chapter 24 the origin of species

speciation

the process of which one species splits into two

speciation is the conceptual bridge between what?

microevolution

macroevolution

evolutionary changes that ceate new species and groups of species

what is the biggest hindrance to speciation?

gene flow

species

a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring

reproductive isolation

the existence of biological factors (barriers) that impede members of two species from interbreeding and viable, fertile offspring

what are the two types of reproductive isolation?

prezygotic and postzygotic

prezygotic barriers

block fertilization from occurring

postzygotic barriers

contribute to reproductive isolation after a zygote is formed

what are the types of prezygotic barriers?

1) habitat isolation

2) temporal isolation

3) behavioral isolation

4) mechanical isolation

5) gametic isolation

habitat isolation

two species occupy different habitats within the same area but rarely interact

temporal isolation

species that breed during different times of the day, different seasons, or different years

behavior isolation

courtship rituals that attract mayes and other unique behaviors are effective reproductive barriers

mechanical isolation

morphological differences prevent successful mating

gametic isolation

sperm of one species cannot fertilize the eggs of another species

what are the types of post zygotic barriers?

1) reduced hybrid viability

2) hybrid breakdown

reduced hybrid viability

the genes of differnt parent species may interact in ways that impair the hybrid’s development or survival

hybrid breakdown

some first-gen hybrids are viable and fertile, but when they mate, their offspring are feeble or sterile

what are the ways to define a species?

1) morphological species concept

2) ecological species concept

3) phylogenetic species concept

4) evolutionary/general lineage concept

morphological species concept

distinguishes a species by body shape and other structural issues

ecological species concept

defines a species in terms of its ecological niche

phylogenetic species concept

defines a species as the smallest group of organisms that share a common ancestor and form one distinct branch on a tree of life

evolutionary/general lineage concept

views a species as a single, independently evolving lineage with its own historical fate and tendencies

allopatric speciation

populations are geographically isolated

sympatric speciation

occurs in populations that live in the same geographic area

polyploidy

a species may originate from an accident during cell division that results in extra sets of chromosomes

allopolyploid

a sterile hybrid that is changed into a fertile polyploid

autopolyploid

an individual that has more than two chromosome sets derived from a single species

what are the 3 possible outcomes for hybrids?

1) reinforcement

2) fusion

3) stability

reinforcement

strengthening of reproductive barriers and hybrids cease to be formed

fusion

the weakening of repriductive barriers and the two species fuse

stability

continued production of hybrid individuals

hybrid zone

a change in environmental conditions that can alter where habitats of interbreeding species meet

punctuated equilibrium

periods of apparent stability punctuated by sudden change