B1

The body must respond to internal and external conditions

-You have glands that produce hormones. The hormones are transported around your body by the blood.

-Electrical impulses pass along the nervous system

-All responses must be co-ordinated

Ears- Sensitive to sound, Ears- Sensitive to change in position, Eyes- Sensitive to light, Nose and tongue- Sensitive to chemicals, Skin-Sensitive to touch, pressure, pain and temperature

-Being able to detect changes in the environment is important

Steps Involved in a reflex action:

• A receptor detects a stimulus (e.g. Sharp pain).
• A sensory neurone transmits the impulse
• A relay neurone passed the impulse on
• A motor neurone is stimulated
• The impulse is sent to the effector (muscle or gland)
• Action is taken

AT THE JUNCTION BETWEEN TWO NEURONES IS A SNYAPSE. CHEMICALS TRANSMIT THE IMPULSE ACROSS THE GAP

• The contraceptive pill contains oestrogen. This prevents the production of FSH so no eggs mature
• If a woman cannot produce mature eggs then FSH can be given. This is known as 'fertility treatment'

Processes of fertility-
1. Fertility drugs are used to make lots of eggs mature at the same time for collection
2. The eggs are collected and placed in a special solution in a Petri dish
3. A sample of semen is collected
4. The eggs and sperm are mixed in the Petri dish
5. The eggs are checked to make sure they have been fertilised and the early embryos are developing properly
6. When the fertilised eggs have formed tiny balls of cells, 1 or 2 of the tiny embryos are placed in the uterus of the mother. Then If all goes well, at least one baby will grow and develop successfully.

Internal conditions that are controlled include-
-Water content
-Ion content
-Temperature
-Blood sugar level

Water is leaving the body all the time as we breathe out and sweat. We lose any excess water in the urine (produced by the kidneys). We also lose ions in our sweat and in the urine.

We must keep our temperature constant otherwise the enzymes in the body will not work properly (or may not work at all)

Sugar in the blood is the energy source for cells. The level of sugar in our blood must be controlled

Internal conditions that are controlled include-
-Water content
-Ion content
-Temperature
-Blood sugar level

Water is leaving the body all the time as we breathe out and sweat. We lose any excess water in the urine (produced by the kidneys). We also lose ions in our sweat and in the urine.

We must keep our temperature constant otherwise the enzymes in the body will not work properly (or may not work at all)

Sugar in the blood is the energy source for cells. The level of sugar in our blood must be controlled

• Food provides the energy that your body needs to carry out its activities
• If you exercise you will need more energy
• Exercise increases the metabolic rate. This is the rate at which your body uses energy needed to carry out chemical reactions.

If it is warm you will need less energy than when it is cold.

The amount of energy you need depends on many things. e.g.

• your size
• your sex
• the amount of exercise you do
• outside temperature
• pregnancy

• If you take in more energy then you need you will become fat
• If you are very fat you are said to be obese

Obese people are likely to suffer more from-
-arthritis
-diabetes
-high blood pressure
-heart disease

-If you take in less energy then you need you will lose weight

-In developing countries some people have health problems linked to too little food. These include reduced resistance to infection and irregular periods in women

Fast food can contain too much salt and fat

Too much salt can lead to increased blood pressure

Cholesterol is made by the liver and the amount made depends upon diet and inherited factors. We need cholesterol, but too much in the blood leads to an increased risk of disease of the heart and blood vessels

Two types of lipoproteins carry cholesterol around the body

• low density lipoproteins which are bad and can cause disease
• High density lipoproteins which are good for you

Saturated fat in your diet increases you cholesterol level

Mono-unsaturated and polyunsaturated fats help reduce cholestrol level

We can use statins to stop the liver producing too much cholesterol

• Useful drugs, made from natural substances, have been used by indigenous people for a very long time

When we develop new drugs to help people, we have to test them over a long time to make sure that there are no serious side effects

-Thalidomide was used as a sleeping pill and to prevent morning sickness in pregnant woman. It had very serious side effects on fetuses developing in the womb. It is now used to help cure leprosy

• Recreational drugs are used by people for pleasure
• Heroin and cocaine are recreational drugs. They are very addictive and illegal

-Cannabis is a recreational drug. It is also illegal. It is argued that Using cannabis can leading to using harder drugs

• if you try to stop taking addictive drugs you will suffer withdrawal symptoms

• Useful drugs, made from natural substances, have been used by indigenous people for a very long time

When we develop new drugs to help people, we have to test them over a long time to make sure that there are no serious side effects

-Thalidomide was used as a sleeping pill and to prevent morning sickness in pregnant woman. It had very serious side effects on fetuses developing in the womb. It is now used to help cure leprosy

• Recreational drugs are used by people for pleasure
• Heroin and cocaine are recreational drugs. They are very addictive and illegal

-Cannabis is a recreational drug. It is also illegal. It is argued that Using cannabis can leading to using harder drugs

• if you try to stop taking addictive drugs you will suffer withdrawal symptoms

Medicinal drugs are developed over many years and are used to control diseases or help people that are suffering. Many medicinal drugs are only available on prescription from a doctor. Recreational drugs are used only for pleasure and affect the brain and the nervous system.

Recreational drugs include cannabis and heroin which are both illegal. As recreational drugs affect the nervous system it is very easy to become addicted to them. Nicotine and caffeine are legal drugs which are used recreationally, alcohol is also legal for people over the age of 18 in this country. Some drugs which are used for medicinal purposes can be used illegally, e.g. Stimulants used by sports people.

• Alcohol slows down the nervous system and therefore slows down your reactions. This will cause problems when driving.
• Too much alcohol leads to loss of self control
• Drinking too much alcohol may cause a person to lose consciousness or go into a coma
• The use of alcohol over a long time will damage the liver and brain

• Alcohol slows down the nervous system and therefore slows down your reactions. This will cause problems when driving.
• Too much alcohol leads to loss of self control
• Drinking too much alcohol may cause a person to lose consciousness or go into a coma
• The use of alcohol over a long time will damage the liver and brain

• Pathogens cause infectious diseases
• Some bacteria and viruses are pathogens. These bacteria and viruses reproduce inside the body producing poisons that make us feel ill.
• Semmelweiss discovered that infection could be transferred between treating patients in a hospital. He said that washing your hands between treating patients helped stop the transfer of infection. However, it was many years before other doctors took his ideas seriously.

White blood cells do three things to help us protect ourselves-

• They can ingest pathogens. This means that they digest and destroy them.
• They produce antibodies to help destroy particular pathogens
• They produce antitooxons to counteract (neutralise) the toxins that pathogens produce

• Antibiotics kill infective bacterial in the body. penicillin is a well know antibiotic
• Viruses are much more difficult to kill, as they live inside the cells
• Painkillers make you feel better, but do nothing to get rid of the disease causing the pain

The MRSA super bug is a bacterium that has evolved in hospitals through natural selection. It is resistant to commonly using antibiotics

Some pathogens, paticularly viruses, can mutate resulting in new forms

Very few people are immune to these new pathogens and so disease can spread quickly within a country of across countrie

It costs a lot of money to develop a new medicine. It also takes a long time. New medicines must be tested to see if they are toxic and to see if they are effective . This work is carried out in laboratories (animals) and on human volunteers.

If these tests are not thorough enough then a new medicine may have dangerous side effects. Thalidomide is a medicine that was used widely in the 1950s as a sleeping pill. It also helped to prevent morning sickness in pregnant women. It was not tested thoroughly enough and women started to give birth to babies with sever limb abnormalities. It is now not used with pregnant women but is proving an effective treatment for leprosy

It costs a lot of money to develop a new medicine. It also takes a long time. New medicines must be tested to see if they are toxic and to see if they are effective . This work is carried out in laboratories (animals) and on human volunteers.

If these tests are not thorough enough then a new medicine may have dangerous side effects. Thalidomide is a medicine that was used widely in the 1950s as a sleeping pill. It also helped to prevent morning sickness in pregnant women. It was not tested thoroughly enough and women started to give birth to babies with sever limb abnormalities. It is now not used with pregnant women but is proving an effective treatment for leprosy

• Dead or inactive friend if an organism can Ben made into a vaccine. Vaccines can be injected into the body.
• The white blood cells react by producing antibodies. This makes the person immune and prevents further infection, as the body responds quickly by producing more antibodies
• There is argument over whether some vaccines are completely safe e.g. The MMR vaccine

• Animalsnin cold climates have thick fur and fat under the skin to conserve heat.
• Some animals in the arctic (e.g. Arctic ford, Arctic hate) are white in the winter and brown in the summer. This means that they are camouflaged so they are not easily seen.
• Bigger animals have smaller surface areas compared to their volume, this means that they can conserve heat more easily but it is also more difficult to lose heat
• In dry conditions (desert) animals are adapted to conserve water and to stop them getting too hot. Animals in the desert may hunt or feed at night so that they remain cool during the day

• Plants compete for light, water and nutrients

A- In dry conditions e.g. Deserts, plants have become very well adapted to conserve water e.g. Cacti

• plants are eaten by animals. Some plants have developed thorns, poisonous chemicals and warning colours to put animals off

• Animals compete with each other for water, food, space, mates, and breeding sites
• An animals territory will be large enough to find water, food and have space for breeding
• Predators compete with their prey, as they want to eat them
• Predators and pret may be camouflaged, so that they are less easy to see
• Prey animals compete with each other to escape from the predators and to find food for themselves
• Some animals e.g. Caterpillars, may be poisounous and have warning colours so that they are not eaten

• All plants compete for water, nutrients and light. For example in woodland some smaller plants (e.g. Snowdrops) flower before the trees are in leaf, so that they have enough light, water and nutrients
• Some plants spread their seeds over a wide area so that they do not compete with themselves

• The cell nucleus contains chromosomes
• Chromosomes are made up of genes
• The male and female sex cells (gametes) contain the genes so the genetic information is passed on to the offspring
• Genes control the development of the characteristics of the offspring

• Sexual reproduction involves the fusion of sex cells. There is a mixing of genetic information so the offspring show variation
• Asexual reproduction does not involve the fusion of sex cells. All of the genetic information comes from one parent. All of the offspring are identical to the parent. These identical individuals are known as clones

Clones are identical to the parent. Cloning is used to produce new individuals that you want.

• In plants the process is cheap and effective. Plants can be cloned by taking cuttings and growing them, or taking groups of cells and growing them under special conditions
• With animals it is much more difficult to clone. Embryo transplants are used to clone animals. In this process, embryos are split into smaller groups of cells then each group is allowed to develop in a host animal

• Genetic engineering involves changing the game tic make up of an organism
• Genes are cut out of the chromosome of an organism using an enzyme. The genes are then placed in the chromosome on another organism
• The genes may be placed in an organism if the same species so that it has desired characteristics or in a different species. For example, the gene to produce insulin in humans can be placed in bacteria so that they can produce insulin
• Many people argue about whether or not genetic engineering is right. Will it create new organisms that we know nothing about? Is it going against nature?

• It is believed that the earth is about 4500 million years old and that life began about 3500 million years ago
  There is some debate as to whether the first life developed due to the conditions on earth, or whether simple life-forms arrived from another planet
• We can date rocks. Fossils are found in rocks, so we can date when different organisms existed

Lamarck's theory stated that acquired characteristics can be passed on to the next generation. People found this difficult to believe. For example, if two parents were to build up their muscles in the gym, Lamarck's theory would predict that this characteristic would be passed on to their offspring
It took a long time for Darwin's theory to be accepted. Many people wanted to believe that god was responsible for the creation of new species

Due to sexual reproduction, there is variation between members of a species. For example, all antelope are different to each other. Those members of a species with the best characteristics survive to breed.

Weaker members of the species may die from-

• disease
• lack of food
• variation in the climate

The survival of the organisms with the best characteristics is known as survival of the fittest

The fact that the best adapted animals and plants survive is known as natural selection

Extinction means that a species that once existed hads been completely wiped out.

Extinction can be caused by a number of factors, but always involves a change in circumstances-

• A new disease may kill all members of a species
• Climate change may make it too cold or hot, or wet and dry, for a species and reduce its food supply
• A new predator may evolve or be introduced to an area. The original species may be left with too little to eat
• The habitat the species lives in may be destroyedn

Extinction means that a species that once existed hads been completely wiped out.

Extinction can be caused by a number of factors, but always involves a change in circumstances-

• A new disease may kill all members of a species
• Climate change may make it too cold or hot, or wet and dry, for a species and reduce its food supply
• A new predator may evolve or be introduced to an area. The original species may be left with too little to eat
• The habitat the species lives in may be destroyedn

There are increasing numbers of people on our planet.

Many people want and demand a better standard of living

We are using up raw materials and those that are non-renewable cannot be replaced

We are producing more waste and the pollution that goes with it

We are also using land that animals and plants need to live on. It is being used for building, quarrying, farming and dumping waste

We pollute-

• The water with sewage, fertiliser and toxic chemicals
• The air with gases such as sulfur dipxide and with smoke
• The land with pesticides and herbicides and these can be washed into the water

• Burning fuels can produce sulfur dioxide
• These dissolve in water in the air, forming acidic solutions
• The solutions then fall as acid rain- sometimes a long way from where the gases were produced
• Acid rain kills organisms, enzymes, which can control reactions , are very sensitive to PH

• Burning fuels releases carbon dioxide
• Cows and rice field release methane gas
• Both of these gases are greenhouses gases. As these gases increase in the atmosphere, it retains more heat from the sun. The earth is therefore warming up
• This warming may cause a number of changes in the earths climate and cause sea levels to rise
• We are cutting down forests. This is making the problem wirse because trees take up carbon dioxide. When the trees die, they release this carbon dioxide back to the atmosphere

As our population rises, we use up more of the earths resouces. There are many examples, e.g. Land, fossil fuels and minerals

Sustainable development means finding ways of reducing this need for more resources

This may mean finishing alternatives to some resources. For example

• fuels for cars
• recycling what we already have e.g. Plastics, aluminium in cans
• Using land that has already been used previously, e.g. For building new homes

• Lichens indicate the level of air pollution. The more pecked of lichen growing, the cleaner the air.
  Freshwater invertebrates indicate the level of water pollution in the same way.
  The wider the range of these invertebrates will only live in polluted water.
• The world population is growing and needs suitable housing. It is important not to use up green areas of the countryside too much but to use areas that have already been built upon (called brown field sites)
  Many countries put aside areas of land which are important for wildlife and will not allow any development on them.