Chapter 20 bio 103, speciation and macro evolution

adaptive radiation

evolution of several species from one or a few ancestral species; occurs in a relatively short time frame

allometric growth

growth of different body parts at different rates

allopatric speciation

formation of two new species following the physical separation of individuals of a single population

gradualism

evolution occurs as a result of slow steady changes over time

hybrid inviability

egg and sperm of two different species are genetically incapable of producing a viable zygote and embryo

hybrid breakdown

the hybrid is unable to continue to reproduce successfully;F1 and F2 generations may be produced

hybrid zone

an area of overlap between closely related species or subspecies in which interbreeding occurs

hybrid sterility

gametes of interspecies, hybrid are not normal and able to produce zygote(mule)

macroevolution

large-scale changes over long time periods resulting in phenotypic changes that warrant placement of the organism into a new taxonomic group at or above the species level

microevolution

small-scale changes that occur within a species as a result of changes in the

allele or genotype frequencies

paedomorphosis

retention of juvenile features in the adult body form

Preadaptation

a characteristic that functioned in one way originally but later changed in a

way that was adaptive to the structure having a different role

Prezygotic Barrier

something that prevents fertilization from occurring (prevents formation of a

zygote); prevents hybrid formation

postzygotic Barrier

something that occurs after fertilization (formation of a zygote) that prevents

a hybrid from living long enough to form a new species

punctuated Equilibrium

evolution proceeds with period of little or no change and then rapid changes

occur over a relatively brief period of time

Sympatric Speciation

formation of two new species within the geographic region of the parent

population; no physical barrier is present but reproductive isolating

mechanisms are

biological species

maintains reproductive isolation and produces fertile offspring, sometimes successful interbreeding does occur

temporal isolation

species reproduce at different times of day, season, or year. prevents cross fertilization

habitat isolation

live and breed in different habitats within the area

behavioral isolation

distinct signals(visual, chemical, oral) to begin mating might restrict different species from mating

mechanical isolation

structural differences in reproductive organs prevent mating

gametic isolation

molecular and chemical differences between games prevent zygote formation

speciation

evolution of new species

reinforcement zone (hybrid initially formed)

overtime the hybrid becomes less fit than either parent and hybrid is no longer produced (reinforces species separation)

fusion zone

overtime, differences in parent species weaken and hybrid increases

Stability zone

overtime, hybrid stabilizes as new species along with parent species

predomorphosis

occurs when juvenile characteristics are retained in adult (axolotl)

what causes mass extinctions

abiotic factors(meteor), biotic(competition), humans

what follows mass extinction?

period of adaptive radiation of survivors