Biology paper 2 practicals

• Meiosis :

  •The chromosomes in A diploid cell(23 pairs)are copied .

  •Similar chromosomes then pair up and the genes are swapped between them.

  •The cell then divides to make two diploid cells.

  • These divide again to produce 4 haploid cells (gametes).
• Selective breeding :

  •From your existing stock select the ones which have the characteristics you’re after.

  •Breed them with each-other.

  •select the best of the offspring and bread them together.

  •continue this process over several generations and eventually all the offspring will have the characteristic.
• Genetic engineering:

  • A useful gene is isolated from one organisms genome using enzymes and is inserted into a vector.

  •The vector is usually a virus or a bacterial plasmid, depending on the type of organism that the gene is being transferred to.

  •When the vector is introduced to the target organism, the useful gene is inserted into its cell.
• Quadrats:

  •Place a 1m^2 quadrat on the ground at a random pint in the first sample area.

  •Count all the organisms within the quadrat.

  •Repeat the steps.

  •Work out the mean number of organism per quadrat

  •Repeat steps in the second sample area.

  •Compare the two means.
• Transects:

  •mark a line in the area you want to study.

  •Collect data along the line.

  •Count all the organisms you’re interested in that touch the line.

  •count the number of squares.

  •make it into a percentage (divide by total number of squares then multiply by 100).
• The water cycle:

  •Energy from the sun makes water evaporate turning it into water vapour.

  •Then transpiration happens

  •Warm water vapour is carried upwards then condenses to form clouds.

  •Water falls as precipitation onto land where fresh water is provided for plants and animals.

  •Water is absorbed by the soil and plants.

  •animals return water to soil and atmosphere through excretion
• Reflexes:

  •A stimulus is detected by a receptor.

  •The impulses the travel from the relay neurone through the synapse and to the motor neurone

  •The impulses then travel through the motor neurone to the effector.

  •The effector produces a response
• Reaction time:

  •Drop a ruler between a finger and a thumb

  •Measure the distance fallen before caught.

  •Repeat calculate mean
• Blood glucose :

  Too high (glucose)

  •insulin is added

  Too low(glycogen)

  •glycogen is added
• IVF- eggs are collected after inducing release with LH to be fertilised in a lab

  viable embryos inserted back into women’s uterus.

  success rate is low

  very expensive