Week 8 - Extremophiles and Rise of Life

Question 1

What are the basic properties of extremophiles?

Answer 1

Resistance to:

Radiation
Hot
Cold
Acid
Pressure
Salinity

Found in extreme environments

Question 2

Identiy types of locations where life exists in extreme conditions

Answer 2

Hydrothermal vents
Hot springs
Deep rock 4-5 km below surface
Acidic conditions pH < 3
Basic conditions pH > 9
High salt concentration ( > 0.2 M)
High temp 60 to 122
Low temp below 15

Question 3

Explain how lifeforms have adapted to exist in extreme conditions

Answer 3

Developed chemical or physical barriers to protect from outside

Developed protective mechanisms to repair damage done

DNA has larger fraction of G-C pairs than A-T pairs

Question 4

Describe where extremophiles appear on evolutionary tree

Answer 4

Archaea - base of evolutionary tree

Question 5

Name the first eon in the history of the Earth and its defining characteristics

Answer 5

1. Hadean “Hellish”

Earth accretes from smaller rocks
Hadean phase of accretion & impacts
Lasts for ~ 0.6 GYA

Question 6

Name the second eon in the history of the Earth and its defining characteristics

Answer 6

2. Archaen “ancient life”

Carbon isotope evidence for life
Oldest stromatolites
Oldest micro fossil evidence for life

Question 7

Name the third eon in the history of the Earth and its defining characteristics

Answer 7

3. Proterozoic “early life”

Earliest evidence of oxygen in atmosphere
Oldest eukaryotic fossils
Photo-synthesis arose quickly
Cyanobacteria absorb UV ration and released oxygen into atmosphere
Evidence of repeated ice ages

Question 8

Name the fourth eon in the history of the Earth and its defining characteristics

Answer 8

4. Phanerozoic “visible life”

Only the last 0.5 billion years
Cambrian explosion
plants and fungi colonise land
Animals colonise land
Mammals and dinosaurs appear
K-T event (dino = dead)
Hominids appear

Question 9

Define prokaryotes

Answer 9

Organism who’s cells lack a nucleus and other organelles
Simple structure
Divided into bacteria and archaea

Question 10

Define eukaryotes

Answer 10

Organisms who’s cells have a nucleus enclosed within a nuclear membrane

Question 11

Describe snowball Earth Hypothesis

Answer 11

Runaway effect involving an ice-albedo feedback loop: as incoming sunlight is reduced, ice expands from poles to equator

Question 12

Explain what is a mass extinction

Answer 12

Any circumstance that results in the loss of a significant portion of Earths living species across a wide geographic area within a relatively short period of geologic time