24.1 The biological species concept emphasizes reproductive isolation

Question 1

1) Which of the following statements about species, as defined by the biological species concept, is (are) correct?
I. Biological species are defined by reproductive isolation.
II. Biological species are the model used for grouping extinct forms of life.
III. The biological species is the largest unit of population in which successful reproduction is possible.
A) I only
B) II only
C) I and III
D) II and III
E) I, II, and III

Answer 1

C) I and III

Question 2

2) What is generally true of two very closely related species that have diverged from each other quite recently?
A) They shared a common ancestor recently in evolutionary time.
B) Genes are unable to pass from one speciesʹ gene pool to the otherʹs gene pool.
C) They are unable to produce hybrid offspring upon interbreeding.
D) Their reproductive isolation from each other is complete.

Answer 2

A) They shared a common ancestor recently in evolutionary time.

Question 3

3) Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools?
A) phylogenetic
B) ecological
C) biological
D) morphological

Answer 3

C) biological

Question 4

4) Which species concept is currently most popular among most biologists?
A) phylogenetic
B) ecological
C) biological
D) morphological

Answer 4

A) phylogenetic

Question 5

5) There is still some controversy among biologists about whether Neanderthals should be placed within the same species as modern humans, or into a separate species of their own. Most DNA sequence data analyzed so far indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species concept is most applicable in this example?
A) phylogenetic
B) ecological
C) morphological
D) biological

Answer 5

D) biological

Question 6

6) A biologist discovers two populations of wolf spiders whose members appear identical. Members of one population are found in the leaf litter deep within the woods. Members of the other population are found in the grass at the edge of the woods. The biologist decides to designate the members of the two populations as two separate species. Which species concept is this biologist most closely utilizing?
A) ecological
B) biological
C) morphological
D) phylogenetic

Answer 6

A) ecological

Question 7

7) What was the species concept most used by Linnaeus?
A) biological
B) morphological
C) ecological
D) phylogenetic

Answer 7

B) morphological

Question 8

8) You are confronted with a box of preserved grasshoppers of various species that are new to science and have not been described. Your assignment is to separate them into species. There is no accompanying information as to where or when they were collected. Which species concept will you have to use?
A) biological
B) phylogenetic
C) ecological
D) morphological

Answer 8

D) morphological

Question 9

Several closely related frog species of the genus Rana are found in the forests of the southeastern United States. The species boundaries are maintained by reproductive barriers. In each case, match the various descriptions of frogs below with the appropriate reproductive barrier listed.

9) Males of one species sing only when its predators are absent; males of another species sing only when its predators are present.
A) behavioral
B) gametic
C) habitat D) temporal
E) mechanical

Answer 9

A) behavioral

Question 10

10) One species lives only in tree holes; another species lives only in streams. A) behavioral
B) gametic
C) habitat
D) temporal
E) mechanical

Answer 10

C) habitat

Question 11

11) Females of one species choose mates based on song quality; females of another species choose mates on the basis of size.
A) behavioral
B) gametic
C) habitat
D) temporal
E) mechanical

Answer 11

A) behavioral

Question 12

12) One species mates at the season when daylight is increasing from 13 hours to 13 hours, 15 minutes; another species mates at the season when daylight is increasing from 14 hours to 14 hours, 15 minutes.
A) behavioral
B) gametic
C) habitat
D) temporal
E) mechanical

Answer 12

D) temporal

Question 13

13) Males of one species are too small to perform amplexus (an action that stimulates ovulation) with females of all other species.
A) behavioral
B) gametic
C) habitat
D) temporal
E) mechanical

Answer 13

E) mechanical

Question 14

14) Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile. This kind of isolation is most similar to which of the following reproductive isolating mechanisms?
A) reduced hybrid fertility
B) hybrid breakdown
C) mechanical isolation
D) habitat isolation
E) gametic isolation

Answer 14

D) habitat isolation

Question 15

15) Rank the following from most general to most specific: 1. gametic isolation
2. reproductive isolating mechanism
3. pollen-stigma incompatibility
4. prezygotic isolating mechanism

A) 2, 3, 1, 4
B) 2, 4, 1, 3
C) 4,1,2,3
D) 4, 2, 1, 3
E) 2, 1, 4, 3

Answer 15

B) 2, 4, 1, 3

Question 16

Two species of frogs belonging to the same genus occasionally mate, but the offspring fail to develop and hatch. What is the mechanism for keeping the two frog species separate?
A) the postzygotic barrier called hybrid inviability
B) the postzygotic barrier called hybrid breakdown
C) the prezygotic barrier called hybrid sterility
D) gametic isolation
E) adaptation

Answer 16

A) the postzygotic barrier called hybrid inviability

Question 17

17) Theoretically, the production of sterile mules by interbreeding between female horses and male donkeys should
A) result in the extinction of one of the two parental species. B) cause convergent evolution.
C) strengthen postzygotic barriers between horses and donkeys.
D) weaken the intrinsic reproductive barriers between horses and donkeys.
E) eventually result in the formation of a single species from the two parental species.

Answer 17

C) strengthen postzygotic barriers between horses and donkeys.

Question 18

18) The biological species concept is inadequate for grouping A) plants.
B) parasites.
C) asexual organisms.
D) animals that migrate.
E) sympatric populations.

Answer 18

C) asexual organisms.

Question 19

19) Which example below will most likely guarantee that two closely related species will persist only as distinct biological species?
A) colonization of new habitats
B) convergent evolution
C) hybridization
D) geographic isolation from one another
E) reproductive isolation from one another

Answer 19

E) reproductive isolation from one another

Question 20

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila yakuba inhabits the islandʹs lowlands, and is also found on the African mainland, located about 200 miles away. At higher elevations, and found only on Sao Tomé, is found the very closely related Drosophila santomea. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, though hybrids there are greatly outnumbered by D. santomea. Studies of the two speciesʹ nuclear genomes reveal that D. yakuba on the island is more closely related to mainland D. yakuba than to D. santomea (2n=4 in both species). Sao Tomé rose from the Atlantic Ocean about 14 million years ago.

36) Which of these reduces gene flow between the gene pools of the two species on Sao Tomé, despite the existence of hybrids?
A) hybrid breakdown
B) hybrid inviability
C) hybrid sterility
D) temporal isolation
E) a geographic barrier

Answer 20

C) hybrid sterility