Chapter 15 - Speciation and Phylogeny

Question 1

Speciation

Answer 1

Occurs when the population has changed enough that it diverges from a present species to become a new species.

Question 2

What are the 4 definitions of species?

Answer 2

1. Biological species concept
2. Morphological species concept
3. Ecological species concept
4. Phylogenetic species concept

Question 3

The biological species concept

Answer 3

Defines a species as:
A group or population, whose members have the potential to interbreed and produce fertile offspring.

Question 4

The morphological species concept

Answer 4

Defines a species as:
A group or population that have the same physical traits such as size, shape, and appearance

(This concept has been used to classify most the species we have)

Question 5

The ecological species concept

Answer 5

Defines a species as:
A group or population that have the same ecological niches.

Ecological niche = the role and organism or population plays within an ecosystem.

Question 6

The phylogenetic species concept

Answer 6

Defines a species as:
The smallest group of individuals that share a common ancestor (and form one branch on the tree of life)

Question 7

Phylogeny

Answer 7

The evolutionary history of a species, or group of related species.

Determined by comparing morphologies, and DNA sequences between organisms

Question 8

Reproductive barriers

Answer 8

Prevents closely related species from producing viable offspring.
(ex. a horse and a donkey)

2 types:
1. Prezygotic - occurs before fertilization takes place.
2. Postzygotic - occurs after fertilization takes place

Question 9

What are the 5 prezygotic barriers?

Answer 9

1. Habitat isolation
2. Temporal isolation
3. Behavioural isolation
4. Mechanical isolation
5. Gametic isolation

Question 10

Habitat isolation

Answer 10

A prezygotic barrier

When two species live in the same area, but in different habitats that rarely ever encounter each other.

Question 11

Temporal isolation

Answer 11

A prezygotic barrier

When organisms breed at different times of the day, seasons, or year.

Question 12

Behavioural isolation

Answer 12

A prezygotic barrier

When the two species have different mating rituals so they don’t understand each others mating signals.

Question 13

Mechanical isolation

Answer 13

A prezygotic barrier

When the reproductive parts of two species don’t fit or align.

Question 14

Gametic isolation

Answer 14

A prezygotic barrier

When the sperm of one species may not be able to fertilize the egg of another species.

Question 15

What are the 3 postzygotic barriers?

Answer 15

1. Reduced hybrid viability
2. Reduced hybrid fertility
3. Hybrid breakdown

Question 16

Reduced hybrid viability

Answer 16

A postzygotic barrier

When most hybrid offspring do not survive (they die before making it through the embryonic stage)

Question 17

Reduced hybrid fertility

Answer 17

A postzygotic barrier

When a hybrid offspring survives, but they may not be able to reproduce.

Ex. Horse + donkey = sterile mule

Question 18

Hybrid breakdown

Answer 18

A postzygotic barrier

When hybrid offspring can mate successfully with their parent species, or another hybrid, but their offspring are not successful.

Question 19

Allopatric speciation

Answer 19

When groups from an ancestral species evolve into separate species, due to a period of geological separation (such as a lake or mountain range)

Question 20

Sympatric speciation

Answer 20

The splitting of an ancestral species, into two or more reproductively isolated species without geological separation

Question 21

Punctuated equilibria

Answer 21

A term used to describe long periods of time with little change, punctuated by abrupt rapid change

Question 22

Phylogeny

Answer 22

The history of the evolution of a species or group

(especially in reference to the lines of descent)

Question 23

Convergent evolution

Answer 23

The evolution of similar features in different species, which can result from living in very similar environments.

Question 24

Analogy

Answer 24

The similarity between two species due to convergent evolution rather than descent from a common ancestor

Question 25

Homology

Answer 25

The similarity of two species due to common ancestry

Question 26

Systematics

Answer 26

Classifies organisms and determines their evolutionary relationships

Question 27

Cladistics

Answer 27

A type of systematics in which common descent is the primary criteria used to classify organisms by placing them into groups called clades

Question 28

Shared ancestral characters

Answer 28

A character shared by members of a particular clade that originated in an ancestor that is not a member of the clade

Question 29

Shared derived characters

Answer 29

A characteristic that is present in a clay due to evolution that is not seen in the ancestor

Question 30

Outgroup

Answer 30

A taxon outside of the group of interest that is known from other evidence to be closely related to that group of interest

Question 31

Ingroup

Answer 31

The group of taxa, whose evolutionary relationships are being determined.

(the group you’re focussed on)

Question 32

Molecular systematics

Answer 32

Uses DNA or assessment of other molecules to assess the relatedness of certain organisms

Question 33

How can we study the evolutionary history of a species?

Answer 33

• fossils
• homologies
• molecular systematics