# QWC's for Biology 3

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• Created by: Katy **
• Created on: 04-04-14 19:11

## Investigating the loss of water in Plants

It is not easy to see the water loss in leaves. It is easier to measure how fast the plant takes up water. To do this, you would use a potometer.

The rate at which a plant takes up water depends on the rate of transpiration. The faster the plant transpires, the faster it takes up water.

As the plant transpires, the water loss is replaced by the water drawn up by the stem. The air will be drawn at the end of the capillary tube.

By recording how fast the air/water menisus moves along the capillary tube, you can compare how fast the plant is taking up water.

The equation to work out the plants up take is:

• speed of movement of air bubble (mm/s) x cross section area of capillary tube (mm2) = rate of water uptake (mm3/s)
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## Explain the effects on transpiration

Transpiration is the loss of water from the leaves by evaporation. The water vapour passes out through tiny pores in the leaves called the stomata. The rate of transpiration is affected by many changes in the environment.

Transpiration rate is affected by temperature, the higher the temperature the faster the rate of transpiration, this is because the water will evaporate quickly.

Humidity will also affect the rate of transpiration as the more humid the air, the slower the rate of transpiration because less water will evaporate.

The windier the day it means a faster rate of transpiration because more water will evaporate quicker.

Also if you increase light intensity the stomata open causing more water to evaporate. This means that there will the a faster rate in transpiration.

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## Explain the movement of water through a plant

Firstly the water moves from the soil to the root hairs by a process called osmosis. This is the movement of water from an area of high concentration to an area of low concentration through a semi-permeable membrane.

The water moves up the xylem tubes by the process of osmosis to the rest of the plant.

The minerals & salts are taken up by the root hairs by a different process called active transport. This is the movement of molecules from an area of low concentration to an area of high concentration throught a semi-permable membrae. It also requires energy.

Transpiration is also involved in the movement of water through a plant. This is because as the water evaporates through the stomata it causes water to be "pulled up" during transpiration. Water then moves from the soil to the root hairs & so on.

A leaf can reduce transpiration by closing the stomata, having less stomata on the underside of the leaf & having a waxvy surface called the cuticle that will minimize the water loss.

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## How are the Xylem & Phloem similar & different

Plants have different types of 'transport tissues'.

The xylem transport water & solutes from the roots to the leaf, & the phloem transports food from the leaves to the rest of the plant.

Both of these transport tissue are used in the process of transpiration, this is the process by which water evaporates from the leaves. This results in more water being drawn up from the root hairs. Both of these tissues are rows of cells that make continuous tubes running the full length of the plant.

Another way in which these tissues differ is that the xylem is made out of dead cells that make hollow collums. The dead cells are cause by lignin. However the phloem are collums of living cells.

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## Explain what the double circulatory system is

Blood passes throught the heart twice for one circuit of the body. There are two circulation systems, one is the pulmonary circulation & the systemic circulation.

The pulmonary circulation is on the right side of the heart. It pumps deoxygenated blood to the lungs, the lungs then convert the blood to oxygenated blood for it to return to the heart on the left side. There is low pressure because the heart walls are thinner.

The systemic circulation is on the left side of the heart. It pumps oxygenated blood to the tissue (the body & its organs), deoxygenated blood reurns to the heart on the right side. There is high pressure because the heart walls are thicker and have to pump more blood to the rest of the body.

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## Passage of blood through the heart & organs

Deoxygenated blood from the body entres the right atrium via the vena cava.

The right atrium contracts to pump the blood through the atrio-ventricular valves into the right ventricle.

The right ventricle contracts & the semi-lunar valves open & deoxygenated blood travels back to the lungs.

After the blood has gone to the lungs, the oxygenated blood then returns to the heart in the left atrium via the pulmonary vein.

The left atrium will contract to pump blood throught the atrio-ventricular valves.

The left ventricle will then contract & the semi-luanr valves will open & the oxygenated blood will travel around the body again.

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## pathway from a stimulus to the response

In this example, I am going to use a fire touching a persons hand.

First there is a change in the environment called a stimulus, in this case it is heat.

The heat sensitive receptors in the skin on the fingertips are stimulated by the heat.

An electrical nerve impulse then travels up the sensory neurone to the spinal cord.

The message will have to cross the synapse between the sensory neurone & the relay/connecting neurone in the spinal cord, 'short-circuiting' to the brain.

The electrical nerve impulse will run along the relay/connecting nerurone and through the synapse to the motor neuron.

The electrical nerve impule will go down the motor neurone until it reaches the muscle (effector).

The impulses cause the muscles to contract & pull the hand away from the heat.This is called the response.

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## Kidney in the excretory system

The blood leaves the kidney via the renal vein to the vena cava. This blood is low in glusoce, carbon dioxide & urea.

The blood from the aorta entres the kidney via the renal artery, this blood is high in oxygen, glucose & urea.

The kidney adjusts the bodies water level & filters the urea, salt & water from the blood to create urine.

The urine travels down the ureter which is a narrow tube from the kidney to the bladder.

This is where the urine is stored until it passes through the sphincter muscle.

The urethra takes the urine out of the body.

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## Describe the role of the kidney in homeostasis

Blood entering the kidney is under high pressure as the arteriole leading to the capillaty knot is wider, this blood contains large & small molecules. The large molecules like blood cells & plasma proteins don't pass throught the pores so they remain in the blood. Ultra-filteration removes both waste products & essential nutrients from the blood, this is why selective reabsorbtion occurs to recapture the lost nutrients.

The first part of the tubule is the Bowman's Capsule, the filtrole in the Bowman's Capsule contains water, glucose, salts & urea. As the filtrole passes along the nephron some of the water & salts are reabsorbed & all of the glucose is reabosrobed back into the blood via the capillary network surrounding the nephron. These reabsorbed products leave the kidney in the renal vein to be used by the body cells. This process uses active transport so it requires energy.

After seletive reaborption has occured all of the urea, the excess water & some salts are left in the nephron. The left over substances are .... urine & into the collecting duct. It then enters the ureter & passes to the bladder to be stored & it leaves the body via the urethra.

Through ultra-filteration & slective reabsorption the kidney makes sure that the composition of the blood is constant.

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## Negative feed back of ADH

ADH is a hormone produced by the brain.

If blood water level increases over the normal blood water level the brain will release less ADH so less of it entres the blood. Less ADH entres the kidney so the collecting duct walls are less permeable to water. This means less water is reabsorbed into the blood and more dilute urine is produced.

If the blood water levels decreases under the normal blood water level then the brain will release more ADH so more of it entres the blood. This is will cause more ADH to entre the kidney so the collecting duct walls are more permeable to water, resulting in more water being reabsorbed in othe blood. This will mean that the urine will be less and more concentrated.

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A dialysis works as a nephron.

The advantages of this treatement for kidney failture is that there is no waiting list, it will keep the patient alive and it can work at home as well as in the hospital.

The disadvantages are that it is expensive, time consuming, only does the nephrons job (can't cover other functions like iron storage), not as healthy as transplants and there is a restriction on the patients diet and fluid consumption.

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A dieased kidney can be replaced by a healthy one.

The advantages of a kideny transplant is the potential prolongation of life, improved quality of life, no dialysis is involoved and fewer diet and fluid restrictions.

The disadvantages of kideny transplants is that it is expensive, possible rejection of organ, risk of infection, risks of surgery and the effects of daliy medication.

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## How does the body stop pathogen from entering

There is a first line of dendense, which is the skin & blood clotting, these act as a barrier to make it harder for the pathogens to enter the body. Also a community of microorganisms on the skin called skin flora make it difficult for pathogens to be established.

If microbes do entre the body the white blood cells will act, these are phagocytes & lymphocytes.

The phagocyte cell membrane in the blood ingests and engulfs the bacteria.

Lymphocytes produce antibodies and antitoxins. These works because the antigen molecules found on the pathogen is foreign to it & is specific to the antibody that is secreated. The antibody (protein) will meet the antigen & produce quickly & makes copies to neutralise the pathogen. They do this by damaging or destroying the pathogen by coating and clumping them together to make it easier for the phagocytes to ingest them. They then bind to the pathogens & release chemicals to attract more pathogens. Once the antibody is made the body can become immune to the pathogen.

The antitoxins then counteract the pathogen toxins.

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## How do vaccinations work

The white blood cells divide by mitosis to make memory cells, these cells can remember the disease (antigen) & produce the specific antibodies. These memory cells will stay in the body & the anitbodies will be produced more quickly if the antigen is very encountered again.

The memory cells will cause immunity following the natural injection of the vaccination.

A booster is often needed to increase the number of white blood cells & memory cells.

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## How can MRSA become resistance to antibodies

There is a change in the protein of the MRSA which will cause a change in the DNA. This mutation will cause variation.

When the antibiotic is place there is a change in the environment.

The antibiotic will kill of some of the MRSA, the MRSA with the vartiation will most likely survive & only some of the MRSA without the variation.

This will lead to competition, but the mutation will have a higher chance of survival so it will pass on its benifical gene/mutation to its offspring.

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## Making yogurt from starter culture

Partically skimmed milk is warmed & bacterial 'stater culture' is added.

The stater consits of two different kinds of harmless bacteria. The bacteria acts together to thicken the milk & to make the milk sour. Anaerobic respiration will make the milk lactose turn to lactic acid at 30'c.

When the lactose is turned to lactic acid, acidic conditions will be made. The production of the lactic acid is the basic structure & texture of yogurt.

The yogurt has to be cooled which will slow the activity of the starter bacteria.

These bacteria will stay alive so the yogurt has to be stored in the fridge to prevent too much acid being produced.

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## Role of microorganisms in decay

Microorganisms (like bacteria & fungi) have improtant roles in the carbon cycle & the nitrogen cycle.

The potential environmental benifits of microorganisms is that they can be used a a pollutant removal of toxic spills also after a genetic modification, bacteria will consume & digest the mercury from the highly radioactive nuclear waste. In waste treatement the bacteria can degrade organic compounds.

In oil spills the microbes will break down the oil, for example in the Exxon oil spill microbes were used.

Microbes an also breakdown plastics to make biofuels (ethanol) which can power motor vehicles to reduce the use of fossil fuels.

The biofuel is made from sugar corn or sugar beet as it is easily grown. The sugar is then fermented to ethanol by microorganisms.

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## Nephron

To begin with, filteration takes place. The blood is under high pressure because the arteriole before the capillary knot is wider. The small soluble molecules (urea/water/salts) are filtered into the Bowman's Capsule, however the red blood cells & the proteins are too big.

Next selective re-absroption occurs. In the tublule some of the water & salts are reabosrbed, but all of the glusoce is reabsorbed into the blood. The urea/water/salts will make urine which is a stored in the bladder.

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## Aseptic Techniques

1. Put the loop in the flame until it burns red = kills microbes

2. Cool loop & bacteria from sample jar

3. Spread sample on sterile agar

4. Don't open Petri dish full = airborne microbes can't contaminate agar

5. Seal with tape = stop microbes escaping

6. Grown in oven at 25'c = stop growth of human pathogen

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## Structures of Eye

The cornea is the clear part in front of the eye that allows light to pass throught the lens.

The iris is a muscle that controls the amount of light into the retina. It also controls how big or small the pupil will be.

The light will hit off the retina & the message will be sent to the brain via the optic nerve where the brain determines what will be seen.

Each image is focused upside down by the lens onto the retina.

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