variation and evelution Flashcards
what is variation
Variation is the differences between individuals of the same species.
what are the two things that affect variation
environmental
genetics
what are the 2 types of variation
continuous and discontinuous
continuous
controlled by many genes and the environment there is a continuous range of possibilities with no categories
discontinuous
controlled by a single gene there are distinct groups
Explain how sexual reproduction results in the variation seen in the plants in box Y
genes of gametes is not identical
They inherit different {genes} from both parents
what is a mutation
a change in the sequence of DNA
what affects the rate of mutation
Mutations are random and there is a greater chance of mutation if you are exposed to ionising radiation. The greater the exposure to ionising radiation the greater the chance of mutation.
what is the cause of cystic fibrosis
a mutation in a single gene
what does cystic fibrosis cause
cystic fibrosis causes a thick mucus to build up in the lungs, leading to the blocking of the bronchioles. It is caused by a mutation.
what is the allele for cystic fibrosis
n
natural selection
rules (VISITED)
Natural selection states that:
There is variation within a species due to difference in genes. This is called heritable variation.
Individuals with features that make them better adapted to the environment will survive and breed. This is ‘survival of the fittest’.
Genes are passed to offspring. This means that offspring inherit the features that make them better adapted to the environment.
As a result of this, over many years, a species may evolve and change.
what causes extinction
Sometimes natural selection occurs too slowly for organisms to adapt to new environmental conditions. This means that organisms may become extinct.
who introduced the theories of natural selection
Charles Darwin
Alfred Russel Wallace
why are models of natural selection limiting
The prey animals do not move.
In reality, the background environment is usually more than one colour.
In reality, the number of offspring is not always the same.
what is environmental variation
is caused by the environment in which the organism has developed in (eg) scars tattoos piercings this cannot be passed onto the next generation
what is heritable variation
caused by differences in genesso thsi can be passes on fro m parent to child (eg) hair colour eye colour shape of nose
what feature are a combination of both heritable and environmental variation
height and weight
if some body had the genetics to be tall but didn’t have the right diet when they ere younger then they may not reachtheir potential height
how can a mutation be passed on
it will be passed on if there was a mutation in the sex cells but not if there was a mutation in the body cells
what is sexual reproduction
Sexual reproduction is when the nuclei of the male and female gametes join together. This process is called fertilisation.
hat does fertilisation produce
Fertilisation produces variation in the offspring. This means that offspring that are genetically different from the parents.
asexual reproduction
Asexual reproduction produces offspring from one single parent. There are no gametes involved.
The offspring produced are genetically identical to the parent. The offspring are called clones.
what is the advantage for farmer if their palnts have rproduced asexually
they will have the same cloned nice juicy fruits but the problems is that they can all die from the same disease
what is gene therepy
Gene therapy involves inserting copies of a normal allele into the DNA of a person who carries the faulty cystic fibrosis allele.
Problems that are linked to gene therapy include:
Problems that are linked to gene therapy include:
The alleles may join with DNA in incorrect places.
The alleles may not enter every target cell.
Treated cells (with the normal allele) will eventually be worn away and replaced by the patient’s own untreated cells (with the faulty allele). Gene therapy is therefore not a long-term solution as the normal alleles have to be continually reintroduced.
how is the normal alle introduced in the lungs
The genes are introduced into the lung tissue using an inhaler.
natural selction
process where organisms that are better adapted to an environment will survive and reproduce.
