2.69- Urinary System

Describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra

• 2 Kidneys- Carries out the process of excretion, filtration and osmoregulation
• 2 Ureters- Carries urine to the bladder
• Bladder- Stores urine
• Urethra- Urine is conducted out of the body through the urethra

1- 2 Kidneys

2- 2 Ureters

3- Bladder

4- Urethra

2.68b)- Osmoregulation

Understand how the kidney carries out its role of osmoregulation


Osmo- Osmosis
Regulation- Control

• The tissue fluid must be isotonic (equal amount of water going in and out) so that the cells retain their shape and size and are able to function
• Blood circulating into the tissue may be too concentrated (hypertonic tissue fluid) or may be too dilute (hypotonic tissue fluid)
• To keep the tissue fluid isotonic, the composition of the blood must be controlled by the kidney
• Excess water and salts can be removed and excreted through the ureter to control the composition of the blood
• This would mean that the tissue fluid could be kept isotonic with the cells cytomplasm

2.68a)- Excretion

Understand how the kidney carries out its role of excretion 

• Kidney excretes the urea ( contains Nitrogen- toxic and can't be stored)

1. Blood circulates to the liver and amino acids are broken down into urea
2. Urea circulates to the kidneys and is filtered from the blood
3. The urea is added to water to form urine
4. Urine drains down the ureter to collect in the bladder

2.67b)- Human Organs of excretion

Recall that the lungs, kidneys and skin are organs of excretion

1. Lungs- Carbon dioxide 
2. Kidney- Excess water, Urea (Waste from amino acids) and salts
3. Skin- Water, Salts and urea (not much)

Metabolic waste- Carbon dioxide, Water, Urea and Salts

2.67a)- Excretion in Plants

Recall the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf


Photosynthesis: 
CO₂ + H₂O ==> C₆H₁₂O₆ + O₂

• Oxygen is a waste molecule and is an example of excretion

Respiration:

 C₆H₁₂O₆ + O₂ ==> ATP+ CO₂ + H₂O

• Carbon dioxide is excreted by the plant as it is a metabolic waste

3.34- Causes of mutation

Mutation- change in base sequence

1. Radiation
• Ionising radiation (x-rays, gamma rays)
• UV-B rays which can cause skin cancer
2. Chemicals-  
• Tars in tobacco- causes cancer
• Chemicals that cause mutations are called Mutagens
• Chemicals that cause cancer and mutations are called Carcinogens

3.33- Antibiotic resistance

Understand how resistance to antibiotics can increase in bacterial populations

• Staphylococcus aureus causes skin and lung infection
• Can be treated with methicilline (antibiotic which kills Staphylococcus aureus)
• The susceptible form of Staphylococcus aureus is the form which can be killed by the antibiotic
• There was a random mutation to the genotype of Staphylococcus aureus
• This didn't die when given the antibiotic, also known as the resistant form (MRSA)
• The mutation is helpful to the Staphylococcus aureus as it survives the antibiotic

3.32-Types of mutation

3.31- Evolution

Describe the process of evolution by means of natural selection

Evolution:

• Change in the form of organisms
• Change in the frequency of alleles

Natural selection is the mechanism of evolution. (first proposed by Charles Darwin)

Eg:
Staphylococcus aureus which causes skin and lung infection

• The original form is susceptible to to being killed by antibiotic. This is known as MSSA
• It then, by random mutation, forms a form which is resistant to antibiotics. This is known as MRSA
• The change to MRSA caused the change in the frequency of the alleles and the frequency of the resistant form increased

3.30- Mutation

3.29- Species variation

Variation= differences in phenotypes
Phenotype can be modified by the genotype + environment

1- Discontinuous

2- Continuous

3- Entirely depends on environment  

3.20- Pedigree Diagrams

3.21b)- Genetic Probabilities

3.21a)- Genetic Probabilities

3.18c)- Codominance