2.75 Urine

• Urine contains water, salts and urea.

2.74 ADH

• ADH stands for Anti-diuretic hormone.
• ADH is produced in the region of the brain known as the Hypothalamus.
• It flows through the blood stream and its target is the kidney.
• The effect of ADH is to control or alter the quantity or composition of water in blood.
• ADH has the ability to make the blood more or less concentrated.
• ADH targets the collecting duct.
• ADH is responsible for increasing the amount of water added to the blood.
• The urine becomes more concentrated and the volume decreases.

2.73 Glucose Reabsorption

• The glomerula filtrate contains glucose.
• Normally urine does not contain glucose unless this person has diabetes.
• In the proximal convoluted tubule glucose is removed.
• Glucose is then taken back into blood.
• Glucose is selectively reabsorbed into blood in the proximal convoluted tubule.
• 
  

2.72 Water re-absorption

• When the filtration occurs it will filter out too much water.
• As the filtrate passes through the structure to the collecting duct, water is removed from the filtrate.
• The water is then returned back into the blood vessels.
• The water will go back into the blood stream.
• The water has been selected and been reabsorbed into the blood.
• Then we get the phrase selected reabsorption.

2.71 Ultrafiltration

• Nephron is the structure which carries out the filtration of our blood.
• The filtration of blood begins with the arrival of blood in the afferent arteriole.
• The blood is under high pressure.
• The blood vessel starts to branch and become much smaller. This coiled structure is known as the glomerulus.
• The blood vessel coming out of the Bowman's capsule has a smaller diameter than the blood vessel going in.
• The blood pressure increases in the glomerulus.
• The high pressure forces the liquid within blood (plasma) out of the blood vessel.
• Plasma contains water, salts, amino acids, glucose and urea.
• The plasma is then referred to as the glomerula filtrate.

2.70 Nephron Structure

• The dead-end, cup shaped structure is known as the Bowman's capsule.
• The Nephron structure is made up of twisted structures known as the convoluted tubules.
• The tube that begins from the medulla to the cortex is known as the collecting duct.
• The dip down from the cortex to the medulla then back to the cortex is called the loop of Henle.
• The tight knot of blood vessels in the Bowman's capsule is known as the glomerulus.
• The first twisted section is known as the proximal convoluted tubules (PCT) and the second twisted section is known as the distal convoluted tubules (DCT).
• There are millions of these Nephrons in a single kidney.

2.69 Urinary system

• In the urinary system there is the right kidney and the left kidney
• Each with its own separate blood supply.
• Carrying out the process of excretion and filtration.
• From each kidney there is a tube that leads to the bladder,(ureter)
• The ureter carries urine from the kidney to the bladder.
• The urine is conducted to the outside of the body.
• To be excreted down the structure called the urethra.
• Then either travels down through the vagina or through the penis.

2.68b Osmoregulation

• Osmo refers to osmosis and regulation to control.
• Isotonic with the cytoplasm of the cells.
• This means that the amount of water going into
  and out of the cells is equal.
• The cells will remain the same size and shape
  and maintain their function.
• Danger to the tissue is that blood circulating into
  the tissue would be concentrated.
• This causes a Hypertonic tissue fluid or a(concentrated)
• Hypotonic tissue fluid. (dillute)

2.68a Excretion

• Urea contains nitrogen.
• Nitrogen is toxic to the body and cannot be stored.
• The original form of nitrogen are the amino acids.
• Blood circulates to the liver and the amino acids are
  broken down into the molecule known as urea.
• This then circulates to the kidneys.
• The kidneys will filter the urea from the blood.
• The urea will be added to water to form urine.
• This urine drains down the ureters.
• To then collect in the bladder.

2.67b Human organs of excretion

• Lung, kidneys and skin are organs of excretion
• The metabolic waste that the lungs excrete is carbon dioxide.
• Kidneys are responsible for the excretion of excess water, the molecule urea and salts.
• The skin is known to excrete water, salts and little urea.
• The skin excretes salts and water through sweat.
• The lung excretes carbon dioxide through the respiratory system.
• The kidney excretes water, salt and urea through urine.

2.67a Excretion in plants

• Considering the process of photosynthesis
• Involves leaf absorbing light energy.
• In the process of doing so it combines C02 with water
• This forms molecules such as glucose.
• Gives off the gas oxygen, this is a waste molecule so is an example of excretion
• Respiration, aerobic respiration to supply oxygen.
• Through a series of enzyme reactions the glucose is broken down.
• The waste carbon dioxide and water. 
• Plants excrete water and excrete carbon dioxide.

3.33 Antibiotic Resistance

3.32 Types of Mutation

3.31 Evolution

3.30 Mutation

3.29 Species Variation

3.22 Chromosomes and sex Dertemination

3.21b Genetic Probabilities

3.21 Predict probabilities of outcomes from monoybrid crosses.

• Both parents are heterozygotes
• The next process is Meiosis, the alleles need to be seperated
• 50% chance that they will be carrying the big R or little r allele
• RR:2Rr:rr , Red:Red:White
• 75%:25% or 3/4:1/4
• 
  

3.21a Genetic Probabilities

3.21 Predict probabilities of outcomes from monohybrid crosses

• Gamete will contain only one of the 2 alleles
• Then we consider random fertilisation
• Do this by drawing a table to illustrate the possibly fertilisations  that can occur between the pollen grains and the ovules
• In this example it would give us heterozygotes in all squares
• The Genotype of the offspring is big Rr.

3.20 b Pedigree2

3.20 Understand how to interpret pedigree diagrams.