Ch 22: The Origin of Species

Question 1

What is a species?

Answer 1

a population 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 such groups.

Question 2

Species is Latin for…

Answer 2

…“kind” or “appearance”.

Question 3

There are 3 major concepts by which we can categorize species.

Answer 3

Morphological species concept –
(defined by structural features)

Phylogenetic species concept (this is not in the textbook)-
Species are defined by position on a cladogram. They are the tips of the phylogenetic trees.

Biological species concept–
Species are populations that interbreed, and are reproductively isolated from other such groups.

Question 4

What are cryptic species?

Answer 4

Species which look alike, but do not/cannot interbreed.

Question 5

By definition, which species concept cannot identify cryptic species?

Answer 5

the morphological concept

Question 6

In this class, we are going to rely on the biological species concept.
Plant ecologists don’t like this concept, bc plants don’t act like animals (birds more specifically), which is where this concept came from.

Answer 6

**

Question 7

Reproductive isolation is a barrier to ____ ____.

Answer 7

gene flow

Question 8

What are the 3 examples of prezygotic (before the zygote forms) barriers?

Answer 8

habitat isolation – example of flies which breed only on specific kinds of fruit

temporal isolation – reproduce at different times of the year

behavioral isolation – courtship behaviors (ex of the blue-footed booby. These birds only mate with birds with blue feet, not other colors.) “Courtship” is the key word.

Question 9

What is an autopolyploid?

Answer 9

(from the Greek autos, “self”) is an individual that has more than two chromosome sets that are all derived from a single species. In plants, for example, a failure of cell division could double a cell’s chromosome number from the diploid number (2n) to a tetraploid number (4n).

Question 10

Most causes of speciation are relatively slow, in that the differences separating species take many generations to accrue and establish reproductive isolation. Which mechanism is most likely to produce a species in just a few generations?

Answer 10

Polyploidy would be most likely to produce a species in a few generations. A polyploid individual is one possessing extra sets of chromosomes.

Question 11

Most such hybrids are sterile because…..

However, an infertile hybrid may be able to propagate itself asexually (as many plants can do).

Answer 11

….the set of chromosomes from one species cannot pair during meiosis with the set of chromosomes from the other species.

Question 12

In subsequent generations, various mechanisms can change a sterile hybrid into a fertile polyploid called an __________. The _____________ are fertile when mating with each other but cannot interbreed with either parent species; thus, they represent a new biological species.

Answer 12

allopolyploid

allopolyploids

Question 13

Define reproductive isolation.

Answer 13

The existence of biological barriers that impede members of two species from interbreeding and producing viable, fertile offspring.

p. 441

Question 14

Biological reproductive barriers such as these are intrinsic to the organisms themselves. Hence, it is biological barriers that can prevent interbreeding when members of different populations come into contact with one another. Mechanical, behavioral, gametic, and temporal isolation are all biological reproductive barriers and intrinsic to organisms themselves.
What is an example of something that is NOT a type of intrinsic reproductive isolation?

Answer 14

geographic isolation

Question 15

_________ speciation can occur by a number of different mechanisms, including:

polyploidy
habitat differentiation
female male preference
host switching

Answer 15

Sympatric

Question 16

Where does the term “allopatric” come from?

Answer 16

the Greek ‘allos’, meaning other, and ‘patra’ meaning homeland

p. 445

Question 17

Allopatric speciation can also occur without geologic remodeling, such as when individuals colonize a remote area and their descendants become geographically ________ from the parent population.

Answer 17

isolated

p. 445

Question 18

Speciation can take place with or without __________ ___________.

Answer 18

geographic separation

p. 444

Question 19

What is the term for the condition in which a species originates as a result of an accident during cell division that results in an extra set of chromosomes?

Answer 19

polyploidy

p. 447

Question 20

A species with a diploid number of 6 has….

Answer 20

….3 pairs of chromosomes.

Question 21

During meiosis in each species, the chromosome number in each species is reduced from diploid to _______.

Answer 21

haploid

p. 448

Question 22

In species X, 2n=8. How many chromosomes would a gamete of species X have?

Answer 22

4 chromosomes

Question 23

_____________ occurs when two different species interbreed and produce hybrid offspring.

Answer 23

Allopolyploidy

Question 24

Hybridization, along with nondisjunction, however, can lead to speciation through allopolyploidy.

Answer 24

nondisjunction

Question 25

Nondisjunction occurs when members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids fail to separate during meiosis II. In nondisjunction, one gamete receives ___ of the same type of chromosome and another gamete receives no copy.

Answer 25

two

review from Ch 12; p. 252

Question 26

Macroevolution is sometimes defined as the broad pattern of evolution _____ ___ _______ level.

Answer 26

above the species

Question 27

For which of the following is the biological species concept least appropriate?

a. ) both prokaryotes and fossils
b. ) fossils
c. ) prokaryotes
d. ) plants
e. ) animals

Answer 27

a.

There is no way to evaluate the reproductive isolation of fossils. The biological species concept also does not apply to organisms that reproduce asexually all or most of the time, such as prokaryotes.