Topic 9 Flashcards
What six features do organisms need to be considered alive?
i) Organization
ii) Metabolism
iii) Response to stimuli
iv) Homeostasis
v) Adaptation
vi) Reproduction
What term describes the maintenance of some internal chemical and/or thermal consistency relative to variation outside of the entity?
Homeostasis
Are viruses alive?
No
What components of life do viruses lack?
Metabolism, homeostasis and cannot reproduce without a host cell
What three large eons is the geologic record divided into?
i) Archaean
ii) Proterozoic
iii) Phanerozoic
What three eras is the Phanerozoic eon divided into?
i) Paleozoic
ii) Mesozoic
iii) Cenozoic
What is a preserved remnant/evidence of organisms that lived in the past?
Fossil
Why is the fossil record biased and incomplete?
i) Requires burial in sediment
ii) Probability of an organism getting fossilized is low
iii) Few organisms are fossilized and discovered
What increases the probability of an organism becoming fossilized?
i) existed for a long time
ii) abundant and widespread
iii) hard-bodied
iv) aquatic
v) inshore marine
vi) decomposing organisms absent
What is a cast fossil?
A cast forms when minerals fill space in sediment where the organism decayed after having been buried
What type of fossil have had their tissues replaced by minerals?
Replacement (petrified) fossils
What is a trace fossil?
Fossils that record evidence of behaviour (tracks, burrows, feces, etc.)
What type of fossil has original organic material retained (carbon films, amber, tar or peat, permafrost)?
Preserved fossil
What is relative dating of fossils?
The sedimentary strata reveal the relative ages of fossils (indicates which fossil came first, second, etc.)
What is a downside of relative dating fossils?
i) Does not indicate how long ago the fossil was created
ii) Gaps are created by erosion or major land movements
What is absolute dating (radiometric dating)?
Using radioactive decay of specific isotopes of elements in fossils or rocks
What term describes 50% of atoms in a given amount of radioactive substance that has decayed?
Half-life
What is plate tectonics theory?
Earth’s crust is composed of plates floating on the Earth’s mantle that move slowly through the process of continental drift
What is continental drift?
Oceanic and continental plates can collide, separate, or slide past each other and their interactions cause the formation of mountains and islands
What were the three effects of Pangaea?
i) Deepening of ocean basins
ii) Reduction in shallow water habitat
iii) Colder and drier climate inland
What are three consequences of continental drift?
i) Changes to the environment and climate
ii) Opportunities for the diversification of life via allopatric speciation
iii) Mass extinctions
How many mass extinctions have occurred and what are the two main extinctions?
Five
Permian and Cretaceous
What is the Permian mass extinction?
Defines the boundary between Paleozoic and Mesozoic eras 251 million years ago that occurred rapidly and had the extinction of about 60% of all families and 96% of marine animal species
What are the two hypothesized causes of the Permian mass extinction?
i) Catastrophic environmental change, such as large meteorite impacts and increased volcanism
ii) Gradual environmental changes including sea-level change, oceanic anoxic events (O2 depletion) and changes in ocean circulation due to climate change
What is the Cretaceous mass extinction (dinosaurs)?
Occurred 65.5 million years ago that separated Mesozoic from Cenozoic in which 20% of all families went extinct including 50% of marine species
What is a hypothesized cause of the Cretaceous mass extinction?
Presence of iridium in sedimentary rock suggests a massive meteorite impact about 65 million years ago
What are three consequences of mass extinctions?
i) can take a long time for diversity to recover
ii) changes the types of organisms found in communities
iii) lineages with advantageous features can be lost
What term describes the evolution of diversely adapted species from a common ancestor?
Adaptive radiation
What are three things adaptive radiation may follow?
i) Mass extinctions
ii) Evolution of novel characteristics
iii) Colonization of new regions
What are the four steps that may have produced very simple cells as the origin of life?
i) Abiotic synthesis of small organic molecules
ii) Joining of small molecules into macromolecules
iii) Packing of molecules into protocells (micells)
iv) Origin of self-replicating molecules
How did the abiotic synthesis of small organic molecules occur?
Thought to have formed in the early atmosphere (water vapour, ammonia and methane, reducing environment, frequent lightning) but now thought to have been synthesized near volcanoes or deep-sea vents (strongly reducing conditions)
Amino acids have also been found in meteorites
How did the abiotic synthesis of macromolecules occur?
Small organic molecules polymerize when they are concentrated on hot sand, clay or rock
How did protocells form?
Organic molecules can spontaneously form hollow vesicles with a lipid bilayer and experiments show vesicles form faster in the presence of volcanic clay
How did self-replicating molecules form?
Via natural selection that produced self-replicating RNA molecules that stored genetic information
What is the oldest fossil evidence of life? (3.5 bya)
Prokaryotes
What describes organisms without DNA contained in a nucleus and without membrane-bound organelles?
Prokaryotes
What are the two domains of prokaryotes?
i) Bacteria
ii) Archaea
What are the oldest known fossils?
Stromatolites
What are stromatolites?
Rocks formed by the accumulation of sedimentary layers on bacterial mats
What organism used the sun’s energy to fix CO2 and produced )2 as a by-product?
Cyanobacteria
What is the oxygen revolution?
The accumulation of O2 was toxic to most early prokaryotes but some groups survived by using anaerobic respiration to harvest energy
