B2.8 - Speciation Flashcards
Where does evidence for early forms of life come from?
Evidence for early forms of life comes from fossils.
What are fossils?
Fossils are the remains of organisms from many years ago, which are found in rocks.
How are fossils formed?
Hard parts of an organism (teeth, shells, bones, etc) do not decay easily.
As hard parts decay, they are replaced by minerals, forming a rock-like substance shaped like the original hard part.
Preservation - if the conditions for decay are absent (warm, moist, aerobic) then the organism is preserved.
Preserved traces of an organism (footprints, burrows, etc) can leave an impression in initially soft materials.
What can fossils show?
How new organisms and species arise.
How some species may become extinct.
Why can’t we prove theories about early life on Earth?
There is a lack of valid and reliable evidence.
Why is the fossil record incomplete?
Early organisms were soft-bodied, so their remains decayed quickly.
Geological activity (earthquakes, etc) destroyed rocks in the ground.
Some fossils haven’t been found yet.
What is extinction?
Extinction is where all of the individuals of a species die out.
What are the causes of extinction?
The environment changes too quickly.
New predators
New diseases
New, more successful competitors
Catastrophic event - volcanic eruptions, collision with asteroid, etc can wipe out a species.
A new species forms under the cyclic nature of speciation.
What is a species?
A species is a group of similar organisms that can reproduce to give fertile offspring.
What is speciation and when does it occur?
Speciation is the development of a new species. It occurs when populations of the same species become so different that they can no longer breed to produce fertile offspring.
Describe the process of speciation.
Isolation (separation) may occur.
Conditions on either side will be different (climate, etc) and different characteristics may arise.
Each population has a wide range of alleles that will control their characteristics. Organisms with characteristics better suited to their environment will have a better chance of survival, so they will be more likely to breed successfully.
Alleles that control beneficial characteristics will be more likely to be passed on to the next generation.
The two groups will have changed so drastically that they can no longer interbreed. The groups have become separate species.
What is isolation?
Isolation is where populations of a species are separated by a barrier of some sorts, such as a geographical barrier formed by an earthquake or flood.
Organisms with characteristics better suited to their environment will…
Organisms with characteristics better suited to their environment will have a better chance of survival, so they will be more likely to breed successfully.
