Chapter 13 Part 2 - Evolution Flashcards
What is phylogeny?
The evolutionary history of a species or group of related species.
Phylon = tribe, genesis = origin.
What is a phylogenetic tree?
A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms (attempts to show how they’re related).
Does the theory of evolution tell us how life first arose?
No, not at all.
Why does it seem likely that all living things descended from a common ancestor?
All life forms use the same genetic code.
When do physicists think the Big Bang happened?
13.8 billion years ago.
How old does scientific evidence suggest the planet is? What did the earth look like at the very beginning?
About 4.6 billion years old and that it began as a vast swirling cloud of dust which fused together.
How did the solid surface of the earth form and when?
Earth probably stared as a molten mass. The liquid sorted into layers of varying density, with the least dense material on the surface, solidifying into a crust (~ 4.1 b.y.a.).
What was early earth’s atmosphere like? How did that change as it cooled?
Probably thick with water vapour and compounds from volcanoes.
Water vapour condensed into oceans but there was still no oxygen or ozone.
What is the oldest fossil? How old is it?
Prokaryotes that have been
dated back to 3.5 billion years ago
What are stromatolites?
Layered, rock-like formations built up by ancient photosynthetic prokaryotes (some of the first evidence of life on earth but probably not the first ever living things).
What are the chemical and physical processes could have produced very simple cells through a sequence of 4 main stages?
- Abiotic synthesis of small organic molecules.
- Joining of these small molecules into polymers.
- Packaging of these molecules into protocells.
- The origin of self-replicating molecules that eventually made inheritance possible.
What are protocells?
Membrane-bound droplets that maintained an internal chemistry different from that of their surroundings.
What was Stanley Miller’s experiment and what did it show?
It simulated the early earth’s atmosphere and lighting. “In 1952 he … showed that complex organic molecules could be synthesised from inorganic precursors.”
- from the Stanley Miller Wikipedia
How can polymers be formed without the use of enzymes? a.k.a. how did polymers form before living things existed?
Dripping dilute solutions of amino acids or RNA onto hot sand, clay or rock vaporizes the water and concentrates the monomers, some of which spontaneously bond together in chains.
How have researchers formed protocells in experiments?
By adding lipids to water with clay. Vesicles naturally form and organic molecules become concentrated on the clay. These vesicles can grow and divide.
What are the 3 steps in scientist’s hypothesis for the origin of genes?
- RNA monomers adhere to clay particles and become concentrated;
- Monomers spontaneously join, forming the first “small” genes;
- An RNA chain complementary to the genes assembles
What is one theory for where on earth life may have originated?
In submerged volcanoes or deep-sea hydrothermal vents
What is chemosynthesis? Where is this process found?
The process of convert chemicals into usable energy (instead of using sunlight as a source of energy like in photosynthesis) as seen in microbes at deep-sea vents.
What is panspermia? Is there evidence for this?
A theory that organic molecules came to Earth in the form of meteorites.
A 4.5 b.y.o. meteorite showed evidence of amino acids, lipids, etc.
What are the 3 eons of geologic time?
- The Archaean
- The Proterozoic
- The Phanerozoic
What are the dates of the Archaean eon? What life existed/what are some notable events in this time?
From the origin of the Earth 4.6 bya to 2.5 bya. No or only prokaryotic life. Atmospheric oxygen appeared around 2.7 bya
How long were prokaryotes the only life forms on earth?
From at least 3.5 bya to about 2.1 bya.
However, the first prokaryotes likely appeared roughly 3.9 bya.
What are the dates of the Proterozoic eon? What life existed/what are some notable events in this time?
From 2.5 bya to 542 mya.
The first eukaryotic cells and multicellular eukaryotes appeared. Atmospheric oxygen increases and animals appear at the end of the eon.
When did the first single-celled eukaryotes and first multicellular eukaryotes appear?
Eukaryotic appeared about 2.1 bya.
Multicellular eukaryotes appeared about 1.5 bya.
