Evolution Lecture 9

Front 1

Earth is thought to have formed how many years ago?

Back 1

4.5 billions of years, or gigaannum (Ga)

Front 2

Six stages for the evolution of life

Back 2

-Earth forms from interstellar material

-Earth cools; early atmosphere and ocean forms

-prebiotic chemical reactions

-RNA evolves

-First cellular life-forms evolve

-The process of diversification begins

Front 3

What is unique about Earth's history?

Back 3

Large bodies of water formed

Front 4

Six stages of Earth History

Back 4

-Hadean Era

-Archean Era

-Proterozoic Era

-Paleozoic Era

-Mesozoic Era

-Cenozoic Era

Front 5

Hadean Era

Back 5

The solar system was still coming together; all sorts of stuff was flying around. Earth was bombarded by large, ET objects which repeatedly sterilized the surface, making life impossible (4.55 Ga to 4 Ga)

Front 6

Archean Era

Back 6

First clear fossil evidence that life existed. Little oxygen, all life is prokaryotic (4 Ga to 2 Ga)

Front 7

Proterozoic Era

Back 7

We see oxygen building in the ocean and then in rock sediments. Proliferation of organisms, eukaryotes appear: sans hard parts such as bone and teeth (2 Ga to 550 million years ago)

Front 8

Paleozoic Era

Back 8

Hard-bodied fossils appear, complex multicellular organisms, invasion of the land by plants and animals (550 to 250 million years ago) --> HUGE extinction event where Earth almost lost life completely, possibly due to volcanic activity

Front 9

Mesozoic Era

Back 9

Mammals and flowering plants arise; but the land is dominated by dinosaurs, gymnosperms, ferns and lycopods (250 to 65 million years ago)

--> Asteroid extinction event

Front 10

Cenozoic Era

Back 10

Land dominated by mammals and flowering plants (65 million years to present)

Front 11

Pre-Cambrian Era

Back 11

Includes the Hadean, Archean, and Proterozoic Eras

Front 12

Macromolecules of life

Back 12

Nucleic acid, DNA, RNA, proteins (vital) AND lipids & carbohydrates (less important)

Front 13

Murchison Meteorite

Back 13

Contained tens of thousands of different organic compounds including 70 amino acids

Front 14

Panspermia

Back 14

Extraterrestrial Sources of Organic "Seed" Material

Front 15

Directed Panspermia

Back 15

Life on Earth was seeded intentionally

Front 16

Crick and Orgel

Back 16

Came up with Directed Panspermia Theory

Front 17

Autotrophy

Back 17

An organism capable of synthesizing its own food from inorganic substances

Front 18

Isua, Greenland

Back 18

A 3.7 billion year old rock was discovered

Front 19

Stromatolites

Back 19

Layered mats of sediment trapped within bacterial biofilms; some of the oldest fossil evidence of life

Front 20

William Schopf

Back 20

Big name in ancient microfossil discoveries

Front 21

Archaean Era was dominated by...

Back 21

Anaerobes

Front 22

Unambiguous cyanobacterial fossils arise at...

Back 22

2.5 Ga

Front 23

Cyanobacteria

Back 23

Produce oxygen

Front 24

4 Stages of oxygenation on Earth

Back 24

- No atmospheric oxygen

-Oxygenic photoautotrophy; oxygen absorbed by oceans

-Oceans saturated with oxygen, terrestrial sediments begin to absorb oxygen

-Sedimentary sinks saturated; oxygen accumulates in the atmosphere

Front 25

Great Oxygenation Event

Back 25

-2 Ga to 2.5 Ga

-An assumed (no evidence) catastrophic extinction of anaerobes

-Methane is oxidized and the earth's climate starts to cool

Front 26

Huronian Glaciation

Back 26

-2 Ga to 2.5 Ga

-Earth cools as methane is oxidized

-AKA Snowball Earth

-Nearly the entire earth was covered in ice

Front 27

LUCA

Back 27

Last universal common ancestor of all currently extant life; not the first living thing

Front 28

Definition of life

Back 28

-Ability to store and transmit information

-Ability to express stored information

-Ability to evolve --> information can be altered and these alterations permit differential survival

Front 29

Abiogenesis

Back 29

The original evolution of life or living organisms from inorganic or inanimate substances.

Front 30

Abiogenesis Challenges (4 requirements for it to occur)

Back 30

-Information-containing molecules come from inorganic compounds

-The chemical reactions involved must be favored by environmental conditions

-Self-assembly is a crucial feature of the macromolecules

-Processes that degrade macromolecules must be thwarted in some fashion

Front 31

Montmorillonite (AlSi clay)

Back 31

An example of how minerals may have "nursed" oligonucleotides into macromolecule status. It could be an incubator by protecting molecules from UV light, temperature extremes, and degradation.

Front 32

Heritable variation

Back 32

Variation that is able to be handed down to offspring

Front 33

Oparin-Haldane Model (Replicator First)

Back 33

-Assemble simple molecules into building blocks for complex polymers

-Assemble polymers that can store information and catalyze reactions

-Add membranes and an energy source to make a living organism

Front 34

Stanley Miller

Back 34

Miller was the first to actually experiment with "origin of life" conditions. He did his famous experiment as a first year graduate student.

Front 35

Miller & Urey experiment

Back 35

Created a reducing environment rich in methane, ammonia, and hydrogen. After a spark of electricity and some time, amino acids had formed.

Front 36

Possible energy sources for life

Back 36

Lightning, UV light, cosmic rays, volcanic eruptions, and Earth's own internal heat.

Front 37

Environment of early Earth

Back 37

The environment was not as oxidizing as we thought. It was rich in carbon dioxide and nitrogen, which favors the formation of aldehydes rather than amino acids.

Front 38

RNA World

Back 38

The idea the RNA was formed first, and eventually led to the DNA world

Front 39

Spiegelman

Back 39

Experimented on the origins of life: Transferred an RNA template to an RNA primordial soup; showed the RNA got smaller as a result of competition

Front 40

Self-assembly and Autocatalytic

Back 40

The holy grail of RNA world research

Front 41

Metabolism First

Back 41

Idea that the metabolic pathways occurred before RNA; metabolic pathways can be disassembled and re-assembled sequentially

Front 42

"Black Smokers"

Back 42

-Smoke billows out of deep sea vent; contains organic materials

-The temperature differential is likely too high to be conducive to chemical evolution

Front 43

Alkaline smokers

Back 43

More recent discovering; alkalinity allows for pH gradient; smaller thermal gradient; can have carbonate chimneys which have eukaryotic-cell sized pores

Front 44

Black smokers

Back 44

Acidic, large temperature gradient

Front 45

Chemiosmosis

Back 45

The movement of ions across a semipermeable membrane, down their electrochemical gradient. An example of this would be the generation of adenosine triphosphate (ATP)