Speciation Flashcards
the process by which one species splits into two or more species
speciation
What does speciation do?
bridges microevolution & macroevolution
change in allele frequency in population over time
microevolution
broad patterns of evolutionary change above the species level
macroevolution
a group of population whose members can interbreed and produce fertile, viable offspring
species
What does the biological species concept believe?
(1) gene flow holds populations together genetically
(2) reproductive isolation keeps species apart
(3) phenotypic similarities or differences don’t matter
when biological barriers impede 2 species from producing viable, fertile offspring
reproductive isolation
Types of reproductive isolation
pre-zygotic barriers & post-zygotic barriers
offspring of crosses between different species
hybrids
blocks fertilization by hindering mating or fertilization
pre-zygotic barriers
5 types of pre-zygotic barriers
(1) habitat isolation
(2) temporal isolation
(3) behavioral isolation
(4) mechanical isolation
(5) gametic isolation
Which type of pre-zygotic isolation deals with water versus land?
habitat
Which type of pre-zygotic isolation includes mating in the summer versus winter?
temporal
Which type of pre-zygotic isolation includes knowing mating rituals?
behavioral
Which type of pre-zygotic isolation is where the organisms are physically inhibited from mating?
mechanism
Which pre-zygotic isolation is where gametes cannot fuse?
gametic
prevents the hybrid zygote form developing into a viable, fertile adult
post-zygotic barrier
3 types of post-zygotic barriers
(1) reduced hybrid viability
(2) reduced hybrid fertility
(3) hybrid breakdown
Which type of post-zygotic barrier is where the offspring have low fitness?
reduced hybrid viability
Which type of post-zygotic barrier is where the number of chromosomes in parents affect the fertility of offspring?
reduced hybrid fertility
Which type of post-zygotic barrier is where the offspring of hybrid are sterile?
hybrid breakdown
What are the limitations to the biological species concept?
(1) cannot be applied to fossils or asexual organisms
(2) difficult to apply to allopatric population
(3) emphasizes absence of gene flow, but gene flow can occur between species
populations that live in different geographic locations
allopatric
groups species by structural features
morphological species concept
groups species by ecological niche
ecological species concept
groups species as the smallest group of individuals on a phylogenetic tree
phylogenetic species concept
Types of speciation
allopatric & sympatric
What are the mechanisms of allopatric speciation?
(1) populations are geographically isolated
(2) reproductive isolation arises by natural selection, genetic drift, or sexual selection
(3) ‘barriers’ depend on the organisms’ dispersal
(4) interbreeding is no longer possible even if contact is restored
What are the mechanisms of sympatric speciation?
(1) populations live in the same geographic area
(2) they are in contact, but gene flow between theme is reduced
How is gene flow reduced in sympatric selection?
polyploidy, natural selection, & sexual selection
On average, how long does speciation last?
6.5 million years
periods of no change punctuated by short bursts of rapid change
punctuated equilibrium
gradual change over a long period of time
gradualism
What is the time range of speciation?
4,000 to 40 million years
Does speciation involve few or many genes?
few
