Types of reproduction

Asexual/ sexual reproduction

Sexual reproduction is when two organisms from the same species are required to produce  non-idential offspring where characteristics are acquired from both parents. This is typical in most animals.

Asexual reproduction on the other hand is when one organism is required to produce genetically identical offspring. This occurs in some plants and in bacteria [binary fission].

A cell is diploid if it contains two copies of each chromosome [sexual].
A cell is haploid if it contains one copy of each chromosome [asexual].

Gametes are sex cells and and they are only utilised in sexual reproduction.
Fertilisation is the fusion of two gametes to produce a zygote which undergoes cell division and forms an embryo.

Structure of circulatory system

There are several significant arteries and veins leading away from important organs in the body such as:

Heart - Aorta/ Vena Cava
Lungs - pulmonary
Liver - hepatic
Kidneys - renal
Stomach - gastric

Effect of exercise on the heart

How the heart rate changes during exercise:

When you exercise, your muscles are moving more and at a greater rate hence the muscle cells respire more. Respiration requires a continuous flow of oxygen in order to release the maximum amount of energy as possible from glucose. Therefore the heart rate needs to increase so that the oxygen is pumped at a greater rate around the body to all the respiring cells primarily the muscle cells. More oxygen is breathed in and blood is pumped at a greater rate to and from the lungs where it is oxygenated. More carbon dioxide needs to be removed from cells also. As a result the heart rate increases.

Adrenaline

Adrenaline is produced in the adrenal glands above the kidneys. It stimulates receptors in the heart which increases the rate at which it works at. 

Immune system

Pathogens are harmful bacteria/ viruses that disrupt the normal functioning of tissues or organs or an entire organism. However, if the rate of their reproduction is less than the rate at which they are killed, one does not feel the effects of it and they show no symptoms.

If the rate of reproduction is higher than the rate at which they are killed, symptoms arise and one would feel ill.

Pathogens are destroyed by white blood cells. There are two different types:

1. Phagocytes
2. Lymphocytes

Phagocytes kill pathogens by engulfing them. However, this does not necessarily occur at a high rate and most of the time, lymphocytes are involved.

There are two types of lymphocytes: T cells and B cells.

Sequence of specific immunity

Phagocytes encounter a pathogen and begin to engulf it. Whilst doing so, it displays the pathogen's antibodies which alerts a t cell.
The t cell in turn alerts a b cell with the specific antibodies needed to target this pathogen.
The b cell begins to divide and produce antibodies in huge quantities.
The antibodies neutralise the toxins produced and cause the pathogens to clump together so that the phagocyte may engulf them all at the same time.
Some of the b cells are stored in the lymph nodes incase this pathogen is encountered again.

This sequence of events is called the specific immune response as it is targeting specific pathogens through the use of antibodies.

Vaccinations

Vaccinations work by injecting a weak version of a pathogen into the body. The antibodies specific to these pathogens are then produced by b cells. These increase the rate of destruction of these pathogen then they are stored in the lymph nodes where they are kept until the same pathogen is encountered again and a faster response is required. Future antibody production would be quicker and in a larger quantity thus targeting the pathogen faster.

Structure of the heart

There are four chambers in the heart:

1. Right atrium
2. Right ventricle
3. Left atrium
4. Left ventricle

The atria are where blood flows into the heart from [lungs/ body] i.e. from veins.
The ventricles have thicker walls as they generate the pressure to pump blood away from the heart. The left ventricle generates more pressure to pump blood around the entire body.

The atrio-ventricular valves are valves situated between the atria and ventricles to prevent blood from flowing in the wrong direction.

Tendinous chords prevent the valves from turning inside out in the event of high blood pressure.

The main blood vessels are:

1. Aorta
2. Vena Cava
3. Pulmonery artery
4. Pulmonery vein
___________

1. Arteries
2. Veins
3. Capillaries

1. The Aorta is the main artery taking oxygenated blood away from the heart to the rest of the body. It has thick muscular walls and a narrow lumen to deliver blood under a high pressure.

2. The Vena Cava is the main vein taking deoxygenated blood to the heart from the rest of the body. It has thin walls and a wide lumen. It delivers blood under a low pressure but contains valves to prevent blood from flowing the wrong way.

3. The pulmonary artery is the blood vessel that takes deoxygenated blood away from the heart to the lungs. It has thick muscular walls and a narrow lumen to increase the blood pressure.

4. The pulmonary vein takes oxygenated blood away from the lungs to the heart under low pressure. This is a result of the blood passing through small capillaries where it loses its pressure.

5. Arteries in general transfer oxygenated blood to tissues and organs all over the body. They have thick muscular walls and a narrow lumen to increase the blood pressure. Therefore they have no valves - the blood already flows at a high pressure. They have elastic walls to allow the artery to expand and recoil.

6. Capillaries are have walls one cell thick to decrease the diffusion distance for gases during gas exchange. They allow the exchange of substances into and out of the blood.

7. Veins have thin walls and a large lumen. They contain blood under a low pressure therefore they have valves to prevent it from flowing in the wrong directions. They contain deoxygenated blood except the pulmonary vein which transfers oxygenated blood from the lungs to the heart.


Note that smoking can severely increase blood pressure resulting in blood vessels from bursting. The bad cholesterol levels are raised due to the chemicals in tobacco smoke and they block the lumen.

Composition of the blood

Transport tissue

Blood is a transport tissue despite it containing a vast number of different types of cells. Blood cells transport oxygen around the body. However, all other components in the blood stream are being transported around the body in plasma. This is a yellow liquid containing water with dissolved solutes in it. Platelets are dead red blood cells that are significant in getting wounds to clot.

Components of the blood stream and where they are transported to/ from

White blood cells/ memory cells are transported from the lymph nodes to anywhere around the body that may have been infected with a pathogen. They consist of phagocytes and lymphocytes. Lymphocytes are divided into t and b cells for specific immunity.

Oxygen is transported from the alveoli to all cells in the body that respire.

Carbon dioxide is transported from all cells [as a waste product of respiration] to the alveoli where it is removed through diffusion.

Glucose is transported from the capillaries in the villi to everywhere in the body, to cells that respire.

Urea is transported as a waste product from all cells to the kidneys where it is removed as part of excretion. In particular, it is a waste product from the breakdown of proteins.

Hormones are transported from glands, the ovaries to specific cells.

How is a red blood cell adapted to transport as much oxygen as possible

A red blood cell is a bioconcave shape. This means it can travel through very small blood vessels such as capillaries.

It is enucleate. They have no nucleus to make space for more haemoglobin to absorb as much oxygen as possible.

Haemoglobin is made from iron.

Blood cells respire anaerobically as to not take any oxygen hence they have no mitochondria.

Their shape is essentially a flat disk with a dip in the middle to increase the surface area. A large surface area means a large volume of oxygen that can be transported. The diffusion distance is also decreased with this structure enabling oxygen to diffuse quickly into cells.

Transpiration

Transpiration is the evaporation of water from the surface of a leaf.  A plant loses around 90% of its water from transpiration.

Water is on the spongy mesophyll cells in a leaf. However, when it evaporates, it diffuses out of the leaf into the atmosphere. This is because the area on the outside of the leaf has a lower water potential than that inside of the leaf where the water vapour is currently situated. The xylem is a continuous tube from the roots to the leave therefore, as the water is being lost, more water is being drawn up through the xylem to replace it thus creating a flow of water.

Note: the water continues up the xylem due to intermolecular forces.

There are various factors that influence the rate of transpiration such as:

1. Light intensity
2. Temperature
3. Humidity
4. Wind intensity

1. If the light intensity increases, the stomata open to absorb carbon dioxide for photosynthesis. They do this as the guard cells [of stomata] gain water through osmosis. This results in them becoming turgid and opening the stomata. When the stomata are opened, water vapour is lost hence the transpiration rate increases.

2. If you increase the temperature, more water would be evaporated from inside the leaf on the spongy mesophyll. Transpiration is the evaporation of water from the surface of a plant hence greater heat = more evaporation = greater rate of transpiration. Remember, water can only escape from leaves in a gas form.

3. If you increase the humidity of the atmosphere this means that the volume of water vapour in an atmosphere increases. Therefore there is a smaller difference in water potential between the inside of the leaf and in the atmosphere. As a result, less water evaporates and diffuses into the atmosphere. Hence the rate of transpiration decreases.

4. If you increase the wind intensity of the atmosphere, more water molecules are going to be removed from the outside of the leaf therefore decreasing the water potential. To balance the concentration gradient,  more water diffuses into the atmosphere to replace the water vapour hence the rate of transpiration increases.

Prevention

Sometimes, the rate of transpiration is too great for a plant and they are losing a lot of water. To prevent this from happening, leaves are covered in wax. There are also much fewer stomata on the top of the leaf than at the bottom to restrict the water vapour from diffusing. The top of the leaf is more exposed to the light intensity,temperature, wind intensity more than the bottom side of the leaf. When flaccid, the guard cells will close. Every cells'  'turgor pressure' is lost meaning the plant is no longer supported and will die.

Turgor pressure and plant support

Remember, turgid cells are those that contain a large volume of water. They have a large turgor pressure which supports the plant and keeps it growing upwards and not wilting. Turgor pressure is the pressure of the water contained within the cell acting upon its cell wall. If all cells are turgid they are strongly pushing towards each other thus propelling the plant to grow upwards. A cell with a lack of water would have lost its turgor pressure and would wilt.

Experiments to investigate the role of environmental factors in the rate of transpiration

A potometer is simply used to measure the rate of water taken up through a plant.

Set up a basic potometer comprising of a beaker of water with a known volume, a capillary tube and a plant and rubber tubing.

Using a hairdryer, desk lamp and candle, situate each object one at a time near to the plant for a time of an hour.

Then measure how much water has been taken up by the plant by subtracting the new volume of water in the beaker by the new volume.

To ensure no water has been lost by evaporation [from the beaker] place a layer of oil on top.