Variation Flashcards
What does variation mean
the differences between organisms
where is there variation
there is variation between species and within species (between members of the same species)
what are the different variation within species
continuous variation and discontinuous variations
what is continuous variation
variation shows a range which are affected by genes and environmental factors
What are examples of continuous variation
height and body mass
what is discontinuous variation
small number of distinct groups- not a range which are affected by genes
what are examples of discontinuous variation
tongue rolling or not, blood groups and ears with or without lobes
what are the causes of variation
variation is due to inherited factors (genes) and environmental factors
what are the examples of causes of variation
height is affected by genes and by the nutrition during developement
skin colour is affected by genes and by exposure to light
What is the DNA
the DNA is the genetic material which organisms inherit characteristics from their parents through
where is the DNA found
in the nucleus in eukaryotes and it contains the information that controls the characteristics
what is the DNA made up of
it is made up of a sequence of bases and has the structure of a double helix
what is a change in the base sequence called and what is it
it is called a mutation. Mutations can confer new characteristics to organisms and if they are passed on in the next generation they can lead to new varieties.
what does the DNA have and what are they.
it has genes which are lengths of DNA that code for protein and control
what is the DNA organised as
it is organised in thread-like structures called chromosones
what does each chromosone have
many genes
how many chromosones does a human have
humans have 46 chromosones and in particular 23 pairs
all human cells have 23 pairs of chromosones except for
the gametes: the sperm and the egg/ovum which do not have pairs but 23 chromosones in total. So when they fuse at fertilisation, the zygote formed has 46 chromosones.
what is selective breeding
choosing organisms with specific characteristics to breed together and produce an offspring with more desirable characteristics
why is selective breeding done?
to create new varieties of plants and animals with desirable characteristics e.g. dog breed, racing horses, wheat producing many grains
how is selective breeding done?
- organisms with the desirable charcteristic are selected
- they are bred together
- offspring with the desirable characteristics are selected and bred together
- this is repeated for many generations
how are plants bred together
artifitual pollination is done; pollen is transferred from anther to stigma with a brush and the plant is covered so that no more pollen lands
what is genetic modification
to make plant and animal varieties with desirable features, humans have also transferred genes to a plant/animal from another species
what is an organism called with a foreign gene
genetically modified organism (GMO)
