Species And Speciation

Question 1

Biological species concept

Answer 1

Groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups

Question 2

Limitations of BSC

Answer 2

Reproductive isolation evolves slowly
Good for sexual species but not asexual species
Not very good for allopathic populations

Question 3

Phylogenetic species concept

Answer 3

An irreducible cluster of organisms diagnosably different from other such clusters, and within which there is a parental pattern of ancestry and decent
Can be used for allopathic populations

Question 4

Parapatric speciation

Answer 4

A graded level of gene exchange among adjacent populations

Question 5

Introgression

Answer 5

Movement of genes from one species or population into another by hybridization and backcrossing
Suggests that some genes in a genome undergo such movement but some don’t

Question 6

Reproductive isolating barriers

Answer 6

Reduce gene flow between biological species
Prezygotic and postzygotic
Based on biological differences

Question 7

Prezygotic barriers

Answer 7

Reduce likelihood that hybrids form
- geographic/habitat segregation, pollinator segregation, seasonal mating
Can evolve by reinforcement

Question 8

Postzygotic barriers

Answer 8

Reduce gene exchange between populations even if hybrids are produced
Reduce hybrid viability/survival
-extrinsic (low fitness due to environment)
-intrinsic (independent of environment)
Can’t evolve by reinforcement

Question 9

Haldanes rule

Answer 9

When only one sex manifests sterility/inviability in hybrids between species, it is the heterogametic sex (with two different sex chromosomes) that does so

Question 10

Dobzhansky-muller incompatibilities

Answer 10

Reduction in the fitness of a hybrid because of an interaction between certain alleles in one parent population with specific alleles at other loci in the other parent population
Type of gene conflict

Question 11

Ecological speciation

Answer 11

Occurs when natural selection acts differently on two populations
E.g pollinator isolation

Question 12

Speciation by genetic conflict

Answer 12

Occurs when an allele increases its own transmission to the detriment of other alleles
Eg segregation distortion

Question 13

Segregation distortion

Answer 13

Allele inherited by non-Mendelian ratio

Question 14

Speciation by sexual selection

Answer 14

Mate choice, primarily by females

Question 15

Speciation by polyploidy

Answer 15

Chromosomes fail to segregate during meiosis

Impacts gene dosage = altered phenotypic traits

Question 16

Autopolyploidy

Answer 16

Both unreduced gametes come from same species

Question 17

Allopolyploidy

Answer 17

Unreduced gametes come from different species

Question 18

Hybrid speciation

Answer 18

Occasionally interspecific hybridization results in new species

Question 19

Speciation by genetic drift

Answer 19

Likelihood of drift increases with small Ne
Rare alleles fix more readily
Other loci interact more favorably with these rare alleles
Increased intragenomic compatibility
Reduced intragenomic compatibility with parent population

Question 20

Speciation genes

Answer 20

Loci that contribute to the evolution of reproductive isolation
ZW (reptiles, birds, some insects)
XY (vertebrates, some insects)
Y/W never recombines