CH. 7 (Origin of Species)

Question 1

What did Darwin not explain?

Answer 1

How the continuous process of evolution produced discrete groups—speciation

Question 2

Problems with the morphological species concept

Answer 2

• Some species are sexually dimorphic (would we classify males and females as separate species? no)
• Sometimes members of the same species look different (humans)

Question 3

cryptic species

Answer 3

Species that are morphologically identical but still different from each other ex. Drosophila and Anopheles Gambiae (mosquitoes)

Question 4

reproductively isolated

Answer 4

distinct gene pools that do not intermingle

Question 5

Ernst Mayr and Theodosius Dobzhansky

Answer 5

first to realize differences in gene pool meant different species.

Question 6

biological species concept

Answer 6

a species is a group of interbreeding natural populations that are reproductively isolated from other such groups (genetic difference that arose by their behaviour, appearance, physiology)

Question 7

What organisms do not fit under BSC

Answer 7

There has to be potential for gene flow thus asexually reproducing organisms (bacteria, funghi) do not fit criteria. We also can’t apply this theory to fossil remains.

Question 8

pre-mating barriers

Answer 8

different mating displays, pheromones, habitats, different pollinators (flowers)`

Question 9

Post-mating barriers

Answer 9

pollen doesn’t germinate, fetuses die before birth, hybrids are sterile if they do survive

Question 10

sister species

Answer 10

species that are each others closest relatives—often separated in nature by geographical barriers (close to each other ex. flowering species of plants found in east Asia and eastern USA)

Question 11

geographic barriers

Answer 11

different evolutionary forces causing natural selection to work in different ways leading to different species

Question 12

if genomes are differentiated enough…

Answer 12

the hybrid will die

Question 13

Theory of Geographic Speciation

Answer 13

evolution of genetic isolation first requires that they be geographically isolated. Species cannot possibly split if they retain the opportunity to interbreed.

Question 14

Where are “radiations” often found and why?

Answer 14

Archipelagos. As species move from island to island they become isolated (Anolis lizard, finches of Galapagos)

Question 15

What characterizes reproductive isolation?

Answer 15

mating discrimination between pairs, sterility of hybrid, inviability of hybrid

Question 16

sympatric speciation

Answer 16

speciation without geographic isolation

Question 17

Why is it hard to find evidence for sympatric speciation?

Answer 17

Even if you find two related species in the same area how would you know they arose in the same area rather than just moving together?

Question 18

allopolyploid speciation

Answer 18

hybridization of 2 different species that live in the same area (most common with plants). Usually requires that the two species have different numbers of types of chromosomes. The hybrid will be sterile because it wont have the proper pairing of chromosomes when it attempts to make pollen or ovules.
- HOWEVER double chromosome allopolyploids can reproduce because they have double the alleles and can pair

Question 19

autopolyploidy

Answer 19

When chromosomes of single species are doubled. Doesn’t require hybridization. They can mate with each other but not with parent species (immediate speciation)

Question 20

What does polyploid speciation necessitate?

Answer 20

The rare event of formation and union of sperm and eggs with abnormally high numbers of chromosomes. This must happen in two successive generations.

Question 21

What proportion of species of flowering plants were formed via polyploidy?

Answer 21

Quarter of all flowering species. Polyploid speciation is found in nearly every group of plant except trees.

Question 22

Example of animal polyploid

Answer 22

Red viscacha rat of Argentina (animal polyploids are very rare—mostly fish, insects, worms)

Question 23

Polyploid speciation

Answer 23

changes in the chromosome numbers rather than the genes themselves meaning speciation occurs much faster. Genomes are inherently incompatible.

Question 24

How can we check to see if wild species have hybridized?

Answer 24

artificially resynthesize the wild hybrid (will often have same phenotype)