history of life 4-2

Question 1

where did life likely begin? (darwin quote)

Answer 1

Life may have begun in…
“…some warm little pond, with all sorts of
ammonia and phosphoric salts, lights, heat,
electricity, etc. present, so that a protein
compound was chemically formed ready to
undergo still more complex changes…
- a (1 1871)

Question 2

3 important major transitions leading to higher levels: 1st one, genes

Answer 2

1. separate replicators (genes) and formation of cell membranes -> genome within the cell. group formed: compartmentalized genomes. group transformation: evolution of large, complex genomes

Question 3

3 important major transitions leading to higher levels: 2nd one, unicells

Answer 3

major transition: separate unicells -> symbiotic unicell
group formed: eukaryotic cells
group transformation: evolution of symbiotic organelle and nuclear genomes; transfer of genes between them; formulation of hybrid genomes

Question 4

3 important major transitions leading to higher levels:3rd unicells

Answer 4

major transition: unicells -> multicellular organism
group formed: multicellular organisms
group transformation: evolution of cell and tissue differentiation and somatic vs germ cells

Question 5

Haldane-Oparin hypothesis for orgin of life

Answer 5

• Haldane-Oparin hypothesis
○ Abiotic synthesis of organic monomers
§ “reducing” atmosphere; higher UV radiation, lightning = great potential for synthesis of amino acids, sugars, lipids, nucleotides
Significant contribution

Question 6

complications with Haldane-Oparin hypothesis

Answer 6

○ No fossil record!!
○ Cant recreate exact conditions - oxygen in our environment now attacks chemical bonds and removes chemical bonds - oxidizing environment
○ Primitive earth had the right conditions
○ Experiments (such as miller-Urey’s) explore possible models for what might have happened
Could also be other sources - deep sea vents ie.

Question 7

can natural selection occur in non-living molecules?

Answer 7

Natural selection can occur in non-living systems of replicating molecules

Question 8

pre cambrian fossils? organisms found

Answer 8

• Stromatolites
○ Dome shaped sedimentary rocks
○ Fossils remain of bacteria at least 3-3.5 byo
○ shark bay aus

• Organisms were likely chemoautotroph or chemoheterotrophs  Photoautotroph did not come after

Question 9

when did bacteria and archaea evolve? eukaryotes?

Answer 9

• First 2 billion years
○ Bacteria and archaea
Eukaryotes evolved between 2.7 (chemical evidence) and 1.8 (fossil evidence) bya

Question 10

endosymbiotic relationships for early eukaryotes?

Answer 10

• Endosymbiotic relationships
○ Chloroplasts and mitochondria lineages to early eukaryotes
○ Green algae to plants and other eukaryotes
Eukaryotes remain unicellular for another billion years

Question 11

ex of eukaryotic fossils - grand canyon

Answer 11

○ Ex. Proterozoic unicellular eukaryotes 780-740 mya, grand canyon
○ Earliest eukaryotic fossils 1.8 byo
§ Consistent with estimates derived from DNA analysis
Phylogenetic relationships among various early groups not well understood

Question 12

eukaryote multicellularity: evolution, why?

Answer 12

• Evolved many times from unicellular ancestors
• Rapid diversification among eukaryotes
• Availability of nitrogen may have a role to play in this developing
•
Why multicellular? - maintain homeostasis bc big as one group, but bc made up of little cells = more efficient

Question 13

advantages of multicellularity

Answer 13

• Division of labor with specialized cell types - a prerequisite for large size and elaborate organ systems
• Evolution of cell adhesion
Intercellular bridges to move nutrients and signaling molecules

Question 14

first multicellular animals?

Answer 14

came about 575 mya
fossils found in mistaken point nfld 1967, S.B. misra
similar organisms of similar age found in Ediacara hills aus
soft bodied organisms