B16- Evolution Flashcards
What is evolution
Evolution is the change in the inherited characteristics of a population over time through a
process of natural selection which may result in the formation of a new species.
What is the most widely accepted theory of evolution?
Charles Darwin’s theory called ‘the theory of natural selection’.
What are the stages of the theory of natural selection
- In a species all the individuals are different and show a wide range of variation
- This variation is because of differences in their genes (continuous mutations).
- Individuals with characteristics most suited to the environment (have an advantage) are more likely to survive and reproduce
- The genes/alleles that allow these individuals to be successful (have an advantage) are passed to their offspring.
How do 2 populations form two different species?
If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed two new species.
Evidence that evolution actually has/is occurring
If you get asked about the evidence that is available for evolution you either need to talk about fossils or antibiotic resistance in bacteria.
How are fossils formed?
Organism dies and is covered in sediment / mud or sinks into the mud.
The soft parts decay or are eaten.
The bones and other hard parts do not decay.
So minerals enter bones and they are preserved.
Conditions needed for decay may be absent.
Preserved traces of organisms, such as footprints, burrows and rootlet traces - these become covered by layers of sediment, which eventually become rock.
Why can we not totally rely on fossils for evidence for evolution.
Fossils form rarely and only in certain conditions. Parts of early organisms were mostly soft bodied so they couldn’t form fossils.
Not all fossils for every organism have been found and there are gaps in the fossil records.
How does bacteria become resistant to antibiotics
Bacteria can evolve rapidly because they reproduce at a fast rate.
Mutations of bacterial pathogens produce new strains.
Some strains might be resistant to antibiotics, and so are not killed.
They survive and reproduce, so the population of the resistant strain rises.
The resistant strain will then spread because people are not immune to it and there is no effective
treatment.
Name some ways antibiotic resistance can be reduced:
Always take the full course of antibiotics
Doctors should only prescribe antibiotics when they are required (i.e. not for viral infections).
Patients should complete their full course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
The agricultural use of antibiotics should be restricted.
