Lecture 4: Emergence of Life

Question 1

What “had to go our way”

Answer 1

• matter & antimatter produced in pairs that annihilate on contact; more matter
• uneven distribution of ordinary matter
• stars were born and died
• liquid water arrives on earth & stays

Question 2

Features that all living organisms share and what “deepest homology’ means

Answer 2

1. boundary between it and its environment (membrane)
2. exploits eletrical tension for power (ATP)
3. uses DNA to store heritable information
4. uses RNA and ribosomes to create proteins

deepest homology: traits shared by 2 organisms due to common ancestry

Question 3

Three general hypotheses explaining the origin of life (and their problems! )

Answer 3

1. membranes first
   - phospholipids have special properties in aq sol and easily form boundaries
   - boundaries allow electrical tension via gradient
   - “prebiotic soup” hypothesis

• “how do we power the membrane?”

2. metabolism first
   - living organisms require constant input of energy to maintain ordered structures

• “how do we maintain it?”

3. RNA first
   - organisms need to reproduce and store genetic information
   - autocatalytic RNA: molecules that self-replicate

• “where do we get the nucleotides”?

Question 4

what is an isotope? how is it used to date objects

Answer 4

• a form of the same element with different neutron numbers
• the half life decays are measured like a clock

Question 5

what a ‘highly conserved’ gene is and how we use them to determine deep evolutionary relationships

Answer 5

• genes inherited from a common ancestor that change very little over time
• ???

Question 6

How Archaea was discovered and the hypothesized relationship between the 3 domains

(you should also know cell types they contain!)

Answer 6

• Archaea was discovered using highly conserved genes
• 3 domains are bacteria, archaea and eukarya
• Prokaryotes make up bacteria and archaea
• eukaryotes and archae are sister groups in tree of life