Chapter 22

Question 1

The concept of species must account for two phenomena:​

Answer 1

The distinctiveness of species that occur together at a single locality.​

The connection that exists among different populations belonging to the same species.

Question 2

Sympatric species

Answer 2

Sympatric species occur together in an area​

Are distinctive entities​

Are phenotypically different​

Utilize different parts of the habitat​

Behave separately

Question 3

Geographic variation

Answer 3

Within a single species, individuals in populations that occur in different areas may be distinct from one another

Question 4

The Biological Species Concept​

Answer 4

Species are composed of populations whose members mate with each other and produce fertile offspring​

Question 5

Reproductive isolation

Answer 5

do not mate with each other or do not produce fertile offspring

Question 6

Prezygotic isolating mechanisms

Answer 6

Mechanisms that prevent formation of a zygote.

Question 7

Postzygotic isolating mechanisms

Answer 7

Mechanisms that prevent proper functioning of zygotes after they form.

Question 8

Prezygotic isolating mechanisms​ (list)

Answer 8

Ecological isolation​

Behavioral isolation​

Temporal isolation​

Mechanical isolation​

Prevention of gamete fusion

Question 9

Postzygotic isolating mechanisms (list)

Answer 9

Hybrid inviability or infertility

Question 10

Ecological isolation

Answer 10

Species occur in the same area, but they occupy different habitats and rarely encounter each other.

Question 11

Temporal isolation

Answer 11

Species reproduce in different seasons or at different times of the day.

Question 12

Mechanical isolation

Answer 12

Structural differences between species prevent mating

Question 13

Prevention of gamete fusion

Answer 13

Gametes of one species function poorly with the gametes of another species or within the reproductive tract of another species.

Question 14

Hybrid inviability or infertility

Answer 14

Hybrid embryos do not develop properly, hybrid adults do not survive in nature, or hybrid adults are sterile or have reduced fertility.

Question 15

Postzygotic isolating mechanisms

Answer 15

Problems occur as the fertilized eggs develop.​

Many hybrids cannot be produced even in the laboratory.​

Hybrids that do survive may be weaker​

Hybrids may be sterile – mules​

Abnormal sex organs.​

Failure to form gametes.​

Chromosomes cannot pair properly in meiosis.

Question 16

Criticisms of biological species concept:

Answer 16

Reproductive isolation may not be the only force maintaining species integrity.​

Interspecific hybridization​

50% of California plant species, in one study, not well defined by genetic isolation.​

10% of world’s 10,000+ bird species known to hybridize in nature.

Question 17

Ecological species concept

Answer 17

Each species adapted to its environment​

Question 18

Other weaknesses of biological species concept

Answer 18

Difficult to apply the concept to populations that are geographically separated in nature​

Many species that do not hybridize in the wild will do so in captivity​

Many organisms are asexual​

Possible that different processes maintain species identity in different organisms

Question 19

Reinforcement

Answer 19

initially incomplete isolating mechanisms are reinforced by natural selection until they are completely effective

Question 20

Genetic Drift

Answer 20

Random changes may cause reproductive isolation

Question 21

Speciation is a 2-part process

Answer 21

Initially identical populations must diverge.​

Reproductive isolation must evolve to maintain these differences.

Question 22

Allopatric speciation​

Answer 22

Geographically separated, or allopatric, populations appear much more likely to have evolved substantial differences leading to speciation

Question 23

Sympatric speciation

Answer 23

One species splits into two at a single locality, without the two new species ever having been geographically separated

Question 24

Autoploidy

Answer 24

All the chromosomes arise from a single species.​

Error in cell division produces tetraploids.​

Cannot produce fertile offspring with normal diploids.

Question 25

Allopolyploidy

Answer 25

Two species hybridize.​

Resulting offspring have one copy of the chromosomes of each species.​

Infertile: cannot reproduce with either species – chromosomes do not pair correctly in meiosis.​

Can become fertile if chromosomes spontaneously doubled (polyploidy); breed with other tetraploids.

Question 26

Adaptive Radiation

Answer 26

Closely related species that have recently evolved from a common ancestor by adapting to different parts of the environment

Question 27

Key innovation

Answer 27

New trait evolves within a species allowing it to use resources that were previously inaccessible

Question 28

Character displacement

Answer 28

Two reproductively isolated but ecologically similar species come into contact​

Natural selection in each species favors those individuals that use resources not used by the other species​

Greater fitness​

Trait differences in resource use will increase in frequency over time​

Species will diverge

Question 29

Gradualism

Answer 29

Accumulation of small changes.​

Standard view for a long time.

Question 30

Key innovation

Answer 30

carry a second set of functioning jaws

Question 31

Punctuated equilibrium

Answer 31

Long periods of stasis followed by rapid change.​

Stabilizing and oscillating selection is responsible for stasis.

Question 32

Mass extinctions

Answer 32

5 mass extinctions have occurred; as many as 96% of all species have perished in a given extinction​

Not all groups of organisms affected equally; previously dominant groups may perish​

6th extinction is underway; number of species decreasing at an alarming rate due to human activity