Variation & Natural Selection Flashcards
Antibiotics
2 marks
Substance that controls the spread of bacteria in the body by killing them or stopping them reproducing.
Gene
2 marks
A short length of DNA that codes for a particular characteristic.
Histogram
(1 mark)
A graphical representation of the distribution of numerical data.
Mutation
(3 marks)
Random + spontaneous change in the structure of a gene, chromosome or number of chromosomes.
Species
3 marks
Type of organism that is the basic unit of classification.
Individuals of different species are not able to interbreed successfully.
Continuous variation
3 marks
This is a gradual change in a characteristic across a population, e.g human height, mass + shoe size.
- it is represented as a histogram.
Histogram should show
2 marks
Normal distribution, with most individuals around the average value + a few at the extremes.
Discontinuous variation
4 marks
Individuals will fit into a group – there are no intermediates.
e. g ability to roll your tongue, blood group + hand dominance
- it is represented as a bar chart.
How is Discontinuous Variation represented?
1 mark
Bar chart
Main Blood Groups
4 marks
A, B, AB, O
All Blood Groups
8 marks
A-, A+, B-, B+, O-, O+, AB-, AB+
Causes of Genetic Variations
7 marks
Changes to chromosomes or genes (DNA);
- Mutations are random changes in the number of chromosomes or the structure of a gene.
- Independent assortment during meiosis increases variation because it results in genetically different gametes.
- The random nature of sexual reproduction also gives rise to variation.
Mutations are random changes in
4 marks
The number of chromosomes (e.g. Down syndrome)
or the structure of a gene (e.g. cystic fibrosis).
The random nature of sexual reproduction also gives rise to
1 mark
Genetic variation
Independent assortment during meiosis increases variation because
(1 mark)
It results in genetically different gametes.
Example of environmental variation
2 marks
Human height is genetically controlled but actual height reached will depend on the nutrition available.
Causes of Variation
2 marks
Genetic + Environmental factors
How is Continuous variation represented?
1 mark
As a histogram.
Natural selection
1 mark
Living organisms are adapted to their environments in order to survive.
Thorny devil
4 marks
- Lizard native to the Australian Outback.
- In between its scales; microscopic channels that catch + carry water.
- Drink through their scales (like sipping through straws); by opening/ closing mouth
Fennec fox
4 marks
- Has huge, bat-like ears to pinpoint their prey, even when buried under the shifting sands.
- Ears also lined with blood vessels; help regulate + cool body temp.
Cuttlefish
3 marks
- Can change colour + texture of their skin; disguise themselves as clumps of floating seaweed - as they stalk their prey or hide from predators.
Atlantic Bluefin tuna
3 marks
- Has an internal heating sytem; special blood vessel structure allows them to maintain a body temp higher than the cold surrounding water.
Competition makes adaptations for survival
1 mark
Very important - only the best adapted will survive.
