Deep time lecture 2

how old is earth

4.6 billion years old

oldest form of life

bacteria (single-celled organisms)

life has existed on earth for

3.6 billion years

life has been evolving on earth for 3.6 billion years

timing of events

1. single celled organisms (3.6 bya)

2. photosynthetic bacteria (3.4 bya)

3. multicelluar life (1 bya)

4. arthropods (570 mya)

5. fish (500 mya)

6. land plants (475mya)

7. insects (400 mya)

8. amphibians (360 mya)

9. reptiles (300 mya)

10. mammals (200 mya warm blooded organisms)

11. birds (150 mya)

12. flowering plants (130 mya)

13. dinosaurs died out (65 mya)

14. mammals diversified (65 mya)

15. humans (200,000)

why did oxygen breathers appear after photosynthetic organisms

photosynthetic organisms produced the oxygen that aerobic organisms would use later for respiration

new resource for a new niche

why was the shelled egg favored by natural selection

harder —> more protection

Organisms can stay on land

broke the tie between land and water

why did mammals only diversify after dinosaurs went extinct

new niches available

Dinosaurs filled most niches

niches opened up when they went extinct and mammals filled them

early earth

formed 4.6 bya and was very turbulent

anoxic (low oxygen) conditions

surface temp of 100 degrees C

methane, ammonia, nitrogen, CO2, and hydrogen

no liquid water

cyanobacteria

early life on earth

3-4 bya

early photosynthetic bacteria began dumping major amounts of oxygen into the ocean, then the atmosphere via diffusion

historical transitions

emergence of self-replicating molecules 

• RNA sequences can facilitate copying of nucleic acids

• RNA replication

emergence of eukaryotic life (1.8-2 bya)

• involves the acquisition of mitochondria

emergence of multicellularity

The Miller-Urey Experiment (1952)

how life began

Simulate early conditions in the lab with electricity to simulate lightning

results: Organic compounds (amino acids) can form from inorganic matter under these conditions

formed nucleic acids

eukaryotes have membrane bound organelles

like certain free living cells, mitochondria and plastids

• have their own membrane

• can self- replicate

• have haploid genomes

plastid

any of a class of small organelles, such as chloroplasts, in the cytoplasm of plant cells, containing pigment or food

the endosymbiosis theory

endosymbiont- a symbiont that lives inside the host and is vertically transmitted to progeny

• many endosymbiosis genes are lost or transferred to host nucleus

• neither the host nor the endosymbiont can live independently anymore

4 steps of endosymbiosis theory

1. infolding of plasma membrane

2. aerobic proteobacterium enters eukaryote

3. aerobe bility to use oxygen to make energy becomes an asset

4. evolves into chloroplsts

acquisition of  ___ marks one of the origins of ____

mitochondria, eukaryotes

there is ___ evidence for the endosymbiosis theory

phylogenetic

emergence of multicellularity

600 mya

features of multicellularity:

• cells must adhere

• cells must cooperate

• cells must share resources and energy

• cells should show division of labor

specializing

Multicellularity has evolved convergently many times

cambiran explosion (542 mya)

invertebrates

came after plants

natural selection prefers

bilateral symmetry

from radial to bilateral symmetry

plant phylogeny

see attached notes

important ideas