• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

) Explain how natural selction may bring about changes in a population and what conditions may be necessary to bri about speciation

Extracts from this document...


a)} How may Variation Arise in Natural populations b) Explain how natural selction may bring about changes in a population and what conditions may be necessary to bri about speciation A species is a group of organisms that look alike and can reproduce successfully to produce fertile offspring. Within a species there is variation which can be caused my meiosis, random fertilisation, mutations and the natural environment. Genetic variation increases the chance for survival of a population if the environment changes. For example the introduction of a new virus in to the new environment may kill some organisms but others may be resistant to it and survive. If all the organisms had been genetically identical they may have all been killed. The species that survive are likely to live longer and pass on their useful genes to future generations. The change in a species over time is called evolution. There are two types of variation; continuous and discontinuous variation. Discontinuous variation is when there is a complete range of measurements from one extreme to the other for a normal characteristic, such as human height. Discontinuous variation is where characteristics are fit into separate categories with no intermediates such as human blood groups. ...read more.


Far more offspring are generally produced than survive to maturity - they suffer from predation, disease and competition. Populations are usually fairly constant is size. Darwin concluded that individuals that were better adapted to their environment compete better than the others, survive longer and reproduce more, so passing on more of their successful characteristics to the next generation. Darwin used the memorable phrases survival of the fittest, struggle for existence and natural selection. There are three kinds of Natural Selection. Directional Selection, This occurs whenever the environment changes in a particular way. There is therefore selective pressure for species to change in response to the environmental change e.g. The peppered moth.These light coloured moths are well camouflaged from bird predators against the pale bark of birch trees, while rare mutant dark moths are easily picked off. During the industrial revolution in the 19th century, birch woods near industrial centres became black with pollution. In this changed environment the black moths had a selective advantage and became the most common colour, while the pale moths were easily predated and became rare. Populations do not have to decide to adapt, or mutate, after an environmental change. ...read more.


For example horses and donkeys can apparently interbreed, but the offspring (mule) doesn't develop properly and is infertile. This definition does not apply to asexually reproducing species, and in some cases it is difficult distinguish between a strain and a species. New species usually develop due to: geographical isolation (allopatric speciation) andreproductive isolation (sympatric speciation). Allopatric Speciation: It is meaningless to say that one species is absolutely better than another species, only that it is better adapted to that particular environment. A species may be well-adapted to its environment, but if the environment changes, then the species must adapt or die. In either case the original species will become extinct. Since all environments change eventually, it is the fate of all species to become extinct (including our own). Reproductive Isolation (Sympatric Speciation) Reproductive Isolation is a type of genetic isolation. Here the formation of a new species can take place in the same geographical area, e.g. mutations may result in reproductive incompatibility. A new gene producing, say, a hormone, may lead an animal to be rejected from the mainstream group, but breeding may be possible within its own groups of variants. When this mechanism results in the production of a new species it is known as sympatric speciation. ?? ?? ?? ?? Ben Dreyfuss 6mms ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Living Things in their Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Living Things in their Environment essays

  1. Marked by a teacher

    Biology- enzyme coursework

    4 star(s)

    Straight after this, start the stop clock and drop one drop of the mixture into the first depression of the spotting tile. 7. Leave the stop clock running and every 30 seconds, drop one drop of the starch/amylase solution into successive depressions of the spotting tile.

  2. Explain how natural selction may bring about changes in a population and what conditions ...

    The chromatids break at these points and rejoin so that the alleles from one chromatid join alleles on another. An exchange of chromatids takes place between chromatids. Although sexual reproduction produces variation it does not actually introduce new alleles. These are brought in by mutations.

  1. Evolution, Natural selection and Darwinism

    inorganic world, being the result of law, and not of miraculous interposition.' <Ref.3 - Lamarck> A leading geologist of Darwin's era, a Scot named Charles Lyell (1797-1875) introduced a theory known as uniformitarianism, which refers that the profound change is the cumulative product of slow but continuous process that have no changed throughout the Earth's history.

  2. Extended Experimental Investigation - Natural Antibiotics

    Lime is a fruit that is commonly associated with lemon and has similar antibacterial properties. It is because of this that lime is commonly used in cleaning products. Similarly to lemon, lime was more effective on S. Albus but also worked well on lemon.

  1. The comparison of bacterial content in a range of milks.

    This was due to the fact that the milk had started to separate as such-a viscous white mass had formed on the surface of the milk-with a translucent liquid underneath. My research later shows the reason for this. Initially, the amount of lactic acid produced is very similar between semi-skimmed and whole pasteurized; both have undergone the process of pasteurization.

  2. An investigation into whether varying light intensity at a stream affects the species diversity

    The amount of oxygen that a given amount of water will hold in equilibrium decreases as the temperature increases. With a rise of temperature the rate of metabolism of many invertebrates may be trebled and an oxygen shortage can be easily created in the water.

  1. Charles Darwin

    As the environment changes, individuals with these new characteristics will do better, live longer and produce more offspring until eventually, the population will look very different from its original version. If the population changes enough to satisfy some taxonomist, it will be classified as a new species.

  2. Estimating the population of non-grass plants on the school fields.

    so the quardinates will be easy to set. After this it would be quite easy to get random numbers using my scientific calculator and convert them into quardinates. To get a fair test it is important to have a random sample, so all the plants on the field will have an equal chance of being selected.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work