bio 1114

the hadean
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Terms in this set (29)
the hadean
-period from the origin of the solar system- 3850ma
-no fossil record, almost no geologic record
KEY EVENTS
-differentiation of earth into crust mantle and core
-origin of atmosphere via volcanic outgassing
-condensation of water vapor to form bodies of water
-origin of continental crust
attributes of life
1. autonomous replication- mitosis, meiosis
2.critical level of complexity (simpler subunits into multiple complex combos)
3. ability to evolve via natural selection
requirements of life
1. any energy source
2. external environment that sustains life
3. ability to evolve via natural selection
Archean
-early organisms had methane based metabolism
-producing co2 and alcohol as by-products
-photosynthetic organisms appear
-respired o2 accumulates and strengthens the ozone layer trapping free oxygen below
-atmosphere is converted to an oxygen environment
-earliest life most likely consisted of prokaryotic bacteria like organisms
archaean life
various bacteria, thermus aquatics, archaea, cyanobacteria, stromatolites
the proterozoic
-origin of eukaryotes
-rapid diversification of soft-bodied animals and green algae
Eukaryotic cell
-nucleus- DNA storage. RNA transcription
-membrane- bound organelles- compartmentalization of functions
serial endosymbiosis theory (SET)
-eukaryotic cells evolved when aerobic bacteria either infected or were engulfed by a larger host cell and later established a symbiotic relationship
-mitochondria- thought to have derived from purple bacteria
-chloroplasts- thought to have derived from cyanobacteria

EVIDENCE:
-circular genomes in chloroplasts, mitochondria and bacteria
-mitochondria have cell membranes v. similar to prokaryotes
progression towards multicellularity.. (order)
single-celled eukaryotes--> colonial eukaryotes
--> differentiated multicellular eukaryotes
changes of multicellularity
-need for support and rigidity increases
-reproduction becomes more difficult
-suface area- volume ration (S/V) goes down
-as size increases (SA) controls exchange with environment (diffusion, heat exchange)
-metabolic chemicals largely depend on V
-animals adjust S/V by shape, use bulk transport to supplement diffusion for long-distant movement of materials
opportunities of multicellularity-cellular and tissue specialization (greater complexity) becomes possible -distinct reproductive organs, tissues, cells -specialization and compartmentalization -skeleton for support/movement -epidermal layer to keep interior from drying and protection -vascular system- transportationCambrian explosion- relatively sudden appearance of diverse animal forms in fossil record -fossils of many phyla appear in the early cambrian -represented by several "lagerstatten" where soft bodied animals have been preserved -by the end all "major" phyla were present explanations -intrinsic -extrinsicintrinsicCambrian Explosion explanation -something about animals changed (ex: new development patterns) explanation: -hox and hoc-like genes were duplicated in the bilaterians -the number of such genes correlated with complexityextrinsicCambrian explosion- explanation -something about the environment changed (ex: increase in availability of oxygen) explanation: -ancient atmosphere contained insufficient o2 to allow evolution of active life stylesevolution of land plants... what 2 kinds-red algae (5,000 species) -green algae (8,000 species) (both unicellular or multicellular)characteristics of land plants-multicellular or non-motile -cell walls with cellulose -apical meristems -autotrophic -alternation of generations (gametophyte)atrophyresulting from primary endosymbiosis with cyanobacteriacell wall-touch, often flexible layer surrounding the cell membrane -helps prevent cell rupture - in plants, cellulose fibers in pectin matrixapical meristemsregions of rapid cell division (mitosis) and differentiation found both roots and shootsgametophyte-the haploid multicellular stage in the alternation of generations -life cycle of plants and algaesporophyte-the asexual and usually diploid phase -producing spores from which the gametophyte arisesorganisms transitioning to land faced several key challenges-avoiding desiccation while undergoing gas exchange -obtaining key minerals -reproducing in the absence of water -structural support without buoyancykey adaptions for vascular plants...1. vascular tissues (xylem, phloem) 2. Leaves 3. sporophylls 4. secondary growthxylemreinforced hollow pipes for transporting water and inorganic nutrients - water and nutrient transportphloem-sugar transportcarboniferousseedless vascular plants dominated the landscapeseeds-gametophytes surrounded by sporophyte tissue -no external water needed for reproductiongymnospermsnaked seedsconifers-most diverse -many adapted to dry conditions -needle like leaves are common