Studying diversity

Question 1

What is convergent evolution?

Answer 1

Organisms that are not related develop the same characteristics as a result of similar habitats or lifestyles.

Question 2

Sometimes animals do not resemble each other but are closely related. Why?

Answer 2

This happens when a lineage has undergone rapid evolution. Usually when organisms colonise a new ecological niche they become radically different, e.g. whales.

Question 3

What is a plesiomorphy?

Answer 3

A primitive character state.

Question 4

Why might symplesiomorphies be misleading with regards to the relatedness of two species?

Answer 4

When evolution is slow, organisms do not change much from their ancestral morphology. Thus 2 species may have symplesiomorphies but be separated by long periods of geological time.

Question 5

Data matrixes are often created to assess relatedness of taxa based on synapomorphies. Give 3 major steps in this process.

Answer 5

1. Taxa are put in the rows and traits in the columns. Taxa are then scored for each trait.
2. Outgroups are used to polarise character states, i.e. determine where it evolved first.
3. Computer algorithms are then used to assess which lineage is the most parsimonious

Question 6

In a data matrix what do the scores of 0 and 1 mean?

Answer 6

Ancestral condition and derived state respectively.

Question 7

What is dichotomy and what does this tell us?

Answer 7

When a branch on a cladogram splits into 2. The tree is resolved as the relationships between the 2 daughter species is known.

Question 8

What is polytomy and what does this tell us?

Answer 8

When a branch on a cladogram splits into multiple branches. The tree is unresolved as the relationships between the daughter species is unknown.

Question 9

What is a synapomorphy?

Answer 9

A shared derived character.

Question 10

What is anagenesis?

Answer 10

Simple, linear evolution.

Question 11

What is cladogenesis?

Answer 11

Branched evolution.

Question 12

What is a monophyly? Give an example.

Answer 12

A group containing all and only the descendants from a common ancestor. Amniota is a monophyly.

Question 13

What is a paraphyly? Give an example.

Answer 13

A group containing only but not all the descendants of a common ancestor. Reptilia is a paraphyly, as all reptiles also share a common ancestor with birds and mammals.

Question 14

What are the 4 main uses of cladograms?

Answer 14

1. To understand the origin of characters/evolution
2. To reconstruct diversity patterns
3. To test palaeoecological relationships
4. To trace biogeography