Chapter 16: Speciation

Question 1

What are the 5 Prezygotic (operates BEFORE fertilization) Barriers?

Answer 1

1.Mechanical isolation: mating parts do not fit together (Ex: Right vs Left snail shell shape chirality)
2.Temporal isolation: Separation by time of day/ night living
3.Behavioral isolation: Differences in mating calls for identification
4.Habitat isolation: Separation in location and area. When two closely related species evolve preferences for living or mating in different habitats.
5. Gametic isolation: Separation of the sperm and egg to not come together. Protein/ chemical non=recognition and rejection.

Question 2

What are the 3 Postzygotic (operate AFTER fertilization) Barriers?

Answer 2

1.Hybrid zygote abnormality: Cannot form an organism that can reproduce, may die in infancy
2. Hybrid infertility: Offspring are infertile/ cannot produce offspring (Ex: mule).
3.Low hybrid viability: Low survival rates

Question 3

What is Reproductive isolation?

Answer 3

two groups of organisms can no longer exchange genes.

Question 4

What is Allopatric speciation?

Answer 4

when populations are separated by a physical or geographic barrier (think: A in Allopatric for Appalachian Mountains as a barrier example)

Question 5

What is Sympatric speciation?

Answer 5

speciation without physical isolation; often occurs by polyploidy which is when an organism duplicates its set of chromosomes

Question 6

What is a Homologous Trait?

Answer 6

a characteristic shared by two or more species because they inherited it from a common ancestor.

These traits have a common evolutionary origin, meaning they are derived from the same ancestral trait. Homologous traits may have similar functions or appearances in different species, but they can also have diverged in their functions over time (think: structure like bones)

Question 7

What is a Synapomorphy?

Answer 7

a specific type of homologous trait.

a trait that is shared by a group of species (a clade) and their MRCA but is not found in more distant ancestors or other groups

Question 8

What is a species?

Answer 8

A species is a group of organisms that will produce fertile offspring when they reproduce.

Question 9

________________(1) is required to maintain a species. Disruption of _______________(1) leads to speciation.

Answer 9

(1) Gene flow

Question 10

What is Ernst Mayr’s Biological species concept?

Answer 10

Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

Question 11

What is reproductive isolation?

Answer 11

Two groups of organisms that can no longer exchange genes.

Question 12

What is a neutral mutation?

Answer 12

Mutations that are neither beneficial nor detrimental to the ability of an organism to survive and reproduce.

Question 13

What is allopatric speciation?

Answer 13

When populations are separated by a physical or geographic barrier

Most common type of speciation

Barriers can form when continents drift, sea levels rise and fall, glaciers advance and retreat, or climate change

The populations evolve through mutation, genetic drift, and adaptation to different environments in two areas

Question 14

The ________________(1) leads to allopatric speciation.

Answer 14

(1) founder effect

Question 15

Finch species in the Galápagos Islands are an example of _________________(1) speciation

Answer 15

(1) allopatric

Question 16

What is sympatric speciation?

Answer 16

Speciation without physical isolation

Caused by disruptive selections individuals with detain genotypes prefer distinct microhabitats where mating takes place. Can also be caused by chronological differences(i.e. two species being awake/asleep at different times)

Question 17

Sympatric speciation most commonly occurs by _________________(1) which is _____________________(2).

Answer 17

(1) polyploidy
(2) the duplication of sets of chromosomes within individuals

The differences in chromosome numbers make ti impossible for these organisms to interbreed with the normal diploid form of the parent organism as they have different traits and adaptations that allow them to take up a new ecological niche. Animals with the same polyploidy can mate successfully.

Question 18

What is autopolyploidy?

Answer 18

chromosomes fail to separate properly during meiosis, defined as chromosome duplication in a single species.

Question 19

What are the two types of polyploidy?

Answer 19

Autopolyploidy: Chromosome duplication in a single species
- Occurs when the chromosomes fail to separate properly during meiosis

Allopolyploidy: Combining chromosomes of two different species

Question 20

A _____________(1) can result if two accidentally unreduced diploid gametes combine.

Answer 20

(1) tetraploid

Question 21

What is a prezygotic reproductive barrier and what are the types?

Answer 21

Barriers to gene exchange that operate before fertilization.

1. Mechanical isolation(physical incompatibility)
2. Temporal isolation(time)
3. Behavioural isolation(isolation based on the behavior of species in the context of mating rituals and signals.)
4. Habitat isolation(where they live)
5. Gametic isolation(egg and sperm come into contact but nor fertilization occurs because of molecular interactions)

Question 22

What is a hybrid zone? How do they form?

Answer 22

Hybrid zones are regions where genetically distinct populations meet, mate, and produce at least some offspring of mixed ancestry.

Hybrid zones may develop if barriers to gene exchange failed to develop during allopatry. Hybrids may form if operated populations rejoin without sufficient genetic differences having accumulated. Essentially, they form when reproductive isolation is incomplete and where population ranges overlap.

Question 23

What are post zygotic reproductive barriers?

Answer 23

Barriers that operate after fertilizaiton

1. Hybrid zygotę abnormality
2. Hybrid infertility (ability to reproduce)
3. Low hybrid viability(ability to survive)

Question 24

Hyrbids suffer from a ________________(1) and are not as _________(2) as purebred individuals. The hybrid zone is very _______________(3) because there is strong selection pressure ___________________(4) hybrids.

Answer 24

(1) range of defects
(2) fit
(3) narrow
(4) against

Question 25

What factors influence speciation?

Answer 25

1. Ecological specialization(ex. diets)
   - Herbivores have many different species b/c of variety in plants
2. Type of pollination(animal vs. wind)
   - Speciation rates are higher in animal-pollinated than wind-pollinated plants and are correlated with pollinator specializaiton
3. Sexual selection
   - High rates of speciation especially with polygynous systems and sexual dimorphism
4. Population bottlenecks/ dispersal ability(the ability of species to become established in a new area)
   - Speciation rates are faster in species with poor dispersal abilities because they can be separated by narrow barriers.
5. Environmental changes

Question 26

What is reinforcement?

Answer 26

A process in which natural selection favors traits or behaviors that reduce the likelihood of mating and hybridization between two different species, especially when they come into contact in areas of sympatry.

Question 27

Was Darwin’s “tree of life” model better or the “punctuated equilibrium” model?

Answer 27

punctuated equilibrium : represents sudden, rapid changes to adapt to fast changes in environment.

Question 28

What is polygynous?

Answer 28

the state or practice of having more than one wife or female mate at a time

Question 29

What is sexual dimorphism?

Answer 29

Males look different than females