Old and new species: Fossils Flashcards
Where does evidence of early life come from?
fossils
What are fossils?
remains of organisms from many years ago which are found in rocks,ice and other places
How are fossils formed?
- hard parts of animals
- part of animals which havent decayed
- parts of animals replaced by minerals
- preserved traces: footprints/droppings
What do we learn from fossils?
- how organisms have developed over time
- gives us insight into extinct animals and what caused them to be extinct
- shows how some animals haven’t changed much
Why don’t we know the origins of life?
- incomplete fossil record
- many early life forms had soft bodies
- fossils destroyed by geological activity
- still lots of fossils to be found
- some organisms which died did not form fossils
what is extinction?
when a species no longer exists
what is a species?
a group of living things which produce fertile offspring
What changes affect extinction?
- environmental
- biological
Environmental changes causing extinction
- climate change: hot/cold climates - too cold to breed
- natural disasters - volcanic eruptions/earthquakes
Biological changes causing extinction
- new predators
- new competition
- new disease
Other factors affecting extinction
- natural changes in species occuring over time
What did dinosaurs become extinct?
- slow extinction process due to melting ice and cooling sea temperature - less food left over
- collision of giant asteroid caused huge fires, earthquakes, landslides and tsunamis - dust covered the sun so lower temperatures - plants couldn’t grow
What is speciation?
development of new species
How is a species split into two?
geological isolation: a barrier splits species into two
What are the stages of speciation?
- geological isolation
- organisms exposed to different environmental conditions
- genetic variation (wide range of alleles)
- natural selection
- unable to interbreed (produce fertile offspring)
- new species formed
