bio210b lect. 3

02/05/2024

two examples of how sympatric speciation can occur

1. habitat differentiation: specializing on different resources

2. sexual selection: different mating preferences

what happened 3.5 bya?

oldest fossils of prokaryotes: cyanobacteria evolved, creation of photosynthesis and cell respiration

what happened 1.8 bya?

first eukaryotes: nucleus, membrane-bound organelles(endosymbiont theory), large in size

what is the endosymbiont theory?

eukaryotes supposedly ate prokaryotes. whatever they ate did not digest but fused with the eukaryotes (with protective shell)

what happened 1.2 bya?

first signs of multicellular life

how did cells become multicellular?

• attachment of cells:

• communication of cells as a whole

• ex: sponge

what happened 540 mya?

cambrien explosion: huge boost in life diversity

• introduced bilateral symmetry

what happened 488-475 mya?

life moves onto land (fungi & bacteria) because less competition, more resources, less predators

what happened 250 mya?

permian extinction

what was the permian extinction?

• about 96% of all life become extinct due to volcanic activity (volcanic debris filled the atmosphere)

• the other 4% were dinosaurs !

what happened 65 mya?

cretaceous extinction

what is the cretaceous extinction?

meteorite kills dinosaurs, leading into extinction

what is systematics?

study of the diversity of life, both past and present, and the relationships of organisms through time

what is phylogeny?

the representation of the evolutionary history and relationships between groups of organisms

• ex: ancestral lizard

what is morphology?

study of the form and structure of organisms and their specific structural features (relating to homologous structures)

what is basal taxa?

the evolutionary branch, most closely related to the common ancestor

what is sister taxa?

share a direct ancestor

what are ancestral traits?

a character shared by a common ancestor + all decendants

what are derived traits?

a character that is unique to a certain clade (group)

what is a monophyletic clade?

a group that consists of a common ancestor and all of its decendants

what is a paraphylatic clade?

a group that includes a common ancestor and most, but not all decendants

what is a polyphletic clade?

a group that includes members that dont share a direct common ancestor