B2 - Extinction Flashcards
What are the 2 main theories of how life began?
Life formed in a primordial swamp
Simple organic molecules were brought to earth in comets
Describe the 3 ways that fossils are made
Things like teeth, shells and bones which don’t decay easily can last along time when buried. They’re eventually replaced by minerals as they decay
Fossils can formed when an organism is buried in a soft material and the material hardens around it and the organism decays leaving a cast of itself
From preservation where no decay happens (too cold, too acidic etc.)
What are the 3 reasons that the fossil record could be incomplete?
Fossils that formed a long time ago could have been destroyed by geological activity like movement if tectonic plates
They just haven’t been found yet because they are buried very far underground
Conditions not right for fossilisation
What are the 6 reasons for extinction?
The environment changes too quickly
A new predator kills them all
A new disease kills them all
Can’t compete with another species for food
A catastrophic events occurs that kills them all
Speciation happens
What is a species?
A group of similar organisms that can reproduce to give fertile offspring
What is speciation?
The development of a new species
Describe speciation
Populations of a species are separated (called isolation)
Conditions on either side of the isolation barrier will be slightly different
Over time, natural selection causes the different populations to evolve differently
The populations can become so different that they can breed to produce fertile offspring anymore and this means that they are different species
What are the 3 places where fossils are preserved because no decay happens?
In amber or tar pits, there is no oxygen or moisture meaning the decay microbes can’t survive
In glaciers, it’s too cold for the decay microbes to work
Pear bogs are too acidic for decay microbes
