Speciation (Test Two)

Question 1

Why is it important to know what a species?

Answer 1

1. Scientific studies are conducted at the species level
2. Species are considered the unit of evolution, so it guides evolutionary theory
3. The definition we use guides our thinking, so it must be as close as possible to what exists in nature, without excluding entities

Question 2

What did E. O. Wilson say about the concept of species in his book “The Diversity of Life”?

Answer 2

The species concept is crucial to the study of biodiversity…. Not to have a natural unit such as the species would be to abandon a large part of biology into free-fall, all the way from the ecosystem down to the organism.

Question 3

What are the three criteria for identifying a species?

Answer 3

1. Common descent
2. Smallest distinct groupings
3. Reproductive community

Question 4

Explain the criteria of common descent.

Answer 4

Species trace their ancestry to a common ancient population but not necessarily the same exact pair of parents.

Question 5

Explain the criteria of the smallest distinct groupings.

Answer 5

1. Species are the smallest unit sharing patterns of ancestry and descent
2. Morphology has been traditionally used, and now supplemented with chromosomal and molecular characteristics.

Question 6

Explain the criteria of reproductive communities.

Answer 6

Species form reproductive groups that exclude other species.

Question 7

How were species defined before Darwin?

Answer 7

Species was considered a distinct and unchangeable entity that shares an “essence”.

Question 8

How did the Typological Species concept work?

Answer 8

1. A specimen was labeled and deposited in a museum
2. New specimens were then compared to the representative specimen
3. Small differences (variation) were considered imperfect manifestations of an eternal type
4. Large differences led to description of a new species

Question 9

What are some issues with the Typological Species Concept?

Answer 9

1. Does not account for natural variation (sexual dimorphism) (aging) (other polymorphisms)
2. The degrees of difference require a judgment call
3. Species change over time

Question 10

Although scientists have discarded the Typological Species Concept, what still remains of its methods?

Answer 10

1. Morphology still exists
2. Specimens serve as a guide to general morphology features

Question 11

Explain the Biological Species Concept.

Answer 11

Defines a species as a reproductive community of populations (reproductively isolated from others) that share a specific niche in nature.

Question 12

What are the issues with the Biological Species Concept?

Answer 12

1. There are hybrid organisms like Pizzly bears, no clear degree of isolation is mentioned.
2. Doesn’t accommodate for asexual reproduction.
3. Cannot inform about the species status of fossils
4. Breeding experiments are difficult to conduct

Question 13

How is the modern version of the biological species concept define species?

Answer 13

That a species is an interbreeding population of individuals having common descent and sharing intergrading characteristics.

Question 14

Explain the Evolutionary/Cohesion Species Concept.

Answer 14

1. An evolutionary species is a single cohesive lineage of ancestor-descendant populations that maintain its identity from other such lineages and that has its own evolutionary tendencies and historical fate.
2. The most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms.

Simply put, a species is a lineage that evolves together, and separately from other lineages.

Question 15

What are three pros about the Evolutionary/ Cohesion Species Concept.

Answer 15

1. The definition accommodates for both sexual and asexual forms
2. The definition accommodates for fossils
3. Adds the evolutionary time dimension needed by the biological species concept