B6 Variation (page 75) Flashcards
Organisms of the same species have differences, what do this mean?
Different species look different - a dog definately doesnt look lik a daisy.
Organisms of the same species will usually look slightly different, explain this?
in a room full of people you’ll see different colour hair, individually shaped noses, a variety of heights, etc.
What do Variation within a species mean?
differences withing a species means they all look slightly different, hair, height, eye colour etc
(variation can be huge within a population).
Variation can be genetic, what do this mean?
it’s caused by differences in genotype.
What do Genotype mean?
it is all of the genes and alleles that an organism has. An organism’s genotype affects its phenotype - the characteristics that it displays.
An organism’s genes are inherited (passed down), from where?
from its parents (see page 69).
It’s not only genotype that can effect an organism’s phenotype though, what else can effect an organism?
interactions with its environment (conditions in which it lives) can also influence phenotype.
e.g. a plant grown on a nice sunny windowsil could grow luscious and green. The sae plant grown in darkness would grow tall and spindly and its leaves would turn yellow - these are environmental variations.
Most Variation in Phenotype is determined by a mixture of what?
of genetic and environmental factors.
For example, the maximum height that an animal or plant could grow to is determinded by its genes, but whether it actually grows that tall depends on its environment (e.g. how much food it gets).
What are Mutations?
it means that the gene is altered, which produces a genetic variant (a different form of the gene).
Occasionally, a gene may mutate. A mutation is a rare, random change in an organism’s DNA that can be inherited. Mutations occur continuously.
How do a gene mutate?
As the gene codes for the sequence of amino acids that make up a protein, gene mutations sometimes lead to changes in the protein that it codes for.
Most genetic variants have very little or no effect on the protein the gene codes for. Some will change it to such a small extent that its function is unaffected. This means that most mutations have no effect on an organism’s phenotype.
Some varients have a small influence on the organism’s phenotype - they alter the individual’s characteristics but only slightly, give example?
Some characteristics, e.g. eye colour are controlled by more than one gene. A mutation in one of the genes may change the eye colour a bit, but the difference might not be huge.
Very occasionally, varients can have such a dramatic effect that they determine phenotype. Give example?
The genetic disorder, cystic fibrosis is caused by a mutation that has a huge effect on phenotype. The gene codes for a protein that controls the movement of salt and water into and out of cells. However, the protein produced by the mutated gene doesn’t work properely. This leads to excess mucus production in the lungs and digestive system, which can make it difficult to breathe and to digest food.
If the environment changes, and the new phenotype makes an individual more suited to the new environment what happens?
it can become common throughout the species relatively quickly by natural selection (see page 76).
Explain what is meant by environmental variation? (2 marks)
Differences between members of the same species (1 mark) that have been caused by the environment/conditions something lives in (1 mark)
