L3: Timeline (incomplete)

Question 1

Give examples of microbes

Answer 1

microscopic plants, animals, protozoa, fungi, archaea

Question 2

Go through the timeline

Answer 2

• 4.5: Earth formed, no free O2 [reducing]
• 4.5-4 BYA crust cooled, rocks/oceans formed
• 4BYA first microbes, tranistion from chemical/biochemical to cellular lrife
• 3.5 cyanobacteria-like microfossils (stromaltolites)
• 2 gunflint fomration
• 1 bitter springs formation
• 0.5 marine invertbrates
• 0.4 insects
• recent: dinos mammals

Question 3

Describe Earth’s atmosphere at formation

Answer 3

high CO2
low N2, O2
some CH4, H2S
* reducing conditions, high temperature
* greenhouse effect but offset by solar flux which allowed liquid to exist

Question 4

Describe Earth presently

Answer 4

High N, O2
Low CO2
* oxidizing conditions
* transformed atmosphere, terrestrial, aquatic environments because of microbial activity

Question 5

What has been evolving longer, implications

Answer 5

• microbes have been exploiting niches for longer
  meaning…
  1. microbes can live in extreme environments
  2. microbes are very diverse
  3. taxonomic groups are very diverged

therefore
1. microbes created life on earth
2. all life evolved from microbes
3. all life depends on microbes

Question 6

Break down the microbial growth curve

Answer 6

• Lag phase: adjustment to new media before logarithmic growth
• Log phase: exponential growth
• Stationary phase: growth limited by depletion of nutrients, accumulation of waste products, cell death
• draw it

Question 7

How many cells are there on Earth

Answer 7

10^30

Question 8

What would happen if microbial growth was unlimited? Why doesn’t it happen

Answer 8

20cm layer thick round earth, limited by growth conditons like
*ESC WLN2
*microbes exist in nutriently limited state with high competition => survival of the fitess