B2.6 (Janaki)

HideShow resource information
How old is the earth believed to be?
4500 million years old and life is believed to have begun 3500 mill years ago, but there is some debate as to whether the first life developed because of the conditions on earth or if they arrived from another planet.
1 of 13
How can we date when different organisms existed?
We can date when different organisms existed by dating the rocks that fossils are found in.
2 of 13
Why didn’t most organisms leave a fossil?
Most organisms didn’t leave a fossil because the exact conditions for fossil formation were not present. Many early life forms had soft bodies and traces which were left are likely to have been destroyed by geological activity i.e. earthquakes
3 of 13
What is Extinction?
Extinction means that a species that once existed has completely died out.
4 of 13
Extinction always involves a change in circumstance. What can cause extinction?
A new disease. The environment may change over geological time. New predator may evolve/be introduced. New competitor may evolve/be introduced -> little to eat. Natural disaster destroys habitat. Over time natural changes occur in the species.
5 of 13
What is the biggest influence on species survival?
Changes in the environment. Climate change is an important influence in determining which species survive as it may make it too cold/hot, wet/dry for a species. One well adapted to a hot climate may become extinct in the ice age – too cold to breed.
6 of 13
How have many species died out over several million years (short time in geological terms)?
The habitat the species lives in may be destroyed by catastrophic events i.e major volcano eruption. The environment may change dramatically following a collision between a giant asteroid and earth.
7 of 13
What is the most famous of the various ideas suggested to explain the extinction of dinosaurs?
The collision of a giant asteroid caused huge fires, earthquakes, landslides + tsunamis. The dust which rose masked the sun causing darkness so that plant could not grow + temps fell.
8 of 13
What is the less known idea suggested to explain the extinction of dinosaurs?
The idea that the extinction was a slower process as a result of sea ice melting + cooling the sea temperature by about 9 degrees Celsius resulting in less plankton and therefore less food available.
9 of 13
How can new species arise from existing species and how can geographical isolation occur?
New species can arise from existing species if a group becomes isolated from the rest. Geographical isolation could occur if an island separates from the mainland or if a new river separates two areas. Mountain ranges + old craters can isolate organi
10 of 13
How does isolation occur in the case of an island separating from mainland?
The organisms left on the island may be exposed to different environmental conditions, food availability or predators. Natural selection will occur on the mainland + the island but diff characteristics would be beneficial in the 2 populations.
11 of 13
When do we know speciation has occurred?
If the two populations are brought together and cannot interbreed, we say that they belong to two different species.
12 of 13
What is speciation?
Isolation-->genetic variation-->alleles selected-->interbreeding no longer possible-->new species (speciation)
13 of 13

Other cards in this set

Card 2

Front

How can we date when different organisms existed?

Back

We can date when different organisms existed by dating the rocks that fossils are found in.

Card 3

Front

Why didn’t most organisms leave a fossil?

Back

Preview of the front of card 3

Card 4

Front

What is Extinction?

Back

Preview of the front of card 4

Card 5

Front

Extinction always involves a change in circumstance. What can cause extinction?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Adaptations of organisms to their environment resources »