Covering the topics of B2

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  • Created by: Sofia
  • Created on: 24-04-12 19:40

Mitosis and Meiosis


Used for normal cell growth

  • Parent cell
  • Chromosomes make identical copies of themselves
  • They line up along the centre
  • They move apart
  • Two daughter cells from each with 46 identical chromosomes to the parent cell.


Used to make the sex cells (gametes)

  • the chromosomes are copied
  • Cells divide twice to give four cells
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Sexual and Asexual reproduction


Variation is introduced by:

  • Set of genetic info from two parents
  • The gametes are produced by meiosis (each gamete is different)
  • Some inherited characteristics may be more dominant than others e.g: eye colour, brown and blue.

Asexual: example: a spider plant.

  • One parent
  • Offspring produced by mitosis
  • Genetically identical to the parent
  • Are a clone of the parent
  • There is NO variation!
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Genetics, DNA and Chromosomes


Nucleus->Chromosome->Gene->DNA double helix->Bases

46 Chromosomes to fertilised egg, 23 from each parent.

  • Male= x,y the male determines the sex of the baby
  • Female= x,x

If there is an extra chromosome= downs-syndrome.

DNA is a double helix

The order of bases A, T, C, G determine our features

  • A=Adenine   A always pairs with T      A sequence of 3 bases codes for
  • T=Thymine                                         one amino acid. The sequence of
  • C=Cytosine  C always pairs with G     amino acids determine the protein
  • G=Guanine                                         structure and characteristics.
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Constant internal environment.

Temperature in the Thermoregulation system

Too hot:

  • hair lies flat
  • blood vessels dilate-sweat
  • flush-capillaries close to skin

Too cold:

  • goosebumps-hair traps air
  • no sweat
  • shivering-generates heat
  • blood vessels constrict. 
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Animal and Plant Cells

Cell Organelles

Both Animal and Plant cells:

  • nucleus-controls cell functions (brain)
  • cell membrane-controls entry of chemicals into cell
  • cytoplasm-where chemical reactions happen
  • mitochondria-respiration
  • endoplasmic reticulum-makes proteins like enzymes

Plant ONLY:

  • cell wall-supports cell (protection)
  • chloroplasts-site of photosynthesis (chlorophyll)
  • vacuole-contains sap and starch granules
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:) PurpleJaguar (: - Team GR


covering the topicS there is only one section in of B2 in these notes :L sorry,, but the notes for mitosis and meiosis are good :)



Lol, i'm not finished, day by day i'll add more:) x

:) PurpleJaguar (: - Team GR


okay sorry :):) **

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