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

3.32 types of mutation

• gene --->(mutation) new allelels, which can beneficial or harmful, or have no affect (neutral)
• a beneficial enzyme might be the efficiency of an enzyme
• a harmful enzyme might be a non functional enzyme
• a neutral enzyme would have no particular effect, but in time (depending on the environment) it would become a beneficial or a harmful enzyme

3.31

• evolution: is the change in the new forms of organisisms
  as well as: change in the frequency of alleles
• natural selection: the mechanism of evolution

staphlococcus aureus: causes skin infections and lung infections, associated with infected wounds, in particular wounds in operations

the original form of staphlococcus aureus is susceptible to methecilline (antibiotic)
MSSA (methecilline susceptible to staphlococcus aureus): 100% in the original form

a random mutation was able to break down methecilline, making it resistant towards the antibiotic, which keeps on increasing (the allele that can resist the antibiotic is increasing and becoming more common).

• Random muation (the MRSA form)
• non-random selection (antibiotic)

these 2 components are features of natural selection
natural selection is a process, not a thing