bioversity ch.25-26

The Precambrian

what is the precambrian

The Precambrian

what is the precambrian

longest geological time period; 3eons: Hadean, Archean, and Proterozoic

Hadean Eon

formation of solar system, earth moon, and oceans; rain of asteroids bombarded planet

Archaean Eon

asteroid bombardment ends, origin of life, volcanos form island arcs in ocean, origin of photosynthesis, only prokaryotic life exist on earth

stromatolites

oldest known fossils, composed of layers of bacteria and sediment

Proterozoic Eon

cyonabacteria oxygenate the planet, eukaryotic and multicellular life forms appear, sex and animals evolve

Oparin and Haldane hypothesis

early earth had a reducing atmosphere with water vapor, methane, and ammonium

Miller and Urey experiments

found that it was possible to make formaldehyde, amino acids, and other small organic molecules

Abiotic Synthesis of Functional Macromolecules

small organic molecules polymerize spontaneously when concentrated on hot sand, clay or rock

Protobionts

aggregates of abiotically produced molecules surrounded by a membrane; exhibit simple reproduction; no fateful inheritance

Ribozymes

RNA molecules that make complementary copies of their own sequence or other short pieces of

RNA; autocatalytic; protobiont with **** can grow, split, and pass RNA to its daughters

step 1 that made origin of life possible

abiotic synthesis of small organic molecules

step 2 that made origin of life possible

fusion of smaller molecules into large functional macromolecules

step 3 that made origin of life possible

packaging of macromolecules within a membrane to form a protobiont

step 4 that made origin of life possible

origin of a self-replicating molecules to transmit information across generations

Oxygen Revolution

oxygen began accumulating in the atmosphere over a 500 million year period; atmospheric oxygen produced by cyanobacteria; many anaerobic prokaryotes perished

Endosymbiosis

proposes that mitochondria and chloroplasts entered host cell as undigested prey or internal parasites and became interdependent

Evidence supporting endosymbiotic origin origin of mitochondria and plastids

• similarities in inner membrane structure/function

• organelles divide in a process similar to prokaryotes

• organelles transcribe and translate their own dna

• organelle ribosomes are more similar in size to prokaryotic ribosomes

Snowball Earth Hypothesis

suggests that multicellular organisms remained small because the earth was too cold for large organisms

Cambrian Explosion

toward the end of the phanerozoic era, massive diversification of species that created all 50 major groups alive today, greatest history of diversification; split into 3 fossil assemblages

Doushanto Microfossils

formed in China, microfossils of sponges, cyanobacteria, multicellular algae, and animal embryos in early stages

The Ediacaran Faunas

formed in Australia, fossils of sponges, jellyfish, comb jellies… basically small soft bodied organisms that burrowed in sediments, sat immobile on the sea floor, or floated in the water

Burgess Shale Faunas

formed in Canada, every major living animal group is represented; tremendous increase in size and morphological complexity of animals, diversification in how they made a living, basically diverse, large, and have hard parts

1. Increased Oxygen levels: aerobic respiration more efficient → favored evolution of larger bodied organisms

2. Evolution of Predation: exerted selection pressure for prey defense strategies, drove morphological change

3. New Niches: ability to exploit new niches created new niches for predators, drove speciation and diversification

4. New Genes New Bodies: mutation increased # of hox genes → more complex larger bodies evolved

Cambrian Explosion Triggers

Homeotic Genes

master regulatory genes that determine location and organization of body parts

Hox Genes

class of homeotic gene that provide positional information during development; if expressed in wrong location body parts can be produced in the wrong location

Phanerozoic Eon

542 mya- present day, divided into 3 eras: Paleozoic, Mesozoic, and Cenozoic

Paleozic era

542-251mya ; many animal groups appeared: fungi, land plants, land animals; era ends with obliteration of almost all multicellular life-forms at the end of Permian period

Mesozoic era

age of reptiles, 251-65.5mya, rise and dominance of dinosaurs and ended with their extinction

Cenozoic era

age of mammals, 65.5mya-present, mammals diversified after dinosaurs extinction

Mass extinction

rapid extinction of a large number of lineages, caused by catastrophic events that eliminate at least 60% of the species within 1 million years; result from extraordinary, sudden, and temporary changes in environment, cause extinction randomly with respect to individuals’ fitness under normal conditions

Background Extinction

lower, average rate of extinction, relatively constant normal loss of some species; occur when normal environment change, emerging diseases, or competitions reduces certain populations to zero

Permian Extinction

largest mass extinctions, resulted in end of 96% of all species

Hypothesis of why Permian Extinction occurred

flood basalts (siberian traps) added enormous quantities of heat, carbon dioxide, and sulfur to the atmosphere

Siberian Traps

flood basalts, added enormous quantities of heat, CO2, sulfulr dioxide to atmosphere; led to formation of toxic acid rain, CO2 warmed planet by 6 degrees C, CO2 acidified oceans harming reef building organisms, CO2 increased algal blooms leading to large areas of anoxic ocean bottom

End-Cretaceous Extinction

Extinction where the dinosaurs died

Impact Hypothesis

proposes that an asteroid stuck earth 65mya, resulting in 60-80% of multicellular species alive

1. Iridium: rare compound on earth, plentiful in asteroids, earth had high concentration 65mya

2. Shocked quartz: demonstrates impact from asteroids

3. Microtektites: impact melted earth crust was thrown into atmosphere, formed into tear drop, microscopic glass that rained down into earth

4. Huge crater of Mexico Yucatans peninsula

Evidence for Impact Hypothesis

Selectivity

some evolutionary lineages were better able than others to withstand environmental change

taxonomy

ordered division and naming of organisms

phylogeny

evolutionary history of a species or group of related species

systematics

classifies organisms and determines their evolutionary relationships; can use fossils, anatomy, molecules, and genes to infer evolutionary relationships

morphospecies concept

species can be recognized by obvious morphological similarities and differences; also used with extinct species

biological species concept

species are made up of individuals that can interbreed to produce fertile offspring and cannot interbreed with individuals outside their species

evolutionary species concept

species can be thought of as a lineage of organisms connect through time by ancestor descendant relationships

phylogenetic species

species must be diagnosable at the level of the gene

cladogram or phylogenetic tree

summarizes phylogenies in the depicted form of a branching tree that shows ancestor descendant relationships among populations or species

branch

represents species through time

node

branch point where two branches diverge represents the point in time when an ancestral population splits into two descendant populations which may become different species

terminal node

endpoint of branch, represents a group that is living today or extinct

sister taxa

groups that share an immediate common ancestor

synapomorphies

more recent changes in a species that is a shared trait

symplesiomorphy

shared ancestral trait

ancestral trait

trait that existed in an ancestor

derived trait

modified form of the ancestral trait found in the descendant

rooted tree

includes a branch to represent the last common ancestor of all taxa in the tree

polytomy

node or branch from which more than two groups emerge;unresolved pattern of divergence

cladistics

groups organisms by common descent

clade

group of species that includes an ancestral species and all its descendants

monophyletic grouping

valid clade; consists of the ancestor species and all its descendants

paraphyletic grouping

consists of an ancestral species and some, but not all, of the descendants

polyphyletic

grouping consists of various species that lack a common ancestor

homology

occurs when traits are similar due to shared ancestry

homoplasy

occurs when traits are similar for reasons other than common ancestry; analogous traits

convergent evolution

occurs when natural selection favor similar solutions to problems posed by a similar way of life

reversal

loss of a gene that can result in a new species that is more like the ancestral species that other recent species

phylogenetic bracketing

allows us to predict features of an ancestor from features of its descendants

parsimony

principle of logic stating that the most likely explanation or pattern is the one that implies the least amount of change

Occam’s Razor

among competing hypotheses, the one with the fewest assumptions should be selected

outgroup

species that is closely related to monophyletic group but not part of it (has all zeros of synapomorphies)

(SINES)

short interspersed nuclear elements; more effective way to prove evolution theories than morphological traits; shared derived traits shown in genes

fossil

physical trace left by an organism that live in the past

fossil record

total collection of fossils that have been found throughout the world; provides direct evidence about what organisms looked like; where they lived; when they existed

intact fossils

form when decomposition does not occur; still have bones shells or teeth

compression fossils

form when sediments accumulate on top of the material; compressed into thin film

cast fossils

form when the remains decompose after burial and dissolved minerals create a cast in the remaining hole; imprint filled with minerals

permineralized fossils

form when the remains rot extremely slowly and dissolved minerals infiltrate the interior of the cells and harden into stone

habitat bias

occurs because organisms live in areas where sediments are actively being deposited are more likely to fossilize than are organisms that live in other habitats

taxonomic bias

organisms with bones are more likely to decay slowly and leave more fossil evidence

temporal bias

more recent fossils are more common than ancient fossils

abundance bias

occurs because organisms that are abundant, widespread, and present on earth for a long time leave evidence much more than do species that are rare, local, or ephemeral

radiometric dating

method to determine absolute age of fossil; parent isotope decays to daughter isotope at constant rate

half life

time required for half the parent isotope to decay

molecular clock

uses assumed constant rates of evolution in genes to estimate the absolute time of evolutionary change

neutral theory

states that much evolutionary change in genes and proteins is due to genetic drift; has no effect on fitness and is not influenced by Darwinian selection; rate of molecular change in genes and proteins should be regular like a clock

3 Domains

Archaea, Bacteria, Eukarya

horizontal gene transfer

movement of genes from one genome to another; bacteria do this; complicates efforts to build tree of life

molecular systematics

discipline of classifying organisms based on differences in protein and DNA

vestigial

organ/part of body that has become unfunctional due to evolution

collagen

provides support for extracellular tissues; higher oxygen concentrations favored this and other connective tissues to hold cells together

dichotomy

repeated branching in 2 equal parts

genus

taxonomic category; ranks above species, below family

binomial nomenclature

genus, epithet(species)

Pangea

super continent before they split apart

cladogenesis

exisitng species diverges into 2 species; parent species exists with new species

anagenesis

evolution from single lineage; parent becomes extinct

gradualism

smalls changes accumulate to form big changes

punctuated equilibrium

evolution occurs through short bursts of intense periods of speciation; long periods of stasis