Unit 3 Lecture 14

Question 1

What are the two types of reproductive barriers

Answer 1

1. Prezygotic barriers
2. Postzygotic barriers

Question 2

Within prezygotic barriers, what are the two forms of reproductive barriers?

Answer 2

1. Pre-mating: Isolating barriers that impede gene flow before sperm or pollen can be transferred to other species (can’t mate)
2. Postmating: Isolating barriers that impede gene flow after sperm of pollen has been transferred but before fertilization has occurred (can mate but CAN’T produce offspring)

Question 3

Within post zygotic barriers, name the one form of reproductive barrier?

Answer 3

1. Postzygotic: Isolating barriers that act after a zygote begins to develop (Can produce offspring but offspring cannot reproduce)

Question 4

Name the 3 types of isolation for Pre-Mating barriers

Answer 4

1. Behavioral Isolation: Differences in behavior that prevent members of different species from mating, such as lack of attraction
2. Ecological Isolation: Isolating barriers that are by-products of the ecology of different species
3. Reproductive structures (genitalia in animals, pollination structures in flowering plants) do not fit together mechanically, making it difficult for fertilization to occur

Question 5

Name the 2 types of isolation for Postmating barriers

Answer 5

1. Copulatory Behavioral Isolation: Behavior of an individual during copulation is insufficient to allow normal fertilization
2. Gametic Isolation: Transferred gametes unable to fertilize eggs

Question 6

Name the 2 types of isolation for post zygotic barriers

Answer 6

1. Intrinsic: Postzygotic isolation reflects a developmental problem in hybrids that is relatively independent of the environment
2. Extrinsic: Postzygotic isolation depends on the environment

Question 7

Name the 3 types of isolations that ecological isolation has

Answer 7

1. Habitate isolation: Species breed in different places or habitats
2. Temporal isolation: Species breed at different times
3. Pollinator isolation: Flowering plants rely on different species or pollination, or apply pollen to different parts of the same pollinating animal

Question 8

Name an example of Behavioral, Mechanical, and Ecological Isolation

Answer 8

• Behavioral: Fireflies mating call is by flashing their light. The flashing could be different enough where a female does not recognize a male
• Mechanical: Just does not fit; their reproductive structure; makes it difficult for fertilization to occur
• Ecological: Case in which you have isolation barriers that is the by-product of the ecology of different species

Question 9

Give an example of Gametic Isolation

Answer 9

Sea Urchins (red and purple)
- They live in the same habitats outdo not interbreed because the sperm of one is incompatible with the other (sperm CANNOT fertilize the egg)

Question 10

Name the 2 types of factors for intrinsic isolation

Answer 10

1. Hybrid Invariability: Hybrids die before or shortly after birth
2. Hybrid Sterility:
   - Physiological sterility: Hybrids suffer problems in the reproductive system or gametes
   - Behavioral Sterility: Hybrids suffer neurological or physiological defects that prevents them from finding mates

Question 11

Name the 2 types of factors for extrinsic isolation

Answer 11

1. Ecological inviability: Hybrids develop normally but they suffer lower viability because they cannot find an appropriate ecological niche (have traits from both dif. species that makes them maladaptive to their environment)
2. Behavioral Sterility: hybrids can produce normal gametes but cannot obtain mates

Question 12

Name an example of Intrinsic post zygotic barrier

Answer 12

Hybrid sterility:
- Mules (horse x donkey)
- Drosophila simulans x D. mauritiana
- Eastern x Western meadowlarks

Question 13

Name an example of hybrids that may be fertile but not well adapted

Answer 13

Polar bears and grizzly bears can make offspring (making more now due to climate change)
- Grizzlies are Omnivores and polar bears eat fatty seals
- Each species has biochemical adaptations for digesting different diets (hybrids will be fertile but WILL NOT be adapted to their environment due to intermediate phenotype)
- Example of extrinsic barrier

Question 14

Sometimes pre-mating “pollinator isolation” can lead to what

Answer 14

Sometimes hybridize will end up happening with a bunch of F1 hybrids and different morphologies, now having different pollinators

Question 15

What is the difference between allopatric speciation and sympatric speciation?

Answer 15

• Allopatric: geographic barrier leads to evolution of reproductive barriers
• Reproductive barriers can evolve without geographic barrier

Question 16

What is polypoid speciation?

Answer 16

• Usually some type of mistake in meiosis we some plants (and very few animals) can end up with a sperm/egg and evolve a form with 2x chromosomes number (polypoid)
• The two forms CANNOT form hybrid (sterile)

Question 17

Explain the case of the Rhagoletis “apple maggot fly”

Answer 17

• Apples originated in Asia and then developed in North America 350 years ago mainly being popular for making cider
• Johnny apple seed went through the US giving everyone apple seeds basically getting everyone drunk,
  and we now select apples for their flavor so we would enjoy
• Originally had NO native maggots, but maggots on apples appeared 150 years ago

Question 18

Phylogeny tells us what about Apple maggot fly?

Answer 18

Phylogeny tells us that the closest relative to the apple maggot fly is the hawthorn fly
- this tells us that this is a relatively recent speciation event, and an evolution of a hawthorn fly (lays larvae in series of hawthorn plants)
- Apple and hawthorn ripen at different times, reducing chance that the two flies mate at the same time (little bit of overlap so this is how some hawthorn flies lay their eggs in apples)