D.1.1 Describe four processes needed for the spontaneous origin of life on Earth.
• the non-living synthesis of simple organic molecules
• the assembly of these molecules into polymers
• the origin of self-replicating molecules that made inheritance possible
• the packaging of these molecules into membranes with an internal chemistry different from their surroundings.
D.1.2 Outline the experiments of Miller and Urey into the origin of organic compounds.
The Miller-Urey experiment simulated the hypothetic conditions of early Earth and tested the occurance of chemical evolution. The experiment used water, methane, ammonia, and hydrogen gas. Electrical discharges and boiling and condensing water simulated lightning and rainfall. The system yielded carbon in organic compounds, 15 amino acids, sugars, lipids, and some of the building blocks of nucleic acids.
D.1.3 State that comets may have delivered organic compounds to Earth.
Comets contain a variety of organic compounds. Heavy bombardment about 4,000 million years ago may have delivered both organic compounds and water to the early Earth.
D.1.4 Discuss possible locations where conditions would have allowed the synthesis of organic compounds.
Examples should include communities around deep-sea hydrothermal vents, volcanoes and extraterrestrial locations.
· Deep sea vents: ammonia and methane are present, and were not present elsewhere in the early atmosphere. There are many organisms currently living around deep sea vents suggesting this is a possible explanation.
· Volcanoes: volcanic eruptions involve the release of methane, ammonia, and hydrogen gases as well as water vapor. This, when combined with lightning, creates a real-life version of the Miller-Urey experiment.
· Extraterrestrial locations: Comets contain a variety of organic compounds. Heavy bombardment may have delivered both organic compounds and water to the early Earth.
D.1.5 Outline two properties of RNA that would have allowed it to play a role in the origin of life.
Include the self-replicating and catalytic activities of RNA.
D.1.6 State that living cells may have been preceded by protobionts, with an internal chemical environmentdifferent from their surroundings.
Examples include coacervates and microspheres.
D.1.7 Outline the contribution of prokaryotes to the creation of an oxygen-rich atmosphere.
Photosynthesizing prokaryotes, such as cyanobacteria, produced oxygen via photosynthesis.
D.1.8 Discuss the endosymbiotic theory for the origin of eukaryotes.
Both mitochondria and chloroplasts have evolved from independent prokaryotic cells, which were taken into a larger cell by endocytosis. Instead of being digested, the cells were kept alive and continued to carry out aerobic respiration and photosynthesis because this increased energy was beneficial for the larger cell. The smaller inner cell also benefited (symbiotic relationship).
Evidence that supports endosymbiotic theory:
· they grow and divide like cells
· they have a naked loop of DNA like prokaryotes
· they synthesize some of their own proteins
· they have double membranes (because of endocytosis)