Biology-Year 9-Variation

Variation is when there is a difference between living things of the same species.

Variation can be genetic, environmental or both.

Examples of Variation are:

• Zebra stripes = genetic 
• Scar = environmental
• Tree height = environmental or genetic
• Albinism = genetic
• Hair colour = environmental or genetic
• Sun burn = environmental

Species can mutate to benefit themselves for example:

The peppered moth are light or dark coloured, this is because during the industrial revolution the trees were darken because of the soot. This increased the number of the rare dark peppered moths because they were camoflaged. But now that the air is less poluted the lighter coloured peppered moths are increasing in numbers.

Mutation is a rare, random change or mistake made when new genes are formed.

It can be a small change in a long strand of DNA. They are usually very small changes.

Cancer is an example of a mutation that causes cells to spread and multiply rapidly.

It happens when DNA is copied for new cells, this happens when cells reproduce.

The chances are increased when cells are exposed to types of ionising radiation such as x-rays and ultraviolet light (UV rays).

Certain chemicals can cause mutation like the ones found in cigarette smoke. They are harmful to new body cells and then spread the harmful mutation throughout the body.

It is most likely to happen in the reproductive organs (where eggs and sperm are formed) when it is exposed to ionising radiation. When young is developing a mutaion can occure and this could cause the young to die prematurely or develop abnormally.

Mutations can benefit some animals survival can this leads to the species evolving.

Examples of positive mutations are:

• Camouflage
• Speed change
• Height change
• Survival tempretures

Some mutations are that small that they do not affect the organism because the effects are natural or have no difference to the organisms characteristics.

Asexual reproduction = Cells from the body of the parent divide to produce offspring e.g. seeds or saplings.

• No mate is needed
  
• The offspring are clones of the parent
• No sex cells are needed
• Happens in plants and bacteria
• Copies of the current body cell are made
• It is faster than Sexual reproduction

Advantages:

• No need to find a mate 
• Large numbers of the organism can be produced in a short time
• If the parents grow well in a condition then the offspring will grow well as well

Disadvantages:

• Lack of variation means they are not suited for other environments or conditions

Sexual reproduction = Two gametes (sex cells, ova and sperm or ovules and pollen), on from each parent, fuse together and this produces offspring.

• A mate is needed (there are 2 parents)
  
• The offspring will have a variation of both the parents genes
• Two sex cells are needed
• Happens in humans and some plants
• Slower than Asexual reproduction

Advantages:

• Combinations of genetic information from the parents can make the offspring better adapted for different conditions than the parents and other offspring.
• There is a greater chance of survival in changing conditions.

Disadvantages:

• It requires a mate and fertilisation
• Finding a mate takes time and sexual reproduction takes longer than asexual

• It produces new sex cells
• Occurs in the reproductive organs
• Produces 4 new cells
• The new cells are not the same as the original cell
• Each cell has half the amount of chromosomes of the original cell (23 rather than 46)

Diploid cells have 46 chromosomes and they are normal cells.

Haploid cells have 23 chromosomes and they are gametes.

View the diagram for the steps and images.

Darwin:

Survival of the fittest = When an organism is best suited to its surroundings and environments it will survive and reproduce. The strong charactistics will pass on. Weak organisms will die and not reproduce.

Natural selection = darwins theory on how new species arise and evolution. He saw that different variations of the same species would survive in different areas and over time them would become more different. If a species could not adapt then it would become exstinct. Throught natural selection there is evolution of a new species.

The finches on the Galapagas are evidence for natural selection as each bird we adapted to certain conditions and the food there because of the change in their beaks.

Darwin believed that many species evolved from a original species to adapt to its surroundings.

Superbugs = They are bacteria that are resistant to antibiotics and are hard to get rid off when you are ill.

They are an example of evolution as the bacteria with the best resistance will reproduce and pass on the gene that is resistant to the antibiotics whereas other bacteria without the gene will die (survival of the fittest).

After the 1st dose of antibiotics the non-resistant bacteria will die and the weak ones will be killed by the bodies natural defences (engulfing and antibodies).

But the resistant cells will reproduce and they will be uncureable by the original antiobiotics.

There is a basic 5 fingered pentadactyl limb structure and this suggests that all verebrates are eveolved from one common ancestor. 

Pentadactyl limb structure is 5 fingers, 2 off coming bones that lead to joins and the fingers and 1 bone at the top that leats to the 2 bones and the shoulder (humorus).

What makes them different is the fact that they have adaptations for that species habitat so that they can survive.

It can be found in mammals, reptiles and humans etc. It can be seen in human hands and bat wings.

Fossils:

Ways fossils can be made: The body ends up in a place where decay is prevented. Parts of the plant or animals are replaced by other substances as they decay. Hard parts of the body decay very slowly. Skin decays quickly so it is not fossilised. There are other ways animals and plants can be fossilised such as foot prints, droppings or where roots were.

Differences and similarities between Ardi and modern humans:

• They had a smaller brain than us
• They had hair all over the body
• They had long arms
• They had larger toes than us to hold onto branches
• Ardi would walk upright

Differences and similarities between Lucy and modern humans:

• They had hair all over the body
• They had smaller brains than us but larger tha Ardi
• They had long arms
• They had arched feet, showing that they were more adapted to walking than climbing
• They did walk upright and more efficiently than Ardi