2.69 urinary system

• in the urinary system we have a left and right kidnney
• there is a tube for each kidney that leads to the bladder, called the ureter
• then the urine travels out through the urethra

2.68b Osmoregulation

• the water coming into and out of the cells (which is isotonic) remains the same so the cells stay the same size
• the blood circulating into the tissue would be concentrated causing a hypertonic or hypotonic (dilute)  which are both undesirable as hypertonic would remove too much water and hypotonic would add too much water
• this is achieved by controlling the composition of the blood the kidney controls the composition of blood
• the excess salts and water can be excrted through the urintary
• by controlling the salts and water the kidney can keep the blood and therefore the water stays isotonic

2.68a excretion

• urea contains nitrogen which is toxic
• amino acids (that are used for growth) contain nitrogen but excess AA have to be excreted
• the amino acids circulates to the the liver and urea comes out which re-enters into the bloodstream which circulates to both kidneys so that the kidneys can filter the urea from the blood which is added to the water to create urine which circulates to the bladder.

this is an example of excretion.

2.67b human organs of excretion

1. Lungs
• carbon dioxide is the waste of respiration (excretion)

2. Kidneys
• responsible for excretion of excess water, urea (amino acids) and salts

3. skin
• excretes water, salts (in sweat) and a little bit of urea

2.67a excretion in plants

 1.
• photosynthesis - light being absorbed into the leaf = CO2 + H20 -> C6H12O2 + O2
the O2 is the excretion here
2.
•respiration - C6H12O2 + O2 ->(enzyme) A.T.P + CO2 + H20
the CO2 is the excretion here

3.34 causes of mutation

• radiation can cause changes in genes such as x-rays, sunshine (ultraviolet). sunshine can for example cause skin cancer
• second way it can be mutated is by chemicals like tar that can cause cancer. These chemicals that cause mutation are called mutagens and ones that inflict cancer as well are called carcinogens

3.33 antibiotic resistance