Unit II: Speciation

Question 1

Species

Answer 1

group of populations that interbreed and produce fertile offspring

Question 2

Speciation

Answer 2

formation of a new species; a splitting event that creates two or more distinct species from a single ancestral species

Question 3

Gene flow

Answer 3

Transfer of alleles from one population to another
- migration
- makes populations smaller

Question 4

Reproductive isolation

Answer 4

Behaviors or processes that prevent gene flow between populations
- created opportunity for divergence

Question 5

Allopatry

Answer 5

(occurring in different geographical areas) is an effective way to hinder gene flow between populations

Question 6

Allopatric speciation

Answer 6

speciation that occurs via geographical separation
- most common mode of speciation

Question 7

Without gene flow, there is opportunity for populations to _____ and become reproductively isolated.

Answer 7

diverge

Question 8

What are 2 routes to allopatry?

Answer 8

1. dispersal to a new habitat
2. vicariance

Question 9

With dispersal, the likelihood of speciation is ______ correlated with connectively between patches

Answer 9

negatively, high connectivity = low chance of speciation

Question 10

What is Vicariance?

Answer 10

the physical splitting of a population into smaller, isolated populations by a physical barrier

Question 11

With vicariance, the likelihood of speciation is _____ correlated with the strength of the barrier.

Answer 11

positively

Question 12

Isolating mechanisms can be _______ (before zygote formation) or ________ (after zygote formation)

Answer 12

prezygotic, postzygotic

Question 13

What are the types of mechanism that prevent the formation of a zygote?

Answer 13

1. temporal
2. habitat
3. behavioral
4. mechanical
5. gametic

Question 14

What is Temporal Isolation?

Answer 14

differences in breeding schedules that can act as a form of pre zygotic barrier leading to reproductive isolation

Question 15

What is Habitat Isolation?

Answer 15

reproductive isolation resulting when species’ populations move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the same species’ other populations; may never come into contact during mating periods = no hybridization

Question 16

What is Behavioral Isolation?

Answer 16

type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place (e.g. sound frequencies in mating calls are unattractive)

Question 17

Does behavioral isolation extend to plants?

Answer 17

Yes, pollinators may favor different floral shapes or food (nectar)

Question 18

What is Mechanical Isolation?

Answer 18

differences in size and shape of reproductive organs, making mating impossible (e.g. genital lock & key)

Question 19

What is Gametic Isolation?

Answer 19

prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs & sperm) prevent fertilization from happening

Question 20

What are types of mechanisms that prevent zygotes from passing on alleles?

Answer 20

1. Hybrid Inviability
2. Hybrid Biological Sterility
3. Hybrid Ecological Sterility

Question 21

What is Hybrid Inviability?

Answer 21

hybrids do not survive to sexual maturity, instead they die during development or soon after birth

Question 22

What is Hybrid Biological Sterility?

Answer 22

hybrids survive to maturity but do not produce gametes or are not fertile

Question 23

What is Hybrid Ecological Sterility?

Answer 23

hybrids survive to maturity and are fertile, but have an intermediate phenotype that keeps them from reproducing (e.g. don’t attract mates or are not adapted to environment)

Question 24

What is Reinforcement?

Answer 24

continued speciation divergence between 2 species due to low fitness of hybrids between them

Question 25

Since producing hybrids decreased fitness, natural selection results in _____

Answer 25

reinforcement