Lecture 19

Question 1

Tree of Life

Answer 1

By examining the genome of cells, biologists have established that there are two basic forms to all life:

• procaryotes
• eukaryotes

Question 2

Procaryotes

Answer 2

Smallest, least complex cellular organisms. Distinguished from eukaryotes by their lack of a nuclear membrane and any internal organelles.

Question 3

Why are procaryotes central to biosphere?

Answer 3

Procaryotes are central to biosphere because:

1. of the diversity of their metabolic processes
2. they comprise about 90% of biosphere
3. the ability of archaea to live in extreme environments
4. symbiotic relationships with many eukaryotes
5. role in evolution
6. come in 3 basic shapes (spheres, rods, and spirals)

Question 4

Autotrophic

Answer 4

a metabolic process that synthesizes living protoplasm from inorganic matter in the environment (requires non-catabolic energy input).

Question 5

What are the types of autotrophic metabolism?

Answer 5

Lithotrophic (chemoautotrophic) and phototrophic.

Question 6

Heterotrophic

Answer 6

Metabolic process that synthesizes living protoplasm from organic matter in the environment (humans). Uses catabolism.

Question 7

Catabolism

Answer 7

refers to the breakdown of organic material to release energy.

Question 8

Lithotrophic (chemoautotroph)

Answer 8

Uses inorganic compounds as their energy source. Lithotrophs can be facultative or obligate lithotrophs. Facultative lithotrophs can use heterotrophy when organic material is present.

Question 9

Methane bacteria

Answer 9

actually archaea (or archybacteria). They are obligate anaerobes. Only can exist in the absence of O2.

Question 10

Hydrogen Bacteria

Answer 10

convert H2 to H2O using special enzyme (hydrogenase)

Question 11

Sulfur Oxidizing Bacteria

Answer 11

converts H2S to SO4 (Using O2). These organisms along with another group of lithotrophs (iron bacteria) are responsible for acid mine drainage.

Question 12

Nitrifying Bacteria

Answer 12

Convert NH3 to NO3 (Using O2). Important part of nitrogen cycle.

Question 13

Photoautotrophs

Answer 13

Use sunlight as their energy source. These must have a “photon absorber” such as chlorophyll.

Question 14

What are the 2 types of photoautotrophs?

Answer 14

Aerobic photosynthesis and anaerobic photosynthesis.

Question 15

Aerobic Photosynthesis

Answer 15

These include green plants and algae (eukaryotes) and cyanobacteria (also known as blue-green bacteria). Cyanobacteria also fix nitrogen.

Question 16

Anaerobic Photosynthesis

Answer 16

purple and green bacteria.

Question 17

Heterotrophs

Answer 17

In heterotrophy oxygen atoms are used to convert organic C to CO2 and in the process release energy. Examples include fermenting bacteria and some eukaryotes (yeast), sulfate-reducing bacteria, denitrifying bacteria, and respirers.

Question 18

Carbon Cycle

Answer 18

Photosynthesis, respiration, and biodegration.

Question 19

Biodegredation

Answer 19

Depolymerization by enzymes, fermentation, decay of monomers via respiration

Question 20

Nitrogen Cycle

Answer 20

Critical metabolic process in the geochemical cycle. Involves photosynthesis, biodegredation, nitrification, denitrification, and nitrogen fixation.

Question 21

Sulfur Cycle

Answer 21

Important metabolic process. Includes aerobic photosynthesis, anaerobic photosynthesis, and degredation (sulfate reduction).

Question 22

Geologic Time

Answer 22

Eons->Eras->Periods->Epochs

Question 23

Relative Dating

Answer 23

Principal of superposition in stratigraphy.

Question 24

Absolute Dating

Answer 24

Radiometric dating

Question 25

The Hadean

Answer 25

~1billion years ago. Evolution of basic physical environment. The Earth formed: Solid Earth must have been molted and differentiated. The initial atmosphere must have been stripped away. The secondary atmosphere (and ocean) arose from degassing of volatile material from earth’s interior or by cometary bombardment.

Question 26

The Archean

Answer 26

Procaryotes appear. Fossil record indicate 1st appearance of life ~3.5b years ago (evidence: microfossils and stromatolites)

Question 27

Stromatolites

Answer 27

Layered sedimentary mats of limestone presently laid down by cyanobacteria

Question 28

How did life originate? (hypothesis)

Answer 28

from Oparin in 1924. Said that the energy from solar UV light of lightning discharge caused the formation of organic molecules from reduced atmosphere gases. These organic molecules eventually formed amino acids and then protein of increasing complexity, which eventually became self-replicating.

Question 29

Miller and Urey

Answer 29

in 1953 proved that the HCN and eventually amino acids can be generated by electrical discharge in highly reducing atmospheres.

Question 30

Problems with Oparin/Miller-Urey Hypothesis

Answer 30

pre-biotic atmosphere probably not high reducing but only moderately reducing. Experiments produced amino acids but not self-replicating systems.

Question 31

Rise of Photosynthesizers in the Archean.

Answer 31

Geologic record indivates the appearance of photosynthesizers about 2-3.5 bya. This is explained by the BIF.

Question 32

Banded Iron Formations (BIF)

Answer 32

BIF’s are alternating layers of chert (SiO2) and iron. The iron is hematite and magnetite. They are not formed today. In order to form:

1. Reduced iron must have been present so the iron can dissolve and be transported to regions of sediment formation.
2. This reduced iron must have been oxidized to form ferric ion and the oxidize iron sediments.

Question 33

Redbeds

Answer 33

Redbeds are sandy sediments containing hematite. The oldest of these deposits is ~2byo. They formed when BIF stopped forming. This implies that O2 began to accumulate in the atmosphere (and ocean) in significant quantities so that there was a continuous deposition of oxidized iron.

Question 34

The Proterozoic and Beyond

Answer 34

Eukaryotes appear and with the appearance an explosion in biodiversity. 1.4bya: some time in the middle proterzoic the fossil record indicates the first appearance of eukaryotes. 700mya: 1st multi-celled animals.

Question 35

Has oxygen levels varies much over geologic time?

Answer 35

The fire window suggests that O2 has remained constant over the past ~360 my.

Question 36

Terms of Biogeochemical cycles

Answer 36

Reservoir amount, flux, and residence time.

Question 37

Steady State

Answer 37

A reservoir is in steady state if the rate of the inflow equals the rate of outflow. The reservoir will not change.