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

3.29 - 3.30

3.29 Variation

Variation = differences

Individual Phenotype = Genotype + Environment

Variation in the population = Variation in the Gene + Variation in the Environment

Their 3 classes of Variation:

·         Discontinuous – When the variation is caused only by gene

·         Continuous – When the variation is caused gene and the environment

·         Environmental variation- when the variation  is caused by only the environment

3.30 Mutation

·         Mutation is rare

·         It changes the base sequence in the gene

·         It can be inherited