Biology The origin and diversity of life

Raven biology 13th edition, CH25

Deep Time, Geologic time is divided into four eons

Eons are subdivided into eras, which are further subdivided into periods

Deep Time, Geological evidence suggests a meteor hit the earth 4.6 billion years ago

No rocks exist from Hadean eon (first 500 to 700 million years of Earth's history

Deep Time, Hadean Earth was pummeled by asteroids

Could potentially vaporize entire oceans

Deep Time, When meteor hit, debris formed the moon and the rocky mantle melted

Temperatures exceeded 2000° C

Changes in Earth in geological time, CO levels shifted and affected temperature

Early atmosphere high CO levels

Changes in Earth in geological time, Water slowly vaporized

From the molten rock

Changes in Earth in geological time, Increased weathering converted

Silicate rock to soil

Changes in Earth in geological time, CO formed carbonic acid

Carbonic acid released bicarbonate ions (HCO₃⁻) and Ca²⁺ from rock

Changes in Earth in geological time, Decreases in CO

Lowered Earth's temperature

Weathering rocks pull CO₂ from the atmosphere, Weathering rocks pull CO₂ from the atmosphere

Process that removes CO₂ from the atmosphere

Continents moved over geological time, Earth's crust formed rigid slabs of rock called plates

Under continents and oceans

Continents moved over geological time, Two ( important) supercontinents formed

Rodinia (all continents) and Pangea ( separating continents)

Continents moved over geological time, Pangea formed

From Gondwana

Life emerged in the Archean eon, Proterozoic ("early life") eon occurred

Two billion years into Earth's history

Life emerged in the Archean eon, Proterozoic eon was characterized by

Formation of Rodinia

Life emerged in the Archean eon, Rodinia broke up before Phanerozoic eon

Cambrian period showed diversification of multicellular organisms

Life emerged in the Archean eon, Birds and mammals have existed for

4% of earth's existence

Life emerged in the Archean eon, Humans present for

0.2% of earth's history, or 1 second of earths time

Early organic molecules, How first organic molecules formed is not known

Hundreds of thousands of meteorites and comets slammed into early earth; some may have carried organic materials

Early organic molecules, Alternatively

Organic molecules may have originated on early earth

Early Earth's atmosphere, Few geochemists agree on

exact composition of early atmosphere, popular view of early atmosphere

Early Earth's atmosphere, Popular view includes

Carbon dioxide, Nitrogen gas, Water vapor , Hydrogen gas , and other sulfur, nitrogen, and carbon compounds

CO₂, N₂, H₂O, H₂, an S, N , C compounds

Early Earth's atmosphere, Atmosphere was reducing

Because of availability of hydrogen atoms and their electrons

Miller-Urey experiment, In 1953, Miller and Urey did an experiment that reproduced early atmosphere

Assembled reducing atmosphere rich in hydrogen with no oxygen gas

Miller-Urey experiment, Atmosphere placed over

Liquid water

Miller-Urey experiment, Temperature below

100°C

Miller-Urey experiment, Simulated lightning with

Sparks

Miller-Urey experiment, Found within a week that methane gas (CH₄) converted into

Other simple carbon compounds

Miller-Urey experiment, Compounds combined to form

Simple molecules and then more complex molecules

Miller-Urey experiment, Later experiments produced

More than 30 carbon compounds including amino acids

Miller-Urey experiment, Adenine is

also produced

Miller-Urey experiment, Concluded that key molecules of earth could have formed

On early Earth

Evolution of metabolism, Primitive organisms may have been

Autotrophic or heterotrophic

Evolution of metabolism, Landmarks in the evolution of metabolism include

Oxygenic photosynthesis, Carbon fixation, and Nitrogen fixation

Evolution of metabolism, RNA may have been first

Genetic material

Evolution of metabolism, Lipid bubbles could increase the probability of

Metabolic reactions

Evolution of metabolism, Leads to

Cell membranes

Evolution of metabolism, Single-celled organism the first

Life-form

Conditions on early Earth, Seems likely that Earth's first organisms emerged and lived at

Very high temperatures

Conditions on early Earth, Around 3.8 BYA ocean temperatures dropped to

49° to 88° C

Conditions on early Earth, First organisms

emerged around this time

Fossil evidence of life, Evidence of life during the Archean in the form of microfossils is

Difficult to find and interpret

Fossil evidence of life, Two main formations of 3.5- to 3.8- billion-year-old rocks have been found

Kaapvaal craton (South Africa) and Pilbara craton (Australia)

Fossil evidence of life, Structures in each interpreted to be

Biological in origin

Microfossils, Microfossils are fossilized forms of

Microscopic life

Microfossils, Oldest are 3.5 billion years old

Seem to resemble present-day prokaryotes

Microfossils, Fossils from 3.2 BYA could be

Eukaryotic cells but probably cyanobacteria

Stromatolites, Stromatolites are mats of cyanobacterial cells that

Trap mineral deposits

Stromatolites, Indirect evidence for

Ancient life

Stromatolites, Oldest are

2.7 billion years old

Stromatolites, Modern forms are also

Known

Isotopic data, Living organisms incorporate ¹²C into their cells

Before other carbon isotopes

Isotopic data, Work has been done dating and analyzing carbon compounds in the oldest rocks

Looking for evidence of life

Isotopic data, Carbon fixation active as long as

3.8 BYA

Isotopic data, Ancient carbon fixation via

Calvin cycle or a reductive version of the citric acid cycle

Isotopic data, Ability to fix carbon has evolved

More than once

Biomarkers, Look for evidence of

Ancient organic molecules of biological origin

Biomarkers, Simple in theory but

Difficult to find

Biomarkers, Hydrocarbons derived from fatty acid tails of lipids were found in

Ancient rocks

Biomarkers, Analyzed for carbon isotope ratios to indicate

Biological origin

Biomarkers, Indicates that cyanobacteria are at least

2.7 billion years old

Earth's Changing System, Climate (temperature and water availability) and atmosphere among many factors that

Affect organisms' survival

Earth's Changing System, Dramatic shifts in all these factors led to

Mass extinctions influencing the course of evolution

Earth's Changing System, Earth has been cooling since its

Formation

Earth's Changing System, Extreme drops in temperature resulted in

Glacial ice covering Earth, "Snowball Earth"

Shifts in atmosphere, Geological changes explain many changes in

Atmosphere

Shifts in atmosphere, Hot wet climate of tropics accelerated

Weathering

Shifts in atmosphere, Snowball Earth decreased temperature and slowed

Weathering

Shifts in atmosphere, Plate tectonics can also affect

Weathering and atmospheric levels of CO₂

Continental motion affected evolution, Continents sit on submerged plates that are

In motion

Continental motion affected evolution, Shifting plates affect evolution by

Reproductively isolating populations or allowing previously separate populations to interbreed

Continental motion affected evolution, Cenozoic era began

66 mya

Continental motion affected evolution, Australia and Antarctica separated, as did

Greenland and North America

Continental motion affected evolution, The Atlantic Ocean continued to grow as

Plates in the mid-Atlantic spread

Continental motion affected evolution, Greenhouse conditions during Cretaceous period led to

A rise in sea level and continental areas were submerged

Life changes Earth 1, Oxygenic photosynthesis produced atmospheric O₂

200-million-year lag between the origins of photosynthesis and substantial levels of O₂

Life changes Earth 1, Iron oxide in the

Oceans

Life changes Earth 1, O₂ in the atmosphere interacted with ultraviolet (UV) radiation from the Sun and formed

O₃ (ozone)

Life changes Earth 2, Did plants contribute to glaciations?

Growing evidence that plants contributed to two glaciations

Life changes Earth 2, Colonization of land by plants followed by

Gradual cooling and abrupt glaciation 488 to 444 mya

Life changes Earth 2, Vascular plants diversification concurrent with second glaciation

400 to 360 mya

Ever-Changing Life on Earth, Life evolved into three monophyletic domains

Eubacteria, Archaea, and Eukaryotes

Ever-Changing Life on Earth, Eukaryotes divided into 5 supergroups

Excavata, SAR (Stramenopila, Alveolata, and Rhizaria), Archaeplastida, Amoebozoa, Opisthokonta

Compartmentalization of cells, Compartmentalization of cells enabled the advent of

Eukaryotes

Compartmentalization of cells, Bacteria and archaea ruled the Earth for

1 billion years

Compartmentalization of cells, Bacteria and archaea are distinct from eukaryotes in that they have much less

Compartmentalization

Compartmentalization of cells, Eukaryotes developed an extensive

Endomembrane system

Evolution of endomembrane system, Infolding of the

Cellular membrane

Evolution of endomembrane system, Nuclear membrane, not found in bacteria and archaea, accounts for

Increased complexity in eukaryotes

Evolution of endomembrane system, Physical separation of transcription and translation adds additional levels of

Gene expression

Evolution of endomembrane system, Golgi apparatus and endoplasmic reticulum facilitate

Intracellular transport

Evolution of endomembrane system, Not all cellular compartments are derived from

Endomembrane system

Endosymbiosis and the origin of eukaryotes, Mitochondria and chloroplasts entered early eukaryotic cells by

Endosymbiosis

Endosymbiosis and the origin of eukaryotes, Mitochondria are the descendants of the parasite Rickettsia, incorporated into cells

Early in the evolution of eukaryotes

Endosymbiosis and the origin of eukaryotes, Chloroplasts are derived from

Cyanobacteria

Multicellularity leads to cell specialization, Unicellular body plan

Tremendously successful

Multicellularity leads to cell specialization, Unicellular prokaryotes and eukaryotes constitute about half of the

Biomass on Earth

Multicellularity leads to cell specialization, But a single cell has limits with

Cell specialization

Multicellularity leads to cell specialization, Multicellularity allowed organisms to deal with environment in novel ways through

Differentiation

Multicellularity leads to cell specialization 2, Multicellularity has arisen independently in

Different eukaryotic supergroups