Ch.24 - Origin of Species

Question 1

What are the four species concepts?

Answer 1

Biological

Morphological

Ecological

Phylogenetic

Question 2

Describe the biological species concept

Answer 2

A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.

• Individuals of on species DO NOT produce viable, fertile offspring w members of other species.

Question 3

__________ refers to the biological factors that prevent members of two diff species fr producing fertile offspring.

Answer 3

Reproductive isolation refers to the biological factors that prevent members of two diff species fr producing fertile offspring.

Question 4

________ are offspring that result fr interspecific matings.

Answer 4

Hybrids are offspring that result fr interspecific matings.

Question 5

Differentiate pre- and post-zygotic barriers.

Answer 5

Pre-zygotic barriers prevent mating (e.g. habitat, temporal or behavioral isolation/mate recog) and/or prevent fertilization (mechanical or gametic isolation).

Post-zygotic barriers result in inviability, infertility, or breakdown of the hybrid.

Question 6

What is habitat isolation?

Answer 6

Habitat isolation is a pre-zygotic barrier in wh two species rarely encounter ea/o bc they live in sep habitats, even though there is no geo barrier.

Question 7

What is temporal isolation?

Answer 7

Temporal isolation is a pre-zygotic barrier in wh two species breed at diff times (of day/seasons/years).

Question 8

What is behavioral isolation?

Answer 8

Behavioral isolatin is a pre-zygotic barrier in wh courtship rituals and other behaviors do not overlap b/w two species.

Question 9

What is hybrid breakdown?

Answer 9

Hybrid breakdown is a post-zygotic barrier in wh some first-gen hybrids are fertile, but when they mate w another hybrid or w either parent species → offspring of 2+ gen are feeble or sterile.

Question 10

What are some limits of the biological species concept?

Answer 10

Doesn’t work for fossils or asexually reprod orgs.

Not helpful when there is gene flow b/w two groups but they are ecologically or morphologically distinct.

Overemphasizes gene flow and downplays role of NS.

Question 11

What is allopatric speciation?

Answer 11

Pop divided by a geo barrier → gene flow interrupted → ea subpop’s gene pool is subject to unique mutation, drift, and NS → reproductive isolation, i.e. interbreeding prevented, even if contact restored.

• “allos” – other, “patra” – homeland
• Outcome deps on mobility of species
• Caution: geo separation IS NOT a biological barrier.

THINK: german guy saying “Allo!” fr an island.

Question 12

What is sympatric speciation?

Answer 12

Speciation that occurs in pops that live in same geo area → ↓ gene flow. I.e. a reprod barrier isolates a subpop.

• Less common than allopatric speciation
• Caused by polyploidy, habitat differentation, and sexual selection.

Think: sym = same.

Question 13

T/F: polyploidy is much more common in plants than animals.

Answer 13

TRUE

Polyploidy is much more common in plants than animals.

One cause of sympatric speciation in wh extra sets of chromos arise due to accidents during cell division.

Estimated that ~80% of plant species resulted fr polyploid speciation.

Question 14

What is habitat differentiation?

Answer 14

Habitat differentiation is a cause of sympatric speciation in wh subpops use specific habitats or resources NOT avail to all members of pop.

Question 15

How does sexual selection result in sympatric speciation?

Answer 15

Individuals w certain inherited traits are more likely to obtain mates → choosiness of one sex in selecting a mate can result in initial (sympatric) sep of pops.

Question 16

T/F: The definition of species based on the biological species concept does not apply to organisms that reproduce asexually

Answer 16

TRUE

The definition of species based on the biological species concept DOES NOT apply to organisms that reproduce asexually

Question 17

T/F: Vicariance events are more common on islands than in mainland island such as looking at the Galapagos island

Answer 17

TRUE

Vicariance events are more common on islands than in mainland island such as looking at the Galapagos island

E.g. ice age produced many diff species mainly bc of vicariance events → glaciers physically separated pops fr ea/o.

Question 18

T/F: Polyploidy can result in sympatric speciation

Answer 18

TRUE

Polyploidy can result in sympatric speciation

Question 19

T/F: Allopatric speciation is common bc gene flow prevents genetic divergence in sympatric speciation.

Answer 19

TRUE

Allopatric speciation is common bc gene flow prevents genetic divergence in sympatric speciation.

Question 20

Many groups of organisms form _______ in which members of diff species meet and mate, producing at least some offspring of mixed ancestry.

Answer 20

Many groups of organisms form hybrid zones in which members of diff species meet and mate, producing at least some offspring of mixed ancestry.

• Over time, hybrid zones may remain stable, barriers reinforced (↓ reprod), or barriers break down (↑ reprod).

Question 21

T/F: speciation must be driven by many genes

Answer 21

FALSE

speciation can be driven by few OR many genes

Question 22

T/F: The last ice age produced many different species mainly because populations dispersed and colonized new habitats.

Answer 22

FALSE

The last ice age produced many diff species mainly bc of vicariance events; the glaciers physically separated pops fr ea/o.

Question 23

Which of the following statements about reinforcement is true?

• Increases # of intermediate phenotypes.
• Also called dispersive selection.
• A type of natural selection.
• Decreases morphological diff b/w two incipient species.

Answer 23

Which of the following statements about reinforcement is true?

• Increases # of intermediate phenotypes.
• Also called dispersive selection.
• A type of natural selection.
• Decreases morphological diff b/w two incipient species.

Reinforcement—aka disruptive selection—favors extreme phenotypes over intermediate phenotypes.

Question 24

Allopatric speciation can begin w a _______ event, in wh a geo barrier such as water isolates a population, or a ________ event, in wh a subset of a population migrates to a diff habitat.

Answer 24

Allopatric speciation can begin w a vicariance event, in wh a geo barrier such as water isolates a population, or a dispersal event, in wh a subset of a population migrates to a diff habitat.