lecture 4: phylogeny + classification

Question 1

artificial selection

Answer 1

humans choose the traits they want to propagate by breeding certain organisms together. Human choices create differential reproductive success

Question 2

natural selection

Answer 2

the differential reproduction of organisms is determined by how successful they are in their particular environment, how well they hunt for food, attract mates, avoid predators, etc..

Question 3

genetic admixture

Answer 3

occurs when individuals from 2 or more genetically distinguishable groups have offspring together

Question 4

tree of life

Answer 4

the complete, evolutionary history of life; divided into 3 main branches (domains) [eukarya, bacteria, archea]; the tree analogy is used to describe the branching pattern of evolutionary relationships; puts the relationships of all life on Earth in evolutionary context

Question 5

phylogeny

Answer 5

the evolutionary history of relationships among organisms

Question 6

phylogenetic tree

Answer 6

based on similarities & differences in physical or genetic characteristics

- trees represent hypotheses of evolutionary history: the lineage evolves over time through selection, drift, mutation, gene flow
- trees represent evolutionary history: at the split, gene flow between lineages stops so that each lineage evolves independently 
- node: where a split occurs when the ancestral lineage divides into 2 descendant lineages

Question 7

how to read a phylogenetic tree

Answer 7

all phylogenetic trees show the common ancestor for the group on the left; this is called the root of the tree; the split in branches are called nodes & indicate a division of 1 lineage into 2; the positions of the nodes on the time scale indicate the times of the corresponding speciation events; branches can be rotated around any node without changing the meaning of the tree

Question 8

taxon

Answer 8

any group of species that we name (ex. vertebrates)

- a taxon that consists of all the descendants of a common ancestor is called a clade or a monophyletic group

Question 9

homologous traits

Answer 9

features shared by 2 or more species that were inherited from a common ancestor; may or may not appear similar
- phylogenetic trees are constructed based on shared physical or genetic features

Question 10

convergent evolution

Answer 10

independently evolved traits subjected to similar selection pressures may become superficially similar
- homoplasy often results from convergent evolution

Question 11

homoplasy: (analogous trait)

Answer 11

the development of organs or other bodily structures within different species, which resemble each other & have the same functions, but did not have a common ancestral origin

Question 12

ancestral trait

Answer 12

a trait that was present in the ancestor of a group is ancestral (things they have in common; used to group things together)

Question 13

derived trait

Answer 13

a trait found in a descendent that differs from the ancestral trait is derived (evolved later; types of traits we use to identify different groups; used to separate things)