Speciation & Macroevolution

Question 1

Speciation

Answer 1

Creation of a new species

Question 2

Macroevolution

Answer 2

Evolutionary change above the species level (i.e. the evolutionary components of speciation)

Question 3

Microevolution

Answer 3

Change in allele frequency in a local population in time

Question 4

Biological species concept

Answer 4

Individuals are members of the same species if they are capable of interbreeding and producing fertile offspring (does not work in all cases, but works in most)

Question 5

Reproductive isolation

Answer 5

The existence of biological factors (reproductive barriers) that prevent 2 individuals from interbreeding and producing fertile offspring

• key concept of biological species concept
• a single behavior may not give rise to complete reproductive isolation
• many factors can act in concert to create reproductive isolation

Question 6

Reproductive barriers

Answer 6

1. pre-zygotic

2. post-zygotic

Question 7

Zygote

Answer 7

Fusion of sperm and egg

Question 8

Pre-zygotic barriers

Answer 8

1. prevent mating

2. prevent fertilization of egg

Question 9

Post-zygotic barriers

Answer 9

1. prevent survival

2. prevent reproduction of offspring

Question 10

Pre-zygotic isolations: (5 isolations)

Answer 10

1. temporal isolation: timing is off
2. habitat isolation: habitat is off
3. behavior isolation: behavior is off
4. mechanical isolation: mating may be attempted, but prevented by morphological differences (his dick don’t fit)
5. gametic isolation: sperm of 1 species may not be able to fertilize eggs of another species

Question 11

Post-zygotic consequences : (3 consequences)

Answer 11

Fertilization occurs but…

1. reduced hybrid viability (i.e. hybrids do not survive well)
2. reduced hybrid fertility (i.e. hybrids cannot reproduce)
3. hybrid breakdown (i.e. hybrids are non-viable or sterile in subsequent generations)

Question 12

2 ways speciation can occur:

Answer 12

1. Allopatric speciation

2. Sympatic speciation

Question 13

Allopatric speciation

Answer 13

Geographic separation of populations

• divergence
• greatly reduced gene flow
• genetic drift (founder effect)
• natural selection (differences in environment between populations)
• new species can only form when geographic isolation is followed by reproductive isolation

Question 14

Sympatric speciation

Answer 14

Speciation without geographic isolation

-most common mechanism = polyploidy (“many chromosomes”)

Question 15

Polyploidy

Answer 15

Error during meiosis changes the number of chromosomes in gametes -> offspring (may be viable and self-fertile)

• most common in plants
• can occur in animals (much less common)

Question 16

Allopatric vs. sympatric speciation

Answer 16

Allopatric speciation:
-geographic isolation restricts gene flow between populations
-reproductive isolation may then arise via (genetic) drift
-natural selection (sexual selection in the isolated populations)
Sympatic speciation:
-a reproductive barrier still isolates subset of population without geographic isolation
-can result in polyploidy and natural selection (sexual selection)

Question 17

How much genetic change is required for speciation?

Answer 17

Impossible to generalize

Question 18

How quickly does speciation occur?

Answer 18

Patterns can often be inferred from fossil record, morphological, or molecular data

• the interval between speciation events can range from 4,000 - 40,000,000 years
• average = 6,500,000 years

Question 19

Punctuated equilibrium

Answer 19

Periods of little change interrupted by short periods of rapid change

Question 20

Gradualism

Answer 20

Big differences between species accumulated through slow, steady change