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.
What are the dates of the Phanerozoic eon? What life existed/what are some notable events in this time?
From 542 mya to present day.
Saw an explosion of multicellular life of all kinds. Life moved out of the water and colonizes land.
When did larger forms of fungi, plants and animals move out of the water and onto land?
About 500 mya in the Phanerozoic eon.
How are rocks and fossils dated using radiometric dating?
Using radioisotopes (like C-14) with a known half life.
At death organisms have a C-12:C-14 ratio like the atmosphere. Over time, C-14 breaks down. Time passed is measured using the known half-life.
What are the 3 eras of the Phanerozoic eon (including dates)?
Paleozoic (542 – 251 mya)
Mesozoic (251-65.5 mya)
Cenozoic (65.5-present)
What is the Paleozoic era known for? What did life look like in this time?
The ancient animal era, virtually all life was aquatic, by about 400 mya, plants and animals were well established on land.
What is the Mesozoic era known for? What did life look like in this time?
The middle animal era, known as the age of the reptiles (dinos!). But by the end of the era dinos are extinct.
What is the Cenozoic era known for? What did life look like in this time?
The recent animal era. An explosion in the evolution of mammals, birds, insects, and angiosperms (flowering plants). Adaptive radiations.
What two factors have played major roles in how historic life on Earth developed?
Climatic variables and geological events.
Why were the multicellular eukaryotes limited in size and diversity until the late Proterozoic era?
Because of a series of severe ice ages when glaciers covered the planet’s land masses, and seas were largely ice covered limiting where life could exist. (Snowball Earth)
What/When was the Cryogenian Period?
The longest and deepest ice age in Earth’s known history, 720 to 635 million years ago.
What is the snowball earth theory?
Ocean sediments suggest that Earth froze over completely (on and off) for about 200 million years before the Cambrian Explosion.
What is the Cambrian Explosion? When was it?
About 535-525 mya. Life hugely diversified, became more complex and began to resemble current life forms. Many phyla of animals appear suddenly.
What is notable about animals’ bodies before the Cambrian Explosion?
Prior to this Cambrian explosion all large animals were soft bodied.
How did animal behaviour change during the Cambrian Explosion?
We begin to see evidence of predation (like claws) and defensive features (armour/spines)
What two types of adaptations were important for life moving onto land?
Adaptations for reproduction on land and also adaptations that reduced dehydration.
Who proposed the theory of continental drift and when?
Alfred Wegener in 1912.
How many times have Earth’s landmasses come together and broken apart since 1.5 bya?
3 times!
How long ago were the continents all together as one large land mass called Pangaea?
250 mya
When did the modern continents begin to take shape?
By the end of the Mesozoic era, about 65 mya.
When did the India plate collided with the Eurasian plate? What formed as a result?
Around 45 mya.
It formed the Himalayas which are still growing.
How does continental drift work?
The crust of the planet (about 10-70 km thick) is made of irregularly shaped plates that “float” on the underlying mantle, moving at a rate of about 2 cm/year.
What is subduction?
When two tectonic plates come together, the lighter one will rise above other. The heavier plate is pushed down into the hot mantle. It may melt and form volcanoes.
What is the ring of fire?
The Pacific Ocean is encircled by subduction zones with lots of earthquakes and volcanic activity creating a ring of fire.
What is sea floor spreading?
When two tectonic plates pull apart, magma from the mantle rises to fill the forming gap, creating a ridge at the bottom of the ocean.
When was the Permian mass extinction? What percentage of life on earth went extinct?
251 m.y.a. at the end of the Paleozoic era.
Approximate 96% loss.
Referred to as “the great dying”.
When was the Cretaceous mass extinction? What percentage of life on earth went extinct?
65.5 m.y.a. at the end of the Mesozoic era.
Approximate 76% loss. Bye bye dinos.
What caused the Permian mass extinction?
Enormous volcanic activity that released tons of carbon dioxide and warmed the globe enough to dramatically impact the oceans.
What caused the Cretaceous mass extinction?
A 10 km asteroid that landed in the Caribbean Sea near the Yucatan Peninsula in Mexico. The impact ejected material into the atmosphere reducing sunlight levels and preventing photosynthesis, also causing acid rain.
What evidence is there to support the theory that an asteroid caused the Cretaceous extinction?
Unusually high levels of the rare metal iridium in certain layers of rock and the discovery of the crater in the Caribbean Sea.
What is an adaptive radiation?
The evolution of many diverse species from a common ancestor.
What are 3 factors that may trigger adaptive radiations?
- Evolution of key adaptations (i.e. wings)
- Release from competition/vacated niches (i.e. moving to an island)
- Extinctions (which empty ecological niches)
What is a key adaptation?
It usually means an adaptation that allows an organism to evolve to exploit a new niche or resource (i.e. wings).
