Unit 1 Flashcards
Do we know have life arose?
No. We have not proven how life arose on Earth, but scientists believe the Universe began around 13-14 billion years ago via the Big Bang Theory and 4.6 billion years ago, the Earth was formed. Fossil evidence suggests life started 3.5 billion years ago.
Haldane-Oparin Hypothesis (Primordial Soup Hypothesis)
Life spontaneously arose from methane ammonia, water, and energy sources. Simple molecules (ex. C, H, O2, and N) combined to form the building blocks of complex molecules. Heat from volcanoes, lightning and UV radiation could have driven chemical reactions to produce organic monomers, such as amino acids.
Miller-Urey Experiment
Tested Haldane-Oparin Hypothesis by simulating conditions on early Earth by synthesizing organic molecules.
Contemporary Scientists believe…
Methane and ammonia were like absent from the atmosphere and more likely CO, CO2, N2, and H20. Results yielded a variety of organic monomers and other simple organic molecules.
Panspermia
Theory that rocks and meteorites from outer space provided organic materials and microorganisms that could have been a catalyst for life on Earth.
Development of Cell-Like Bodies
All life forms have cell membranes composed of phospholipids.
DNA vs. RNA
RNA is believed to have come first due to the fact that the discovery of retroviruses and their instructions to produce the enzyme (catalyst) reverse transcriptase, despite all eukaryotic cells containing DNA in their chromosomes.
Unresolved Problems
Formation of large, complex, organic molecules via dehydration (or condensation bonds) in an aquatic environment-water actually breaks down large molecules via hydrolysis (protein chain breaks into amino acids, making it difficult to produce proteins) rather than forming smaller molecules into larger ones.
Little evidence that self-replicating systems exist.
The earliest cells were most likely…
heterotrophic anaerobes due to the lack of oxygen but abundance of food molecules on Earth.
Autotrophs
Organisms that produce their own food
Chemotrophs
Energy source for food production comes from chemical processes.
Phototrophs
Energy source for food production comes from sunlight.
Stromatolites
a type of cyanobacteria that can form calcium carbonate rock.
H2S vs. H20
Photosynthesis needs compounds that donate electrons. Early organisms used H2S for photosynthesis, releasing sulfur as a byproduct. When they switch to H20, oxygen was being released as a byproduct. This created an Oxygen Crisis as most organisms were obligate anaerobic microbes.
Obligate Anaerobes
Do not use oxygen, will die in presence of oxygen.
Facultative Anaerobes
Do not use oxygen, but they won’t die because of it.
Neo-Proterozoic Era (Precambrian Era)
-Origin of Earth
-Appearance of earliest prokaryotic and eukaryotic cells
-concentration of oxygen increased
-diversification of algae and soft-bodied invertebrates
Paleozoic Era
-sudden increase in diversification of many animal phyla (cambrian explosion)
-diversification of early vascular plants, bony fishes, and tetrapods
-radiation of reptiles
-amphibians dominant
-extinction of many marine and terrestrial organisms
Mesozoic Era
-cone-bearing (gymnosperms) dominate landscape
-dinosaurs evolve
-origin of mammals
-flowering plants (angiosperms) appear and diversify
-dinosaurs extinguish
-pangaea begins to separate
Cenozoic Era
-current era
-angiosperm dominance increases
-major radiation of mammals, birds, and pollinating insects
-appearance of bipedal human ancestors
-origin of Homo
-historical time
