2.68a:

• The kidneys job is to excrete out waste substances
• Urea is composed of nitrogen which can be toxic to the body
• Nitrogen is usually found around the body in the form of amino acids, these are generally good for the body but can be dangerous when found in large quantities (excess amino acids)
• Amino acids are broken down in the liver to form Urea and is then circulated to the kidneys where the urea is FILTERED out from the rest of the blood stream
• The urea is then added with water to form urine which is then passed down to the bladder where it is ready to be removed
• The filtered blood then returns to the body free of the toxic urea and nitrogen

2.67b:

• In the human body lungs, kidneys and skin are all organs of excretion
• The lungs excrete Carbon dioxide (CO2)
• The kidneys excrete – Water (H2O), Urea (amino acids) and salts
• The skin excretes – Water & salts (through sweating) as well as a small bit of Urea

2.67a

• A leaf photosynthesizes and by carbon dioxide and water to form Glucose and oxygen
• CO2 + H2O  C6H12O6 + O2
• The oxygen is the waste molecule of the process photosynthesis so the leaf is excreting oxygen as a waste gas
• Respiration is when the leaf uses the glucose with oxygen to produce energy (ATP)
• C6H12O6 + O2  ATP +CO2 + H2O
• In this reaction the molecules that are wasted are carbon dioxide and water and the leaf excretes these out.

2.67a

• A leaf photosynthesizes and by carbon dioxide and water to form Glucose and oxygen
• CO2 + H2O  C6H12O6 + O2
• The oxygen is the waste molecule of the process photosynthesis so the leaf is excreting oxygen as a waste gas
• Respiration is when the leaf uses the glucose with oxygen to produce energy (ATP)
• C6H12O6 + O2  ATP +CO2 + H2O
• In this reaction the molecules that are wasted are carbon dioxide and water and the leaf excretes these out.

3.33 -3.34

Antibiotics
• Resistance to antibiotics can increase bacteria population
• The resistant form of the bacteria becomes more common and the rate of its survival increases

Causes of Mutation
• Mutation can be caused by radiation (x-rays, gamma rays) and chemical Mutagens (chemicals in tobacco)
• Changes base sequence and forms new harmful alleles
• Cancer is also caused by Mutations

3.32

• Most mutations are harmful
• However some can be beneficial
• Mutation creates new alleles which could be: Beneficial (creates new enzymes), Neutral (no effect at the current time maybe affected by a change in the environment) and Harmful (non-functional enzyme)

3.31 Evolution

Occurs because of Natural Selection
Evolution:
• Change in the forms of Organism
• Change in frequency of alleles
Natural selection:
• Mechanism of evolution
• For example: a virus is susceptible to an antidote but it randomly mutates and can survive the antidote this form of the virus is called the resistant form
• All the versions of the virus which cannot survive the antidote die out and as a result only the mutated ones remain
• It is a Random Mutation But Non-random Selection