Additional Biology


Different types of cells:

Specialised cells-

Sperm cell: Has a tail so that it can swim to the egg.

  Has mitochondria to provide energy from mitochondria.

Root hair cell: Has hair like structures to increase surface area so it can absorbe more water.

Red blood cell: No nucleus so it has more space to carry oxygen.

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Comparing cells:


  • Loop of DNA.
  • Ribosomes.
  • Cell membrane.
  • Cell wall.


  • Cell wall.
  • Cell membrane.
  • Nucleus.
  • Ribosomes.
  • Mitochondria.
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Organisation of the body:

Cells - Tissues - Organs - Organ systems.


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Organ systems:

Salivary gland: Produces Saliva.

Liver: Produces bile.

Large intestine: Water is absorbed- Produces faeces.

Stomach: Digestion. 

Small intestine: Digestion of soluble foods.

Pancreas: A gland which produces enzymes and hormones.

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Plant organs


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Plant organ jobs

Epidermis is thin and transparent : To allow more light to reach the palisade cells.

Thin cuticlue made of wax: To protect the leaf without blocking out light.

Palisade cell layer at the top of the leaf: To absorb more light.

Spongy layer: Air spaced allow carbon dioxide to diffuse through the leaf, and increase the surface area.

Palisade cells contain many chloroplasts: To absorb all of the available light.

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Plant organs

Shows the waxy cuticle on top of the upper epidermis.Under this is the palisade mesophyll layer and spongy mesophyll layer, which has air spaces in it. At the bottom, is the lower epidermis and wax cuticle. Gases are exchanged through the stoma. On each side of the stoma there is a guard cell with chloroplasts. (

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Carbin dioxide + Water -> Glucose + Oxygen.

       Light energy (Absorbed by chlorophyll)


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Limiting factors:



Co2 concentration.

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Distribution of plants:

Factors which affect distribution of plants: 


Amount of light.

Availability of water.

Availability of nutrients.

Availability of oxygen and carbon dioxide.

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Random sampling with quadrats:

  • quadrats should be placed randomly so that a representative sample is taken.
  • you should look at the results from several quadrats in an area to reduce the effect of an unusual distribution.
  • the results are more reliable when you look at the results from many quadrats.
  • quadrats may also be used for slow moving animals such as snails/slugs.
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Sampling along a transect-

1- Tape measure or marked rope.

2- Place quadrat.

3- Record the presence of each plant type.

4- Place the quadrat at the next point. 

5- Repeat 3 or more times to see if the results are reproducible and repeatable.

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Proteins and enzymes:

Proteins= Are made up of long chains of amino acids.

Examples of proteins = Structural tissues. 



           Biological catalysts (Enzymes).

Enzymes speed up chemical reactions. 

( If the shape of the enzyme changes (The active site) it cannot work as                                         well as a catalyst,it had been denatured.

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Digestive enzymes:

Amylase: A type of carbohydrase, it catalyses the chemical reaction that breaks down starch in to sugars.

Protease: Breaks down proteins in to amino acids.

Lipase: Breaks down (Lipids) fats in to fatty acids and glycerol.

All three enzymes are produced in the pancreas and small intestine.

In addition amylase is produced in the salivary glands and protease is produced in the stomach.

Different enzymes work best at different PH values.

The stomach produces hydrochloric acid – to begin digestion and to kill harmful microorganisms too.

The stomach is a very acidic environment – So enzymes in the stomach work best at low PH values.

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Digestive enzymes:

Bile is made in the liver and stored in the gall bladder- it is released into the small intestine to neutralise the stomach acid.

This creates the alkaline conditions the enzymes need to carry on digesting the food, so by the time we get to the small intestine everything is being digested.

The enzymes from the pancreas mix with those made in the small intestine.

Amylase, protease and lipase digesting carbohydrase, proteins and fats to produce glucose, amino acids, fatty acids and glycerol- These diffuse through the lining of the gut and get into our blood.

They’re all useful chemicals. Everything the body needs.

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Enzymes in industry:

In the home:

Biolgical detergants (Washing powder).

Lipase -> Fats and oil. 

In industry:

Proteases- Protein digesting enzymes : Baby food- enzymes 'pre digest' proteins so that they are easier for babies to digest.

Carbohydrases- Carbohydrate digesting  enzymes - Convert starch to sugar syrup (In food).

Isomerase- Conversts glucose syrup in to fructose syrup. Fructose is much sweeter than glucose so it is used in smaller amounts in slimming foods.

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Advantages and disadvantages of industry enzymes:


They bring about reactions at lower temperatures and pressures.

Avoid need for expensive equipment that use lots of energy. 


Denature at too high temperaures which means the reactions must be carefully controlled.

Are in many cases costly to produce.

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Aerobic respiration-

Aerobic is with oxygen. 

Aerobic = Needs air.

Mostly takes place inside the mitochondria in the cell.

Glucose + Oxygen -> Co2 + Water 

                (Releases energy)


Living things: Amino acids -> proteins.

Animals: Contracts muscles.

Mammals and birds: Produces heat (37 degreese )

Plants: Sugars, nitrates, other nutrients to amino acids, proteins and growth.

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Exercise and respiration:

Rate and depth of breathing increases -> More oxygen gets in to the blood ->

More Co2 is removed from the body -> More oxygen reaches the muscles ->

More Co2 is removed from the muscles -> More glucose reaches the muscles.

Heart rate increases -> Blood flows more quickly around the body and to the muscles ->

More oxygen reaches the muscles -> More Co2 is removed from the muscles ->

More glucose reaches the muscles -> The glucose in the blood comes from ... 

Digested food and muscle stored of Glycogen - Glycogen is converted back into glucose in exercise.

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Anaerobic respiration:

The incomplete breakdown of glucose to release energy -> Much less energy released per molecule of glucose than during aerobic respiration ->

Doesn't use oxygen ->  Can supply energy to muscles when there is not enough oxygen for aerobic respiration. 

In the muscles cells -> It produces lactic acid ->

Blood flowing through muscles then removes the lactic acid ->

It creates oxygen debt -> Oxygen is required to oxidise lactic acid to carbon dioxide and water after exercise. 

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Toe -> Two 

It occurs:

During growth - to produce more body cells.

To produce replacement cells when body cells are damaged

During asexual reproduction ( Producing new individuals wirgout fertilisation)

1- The cell has one large pair and one small pair of chromosomes. (46 total)

2- Each chromosome is copied.

3- When the cell divides in two, each cell gets one copy of each chromosome. (46)

4- The two new cells are genetically identical.

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Gametes are produced from body cells by meiosis.

Gametes are formed in the reproductive organs: The ovaries and testes.

1- This body cell has two sets of chromosomes. (46)

2- Each chromosome is copied.

3- The cell divides in to two then in two again. Each new cell gets a copy of one chromosome from each pair. So each cell has one set of chromosomes. ( 23 chromosomes) 

4- One or more of these cells will decelop in to gametes.

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Mitosis and Meiosis:


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Stem cells:

Animals: Most cells differenciate at an early stage -> In mature animals, cell division is mainly for repair and replacement.

Plants: Many cells are able to divide and differenciate into specialised cells throughout life. 

Cells that remain able to divide to form different specialised cells are called stem cells. 

Stem cells can be used to..

Treat Parkinsons disease.

Spinal cord injuries.

Make new organs.

Treat type 1 diabetes.

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Attitudes to stem cells:

It can save lives

Cure diseases,

Save costs of ongoing treatments. 


Is it killing humans?

We have no right to interfere (Religion).

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Genetic variation:

Human body cell: 46 chromosomes. : 23 from the male, 23 from the female.

Genes control your features: Small sections of DNA.

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Inheritance of sex:

23= From the mother.

23= From the father.

The mother and father chromosomes join up -> Two sex chromosomes are left over...

** = Female.

XY = Male.

The male will either pass on an X or Y chromosome... Not both. 

The female will pass on an X chromosome.

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Gene = Contols features.

Allele = One version of the gene.

Polydactyl is a DOMINANT disorder -> Extra fingers or toes.

P= Affected (Dominant)

p= Not affected (Recessive)

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Cystic fibrosis:

A genetic disorder -. Recessive.

Affects the cell membranes. 

Causes thick, sticky mucus.

Affects the pancreas: Digestion of food. 

Affects the lungs: Breathing.

FF- Unaffected.

Ff- Carrier.

ff- Affected

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Genetic crosses:

Genotype: A combination of alleles for a characteristic.

Phenotype: The feature or characteristic that is expressed.

Heterozygous:Two different alleles.

Homozygous: Two same alleles.

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The work of mendel:

Investigated and bred pea plants.

Crosses tall and short plants and got tall ones as a result.

His work was not fully recognised as: 

  • He was not a scientist... He was a monk. 
  • He did not widely publish his work. 
  • Genes had not been discovered.
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Embryo screening:

It tests the embryo for specific alleles. If it is certain that the embryo will develop a certain disorder it can be aborted. 

Social Implications:

  • It can save lives. 
  • Eradicate diseases. 
  • Give better quality of life.

Ethical implications:

  • Is it killing humans? 
  • No right to interfere (Religion)
  • Can encourage designer babies - Gender choice.

Economical implications:

  • Can save costs: Medical treatment and drugs.
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Hard parts: Teeth and bones can turn to fossils.

Traces: Footprints and burrows.

Absence of the right condidtions to decay (No oxygen or microbes): Fish could be buried.

Soft bodied animals (Slugs): Decay.

Geological: Erosion. 

Fossils can show:

How organisms arise. 

How new species are formed.

How some species may become extinct. 

But there is uncertaity because of the lack of valid and reliable evidence.

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Can be caused by: 

New disease -> Duch Elm.

New predators -> Dodo bird.

Catastrophe -> Earthquake, astroids.

New competitor -> Squirrels.

Environmental change -> Wooly mammoth and heating.

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Specialisation is a form of new species.

Can be caused by: 

Isolation -> Species seperated by barrier: Mountains, sea, river, stream.

Genetic variation -> Caused by a range of alleles.

Natural selection -> Advantagous characteristics ( Caused by alleles ) are selected.

Specialisation -> Species become too different to interbreed.

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