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
Why might a fossil not be formed?
Wrong conditions for fossilisation
Geological activity has destroyed fossils
Fossils not yet found
Describe how different species evolve?
Separation of populations (geographically)
Different environmental conditions between locations
Mutations occur / genetic variation
Better adapted survive (natural selection)
Favourable alleles passed on
Can no longer successfully breed
List the ways a fossil can be formed?
Hard parts of animal do not decay
Parts of the organism are replaced by other materials as they decay
Conditions needed for decay are absent
Preserved trace of organisms eg footprints or burrows
Causes of extinction?
- environment change
- new predators, diseases competitors (more successful)
- single catastrophic event
Cyclical nature of speciation
How do new species arise?
Isolation - two populations of people become separated eg geographically
Genetic variation - population has a wide range of alleles that control their characteristics
Natural selection - in each population the alleles which control characteristics are selected to help the organism survive
Speciation - populations become so different that successful interbreeding is no longer possible
Describe the most common process of fossilisation?
Reptile dies and falls to the ground
The flesh rots, leaving the skeleton to be covered in sand or soil and clay before it is damaged
Protected, over millions of years the skeleton becomes mineralised and turns to rock
The rock shifts in the earth with the fossils trapped inside
Eventually, the fossil emerges as the rocks move and erosion takes place
When is extinction by disease the most likely?
To cause extinction on islands where the whole population of an animal or plant are close together
How does a new predator cause extinction?
The prey animals do not have adaptations to avoid them
How can new predators occur?
Predators may evolve
Or an existing species might simply move into new territory
What is an endemic?
When species evolved in isolation and is found in only one place on the world
Why might two species isolated not become different over time?
Similar conditions
So similar adaptations
Already well adapted
