ch. 25: the history of life on earth

Fossil

any record of a living organism preserved in rock

What four factors make fossilization of a species more likely?

has mineralized parts (teeth, bone, shell). lives in a marine or lake environment. a numerous and widespread species.

What are two ways to determine the age of fossils?

stratigraphy and radioactive dating

Stratigraphy

the relative age of a fossil determined from the layer/strata in which the rock is found

Radioactive dating

the absolute age of the fossil is determined from the radioactive decay of particles within the rock

What is the difference between stratigraphy and radioactive dating in finding the age?

stratigraphy finds the relative age while radioactive dating finds the absolute age

What four eras is the history of life divided into?

pre-cambrian, paleozoic, mesozoic, cenozoic

What features define the Pre-Cambrian era?

first fossils form. prokaryotic cells growing in mounds similar to modern stromatolites. oxygen appears in the atmosphere. first eukaryotic fossils.

How old is the Earth and solar system int he Pre-Cambrian era?

4.5 bya

What is the evidence for oxygen appearing in the Pre-Cambrian era?

banded iron deposits and the first iron oxide/rust in rocks

Where did the oxygen that appeared in the Pre-Cambrian era originate from?

photosynthetic bacteria

What features define the Paleozoic era?

age of fishes. plants invade land. first insects, reptiles, and mammal-like reptiles.

What era do the Burgess shale fossils belong to?

paleozoic era

What features define the Mesozoic era?

age of dinosaurs. cone-bearing plants are still predominant. first flowering plants and mammals

What features define the Cenozoic era?

adaptive radiation of mammals, birds, insects, and flowering plants

Biogeography

study of the spatial distribution of species

Continental drift

plates of the Earth’s crust move over time

Pangea

the supercontinent of today’s continents joined together 300-200 mya

When did Pangea break apart into today’s continents?

over tens of million of years ago

Extinction

every member of one species dies and the species ceases to exist

Mass extinction

many species become extinct at around the same time

What is the difference between extinction and mass extinction?

Extinction is the gradual disappearance of species due to natural evolution. Mass extinction is the sudden and widespread loss of species due to a catastrophic event

What caused the end-Cretaceous mass extinction?

massive volcanic activity and meteor impact

What is the evidence for massive volcanic activity that led to the end-Cretaceous mass extinction?

deccan traps in northern india

What is the evidence for the meteor impact that led to the end-Cretaceous mass extinction?

global iridium layer

How are geological eras defined by?

mass extinction events

End-Permian mass extinction

biggest mass extinction ever

Which era does the end-Permian mass extinction mark the end of?

paleozoic era

End-Cretaceous mass extinction

dinosaur mass extinction

Which era does the end-Cretaceous mass extinction mark the end of?

mesozoic era

Sixth mass extinction

modern mass extinction caused by humans

Speciation

formation of a new species

Adaptive radiation

period of rapid evolution of many species, often into new niches

What is adaptive radiation sparked by?

niches open due to extinction of other species or a species moving into new territory with open niches

What two fossils helped us understand human evolution?

lucy fossil and turkana boy fossil

When was the time of the Lucy fossil?

3 mya

When did human ancestors and chimpanzee ancestors become distinct species?

6 mya

What did the Lucy fossil help us understand about human evolution?

humans and chimpanzees shared the same ancestors