2.69 Urinary System

Key Points:
1. In the urinary system there are two kidneys, the left and right, each with its own separate bloody supply. The kidneys carry out excretion and filtration and osmoregulation.
2. Each kidney has a tube which leads to the bladder.
3. This is called the ureter, and this carries urine from kidneys to the bladder
4. Then there is one bladder.
5. Then the urine is excreted through a structure called the urethra, then excreted out of the vagina or out of the penis

2.68b Osmoregulation

Key Points:
1. Osmoregulation: Osmo = Osmosis and Regulation = To control
2. Ideally, the tissue fluid surrounding cells in the body should be isotonic with the cytoplasm of the cells. This means the amount of water going in and out is equal and they will maintain their size.
3. The danger is that the blood going into the tissue may be concentrated causing a hypertonic tissue fluid. Or it could be dilute causing a hypotonic tissue fluid. The aim would be to maintain a isotonic tissue fluid.
4. This is done by controlling the composition of blood.
5. The kidney controls the composition of the blood. Blood flows into the kidney and excess water or salts will be excreted. The tissue fluid will maintain an isotonic behaviour.

2.68a Excretion

1. The role of the kidney in excretion, is the excretion of urea.
2. Urea is poisonous to the human body because it contains nitrogen.
3. The original form of the nitrogen is in our bloodstream as amino acids, which are used for growth, but if there are any in excess they have to be removed.
4. Blood cirulates into the liver, where the amino acids are broken down and converted into urea. This reenters the blood stream into both the kidneys.
5. The kidneys filter the urea from the blood, and add it with water to form urine and this flows down the uretus into the bladder.

2.67b Human Organs of Excretion

Key Points:
1. The major organs of excretion include the lungs, which waste carbon dioxide,the kidneys, which excrete excess water, urea and salts. Urea is the nitrogen waste from amino acids.
2. The third organ of excretion is the skin, which excretes water, salts and to a partial degree, urea but not in large amounts.
3. All of these organs display the loss of metabolic waste

2.67a Excretion in Plants

Key Points:
1. Photosynthesis involves the leaf absorbing light energy and combines CO2 with H2O to make C6H12O6 and O2
2. The release of oxygen is classified as excretion, the release of metabolic waste.
3. The process of respiration is the second excretion example. C6H12O6 -> ATP + CO2 + H20
4. In that process the CO2 is the waste product, so the plant excretes CO2 while respiring and excretes O2 during photosynthesis.

3.34 Causes of mutation

Key Points:
1. Mutation is a change in the base sequence of the gene. New alleles are produced.
2. An example of what causes this is radiation, or ionising radiation like x-rays or sunlight which cause skin cancer.
3. A second example is chemicals, such as tar in tobacco changing the base sequence of the gene. Chemicals which do this are called mutagens. Carcinagens are mutagens which also cause cancer.

3.33 Antibiotic resistance

Key Points:
1. The bacterial population in here is known as staphlococcus aureus.
2. Those who are infected can be treated with methecilline, which is an antibiotic. This chemical will kill the susceptable form of bacteria. There may be a random mutation to the genotype of the bacteria which lets the bacteria survive the chemical. This is known as the resistant form of bacteria.
3. Their mutation has created genes which allow it to break down the antibiotic.
4. The resistant form will survive, and will become more common.

3.32 Types of mutation

Key Points:
1. We begin with the first copy of the gene, and the process of mutation produces new alleles which in turn make new genes. The alleles are responsible for the phenotype and they can be either, beneficial, harmful or neutral.
2. An example of a beneficial mutation might be a boosted efficiency of an enzyme. Or harmfully a enzyme could be rendered useless. A neutral mutation might be an enzyme with no use at the present time, but in time, when the environment changes there could be some beneficial or harmful purpose of this.

3 31 Evolution

Key Points:
1. Evolution : A change in the form of organisms.
                     A change in the frequency of alleles.
2. Natural selection is the mechanism of evolution, and was proposed by Charles Darwin.
3. A chemical called Methecilline can kill Staphlococcus Aureus. The ones that can be killed are known as the succeptable. A random mutation to the genotype of Staphlococcus Aureus may cause it to be able to methecilline, and this kind of staphlococcus aureus is known as the resistant form.
4. There are now forms of the bacteria, when antibiotics are applied to the population (change in environment) then the susceptable form lowers in numbers, and the resistant ones gain numbers.
5. There are two features to be noticed: 1. Random mutation 2. Non random selection
This is known as natural selection

3.30 Mutation

Key points:
1. In the diagram there is a molecule called DNA.
2. Certain events can result in a change in this sequence, such as UV radiation.
3. Having a mutation in the gene can result in the production of a completely different type of protein.
4. Different alleles exist because of mutation, which changes the base sequence of the gene.

3.29 Species Variation

Key points:
1. Variation can be described as the differences in the phenotype of individuals. How things appear.
2. It is possible to count or measure these differences and show them in a graph form. The appearance is because of their genotype, which can be modified by the environment. Variation is a variation of all these factors.
3. Variation in population = Variation in genotype + Variation in the environment.
4. Blood groups are an example of where the environment has no effect whatsoever on the variation in population.
5. The height of individuals can be affected by both the environment AND the genotype.
6. A third possibility is that the variation in the population is entirely due to environmental variation, so genes have no role in the differences, an example of this would be language.

3.21a Genetic Probabilities

3.20b Pedigree 2

3.20a Pedigree diagrams

3.18C Codominance

As seen in the photo above, the homozygous pairs both have either BB or WW, and are either blue or white. The heterozygous plant's phenotype is orange, and seeing as BB and WW reproduced, they each contributed only one allelle, therefore making the heterozygous plant's genotype BW.