AP Biology Ch. 25 The History of Life on Earth

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What did Oparin and Haldane propose?

Early Earth had a reducing atmosphere that could form organic molecules

What did the Miller-Urey experiment show?

Organic molecules can form abiotically under early Earth conditions

Where might the first organic molecules have formed?

Deep-sea vents or volcanic areas

What are protobionts?

Aggregates of molecules with membrane-like structure showing simple metabolism and reproduction

What are ribozymes?

RNA molecules that act as enzymes

Why is RNA considered the first genetic material?

It can store information and catalyze reactions

What do sedimentary rock layers show?

Relative ages of fossils

What is radiometric dating?

Determining age using radioactive decay of isotopes

What is a half-life?

Time required for half of a radioactive isotope to decay

What is the limit of radiocarbon dating?

About 75,000 years

What are stromatolites?

Layered rocks formed by ancient prokaryotes

When did prokaryotes first appear?

About 3.5 billion years ago

What caused the oxygen revolution?

Photosynthesis by cyanobacteria

Why was the oxygen revolution important?

Allowed aerobic life, created new ecosystems, and was toxic to some organisms

What is endosymbiosis?

Theory that mitochondria and plastids were once free-living prokaryotes

What is an endosymbiont?

A cell living within another cell

What is serial endosymbiosis?

Mitochondria evolved before plastids through multiple events

What evidence supports endosymbiosis?

Own DNA, prokaryote-like ribosomes, similar membranes

When did multicellular eukaryotes arise?

About 1.5 billion years ago

What is the Cambrian explosion?

Rapid diversification of animal life 535–525 million years ago

Why is the Cambrian explosion important?

First appearance of most major animal phyla

What is the snowball Earth hypothesis?

Earth was largely frozen 750–580 million years ago

When did life colonize land?

About 500 million years ago

Which organisms first colonized land?

Plants and fungi

What are tetrapods?

Four-limbed vertebrates evolved from lobe-finned fish

What is continental drift?

Movement of Earth’s plates over time

What was Pangaea?

A supercontinent that existed about 250 million years ago

How does continental drift affect evolution?

Causes geographic isolation leading to speciation

What is a mass extinction?

Event where more than 50% of species go extinct

What caused the Permian extinction?

Volcanism, global warming, low oxygen

What caused the Cretaceous extinction?

Meteorite impact

What is adaptive radiation?

Rapid diversification of species from a common ancestor

When did mammals diversify rapidly?

After dinosaur extinction

What conditions favor adaptive radiation?

New environments with little competition

What are Hox genes?

Genes controlling body structure and layout

What happens if Hox genes are altered?

Body parts develop in wrong places

What is heterochrony?

Change in timing or rate of development

What is paedomorphosis?

Retention of juvenile traits in adults

What is exaptation?

Trait evolved for one function but used for another

Is evolution goal-oriented?

No, it modifies existing structures

How do complex structures evolve?

Gradually from simpler forms

What are the four stages in the origin of life?

Abiotic synthesis of small organic molecules; formation of macromolecules; packaging into protobionts; origin of self-replicating molecules