Biology.

B1

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  • Created by: rio
  • Created on: 05-01-11 17:56

Who am i?

Some characteristics are caused by the environment, some by inherited factors, while some are caused by both environment and inherited factors.

Males carry XY sex chromosomes - female mammals carry XX sex chromosomes. Inherited disorders are caused by faulty genes on these chromosomes.

Different versions of a gene are called alleles, and these alleles can be dominant or recessive. Genetic diagrams can show the possible outcomes of a particular cross.

Environmental & Inherited characteristics.
Some characteristics of an individual are caused by the environment.e.g., the language we use, or whether we have scars, are environmental characteristics. Other characteristics are inherited, e.g. the shape of the earlobes, eye colour, nose shape. But, some characteristics are the result of both environmental and inherited factors, e.g. intelligence and health.

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Who am i?

Genetic Variation
 This can be caused by
- the formation of gametes ( sex cells)
- fertilisation ( joining of gametes )
- a mutation.

A mutation is a hange to the genetic code in a gene. They can either happen spontaneously or by radiation and chemicals. They can be beneficial, but in most cases they are very harmful.Inherited disorders such as cystic fibrosis is caused y faulty genes.

Alleles.
Alleles are different versions of the same gene. An allele can be dominant or recessive. Individuals can either be homozygous or heterozygous.
Homozygous- When an individual carrries two copies of the same allele.
Hetrozygous- Individuals who carry two different alleles.

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Who am i?

A recessive characteristic will only be shown if an individual is homozygous for the recessive allele. A dominant characteristic will be shown even if an individual is heterozygous for the dominant allele.

Genetic Diagrams.
-These are are used to show the possible outcomes of a particular cross. A dominant allele is shown by a capital letter, and a recessive allele by a lower case letter.
-Cystic fibrosis is an inherited disorder caused by a recessive allele. The diagram shows the possible outcomes when both parents are heterozygous for the faulty allele. There is a one in four chance of the offspring being homozygous for the faulty allele, and so having cystic fibrosis.
(http://www.bbc.co.uk/schools/gcsebitesize/science/images/genetic_diag_1.gif)

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(http://www.bbc.co.uk/schools/gcsebitesize/science/images/genetic_diag_2.gif)This shows the chance of having Cystic fibrosis if only one parent has the faulty allele. There is no chance of their child getting it.

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Gene Control

-The nucleus of living cells contain chromosones which are made up of a string of genes.

-Chromosomes are made from long, coilded molecules of DNA.The DNA molecule itself consists of two strands which are coiled to form a double helix.We each have 23 pairs of matching chromosomes.

-Each DNA molecule contains chemicals called bases. There are four bases which are labelled : a, t, c and g.

- Genes code for the production for proteins. Some of these are enzymes which control how the cell functions.

Asexual Reproduction

Asexual reproduction only needs one parent. All the offspring are genetically identical to each other, and their parent, which makes them clones.

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Gene Control & Staying in Balance

Sexual reproduction
This needs two parents, each parent produces sex cells called gametes.The male's is called sperm and the womens are called eggs.

Each gamete contains half the number of chromosomes that a body cell has. After fertilisation, the egg and sperm fuse together and the new cell contails the full number of chromosomes.

Homeostasis
It is important that the body's internal environment is controlled, e.g. the amount of carbon dioxide in the bloodstream.Maintaining a constant internal environment is called homeostasis. Homeostasis  helps to balance the inputs and outputs and remove waste products to ensure that correct levels of: temperature, water, oxygen and carbon dioxide are maintained.

Temperature control
Since the body's ennzymes work best at 37°C it is essential that the body remains very close to this temperature.

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Staying in Balance

Homeostasis is achieved by negative feedback mechanisms.Negative feedback involves the automatic reversal of a change in condition. e.g. if the temperature is too hot, the brain switches on mechanisms to lower it and if the temperture is too low, the brain switches on mechanisms to higher it.

The body’s temperature is monitored by the brain. If you are too hot or too cold, the brain sends nerve impulses to the skin, which has three ways to either increase or decrease heat loss from the body’s surface.
1)Hairs on the skin trap more warm air if they are standing up, and less if they are lying flat.
2)Blood vessels supplying blood to the skin can swell or dilate(vasodilation). This causes more heat to be carried by the blood to the skin, where it can be lost to the air. Blood vessels can shrink down again (vasoconstriction).This reduces heat loss through the skin once the body’s temperature has returned to normal
3)  the body is too hot, glands under the skin secrete sweat onto the surface of the skin, to increase heat loss by evaporation

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Staying in Balance- Hormones

Hormones are chemicals secreted by glands and they are directly released into the bloodstream. In the bloodstream they travel around the body to their target organs.

women- Oestrogen & progestorone are released by the ovaries
men- Testosterone is released from the testes
both- Insulin is released from the pancreas.

Diabetes
This is caused by the pancreas not producing enough insulin, meaning there is no control of blood sugar levels. If this is not treated rapidly by an injection of insulin than a person can end up in a coma.

Insulin helps to regulate blood sugar levels by converting excess glucose in the blood to glycogen in the liver.

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Staying in balance- menstrual cycle & fertility

Menstrual Cycle
The menstrual cycle in women is a recurring process in which the lining of the uterus is prepared for pregnancy. If pregnancy does not happen, the lining is broken down at menstruation. The hormones oestrogen (which causes the repair of the uterus wall) and progesterone (which maintains the uterus lining) are used. Both hormones are secreted by the ovaries. If a woman becomes pregnant, the level of progesterone remains high.

Controlling Fertilty
Human fertility is controlled by hormones. This means that a knowledge of hormones can be used to decide to increase, or reduce, the chances of fertilisation and pregnancy.

'The pill' is an oral contraceptive that greatly reduces the chances of mature eggs being produced. The pill contains hormones which are natrually found in the body during pregnancy.

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Drugs & You

Drugs are chemicals that can alter the way the body works. Some are beneficial, while some are harmful. They can either be used for pleasure or for medicinal reasons.

Stimulants,include things like caffeine, nictoine and ecstasy. They increase brain activity and give us an increased perception of things.

Depressants/Sedatives include things like alcohol. They decrease brain activity and makes you feel tired.

Painkillers/ Anasesthetics include things like aspirin and heroin. They reduce pain by blocking nerve impulses and they tend to be very effective.

Performance enhancing drugs help to increase muscle development.

Hallucinogens include things like Cannabis and they give us distorted perceptions and emotions.

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Drugs & you

Drugs can be categorised into three main categories, class a, class b and class c.
Class A is the most dangerous type and includes things like heroin and cocaine. Class C is the least dangerous and includes things like steroids and painkillers.

Stimulants increase the amount of transmitter substance released at he synapses which gives us outbursts of energy.
Depressants block the amount of transmitter substance in the synapse which will slow down reactions and make us feel dopey.

The carbon monoxide in nicotine combines with the haemoglobin in red blood cells which reduces the ability of the blood to carry oxygen. This puts extra strain on the circulatory system and can cause an increased risk of heart disease and strokes.

Alcohol contains the chemical ethanol, which is a depressant and causes slow reactions.

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Drugs & you

Short term effects
The short term effects can lead to lack of balance and muscle control,blurred vision, slurred speech and vasodilation. Excess alcohol can lead to unconciousness and even a coma or death.

Long term effects
The long-term effects of alcohol include damage to the liver and brain. The liver removes alcohol from the bloodstream, as it is a toxic chemical. Over time, alcohol consumption can lead to liver damage - cirrhosis.

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Senses & Nervous system

Receptors
Receptors are groups of specialised cells. They can detect changes in the environment, which are called stimuli, and turn them into electrical impulses. Receptors are often located in the sense organs such as the:
ear- which is sensetive to sounds,
eye- which is sensetive to light
skin- which is sensetive to temperature, pain, presssure and touch..

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The Eye

The conjunctiva is at the very front of the eye, covering the cornea. Behind this is the pupil, then the lens. The ciliary muscle and suspensory ligaments are attached to the lens. At the back of the eye are the sclera, retina, fovea and opitc nerve (http://www.bbc.co.uk/schools/gcsebitesize/science/images/bieyestructure.gif)

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The Eye

Cornea - refracts light.
Iris- controls how much light enters the eye.
Lens- focuses the light on the retina.
Retina- contains the light recepters.
Optic nerve- carries impulses from the eye to the brain.

Someone whom is short sighted has an eyeball which is too long. It can be corrected by a concave lens which verges the light rays so that they focus on the retina.
the focus is in front of the retina (http://www.bbc.co.uk/schools/gcsebitesize/science/images/sight_myopia.gif)

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The Eye

Someone whom is long sighted has an eye which is too short. They can see distant objects clearly, but can't focus properly on near objects. This is because the lens focuses the sharpest image behind the retina, instead of on it.
The focus is behind the retina (http://www.bbc.co.uk/schools/gcsebitesize/science/images/sight_hypermetropia.gif)

Colour blindness is an inherited condition. The retina contains cells that are sensitive to red, green or blue light. People with colour blindness have a lack of receptors,

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The main parts of the nervous system are the central nervous system - the CNS - the brain and spinal cord - and the peripheral nervous system. Nerve impulses are mainly electrical and carried in the axons in the neurones.

This is a motor neurone:
a neurone has a 'head' at one end where the nucleus, cytoplasm, cell membrane and dendrite are. The axon is tail-like, with nerve endings at the end which look like branches. (http://www.bbc.co.uk/schools/gcsebitesize/science/images/29_neurones.gif)

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Motor neurones have:
-an elongated shape to make connections from one part of the body to another
- an insulating layer which speeds up the impulse.
- Branched endings allow a single neurone to act on many muscle fibres.

Reflex Actions
When a receptor is stimulated, it sends a signal to the central nervous system, where the brain co-ordinates the response; however, sometimes a very quick response is needed which doesn't need the involvement of the brain. This is a reflex action. e.g. you would pull your hand away from a hot flame without thinking about it.
There are 6 stages to having a reflex action which are as follows:

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Reflex Actions

STEP 1: a receptor is stimulated
STEP 2: Signal sent along sensory neuron.
STEP 3: Signal passed along relay neuron
STEP 4: Signal sent along motor neuron.
STEP 5: Effector muscle contracts and responds to the stimulus

You need to remember these in order so try making up a little riddle like
Rio sings Rhianna and MJ like she's in concert.
Now you make one uo , trust me it will help you remember in the exam. write yours below.

....................................................................................................................
...................................................................................................................
..................................................................................................................
.................................................................................................................
...............................................................................................................

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Keeping Healthy

If a tumour grows in one place its called a benign; however, if it breaks off and starts to grow in other parts its described as malignant.

Non-infectious diseases are caused by: genetic inheritance, poor diet or by an organ malfunction.
Infectious diseases are caused by micro-organisms.

Pathogens are micro-organisms which cause disease. They come in four forms.
- Bacteria which cause cholera
-Viruses- which cause flu
-Fungi- Which cause athletes foot
-Protozoa- which can cause dysentery.

The body has many defence against pathogens, which are:
- The skin which acts as a barrier against microorganisms.
- Respiratory system which produces sticky mucus to trap micro-organisms
- Hydrochloric acid which kills the micro-organisms on food.
-Blood clots which prevent micro-organisms entering the blood stream..

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Keeping Healthy.

-Once inside the body, pathogens reproduce. Viruses reproduce inside cells and damage them, while escaping to infect more cells. Bacteria produce toxin/ poisons. which damage the cells and cause the symptoms of infectious diseases. Once pathogens enter the body, the immune system destroys them. White blood cells are important parts of the immune system.

Immunity

Once you have been infected with a particular pathogen and produced antibodies against it, some of the white blood cells remain. So, if you become infected again with the same pathogen, these white blood cells rapidly reproduce and the pathogen is destroyed. This is active immunity.
When you are treated  by an injection of certain antibodies from someone else. This is passive immunity.

Antibiotics
Antibiotics can help to treat some diseases; however, some bacteria is naturally resistant to particular antibiotics.

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Keeping Healthy - Drug testing

New medical drugs have to be tested to ensure they work and are safe before they can be prescribed. There are three main stages:
1) The drugs are tested using computer models and human cells grown in the laboratory. Many substances fail this test because they damage cells or do not seem to work.
2) Drugs that pass the first stage are tested on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects.
3)Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check they are safe. The substances are then tested on people with the illness to ensure they are safe and work.

Immunisation- higher bit
People can be immunised against a pathogen through vaccination.Vaccination involves putting a small amount of an inactive form of a pathogen, or dead pathogen, into the body.Because the vaccine contains only a weakened or harmless version of a pathogen, the vaccinated person is not in danger of developing disease ; however, some people may suffer from mild side effects. 

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A Balanced Diet

-Carbohydrates are made from simple sugars and provide us with energy sources.
-Fats are made from fatty acids and glycerol and provide us with energy sources.
-Proteins are made from amino acids and help with growth and repair.
- Minerals e.g. iron help us to make haemoglobin
- We need vitamins to prevent us from scurvy
-We need fibres to prevent us from becoming constipated
- We need water to stop us dehydrating.

- A lack of protein can lead to a diseas called Kwashiorkor.
You can calculate the recommended daily average (RDA) intake of protein using this formula: RDA in g = 0.75 × body mass in kg

- You can measure BMI by the following formula: mass in kg ÷ (height in m)2

- Physical digestion involves chewing food inorder to break down the food so it can pass through the gut more easily. Physical digestion increases surface area which makes digestion happen faster.

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A balanced Diet

Chemical digestion uses enzymes to break down large insoluble molecules to smaller soluble molecules.

CARBOHYDRASES- are found in the mouth and break down carbohydrates into sugars such as glucose.

PROTEASE- is found in the stomach and breaks down proteins into amino acids.

LIPASE- is found in the pancreas and breaks down fats into fatty acids and glycerol.

HYDROCHLORIC ACID- is found in the stomach and creates conditions that helps enzymes to work effectively.

BILE- is produced in the liver and stored in the gall bladder.It is secreted into the small intestine where it emulsifies fats. It provides a larger surface area so that lipases can work better.

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Fitness & Respiration

-Arteries carry blood away from the heart
Veins carry blood to the heart.
You can remember it as vein has the word 'in' in it and the blood is going in the heart.

-Blood pressure is measured in millimetres of mercury mmHG. On average the normal blood pressure is 120/80 mmHG. There are two measures of it.
1) Systolic blood pressure- this is where blood pressure is at its highest and the blood is being forced into the arteries.
2) Diastolic blood pressure- this is where blood pressure reaches its lowest, the heart relaxes and the pressure in the arteries drop.

Blood pressure can be affected by:
-age
-body mass
-excercise
-stress
-alcohol.

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Respiration

Aerobic Respiration

Aerobic respiration requires oxygen. It happens in cells when glucose reacts with oxygen.
-->glucose + oxygen    →    carbon dioxide + water (+ energy)
-->C6H12O6 + 6O2    →    6CO2 + 6H2O (+ energy)

Anaerobic Respiration

Anaerobic respiration doesn't need oxygen, it happens when there is not enough oxygen for aerobic respiration.
-->glucose    →    lactic acid (+ energy)

 

Much less energy is released by anaerobic respiration than by aerobic respiration

 

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Respiration & Excercise

-During exercise, the muscle cells respire more than they do at rest. This means that oxygen and glucose need to be delivered to them much quicker and waste carbon dioxide must be removed much quicker aswell. This can be achieved by increasing the heart and breathing rate.

-During hard exercise, the oxygen supply may not be enough for the needs of the muscle cells, so when this happens, anaerobic respiration takes place, as well as aerobic respiration.

High blood pressure can cause:
-kidney damage
-burst blood vessels
-damage to the brain, including strokes

Low blood pressure can cause:
-fainting
-dizziness
-poor blood circulation

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Respiration & Excercise.

-During hard exercise when both types of respiration occur, an oxygen debt builds up, because glucose is not broken down completely to form carbon dioxide and water. Some of it is broken down to form lactic acid.

-Panting after exercise provides oxygen to breakdown lactic acid. The increased heart rate also allows lactic acid to be carried away by the blood to the liver, where it is broken down.

WHOOOOOOOOOOOOOOOOOOP! this is the end of B1.
when you think you know all this inside out do the question and quizes pack.

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