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)
examples of genetic modification
crops that are resistant to herbicides, crops that grow in saline soil, crops that produce a toxin to kill a pest, crops that have high vitamin content, bacteria that produce human insulin, etc.
what is natural selection
it is evolution. the mechanism by which species evolve
who discovered natural selection
Charles Darwin years after his trip to the Galapagos islands
what is needed for natural selection
a variation between members of the same species
how does natural selection work
- species produce more offspring than the environment can support
- within a population, individuals compete for reasources-there is a struggle for survival.
- Or there is an environmental change that exerts selelction pressure
- individuals of a population show variation. some individuals are better adapted than others.
- the better adapted individuals tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring
- individuals that reproduce pass on the (alleles that controls the) charcteristic to their offspring.
- over many generations species change and become better adapted.
what are alleles
different versions of a gene
examples of natural selection
antibiotic resistance and industrial melanism
what is an antibiotic
chemical substance used to treat bacterial infections
how does antibiotic resistance develop
- bacteria with antibiotic resitance appear in a population of non-resistant bacteria creating variation
- the can happen by mutation
- if antibiotic is applied (selection pressure), only the non-resistant bacteria die.
- The antibiotic resistant bacteria multiply and pass on the resistance gene
- the more an antibiotic is used, the more resistant bacteria there will be
- therefore it is important to not use antibiotics if it is not necessary and also to always complete the course of the antibiotic
how does industrial melanism develop
- before burning coal the tree trunks are pale
- the white moths are able to camouflage from the birds and are eaten less
-the black moths are visible and are eaten more
-the white moths reproduce and the population of the white moths increase and are more frequent
-after the burning of coal the tree trunk is darker due to the shoot
-the dark moth is able to camouflage better and is eaten less therefore survives longer and reproduces more - the white moths are eaten and decrease
the melanistic moth were more frequent
what did human do about industrial melanism
humans then took measures to reduce pollution and the white moth reappeared.
