Lec 7: Early Diversification of life - in seas Flashcards
What are the different ways of assessing descent?
- comparisons involving simple phenotypic traits (comparing living organisms as well as fossils)
- comparisons involving molecular traits
Name an early marine plankton
acritarchs
- eukaryote fossils
- had shells
Why did eukaryote diversity increase? (4)
- increase in size of genome
- sexual reproduction (increases possible variation)
- increase in structural complexity
- ecological changes (more oxygen and energy sources, physical/biological landscape, photosynthesis)
How did we go from unicellular eukaryotes to multicellular eukaryotes?
colonial hypothesis
- dividing cells did not separate
- mutation in cell membranes or walls
What is the first step in the evolution of multicellular life?
unicellular eukaryotic cells living in a colonial formation develop separate functions for individual cells.
What is the 2nd stage of multicellular life?
Ediacaran fossils, 570 Ma
- small shelly fossils in ocean sediments
What human ancestor existed in the Burgess Shale Diversity?
the Pikaia
What was the Cambrian explosion?
A huge diversification in the animal kingdom
is there a purpose in evolution?
No. Variations arise through chance mutations.
Evolution is a product of chance variations, selection, and probabilities of survival
Where was much of the new diversity during the cambrian explosion?
in shallow water marine environments
What are the mechanisms for the explosion
- tectonic activity
- more CO2 in atmosphere
- melting of the snowball earth
- increased photosynthesis
- more oxygen, enough to support larger predators
