Unit 2: Origin of Species

Question 1

At the genetic and proteomic level, explain why two big cats, that otherwise appear to be very different in terms of pigmentation, are from the same species.

Answer 1

A gene that encodes an enzyme for pigmentation could mutate so that the enzyme that is made will produce a different pigment. As a result, in a normally functioning cat, they would appear one color but in another, the mutation could cause it to appear a different one.

Question 2

Speciation

Answer 2

The separation of two species for long enough to allow them to accumulate significant changes that allow them to become separate species.

It is the appearance of new species and a source of biodiversity.

Question 3

Phylogenetic Species Concept

Answer 3

Species are identified by having a unique combination of traits, usually physical. DNA is primarily used today.

Question 4

What are 3 disadvantages to the Phylogenetic Species Concept?

Answer 4

• Difficult to analyze traits that always vary
• Degree of dissimilarity can be difficult to determine
• Sometimes members of the species can look very different and members of different species can look similar

Question 5

Biological Species Concept

Answer 5

A population/groups of population have the ability to interbreed; depends on reproductive isolation

Question 6

What are some examples of prezygotic barriers?

Answer 6

Geographic
Habitat
Temporal (time of day)
Behavioral
Mechanical (reproductive parts)
Gametic (gametes don’t work together)

Question 7

What are some examples of postzygotic barriers?

Answer 7

Hybrid Inviability
Hybrid Sterility
Hybrid Breakdown

Question 8

Hybrid Inviability

Answer 8

Fertilized egg cannot progress past an early embryo

Question 9

Hybrid Sterility

Answer 9

Interspecies offspring is viable but sterile/cannot reproduce

Question 10

Hybrid Breakdown

Answer 10

Hybrid offspring are viable and sterile but their offspring have genetic abnormalities

Question 11

What are 3 disadvantages to the Biological Species Concept?

Answer 11

• Difficult to determine if populations are reproductively isolated
• Some cases where two species can interbreed and won’t, or choose not to if they cannot
• Cannot be applied to asexual or extinct species

Question 12

Evolutionary Species Concept

Answer 12

A species is derived from a single lineage that has distinction from other lineages; has its own evolutionary tendencies and historical fate

Lineage – genetic relationship between individuals and ancestors

Question 13

What is a disadvantage of the Evolutionary Species Concept?

Answer 13

No easy way to identify a unique species, lineages are difficult to examine and quantify

Question 14

Ecological Species Concept

Answer 14

Each species occupies an ecological niche

Question 15

Ecological Niche

Answer 15

A set of habitat resources that a species requires, as well as its influence on the environment and other species

Question 16

What is a disadvantage of the Ecological Species Concept?

Answer 16

Competition can occur within species

Question 17

What are the two PATTERNS of speciation?

Answer 17

Anagenesis and Cladogenesis

Question 18

Anagenesis

Answer 18

Species formation without branching of the evolutionary lineage

Question 19

Cladogenesis

Answer 19

Species formation as a result of divergence from an ancestral form; branching of the evolutionary lineage

Question 20

What are the two MODES of speciation?

Answer 20

Allopatric and Sympatric

Question 21

Allopatric Speciation

Answer 21

Speciation that occurs when two species are geographically separated from one another

Question 22

Sympatric Speciation

Answer 22

Speciation that occurs when there are no physical barriers preventing any members of a species from mating with one another

Question 23

What is the difference between allopatric and sympatric speciation?

Answer 23

Allopatric speciation requires a geographical barrier, whereas sympatric does not.

Question 24

What is a characteristic of allopatric speciation?

Answer 24

Movement of a small population to a new location

Question 25

What is a characteristic of sympatric speciation?

Answer 25

Abrupt genetic change and exploitation of resources not used by parent population

Question 26

Which of the following best describes adaptive radiation?

A) radiation that allows a new species to evolve
B) radiation that effects the reproductive fitness of a population
C) the evolution of a single species into an array of progeny (descendants) that differ greatly
D) the evolution of a single species into an array of progeny (descendants) that are very similar

Answer 26

C

Question 27

Hybrid Zones

Answer 27

Zones where two populations can interbreed before reproductive isolation is complete

Question 28

What could cause two populations in a hybrid zone to lose the ability to mate?

Answer 28

Accumulation of genetic changes

Once gene flow through a hybrid zone is diminished, the two populations are reproductively isolated

Question 29

Gradualism

Answer 29

Change that occurs gradually over a long period of time

Question 30

Punctuated Equilibrium

Answer 30

Isolated episodes of rapid evolutionary change between long periods of minimal evolutionary change