Chapter 16 Lec. 1

Question 1

The earliest life

Answer 1

Earth is 4.5 billion years old.

Evidence for microbial life can be found in rocks 3.86 billion years old.

Question 2

Evidence

Answer 2

Biomarkers. 
Isotopes 
-Carbon 12 6p and 6n
-Carbon 13 6p and 7n 
-Carbon 14 6p and 8n

Question 3

Stromatolites

Answer 3

Fossilized microbial mats consisting of layers of filamentous prokaryotes and trapped sediment.
Found in rocks 3.5 billion years old.
Comparisons of ancient and modern stromatolites
-Anoxygenic
-Oxygenic

Question 4

Origin of cellular life

Answer 4

Early earth was anoxic and hot.
First biochemical compounds were made by abiotic systems that set the stage.
-Amino acids
-Nucleic acids

Question 5

MIller-Urey Experiment (1953)

Answer 5

Academic “grand father”.
Created early earth atmosphere.
-Formed amino acids, nucleic acids, etc…

Question 6

surface origin hypothesis

Answer 6

First membrane enclosed, self replicating cells arose out of primordial soup in ponds on earth’s surface.
Dramatic temperature fluctuations and mixing from meteor impacts, dust clouds and storms argue AGAINST this hypothesis.

Question 7

Subsurface origin hypothesis

Answer 7

Life originated at hydrothermal springs on ocean floor.

• Conditions more stable.
• Steady and abundant supply of energy (H2 and H2S).

Question 8

RNA world theory

Answer 8

Prebiotic chemistry of early earth set stage for self replicating systems.
First self replicating systems may have been RNA based.
RNA can bind small molecules.
-RNA has catalytic activity; may have catalyzed its own synthesis.
-RNA is an informational molecule.

Question 9

Transition to DNA

Answer 9

DNA is a more stable molecule and became genetic repository.
Proteins took over catalysis jobs.
Three part systems evolved and became universal.
-DNA
-RNA
-Protein

Question 10

Lipid Bilayer

Answer 10

Buildup of lipids.
Can naturally form bilayer.
Enclosed RNA became self replicating.

Question 11

Last universal common ancestor (LUCA)

Answer 11

Populations of early cells from which cellular life may have diverged into ancestors of modern bacteria and archaea.

Question 12

Characteristics of LUCA

Answer 12

Early earth was anoxic, thus energy generating metabolism of primitive cells:
-anaerobic
-chemolithotrophic
-Obtained carbon from CO2
Likely:
-Obtained energy from H2
-Generated by FeS reacting with H2S or UV light. 
-Thermophilic

Question 13

Chemoorganotrophy

Answer 13

Early life forms were chemolithotrophic.
-Produce large amounts of organic compounds.
Organic material provided abundant, diverse and continually renewed source of reduced organic carbon.
-stimulating evolution of chemoorganotrophic metabolisms.

Question 14

Archaea and Bacteria

Answer 14

Evidence suggests ancestors of bacteria and archaea diverged 4 billion years ago.
As lineages diverged, distinct metabolisms developed.
Development of oxygenic photosynthesis changed course of evolution.

Question 15

Oxygenic Photosynthesis

Answer 15

2.7 billion years ago cyanobacteria invented oxygenic photosynthesis.

Question 16

Rise of O2

Answer 16

2. 4 billion years ago.

- Ocean absorbed O2 for ~300 million years.

Question 17

Microbial diversification

Answer 17

Development of oxic atmosphere.
-Evolution of new metabolic pathways
Oxygen spurred evolution of organelle containing eukaryotic microorganisms.
-eukaryotic fossils are around 2 billion years old.
-multicellular and more complex eukaryotes found 1.9-1.4 billion years ago.

Question 18

The global carbon cycle

Answer 18

Volcanism and weather.

-Volcanism: CO2 gas in atmosphere.

Question 19

Weathering

Answer 19

Breakdown of minerals.

-Takes carbon into core.

Question 20

Volcanism vs. weathering

Answer 20

Temperature is controlled by weathering.

-Carbon in the atmosphere.

Question 21

Endosymbiosis

Answer 21

Supported hypothesis for origin of eukaryotic cells.

Contends that mitochondria and chloroplasts arose from symbiotic association of prokaryotes within another type of cell.

Question 22

Endosymbiotic origin of eukaryotes

Answer 22

1. Eukaryotes began as nucleus bearing lineage that later acquired mitochondria and chloroplasts by endosymbiosis.
2. Eukaryotic cells arose from intracellular association between O2 consuming bacteria which gave rise to mitochondria and an archaea.

Question 23

Endosymbiotic origin 2

Answer 23

Eukaryotic cells are chimeric.
Supported by:
-eukaryotes have similar lipid and energy metabolisms to bacteria.
-transcription and translational machinery similar to archaea

Question 24

The evolutionary process

Answer 24

Mutations
-Changes in nucleotide sequence of an organisms genome.
-Occurs because of errors in replication, UV radiation.
-Adaptive mutations improve fitness of an organism, increasing its survival
Other genetic changes include gene duplication, horizontal gene transfer and gene loss.