Week 4: Evolution & Cladistics

Question 1

Classification and why we do it

Answer 1

Classification: putting things into categories

why?: 1. to describe natural categories (taxonomy)
2. help understand relationships (systematics)
3. to communicate effectivley

Question 2

Systematics and taxonomy

Answer 2

systematics: ordering the categories in terms of relationships (evolution) not just similarities

taxonomy: the procedure of naming things

Question 3

Linnaean system

Answer 3

binomial names
genus + trivial name= species name
(ex). homo (genus) sapiens (species) for modern humans

(ex). Canis (genus) familiaris (species) domestic dog

Question 4

Linnaean classification and its problem

Answer 4

Linnaean classified with the hierarchical expressing degrees of similarity.
kingdom, phylum, class, order, family, genus, species

Problem is he classified using morphological similarity (how things looked) not on evolutionary relationships.

Question 5

What is a species

Answer 5

ability to interbreed under natural conditions. Produce viable off spring (biospecies concept)

Question 6

morphospecies concept

Answer 6

different shape or structure (morphology) as indirect evidence that they do not interbreed

Question 7

darwins natural selection

Answer 7

1. more offspring are produced than can survive maturity
2. variations exist among offspring
3. offspring must compete with one another for food, habitat and mates
4. offspring with the most favourable characteristics are more likely to survive and reproduce
5. beneficial traits are passed on to the next generation

Question 8

homology

Answer 8

similarity of organisms from different species due to inheritance from a common ancestor. Features (body parts) that share such similarities are homologus. One feature evolves from a common ancestor (ex) whale fin and human hand

Question 9

analogus

Answer 9

features show similarities in form but have a seperate evolutionary history. Features are similar but do not share a common ancestor. (ex) bee wings and bird wings

Question 10

Cladistics

Answer 10

takes one organism and classifies other organisms by the degree wo which they resemble the first one.

This is a hypothesis of possible evolutionary relationships

Question 11

Cladogram

Answer 11

shows clades (branches) of how similar organisms are.

As clades move away from the original organism, structures become more different
Organisms in clades are grouped by similar structure that are hypothesized to be ‘evolutionary novelties’
SLIDE 18

Question 12

Cladistics assisnging characteristics

Answer 12

Characters: need to be useful for distinguishing between organisms. If all organisms posses the same character it cannot tell us about their evolutionary relationships
(ex) feathers for a bird characteristic will not work

Question 13

Outgroup

Answer 13

The original specimen

Question 14

Best cladogram

Answer 14

the best cladogram is one with the least amount of changes when characters are added

Question 15

parismony

Answer 15

the explanation with the least necessary steps is probably the best one

Question 16

Clades/monophyletic groups

Answer 16

organisims that share a more recent common ancestor to each other than other organisims

Question 17

derived and ancestral

Answer 17

derived: more evolved character
ancestral: characters closer to the outgroup