phylogeny and a brief history of life

what do phylogenies represent

evolutionary relationships and (sometimes) the timescale of change

what can phylogenies help distinguish

homologous traits (traits shared due to common ancestry)

from

analogous traits (produced through convergent evolution, which is when unrelated species display independent evolutionary responses to similar selective pressure)

what does interbreeding within a species allow

gene flow

what is a clade

a monophyletic group of organisms that include a single ANCESTOR and all of its DESCENDANTS. that is a single branch on the ‘tree of life’

what is a common ancestor

an ancestral organism, from which 2 or more different lineages descended

• on a tree, it is represented by a node where a single lineage splits into a sister group

what is a sister group/taxa

two descendant groups that split from the same exact node representing a common ancestor

• they are each other’s closest relatives on the evolutionary tree

what is an outgroup

a distantly related organism that is located outside of the ingroup (group of interest)

• branches off near the base of the tree

• it provides a baseline for comparing traits to see how the main group evolved

paraphyletic group

a collection of organisms that include a common ancestor, and some but not all of the descendants of that ancestor, often because they evolved very different physical traits/new ways of life

when + how was the earth and moon formed

• earth = 5 billion years ago

• moon = 4.5 billion years ago when earth collided with another planet

• life could not have survived this event, but it was present by 4.3.Ga

what are the 4 aeons and what events occurred during them

• Hadean = Earth has formed but too hot for any life to live — heavy bombardment from space, volcanic, co2 atmosphere

• Archean = First fossil evidence of life , reduced bombardment from space

• Proterozoic = GREAT OXYGENATION EVENT 2300 MYA photosynthesis + cyanobacteria increased oxygen

• Phanerozoic = plentiful fossils representing many phyla

Marine sponges, jellyfish, comb jellies existence confirmed

events associates with cambrian period

(540-480 MYa)

rapid emergence of modern animals

events associates with carboniferous period

(360-300 Mya)

large scale emergences of life in land

events associated with cretaceous period

(140-66 Mya)

emergence of flowering plants, ended with a mass-extinction due to asteroid collision

events associated with eocene period

(66-22 Mya)

emergence of mammals as dominant form of large animals on land

events associated with holocene period

(10,000 years ago-present)

from the end of the most recent ice age to present. emergence of human farming and major human impacts