Chapter 6 - Old & New Species Flashcards
Suggest one way how a fossil could have been formed?
- The hard parts of the organism eg shell, teeth or claws
- may not decay and so can be found years later
What is a fossil?
- The remains of an organism
- found preserved in rock/ice
- from thousands of years ago
Describe one other method of forming a fossil?
- Volcanic eruptions/ mudslides cut off the oxygen
- meaning no bacteria can survive therefore the material of the animal is replaced by minerals
Give three factors that can cause extinction
- climate/ environmental change
- killed by predators
- competition with another better adapted species
Why are scientists uncertain about how life began on earth? 3
- gaps in the record exist where we have not found any fossils for the time period
- incomplete parts of the organism are found
- organisms could have lived in parts of the world where fossils are rarely formed or destroyed by tectonic activity
Define the word extinct
There are none of the species left ( permemnant loss of all the species)
What is speciation?
The formation of a new species from a pre existing one
When does speciation occur?
M1 : two ore more populations of a species become isolated by geographical isolation
M2 : a physical barrier prevents the groups from mixing
M3 : there will be a genetic variation between organisms in both groups
M4 : as they had different living conditions natural selection would select different characteristics for survival e.g. Food temp predators.
- over time the proportions of different alleles in the population will change
- mutations occur in each group
M5 s eventually the species become different enough to no longer be able to interbreed to produce fertile offspring - new species is former
Examples of geographical isolation? 3
- islands separated by oceans
- lakes separated by land
- flat lands separated by mountains
Why might mass extinction occur?
1 climate change eg ice ages
2 volcanic eruption
3 asteroid impact
How can fossils give evidence for evolution?2
- how species changed over time
- comparison between older/extinct species
How do fossils prove evolution?
Show that living things have changed over time
And that some no longer exist
Sequence of change
What causes the extinction of a species?
New disease New competitor Loss of food supply Change in environment New predator
Why are scientists unsure about how life began?
Lack of valid evidence
Because the early organisms were soft bodied
Or
Because their remains were destroyed by geological action
How are fossils formed?
Dead animal buried in sediment
Hard parts do not decay and soft parts do decay
Mineralisation of hard parts
