6.1 Origins of Life on Earth Flashcards
How old is the Earth?
4500 million years old
When did life begin on Earth?
3500 million years ago
Where are fossils found?
In rocks
How many ways are there that fossils can be formed?
4
What are the four ways fossils can be formed?
From the hard parts of animals that do not decay easily e.g. bones, teeth
Parts of organisms that have not decayed because the conditions of decay are absent e.g. in ice
When parts of an organism are replaced by other materials such as minerals when they decay
Preserved as traces e.g. footprints, burrows and rootlet traces
How are traces of animals likely to have been destroyed?
In earthquakes (geological activity)
What does extinction mean?
A species that once existed has completely died out
What can we learn from the fossil record?
How organisms have changed over time
What are 5 reasons a species may become extinct?
A new disease Environment changes over geological time New predators and competitors A single catastrophic event e.g. volcano eruption Natural changes in a species over time
What has the biggest influence on extinction?
Changes in the environment
What are the two ideas that have been suggested on why dinosaurs may have become extinct?
A giant asteroid hit the earth and caused fires, earthquakes, landslides and tsunamis. Dust rose and masked the sun causing darkness and lower temperatures
or
The extinction was a slower process; sea ice melted, cooled the sea, less plankton food available
