Classifying Life (Wellman)

Question 1

Taxonomy

Answer 1

Naming of species:
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 2

Cladistic analysis

Answer 2

1970s, Henig invented the method of cladistic analysis while studying insects.
Simplistically, you score characters as being present or not, which leaves you with the ability to make a clear comparison between species.
Cladistics is a method of phylogenetic analysis, based on evolutionary relationships. It classifies species according to how recently they share a common ancestor. It is unambiguous because there is only one phylogenetic tree of living things.
-The presence of outliers, can identify convergent evolution

Question 3

What do cladists assume?

Answer 3

Cladists assume that life evolved only once and the diversity of life originated through descent with modification (via neo-Darwinian evolution).
They therefore assume that there is a hierarchical order of life on Earth and this order is manifested in the distribution of characters shared among organisms.

Question 4

In Henig’s method of cladistic analysis, character’s may be..

Answer 4

• Analogous

- Homologous

Question 5

What are analogous characters?

Answer 5

Similarity due to convergent evolution (homoplasy), e.g. bat/bird wings

Question 6

What are homologous characters?

Answer 6

Similarity due to common ancestry (eagle wings/seagull)

Question 7

How can cladistic characters be described?

Answer 7

• Synplesiomorphies
• Synapomorphies
• Autapomorphies

Question 8

What are synplesiomorphies?

Answer 8

Shared ancestral characters (backbone for vertebrates)

Question 9

What are synapomorphies?

Answer 9

Shared derived characters (birds’ wings)

Question 10

What are autapomorphies?

Answer 10

Characters unique to a taxon (brain for humans).

Question 11

What are plesiomorphies?

Answer 11

An evolutionary trait that is homologous within a particular group of organisms but is not unique to members of that group

Question 12

How does cladistics use synapomorphies and autapomorphies?

Answer 12

Cladistics use synapomorphies (shared derived characters) to workout phylogenetic relationships and autapomorphies (unique characteristics to a taxon) to define groups.
They identify sister groups - two taxa/groups that share the latest common ancestor, i.e. each is the other nearest relation.

Question 13

Monophyletic group

Answer 13

Contains the latest common ancestor plus all, and only all, of its descendants.

Question 14

Paraphyletic group

Answer 14

Diagnosed by plesiomorphies and not including all descendent of a common ancestor. A paraphyletic group remains after one or more parts of a monophyletic group have been removed.

Question 15

Polyphyletic group

Answer 15

A group in which the most recent common ancestor is assigned to some other group and not the group itself. It is defined on the bases of convergence, or by non-homologous characters assumed to have been absent in the latest common ancestor.

Question 16

When was it discovered there were two types of prokaryote?

Answer 16

In the 1980s it was realised that there were two types of prokaryote: Eubacteria (bacteria) and archaebacteria (Archaea).
-Archaebacteria are less numerous and diverse than Eubacteria and inhabit extreme environments - thermophiles (very hot) and halophiles (very salty).