and maintains gap between species
gamete
single set of chromsome
diploid cell
total number of chromosomes
Types of postzygotic barriers
Reduced hybrid viability
Hybrid breakdown
Reduced hybrid fertility
Types of prezygotic barriers
Temporal
Habitat
Mechanical
Gametic
