Biology: The Origin and Diversity of Life, Question flash cards

Raven Bilogy 13th edition, CH 25 : The Origin and Diversity of Life

Deep Time, Geologic time is divided into

four eons which are subdivided into eras and 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, Geological evidence suggests a meteor hit the earth 4.6 billion years ago, Hadean Earth was pummeled by asteroids

which could potentially vaporize entire oceans

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

the moon and the rocky mantle melted as temperatures exceeded 2000° C

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

early atmosphere had high CO levels, water slowly vaporized from molten rock

Changes in Earth in geological time, Increased weathering converted silicate rock to soil

CO formed carbonic acid which released bicarbonate ions and calcium from rock

Changes in Earth in geological time, Decreases in CO₂

lowered Earth's temperature

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 supercontinents formed

Rodinia (all continents) and Gondwana (all current Southern Hemisphere continents), Pangea formed from Gondwana

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

two billion years into Earth’s history, 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; humans present for 0.2% of earth’s history

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

hundreds of thousands of meteorites/comets may have carried organic materials, or they originated on early Earth

Early Earth's atmosphere, Few geochemists agree on exact composition

popular view includes CO₂, N₂, water vapor, H₂, and other sulfur/nitrogen/carbon compounds; was a reducing atmosphere

Early Earth's atmosphere, In 1953 Miller and Urey did an experiment

reproduced early reducing atmosphere over water, simulated lightning, temperature below 100°C

Early Earth's atmosphere, Within a week methane gas converted into other simple carbon compounds

which combined to form more complex molecules; later experiments produced amino acids and adenine

Early Earth's atmosphere, Miller and Urey 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, nitrogen fixation

Evolution of metabolism, RNA may have been first genetic material

lipid bubbles could increase probability of metabolic reactions, leading to cell membranes; single-celled organism the first life-form

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

very high temperatures; around 3.8 BYA ocean temperatures dropped to 49-88°C

Fossil evidence of life, Evidence of life during Archean is difficult to find

two main formations of 3.5-3.8-billion-year-old rocks found in Kaapvaal and Pilbara cratons

Microfossils, Microfossils are fossilized forms of microscopic life

oldest are 3.5 billion years old and resemble present-day prokaryotes; fossils from 3.2 BYA could be cyanobacteria

Stromatolites, Stromatolites are mats of cyanobacterial cells that trap mineral deposits

indirect evidence for ancient life, oldest are 2.7 billion years old, modern forms known

Isotopic data, Living organisms incorporate 12C into their cells before other carbon isotopes

analysis of oldest rocks suggests carbon fixation active as long as 3.8 BYA via Calvin cycle or reductive citric acid cycle

Biomarkers, Look for evidence of ancient organic molecules of biological origin

hydrocarbons from fatty acid tails found in ancient rocks, carbon isotope ratios indicate cyanobacteria at least 2.7 billion years old

Earth's Changing System, Climate and atmosphere affect organisms' survival

dramatic shifts led to mass extinctions; Earth has been cooling since formation, extreme drops caused "Snowball Earth"

Shifts in atmosphere, Geological changes explain many changes in atmosphere

hot wet tropics accelerated weathering, Snowball Earth decreased temperature and slowed weathering, plate tectonics can also affect CO₂ levels

Continental motion affected evolution, Continents sit on submerged plates in motion

shifting plates affect evolution by isolating populations or allowing interbreeding

Continental motion affected evolution, Cenozoic era began 66 mya

Australia/Antarctica and Greenland/North America separated, Atlantic Ocean grew, Cretaceous greenhouse conditions submerged continental areas

Oxygenic photosynthesis produced atmospheric O₂, There was a 200-million-year lag between origins of photosynthesis and substantial O₂ levels

iron oxide in oceans, O₂ interacted with UV to form ozone (O₃)

Did plants contribute to glaciations?, Growing evidence that plants contributed to two glaciations

colonization of land followed by glaciation 488-444 mya; vascular plant diversification concurrent with second glaciation 400-360 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, Rhizaria), Archaeplastida, Amoebozoa, Opisthokonta

Compartmentalization of cells, Enabled the advent of eukaryotes

bacteria/archaea ruled for 1 billion years, have less compartmentalization; eukaryotes developed extensive endomembrane system

Evolution of endomembrane system, Infolding of the cellular membrane

formed nuclear membrane (not in bacteria/archaea), allowing physical separation of transcription and translation for added gene expression control

Evolution of endomembrane system, Golgi apparatus and endoplasmic reticulum

facilitate intracellular transport; not all cellular compartments derived from endomembrane system

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

mitochondria descendants of parasite Rickettsia, chloroplasts derived from cyanobacteria

Unicellular body plan, Tremendously successful

unicellular prokaryotes/eukaryotes constitute about half of biomass on Earth, but a single cell has limits with specialization

Unicellular body plan, Multicellularity allowed organisms

to deal with environment in novel ways through differentiation

Multicellularity, Has arisen independently in different eukaryotic supergroups

requires cells to connect and communicate; gene expression varies to allow specialization

Sexual reproduction increases genetic diversity, Allows greater genetic diversity through

meiosis and crossing over

Sexual reproduction increases genetic diversity, First eukaryotes were probably haploid

diploids arose on separate occasions by fusion of haploid cells

Rapid diversification occurred during the Cambrian, Evolutionary innovations occurred while life was primarily aquatic

established foundations for tremendous diversity

Rapid diversification occurred during the Cambrian, Extremely rapid expansion of life called the Cambrian explosion

occurred 542 to 488 MYA; first multicellular animals appeared 50 million years following

Major innovations allowed for the move onto land, Plants and then animals colonized terrestrial environments after Cambrian radiation

evolution of photosynthesis protected organisms, ozone layer protected from UV

Major innovations allowed for the move onto land, Successful movement from water to land required innovations

to prevent desiccation and to obtain wate