Chapter 24 terms/concepts

Question 1

Biological species concept

Answer 1

Definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do not produce viable, fertile offspring with members of other groups

Question 2

Hybrid(s)

Answer 2

Offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species.

Question 3

Speciation

Answer 3

An evolutionary process in which one species splits into two or more species

Question 4

Reproductive Isolation

Answer 4

The existence of biological factors that impede members of two species from producing viable, fertile offspring

Question 5

Prezygotic mechanisms (barriers)

Answer 5

Prevent mating or fertilization

Question 6

Postzygotic mechanisms (barriers)

Answer 6

prevent zygote development or reproduction

Question 7

Strengths and Weaknesses (limitations) of the biological species concept

Answer 7

Strength: directs our attention to a way by which speciation can occur: by evolution of reproductive isolation

Limitation: The number of species to which this concept can be usefully applied is limited (no fossils, or prokaryotes)

Question 8

Morphological species concept (what is it, and strengths and weaknesses?)

Answer 8

Definition: distinguishes a species by body shape and other structural features.

Strength: can be applied to both asexual and sexual organisms, and it can be useful even without information on the extent of gene flow

Weakness: it relies on subjective criteria; researchers may disagree on which structures distinguish a species

Question 9

Ecological species concept (definition, strengths and weaknesses)

Answer 9

Definition: defines a species in terms of its ecological niche, the sum of how members of the species interact with nonliving and living parts of the environment

strength: Accommodates both asexual as well as sexual species, and emphasizes the role of disruptive natural selection

weakness: Too many decisions on how much difference between individuals is too much variation

Question 10

Habitat isolation

Answer 10

Animals who live in different habitats within the same area may never encounter each other (prezygotic)

Question 11

Temporal isolation

Answer 11

Mating time differences between species (prezygotic)

Question 12

Behavioral isolation

Answer 12

courtship rituals that attract mates and other behaviors unique to a species (prezygotic)

Question 13

Mechanical isolation

Answer 13

morphological characteristics are not viable for reproduction (prezygotic)

Question 14

Gametic isolation

Answer 14

sperm cannot fertilize egg (prezygotic)

Question 15

Reduced hybrid viability

Answer 15

genes of different parent species may interact in ways that impair hybrid’s development (postzygotic)

Question 16

Reduced hybrid fertility

Answer 16

if parent chromosomes differ in number or structure, meiosis in hybrids may fail to produce normal gametes (postzygotic)

Question 17

Hybrid breakdown

Answer 17

first gen hybrids are viable and fertile, but when they mate with parent species or each other, the next-gen are feeble and sterile (postzygotic)

Question 18

Allopatric speciation

Answer 18

species are geographically isolated from one another

Question 19

Sympatric speciation

Answer 19

a subset of a population forms a new species without geographic separation

Question 20

Polypoidy

Answer 20

When a species originates by an accident during cell division that results in extra sets of chromosomes

Question 21

Autopolyploid

Answer 21

An individual that has more than two chromosome sets that are all derived from a single species

Question 22

Hybrid zone

Answer 22

a region in which members of different species meet and mate with one another

Question 23

Reinforcement

Answer 23

1st possible outcome concerning hybrid zones and formation of hybrid species - hybrid species is weak and unfit, and natural selection selects for prezygotic factors that eliminate the hybrids between the two species, thus reinforcing the reproductive barriers

Question 24

Fusion

Answer 24

the 2nd outcome for hybrid zones is when gene flow is increasingly strong between two species that the zone deteriorates, and the two (once) separate species now converge as their gene pools become increasingly similar due to cross-breeding

Question 25

Stability

Answer 25

the 3rd outcome of hybrid zones: is where hybrids reproduce better than members of either parent species, and thus allow for the hybrid zone to remain between the two parent species

Question 26

Punctuated model of speciation

Answer 26

New species change most as they branch from a parent species and then change little for the rest of their existence

Question 27

Gradual model of speciation

Answer 27

Species diverge from one another more slowly and steadily over time

Question 28

Allopolyploid

Answer 28

A fertile individual that has more than 2 chromosome sets as a result of 2 different species interbreeding and combining their chromosomes