GCSE AQA Biology unit 1

Body must respond to internal and external conditions

Glands produces hormones. It's transported around your body by blood.

Nervous system: Electrical impulses [short lasting, quick effects]

Hormones: Chemical messengers [long lasting, slow effects]

The way your nervous system works:

Stimuli -----> Receptor -----> Sensory Neurone -----> Co-ordinator (CNS) -----> Motor Neurone -----> Effector (muscles or glands)

Effectors:

Muscles respond like contracting

Glands respond like releasing (secreting) chemical substances

Reflex actions are important because they help you to avoid danger and harm.

Reflex actions takes place in our body all the time eg. breathing, blinking, etc.

The way your reflex action works:

Stimuli -----> Receptor -----> Sensory Neurone -----> Relay Neurone ( co-coordinator) -----> Motor Neurone -----> Effector (muscles or glands)

Synapse

The junction between two neurones.

• The electrical impulses from the neurones

• converts to chemical messages (neurotransmitter) diffused to the next neurone

• then converts back to electrical impulses.
  

Pituitary gland: FSH, LH & ADH

Ovaries: Oestrogen, progesterone

FSH: maturity of the egg

  Stimulates the production of the oestrogen

Oestrogen: build up the lining of the uterus

     Inhibits the production of FSH

     Stimulates the production of LH

LH: Stimulates the release of an egg

Menstrual cycle is about 28 days.

Day 14 where ovulation takes place (eggs are released)

(oral) Contraceptive pill: contains oestrogen

As it inhibits the production of FSH so no eggs matures.

Fertility treatment: Contains FSH

As it stimulates the eggs in the ovaries to mature & triggers oestrogen production.

IVF: egg is fertilized outside the body, then place the tiny developing embryo back in the uterus. It's expensive and not always successful.

Advantages:

• Helped to make the families smaller, less poverty (few mouths to feed)
• Control population growth (eg China) not available in all countries because of lack of money, education & doctors

Disadvantages:

• Can cause health problems
• raises many ethical issues for society

Homeostasis: Control the internal environment

Internal conditions that are controlled:

• Water content
• Ion content
• Temperature
• Blood sugar level

Water is lost through:

• Urine (ion is also lost)
• Sweat (ion is also lost)
• When we breathe out

Temperature must be constant (37 C), to be suitable for enzymes (may not work)

The sugar level must be controlled (it's an energy source for cells)

Healthy diet contains:

• Carbohydrates
• Proteins
• Fats
• Vitamins
• Minerals
• Roughage (Fibre)
• Water

Balance diet: Eating the right amounts of the different foods that you need

Malnourished: Diet not balanced

Scurvy (disease): lack of vitamin C

Metabolic rate: measure of how quickly your cells are converting food into energy

If you exercise you need more energy. Exercise increases metabolic rate.

If you're warm you need less energy than when it's cold

The amount of energy you intake depends on:

• size
• sex (gender)
• how active you are
• outside temperature
• pregnancy

Exercise increases the metabolic rate because it's the rate at which your body uses energy needed to carry out chemical reactions.

If you take more energy (food) than you need you will become fat, as the excess is stored in you body as fat.

The health problems of obesity:

• arthritis (worn joints)
• Diabetes
• High blood pressure
• Heart disease

Can lose wait by:

• reduce the amount of energy
• Increase the amount of energy you use up
• Do both reduce energy intake and exercise more

Starvation is lack of food.

Civil wars, droughts and pests can destroy local crops so people cannot get enough to eat.

Starvation symptoms:

• Become very thin & muscles waste away
• immune system can't work properly, so you pick up infections
• if you're a woman: periods will become irregular or stop altogether

It also seen in the developed world in people suffering from the mental disorder called anorexia or nervosa

Fast food: contains lots of fat & salt

Too much salt - causes high blood pressure

Too much fat can cause cholesterol. It's made in the liver. it depends on diet & inherited (genetic) factors.

We need cholestrol but too much can lead to:

• heart disease
• diseased blood vessels

the amount of cholesterol you have depends on:

• The way your liver works (something you inherit from parents)
• Amount of fat in your diet

Cholesterol is carried around you body by 2 types of lipoproteins:

• LDL [Low-density lipoproteins]: bad cholesterol.  can cause diseases
• HDL [High-density lipoproteins] : good cholesterol. reduce risk of disease

3 types of fat in food:

• Saturated fats: increase blood cholesterol level. found in animal fat
• Mono-unsaturated fat: can reduce blood cholesterol level & improve balance between HDL & LDL in blood
• Poly-unsaturated fat: better at reducing blood cholesterol level & balancing HDL & LDL.

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

Drug: substance that alters the way in which your body works

can affect your body, mind or both

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

indigenous people: ethnic group

Addiction:

Some drugs change the chemical processes in your body so that you may become addicted to them.

You can become dependent on them. Once addicted you need more & more of it.

When addicts tries to suddenly stop it, you get withdrawal symptoms

Withdrawal symptoms: aches, pains, sweating, shaking, & cravings for the drug

Many problems are caused by legal drugs, because they're widely used and abused.

Recreational drugs are used by people for pleasure

Cannabis: a recreational drug. It's illegal and people believe it can lead to harder drugs.

Thalidomide: a sleeping pill. also prevented morning sickness for pregnant woman. I had side effect on growing fetuses. It's now used for leprosy.

Hard drugs: Cocaine & Heroin, are extremely addictive and expensive.Because they're illegal they're expensive. Young people end committing crime to pay for the drug habit.

Sedatives: slow down your reaction. Eg Alcohol (depressant)

Stimulants: Speeds up your reaction. Eg Nicotine, Caffeine

Class A drugs: Heroin, LSD, Ecstasy & Cocaine [the most dangerous]

Class B drugs: Amphetamines (speed)

Class C drugs: Cannabis, steroids, tranquillisers

Alcohol is very addictive and it is also very poisonous. Is most widely used drugs.

Alcohol is poisonous. It's usually broken down by the liver.

When you have alcoholic drink:

Passes through the wall of your gut, and goes into the bloodstream. from blood it goes to every tissues of your body. It then goes to the nervous system and brain.

Drinking too much alcohol makes you lose consciousness or go into coma. also lack of judgement.

Using alcohol for a long time can develop cirrhosis of the liver and get liver cancer.

Binge drinking: short bouts of very heavy drinks.

When you smoke, the cigarettes makes the hair immobile.They stop working, allowing dirt down into your lungs. This eventually causes lung infections, etc

Emphysema: makes lungs less efficient, breathing becomes difficult & less oxygen.

Tobacco smoke also contains carcinogen (cancer causing substance)

Carbon monoxide in tobacco reduces the amount of oxygen the blood can carry.

Babies born to mothers that smoke have low birth weights. The babies receive less oxygen to release the energy from food (in respiration) that is needed for growth. [nicotine is very addictive]

Pregnant mothers higher risk of having:

• Premature birth (baby born to early, may struggle to survive)
• Baby with low birth mass (risk of developing problems)
• still birth (baby born dead)

Pathogens causes infectious diseases.

Some pathogens that causes diseases are: bacteria & viruses

Pathogens reproduce inside the body before they make enough toxins to make you feel ill.

People can pass these micro-organisms from one person to another. This called infectious.

Semmelweiss discovered that infection could be transferred between the patients.

He suggested that washing hands between treating people helped stop the transfer of infection.

It took many years before his idea was accepted:

• doctors thought child bed fever was caused by god's punishment.
• didn't want to accept disease was caused by something invisible
• It's also hard to admit that they spread the disease instead of curing.

There are numerous way we can spread pathogens:

• Droplet infection
• Direct contact
• Contaminated food & drink
• Through a break in your skin

White blood cells protect ourselves by:

• Ingesting the pathogens [they digest & destroy them]
• Produce anti-bodies [to help destroy particular pathogens]
• Produce anti- toxins [to counteract the toxins released by the pathogens]

Body has several methods of defending itself (first line defence)

• By skin
• mucus of the breathing system
• clotting of the blood

Antibiotics kill infective bacteria inside your body. [only bacteria not virus]

Painkillers do not cure the disease it only relieve the symptoms of a disease.

Alexander Fleming was a scientist that first discovered penicillin.

After 10 years, Ernst Chain & Howard Florey started to produce the penicillin in an industrial levels. This was used for world war 2 (1940s)

Virus are harder to get rid of, as they reproduce inside the cells. If you destroy the virus, you can easily destroy the cell as well.

Micro-oragnism produce very fast in a host organism

viruses: flu, colds, measles, chicken pox, rubella, polio

bacteria: cholera, tuberculosis, pathogenic bacteria, Tetanus

Mutation: the change in genetic material in an organism

When you use antibiotic, it should kill the majority of the bacteria, the ones not affected they have natural mutation [means not affected by the antibiotic]

Bacteria becomes resistant to antibiotics through natural selection

MRSA is a bacterium that has evolved in hospitals through natural selections. resistant to commonly used antibiotics. MRSA alone causes thousands of deaths in hospital.

How to control the spread of MRSA:

• Doctors, nurses, etc to wash hands between each patients.
• Visitors to wash their hands as they come and leave the hospital.
• Keep hospitals clean

Few people are immune to this new disease so can spread within the country (epidemic) or across countries (pandemic)

A good medicine is:

• Effective [prevent or cure the disease]
• Safe [drug must not be poisonous]
• Stable[able to use the medicine under the normal conditions]
• Successfully taken into and removed from your body

It costs a lot of money to develop new medicine. It also takes a long time.If not thoroughly tested it can have side effects.

New medicines is usually tested on animals first to see if it's toxic.

Thalidomide was a medicine developed in the 1950s. As a sleeping pill. It also helped to prevent morning sickness in pregnant woman. but effected the growing fetuses, limb deformities.

Thalidomide is now used for Leprosy, certain types of cancer.

for & against the use of animals in testing new medicine

Against:

• It can be misleading. animal response can be different from humans.
• the stress the animals have in the labs can affect the experiment and making the results meaningless.
• Animals have as much right to life as human beings
• Deaths through research are absolutely unnecessary and are morally no different from murder.

For:

• Animals testing have helped to develop vaccines against disease
• Operations on animals helped to develop organ transplant and open-heart surgery techniques
• Antibiotics, HIV drugs, insulin and cancer treatments rely on animal tests. Other testing methods aren't advanced enough.
• Few animals feel any pain as they're killed before they have the chance to suffer.

Every cell has unique proteins on it's surface called Antigens.

The antigens on the microorganisms is different from the one in your cell, so it's recognized by the immune system as it's different.

Then white blood cells make antibodies to attack the antigens.

Immune: resistant to a particular infection

Dead or inactive form or an organism can be made into a vaccine.

Vaccines can be injected into the body.

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.

Animals in cold climates (e.g in the arctic) have thick fur and fat under the skin (blubber) to conserve heat.some are white in the winter and brown in summer. so they're camouflaged so not easily seen.

Animals in dry conditions (dessert) are adapted to conserve water and to stop them getting too hot. Animals in the dessert may hunt or feed at night so that they remain cool during the day.

Bigger animals have small surface area compared to the volume. Means they can conserve heat more easily but more difficult to lose heat.

Plants need water for both photosynthesis and to keep their tissue upright.

The water is lost through the leaves in the transpiration stream. It's lost all the time through the leaves.

There are small opening called stomata. These allow gas exchange for photosynthesis and respiration. water is also lost through evaporation.

plants in dry condition have curled leaves. It reduces their surface area to reduce water loss.

They have thick waxy cuticle to keep water loss down. It's waxy to stop the water evaporating away.

cacti has spines which puts animal off eating.

Plants that store water in their leaves, stems or roots are known as succulents.

Animals compete for :

• Water
• Territory
• Mates

Animals territory would be large enough to find water, food & have space to breed.

Predators compete with their prey, as they want to eat them.

Predators and prey may camouflage, to that they are less easy to see.

Some animals, have warning colours to show them they are poisonous. so is not eaten.

Some animals, have colour to attract females or as camouflage.

Plants compete for:

• Water
• Nutrients
• Light

Some plants spread their seeds over a wide area so that they do not compete with themselves.

Structures that enable them to compete:

• extensive roots
• successful growing habits, e.g grow quickly to gain as much as sunlight as possible.

Some characteristics are inherited from our parents.

Gametes: sex cells [sperm or ovum cell]

We resemble to our parents because of genetic information passed from parents.

Nucleus --> Chromosomes --> Genes --> DNA

Genetic information is stored in the DNA

DNA is made up of double helix [two strands twisted together]

Genes: units of inheritance

Humans: have 46 chromosomes

Genes control the development of an organism.

Asexual Reproduction: only involves one parents

• produces organism identical to itself
• No variety in offspring
• Similar to clones
• takes place in our body, example: replace worn out tissues, etc

Sexual Reproduction: involves two parents

• will inherit genetic information from both parent
• Introduces variety
• Variety is important for survival
• Sexual reproduction gene are mixed from the two parents

Alleles: different versions of the same gene

Individual produced asexually from its parent. It's genetically identical to the parent.

Cloning plants

• can produce from taking cuttings. Form of artificial asexual reproduction.
• the cutting is usually from the leaf or stem
• it's cheap and effective
• genetically identical to its parent

Cloning Tissue

• Can produce from tissue culture.
• taking groups of cells and growing them under special conditions
• expensive, but can produce thousands of them
• can stimulate the cells to grow desired plant

Cloning Animals

• embryo cloning is used to produce example: top quality calves
• It's much more difficult to clone
• In embryo transplant, embryos are split into smaller groups of cells then each group is allowed to develop in a host animal.

Adult cell & fusion cell cloning are also used to clone animals.

In adult cell cloning, the nucleus of the animal you want is placed in an empty egg cell. The cell is then developed in a different animal.

Adult cell cloning

Advantages:

• animals with useful proteins in their milk can be cloned.
• Good way of producing medically useful animals.
• Help save animals from extinction or bring back extinct species.
• clone pets to continue even after the original died.

Disadvantages:

• cloning reduces variety in population
• less survival chance, if there's change in the environment
• if one of them don't have a useful mutation then none of them will have.

Genetic engineering also known as genetic modification.

It's used to change the genetic material of an organism.

Genes are 'cut out' of the chromosomes of an organism using an enzyme. The genes are then placed in the chromosome of another organism.

Genes may be placed in an organism of the same species so that is 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 produce insulin.

Genetic Engineering

Benefits:

• of genetically engineered bacteria is that they can make exactly the protein needed.
• helped lower the usage of herbicide and pesticide
• can produce sustainable agriculture
• used to treat genetic disorders and cancers. helps supplying new body parts.
• helped production of other vaccines and other drugs in plants. 
• Develop insulin for diabetic patients.

Disadvantages:

• new science, concerned about long-term effects.
• it's unnatural
• ethical issues
• mistakes have devastating repercussion

Earth is about 4.5 billion years old, life began 3.5 billions years ago

Some species have became extinct or totally wiped out. The fossil records gives us an insight into how much and how little the organisms have changed since life developed on earth.

They're found in different layers. Meaning we can put an approximate date on when different animals and plants existed.

Evolution: change in a living organism over time.

Lamarck's Theory

• acquired characteristics can be passed on to the next generation.
• his idea that every type of animal evolved from primitive worms.
• example:  if two parents build up their muscles in the gym, that would be passed on to the offspring
• theory fell down because: people didn't like the idea of being descended from worms... acquired characteristics were not passed on to the offspring

Darwin's Theory

• stated small changes took place over time
• organism vary, so the survival of the fittest (natural selection)
• those that are best adapted breed and pass on their characteristics.
• Took a long time to be accepted, believed that God was responsible.

Due to sexual reproduction there's variation between species. by a process called natural selection.

Natural selection = Survival of the fittest

Species with the best characteristics survive to breed.

Weaker members may die from:

• Disease
• Lack of food
• Variation in the climate

mutation: change in the genetic material of an organism

Natural selection:

Mutation --> Variation --> Adaptation --> Survival --> Genes passed on to the next generation

There are 6 billion people around the world, and is still increasing.

Many people want and demand a better standard of living.

Increase in population requires more and more building of houses, shops & roads. Which destroys rare species of other living organism.

We reduces the land available for other organisms by:

• building
• quarrying
• Farming
• dumping waste

We pollute by:

• Water: with sewage, fertilizer and toxic chemicals.
• Air: with gases such as sulfur dioxide & with smoke
• Land: pesticide & herbicide, can be washed into water

When fossil fuels are burned:

• carbon dioxide is released as waste product,
• Sulphur impurities which reacts with oxygen to produce sulphur dioxide
• Nitrogen oxides (example in car engines)

Sulphur dioxide and Nitrogen oxide dissolves with in the rain to produce acid rain.

Acid rain damages the environment and organisms. Enzymes which control the reaction only works at specific pH level.

Acid rain can also makes lakes & rivers acidic so the organisms and plants living in them could not live any more.

Acid rain affects other places which didn't produce the pollution. because as they are carried high in the air by the prevailing winds.

To reduce the problems: cars are fitted with catalytic converters (remove the acidic gases before being released into the air.)

Global warming: warming of the earth due to green house gases in the atmosphere trapping infra-red radiation from the surface.

Burning fossil fuels (combustion) releases carbon dioxide.

Global warming causes lots of climate and other changes. Could lead to ice caps melting which leads to sea level rising that then causes flooding,etc.

Deforestation increases carbon dioxide level in the atmosphere.

• trees take-up carbon dioxide during photosynthesis
• When they burn the trees, it releases carbon dioxide through combustion.

Methane levels are rising too:

• by paddy fields, as the population increases so is the farming of rice, ect 
• by cattle, produces methane through digestive processes.

When we lose forest, we lose biodiversity.lots of plants and animals die out.

As the population rises, more earth's resources is being used up, eg land fossil fuels and minerals.

'Sustainable Development' means resources available for the future generation without compromising the present. 

Important part of sustainable development is using natural resources.

Finding alternatives for the following resources:

• fuels for cars
• recycling e.g plastics, aluminium in cans
• using brownfield lands

help by:

• recycling old newspapers (saving trees)
• Glass bottles (saving energy)
• aluminium cans (saving aluminium ores and energy) 

Lichens:

• Used as air pollution indicator
• the more lichens growing the cleaner the air.

Freshwater invertebrates:

• Used as water pollution indicator
• the cleaner the water, the more species you would find
• Some might only live in polluted water

Greenfield sites: countryside, that has not been built on before

Brownfield sites: usually within towns and cities, areas that has already been built on. they're usually expensive, because to build something on it, it needs to be decontaminated.

SSSI: Sites of Special Scientific Interest

Lands that will not be disturbed or built on.