lecture 7 axonomy, Phylogeny and Evolutionary clocks

Question 1

what is taxonomy?

Answer 1

Taxonomy names and classifies extant (living) and extinct organisms

Taxonomy is part of Systematics, the science of comparative biology that study the evolutionary relationship between organism

Question 2

why is taxonomy important?

Answer 2

*Group and arrange organisms in a logical way
*Gives a single, unambiguous name to organisms
*Prevents misleading names

Question 3

Aristotle’s biology

Answer 3

Observational and based on form (Phenetic System)

*Divided based on high-level phenotype and habitat consideration

animals
-classified on where they live and what they eat

plants
- classified on where they live and their properties

Question 4

Linnean classification

Answer 4

Carolus Linnaeus (1707-1778)

-hierarchical order

*Binomial (two names) Nomenclature -Genus species

*Named > 11,000 binomials, many still used today

Each level is known as a Taxon

*All Taxa have a capital letter
*Genus name has a capital letter and is in italics
*species name has a lowercase letter and is in italics

*Species can be abbreviated with sp., or spp

Question 5

what are the rules for naming a species?

Answer 5

*All names must be approved by international congresses

*Names are treated as Latin phrase,second name can be a:
*Noun
*Adjective
*Other (names of people & places, anagrams etc)

*Second name must have Latin ending, e.g. –ii, -i, -us, -um, etc

*Species can have subspecies indication

Question 6

what is Phylogeny

Answer 6

*Phylogeny is the evolutionary history of a species
*Inferred from morphological and molecular data
*Shows how closely related animals are

Question 7

Phylogenetic tree

Answer 7

*Visual representation of lineage
*Chronicle of the evolutionary sequence
*Shows living species and common ancestors of further removed (1) or most recent branch point (2)
*Show hierarchy in descent, not absolute similarity12

Question 8

Reading the cladogram

Answer 8

look at slide

Question 9

Clades and groups

Answer 9

look at slide

Question 10

what does hatch mark indicate?

Answer 10

Hatch mark indicates change even

Question 11

what can Branch length could show?

Answer 11

-Nothing, just based on graphic aesthetics

*Time passed between lineages (all living lineages align on the present time)

*Amount of change between lineages (not all lineages have undergone the same amount of change, and do not necessarily align)

Question 12

Is morphology enough to infer evolution?

Answer 12

no because convergent evolution shows how shared selection pressures can result in similar characteristics even though certain species are not related and are more related to completely different looking species

i.e a dolphin is more closely related to a puma than a shark

Question 13

what are homologous structures?

Answer 13

similar structures and different functions

i.e lizard, bird, human and whale limbs

Question 14

what are analagous structutrs?

Answer 14

different structures and similar functions

i.e fish, whale, turtle and penguin limbs

Question 15

what is Molecular phylogeny?

Answer 15

Molecular systematics
*Uses similarities in DNA and related molecules to assess evolutionary relationships.

*More distant species have more differences in DNA than closely related species

Question 16

Determining dissimilarity: Aligning DNA segments

Answer 16

look at slides

Question 17

Build a tree based on similarity

Answer 17

Parsimony: The most parsimonious tree requires the least evolutionary events

Based on Occam’s razor

In our case, both three 1 and 2 are equally parsimonious, it requires the least number of events in both case

Likelihood: The most likely tree reflects the most likely sequences of events

Question 18

Rate of genetic change

Answer 18

DNA or mtDNA evolves rapidly, used for recent evolutionary events (animal & human)

rRNA changes relatively slowly, used for distant branches (bacteria, plants & animals)

Proteins change in shape, function, and composition.Both for recent and old events

Each protein has a constant rate of AA substitutionWe can use the molecular differences to date groups divergence

Question 19

When did HIV jump to humans from other primates (e.g. chimpanzees)?

Answer 19

Likely several occurrences, but HIV-1 M (shown) is predicted to have spread to humans around 1930