Beginnings of Life

Question 1

What were the conditions of early earth?

Answer 1

H2, N2, CO2, CO

limited O2

rain stripped mineral salts from rocks

early seas formed in depressions in crust

Question 2

How did biological molecules pave the way for cell evolution?

Answer 2

chemical evolution - necessary for formation of first biological molecules

sun, lightning, heat = supply of energy for spontaneous chemical reactions

organic molecules; pre cells, proteins, lipids, carbohydrates, nucleic acids, perhaps RNA preceded DNA

self-replication = NECESSITY

Question 3

What are the evidence against living cells originating from somewhere else in the universe?

Answer 3

1. non-living synthesis of simple organic molecules (sugars, amino acids)
2. assembly of these organic molecules into polymers
3. formation of polymers that can self-replicate (enabling inheritance)
4. formation of membranes to package the organic molecules

Question 4

How were the first biological molecules formed and how does this relate to Miller & Urey?

Answer 4

hypothesised to be formed due to reactions of monomers and chemicals in ocean

Miller & Urey recreated conditions in 1953:

combined molecules of early Earth in closed container

heated water, then mixed it wt CH4, NH3, H2

sparked electricity through gases

mixture enclosed for a week & found to contain some simple amino acids & complex oily carbohydrates

Question 5

How was life created on Earth?

Answer 5

single celled organisms are complex, complexity happens in small steps

1. production of carbon compounds using electrical changes (sugars, amino acids)
2. simple organic molecules formed ( RNA, DNA like structures)
3. replicating molecules evolved & affected by natural selection
4. replicating molecules become enclosed wtin membrane
5. those that evolved metabolic processes outcompeted wt older forms of metabolism
6. multicellularity evolved

Question 6

What was Pasteur’s experiment?

Answer 6

to test whether sterile nutrient broth could spontaneously generate microbial life

How: 2 flasks wt broth boiled, one exposed

Results: 1 clear, 1 cloudy, therefore, microbial growth

Conclusion: reject hypothesis of spontaneous generation

Question 7

What is the classification order?

Answer 7

Dumb Kids Playing Catch On the Freeway Get Squashed

Domain
Kingdom
Phylum
Class
Order
Family
Genes
Species

Question 8

What is the difference btw extinction and mass extinction?

Answer 8

extinction - permanent loss of species is gradual

mass extinction - sudden world-spread extinction
may take 100 million years to recover
6th mass extinction TODAY

Question 9

What can you tell me about the phylogenic tree of life?

Answer 9

node = taxonomic unit, inferred most recent ancestor

internal node = hypothetical taxonomic units ( cannot be directly observed)

edge lengths = time estimate

tree = branching diagram shows inferred evolutionary relationships among various biological species/entities based on similarities & differences in physical &/or genetic characteristics

taxa = segments joining tree

drawn from human perspective, therefore, humankind @ base, falsely suggests humans are ultimate goal of evolution

Question 10

What are cladograms?

Answer 10

are tree diagrams based on similarities & differences btw species in a clade

Question 11

What are clades?

Answer 11

a group of all organisms evolved form a common ancestor

includes species alive today and common ancestor

Question 12

How are members of a clade identified?

Answer 12

base sequences of genes / amino acid sequences are used as evidence for which species are part of a clade

Question 13

What is a molecular clock?

Answer 13

differences in base sequences of DNA & therefore amino acids are a result of MUTATION

there is evidence that mutations occur at roughly constantly so they can be used as a molecular clock

therefore approximate date for splits btw groups can be deduced

Question 14

Why was there a mass reclassification of cladograms?

Answer 14

constructed based on morphology, NOW constructed by amino acid sequences (reclassification process: merges, divisions, transfers)

e.g. figwort family - >5,000 species based on morphology (8th largest), now <2,500 species (36th largest)

Question 15

What is the endosymbiotic theory?

Answer 15

explains existence of several organelles of eukaryotes

states that organelles (e.g. mitochondria & chloroplasts) originated as symbiosis btw seperate single-celled organisms

Question 16

What are the endosymbiotic theory steps?

Answer 16

1. 2 independent bacteria
2. 1 engulfs the other
3. in one another
4. benefit from arrangement
5. internal bacteria passed on to generations

Question 17

Evidence to support endosymbiotic theory?

Answer 17

mitochondria & chloroplast:

have own DNA (naked & circular)

70S ribosomes

double membraned

roughly same size as bacteria & susceptible to antibiotic ?chloraphenal?

can reproduce through binary fission

transcribe DNA & use RNA to synthesis own proteins