Bio - chapter 21

Which time period of Earth represents when evolution was progressing at the most rapid rate, as evidenced by fossils such as those of the Burgess Shale?

Cambrian period

Which time period would hold the record of the oldest fossils of multicellular animals, found in mountainous areas of South Australia, and parts of Canada and China?

Ediacaran

Why is it believed that RNA was the first informational molecule to evolve?

RNA molecules are able to function as both enzymes and substrates for their own replication.

One critical requirement for life to arise on Earth was time for which to occur?

The ozone layer to form, so that the level of ultraviolet radiation was reduced

The mass extinction at the end of the Cretaceous period was likely the result of:

a dramatic change in climate.

Which type of organisms were likely the first land animals?

arthropods

Millions of years ago, the activity of which cellular organelle would have been dependent upon the presence of cyanobacteria?

mitochondrion

One of the most significant steps in the evolution of true cells from macromolecular assemblages was the evolution of:

molecular reproduction.

During the process of splitting water during photosynthesis, the first cyanobacteria released _____ into the atmosphere

oxygen gas

A significant reduction in the amount of which gas would allow more ultraviolet radiation to reach Earth'

ozone

What feature of a dinosaur determines whether it is a saurischian or an ornithischian dinosaur?

pelvic bone structure

Amphibians evolved directly from which ancestral organisms?

fishes

During the Pleistocene epoch, plant communities changed dynamically in response to which mechanism?

fluctuating climates

15. Evidence shows that the earliest life may have existed how long ago

3.5 billion years ago

What is the approximate age of the Earth?

4.5 million years

A ____ forest included low swamps with giant ferns, horsetails, club mosses, seed ferns, and early gymnosperm

Carboniferous

Mammal-like reptiles arose during which time period?

Carboniferous period

Which statement about dinosaurs is FALSE

Dinosaurs were all slow-moving, with relatively low metabolic rates.

During which time period did shallow seas cover much of the land and another burst of evolutionary diversification occur?

Ordovician period

During the __________ epoch, the mammals experienced an explosive adaptive radiation.

Paleocene

The greatest mass extinction of all time occurred at the end of the ____ era, in which more than 90% of all existing marine organisms became extinct.

Paleozoic

Vascular plants and air-breathing animals first appeared during which time period?

Silurian period

What was a significant outcome of the Miller and Urey experiment?

They synthesized organic molecules from inorganic materials

Why is there very little physical evidence of life from rocks of the Archaean eon?

Those rocks occupy inaccessible areas of mountainous regions

Refer to the accompanying figure. Which organelle evolved from the photosynthetic bacteria?

chloroplast

Which were the first organisms to release oxygen by photosynthesis?

cyanobacteria

Which theory states that eukaryotic organelles originated as prokaryotes that survived ingestion by a host cell and ultimately evolved mutualistic relationships with the host cell?

endosymbiont theory

Which is the largest division of the geologic time scale?

eon

The theory illustrated by the accompanying figure is used to explain the origin of which organisms?

eukaryotes

The Holocene epoch marks the appearance of:

humans

The occurrence of an RNA world early in the history of life can never be proven, but experiments with _____ have shown that it is feasible.

in vitro evolution

Which hypothesis suggests that organic molecules formed near Earth's surface in pools of water?

iron-sulfur world hypothesis

The first cells were most likely heterotrophic anaerobes because:

they utilized preformed organic molecules and did not need oxygen.