Unit 2.4 - Variation and Evolution Flashcards
What are the two types of variation within a species in terms of how the variation came to be there; the two types in terms of distribution.
Environmental (affected by factors such as climate, diet, accidents, soil, etc.) and genetic (inherited genetically); continuous (continuous range of values as bell curve) and discontinuous (discrete groups).
What is the difference between sexual and asexual reproduction in terms of effect on the population?
In sexual reproduction, fertilisation produces a single cell with new sets of chromosomes, giving rise to variation in a population; In asexual reproduction, multiple clones are produced from a single parent, leading to no variation.
What is the cause of new genes?
Mutations (changes) in existing genes, which occur at random, result in new genes.
What is the effect of mutations and what increases the rate of them?
Most are neutral or have no effect but some can be beneficial or harmful; increased dose of ionising radiation increases mutation rates.
What is cystic fibrosis in terms of symptoms and how it comes about?
It causes the production of thick mucus and the blocking of the bronchioles. It arises as a mutation and can be inherited as a recessive allele.
Describe the process of gene therapy.
Gene therapy is the insertion of a ‘normal’ allele into the chromosomes of an individual who carries the faulty cystic fibrosis allele (usually genes are introduced into lung tissue via an inhaler)
How effective is gene therapy?
It is not straightforward because the insertion of the genes is not sufficient - they must be able to work within the body. It is also difficult to target the appropriate cells and it is not a cure for the underlying condition.
How can natural selection be modelled (Spec)?
Volunteers pick up pieces of coloured card or string from a green background.
What are the limitations of the spec model of natural selection?
In this model the prey do not move, and there may be bias on the part of the volunteer (they pick based on what they know the results should be rather than which are easier to see)
How does the process of natural selection work?
Begins with variation in a species; organisms which are better adapted to their environment are more likely to survive, reproduce and pass on these beneficial adaptations/traits to the next generation, so these traits become the norm for the species.
What happens when natural selection is too slow to keep up with environmental changes?
A species which cannot adapt fast enough goes extinct.
What are the names of the two scientists who were working on ideas of evolution at around the same time?
Charles Darwin and Alfred Russell Wallace.
What three examples today demonstrate ongoing evolution?
Antibiotic resistance in bacteria, pesticide resistance and warfarin resistance in rats.
Why is it important to increase our understanding of the human genome (e.g. the Human Genome Project)?
We can use information from DNA to develop new ways to treat, cure and prevent disease.
