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31 Cards in this Set

  • Front
  • Back
What are the 3 main domains (branches) of life?
1) Bacteria

2) Eukarya

3) Archaea
What type of environment do you usually find organisms that are members of archaea?
In extreme environments.

i.e. hydrothermal vents in the ocean. In volcanoes, etc.
The "first" common ancestor:

What is hypothesized to be some of its characteristics?
(4 points)
- probably much like modern bacteria

- contained DNA

- fairly complete metabolism

- more like bacteria. Less like Eucarya/Archaea
The "first" common ancestor:

When is it theorized that this common ancestor appeared?
First fossils (3.5 bya) were already highly derived.

Based on fossils and phylogeny, common ancestor probably occurred 4.5 - 3.5 bya
The "first" common ancestor:

During this time period (4.5 bya), how were genes transfered among organisms?
Via. lateral or horzontal transfer. A community of species that traded genes.

*Not* via vertical transfer from a single species to another.
How old is the earth?
4.6 byo
How is the age of the earth and the date that life is theorized to have appeared connected?
They occurred very close (relatively) to one another.

Earth is 4.6 byo. Life theorized to have appeared 4.5 - 3.5 bya.
When did Eukarya first appear?

What are the 2 major characteristics of the Eukarya that set them apart from other life at the time?
Eukarya appeared 2 bya

Characteristics:
1) Linear DNA

2) organelles
- chloroplasts and mitochondria were obtained by acquiring symbiotic bacteria
What is the term for the method by which early Eukarya obtained organelles?
Endosymbiosis
When did multicellular life first appear?
565 mya
Describe the Cambrian Explosion.

What percentage of the history of earth does this time period represent?
After multicellular life appeared (565 mya), over the next 40 million years, an explosive radiation of forms representing different body plans occurred.

This period is known as the "Cambrian Explosion".

This represents 1% of earth's history.
What "group" of gene was likely beneficial for the Cambrian Explosion?
The Hox Gene.
When did the first terrestrial life appear?
400 mya
When did dinosaurs first appear?
250 mya
When did the first mammals appear?

What did they evolve from?
First mammals appeared soon after first dinosaur (250 mya)

They evolved from mammal-like reptiles.
When were mammals able to diversify?
After the dinosaurs went extinct.

(i.e. they were no longer just an appetizer)
Over the history of the earth, how many mass extinctions have there been?
5
True/False:

Global extinction rates are constant through time.
FALSE.

Extinction rates are *not* constant.
When did the End-Permian Extinction occur?
245 mya
Describe the End-Permian Extinction.
(245 mya)

- Happened quickly; in 1 million years
- Biological disaster
- 50% of families went extinct.
- Perhaps 90% of species extinct.
- Dominant amphibians were replaced by ancestors of mammals and dinosaurs.
What 3 events led to the End-Permian Extinction?
1) Sea-level changes

2) Climate change

3) Change in ocean and atmosphere chemistry
When did the End Cretaceous Extinction occur?
65 mya
Describe the End Cretaceous Extinction.
(65 mya)

- Between 60-80% of species extinct
- Dinosaurs and pterosaurs wiped out
- Marine plankton severely effected
- Many marine invertebrates
- Amphibians, crocs, mammals, turtles not affected as much.
What is theorized to have caused the End Cretaceous Extinction?

What evidence supports this?
Caused by an asteroid.

Evidence:
- Chemical and mineral anomalies in soil at the time.
(e.g. Iridium; a rare-metal that is not formed on earth and can only come from extraterrestrial environments)

- 180 km diameter crater off the coast of Mexico.
What were some of the effects of the asteroid impact that caused the End Cretaceous Extinction?
- Affected climate, ocean and atmosphere chemistry

- SO₂ and water vapor thrown in the air creating acid rain.

- particles blocked solar radiation - earth cold and dark

- massive earthquakes trigger volcanic activity

- enormous tidal wave - 4 km high
What are 3 pieces of evidence that suggests we are currently undergoing a contemporary mass-extinction event cause by humans?
1) Pleistocene Megafauna

2) South Pacific birds

3) Historical evidence since 1600
How is the Pleistocene Megafauna used as evidence for the "contemporary mass-extinction theory"?
About 12,000 - 8,000 years ago, selection extinction occurred, affecting large bodied mammals (> 100 lbs)

- The timing of these extinctions coincides with the migration of humans to these areas.
- Americas and Australia hit the hardest, followed by northern Eurasia. Africa affected very little.
What is the current conservative estimate for the percentage of animals and plants that are threatened with extinction?
9%
How much higher is the contemporary extinction rate compared to historical rates of extinction?
100 to 1,000 times above normal background level.
What are 4 examples of contemporary organisms that have gone extinct due to human activities?
1) Carolina Parakeet (1914)

2) Ivory-billed woodpecker (1968)

3) Chiese R. dolphin (2007)

4) Dusky Seaside sparrow (1986)
What are 2 general suggestions for how to curb humanities affect on the increased extinction rates?
1) Curb population growth.

2) Sustainable development