Biology - Unit 1

• Diet and Exercise

A healthy diet is the right balance of certain food groups, these being carbohyrdates, protein, fat, vitamins, minerals, fibre and water.

Each of these food groups has a specific job within the body.

• Carbohydrates - Provide energy
• Protein - Secondary source + Growth and repair
• Fat - Provide energy + Layer of fat for warmth
• Vitamins - Keep the body healthy
• Minerals - Keep the body healthy
• Fibre - Keeps the digestive system moving
• Water - Flushes out toxins from the body

Without the correct balance of these food groups a person can become malnourished.

The more exercise a person does the more energy is used by the body this increases the metabolic rate, which is the rate at which chemical reactions take place within the cells.

• Weight Problems

It is vital that people get their energy balance correct in order to suistain a healthy weight.

If the energy taken in is equal to the amount of energy used the mass will remain the same however gaining too much energy can lead to someone becoming overweight and obese.

There are long term effects of being overweight such as Type 2 Diabetes.

Whilst being overweight is a problem being uderweight is also a problem. Too little food is can lead to someone suffering from deficiecy diseases sue to a lack of vitamins and minerals.

• Inheritace, Exercise and Health

A persons metabolic rate can be affected by the genes inherited from their parents.

Their are two types of cholestrol which a person can have, 'good cholestrol' is required to make cell membranes and to produce vital substances.

However 'bad cholestrol' can lead to heart disease and the main issue with this is that it can be inherited. Also foods high in staurated fat can also contribute to this amount of 'bad cholestrol'.

By exercising people can increase their metabolic rate and lower their high cholestrol levels.

The reason anyone gains weight/mass is because food conatins energy and excess energy is stored as fat within the body.

• Pathogens and Disease

Pathogens cause infectious diseases and are usually caused by microorganisms either bcteria or viruses however they can also be caused by fungi.

Each of these types of microorganism do different things to the body.

• Bacteria - Once they are in the body they can reproduce rapidly and produce toxins which are released into the blood. The toxins are what make people feel ill.
• Viruses - When they get into the they invade cells and reproduce within them. This damage to the cells makes people feel ill.
• Fungi - These eat away at the flesh.

Before the cause of illness was said to be pathogens a doctor called Semmelweiss realised that infection was being transferred from person to person as staff were not washing their hands. This idea was not taken seriously at the time however we now know that this idea was right.

• Defence Mechanisms

Their are many mechanisms which the body has in order to prevent pathogens from getting into the body, some of these are:

• Skin
• Mucus
• Stomach Acid
• Eyelashes

White blood cells are the part of the immune system which come into use once the pathogens are inside. They do 3 things within the body:

• Ingest pathogens - This means they digest and destroy the pathogen.
• Produce antibodies - They help to destroy specific pathogens.
• Produce antitoxins - These counteract the toxins released by the pathogens.

• Drugs to Treat Disease

Antibiotics kill infective bacteria within the body however they can only be used to kill bacteria not viruses due to these reproducing within the cells any treatment could also damage the body cells.

There are many types of antibiotics which are used to treat different diseases.

Painkillers and other drugs relieve symptoms but do not kill the pathogen itself.

Most peoples immune systems will gradually overcome the viral pathogens.

• Growing and Investigating Bacteria

Pure cultures of non-pathogenic bacteria can be used for labatory investgations in order to find the effects of antibiotics on bacteria.

Strict health and safety procedures have to be put in place to prevent the cultures from becoming contaminated as contamination could come from skin, air, soil or water around the investigation.

If the culture is contaminated other bacteria could grow including harmful pathogens.

In order to maintain a non contaminated sample:

• The bacteria must have a culture medium to grow on with access to warmth and oxygen.
• They need to incubated at 25 degrees celsius within schools and 35 degrees celsius in industry.
• To kill bacteria the equipment must be sterlised and to prevent microorganisms from the air the sample must be sealed quickly with tape.

• Changing Pathogens

Some pathogens, particulary viruses, can mutate creating a new form of pathogen this means usually very few people are immune to it. 

These new diseases can cause illness to quickly spread therefore it can result an a epidemic or a pandemic.

MRSA is a type of 'super-bug' whereby the bacterium has evolved through natural selection if thsi happen to other bacteria resistance would build reducing the effectiveness of common antibiotics.

Mutations of pathogens produce new resistant strains which if they survive and reproduce the strain develops via natural selection.

Antibiotics should only be used for mild infections in order to slow down the development of resistant strains.

• Immunity

Dead or inactive forms of a pathogen are used to make a vaccine, which is injected into the body.

When the pathogen is injected the white blood cells act as if they are fighting an actual illness, they do this by producing antibodies. 

This makes a person immune as if the body ever gets reinfected the body can produce more antibodies, faster. 

The antibodies recognise the foreign antigen and produce the antibodies to fit against it, these antibodies are specific to each antigen.

The MMR vaccine is one of several vaccinations to prevent illness, MMR is for Measles, Mumps and Rubella.

• How do we deal with disease?

Most people within society have to be vaccinated to prevent the spread of serious diseases, as some diseases can lead to long term damage to the body or even death.

Some vaccines can have side effects which may be mild or serious so there are a variety of advantages and disadvantages to vaccination.

Doctors do not perscribe antibiotics for mild infections to prevent new strains of bacteria from growing as therefore the vaccinations would not be effective.

• Responding to Change

The nervous system is made up of a variety of stages, these being:

• Stimuli
• Receptor
• Sensory Neurone
• Relay Neurone
• Motor Neurone
• Effector

The receptors are found in the sense organs : eye, ear, nose, tongue and skin.

The receptors release an electrical impulse which is passed to the central nervous system (brain and spinal cord).

The effector organs are either muscles or glands whereby the muscles respond by contracticng and the glands respond by secreting.

• Relex Actions

The sequence from rececptor to effector is a reflx arc, the steps involved with this are:

• A receptor detects a stimulus
• A sensory neurone transmits the impulse to the CNS
• A relay neurone passes the impulse on
• A motor neurone is stimulated
• The impulse passes to an effector 
• Action is taken

The gap between neurones is a synapse where the chemicals diffuse the impulse across the gap.

• Hormones and the Menstural Cycle

The first step in the cycle is FSH which causes the egg to mature and oestrogen to be produced.

The next step is oestrogen inhibits the production fo FSH. Also it stimulates the production of LH and stimulates the womb lining to develop.

LH stimulates the egg to then be released in order for it to be fertilised.

Progesterone is also stimulated to keep the lining thick.

If the egg is not fertilised then the lining is lost through a womens period.

• FSH - Follicle Stimulating Hormone - Pituitary Gland
• Oestrogen - Ovaries
• LH - Lutenising Hormone - Pituitary Gland
• Progesterone - Ovaries

• Artifical Contorl of Fertility

There are a variety of types of contraception whereby some involve hormones and some do not. Furthermore each have different effectiveness.

The contarceptive pill can either be combined (oestrogen and progesterone) or progesterone only. 

The pill prevents the production of FSH therefore no eggs can mature.

However if women struggle to get pregnant FSH and LH can also be given. This is known as fertility treatment.

There are advantages and disadvantages to the contarceptive pill and fertility treatment.

• Controlling Conditions

The body carefully controls its internal environment. Some of these factors are:

• Water content - Lost through breathing, sweating and urine
• Ion content - Lost through sweating and urine
• Temperature - If temperature is not maintained the enzymes will denature
• Blood sugar level - The levls are contolled by insulin which is produced by the pancreas

• Hormones and the Control of Growth

Plants are sensitive to light, gravity and moisture.

• Plant shoots grow towards light - Phototropism
• Plant roots grow down towards gravity - Gravitotropism
• Roots also grow towards water.

Auxin is the plant hormone which controls this unequal amount causes unequal growth. Therefore the shoots or roots bend. Auxin can be used in weed killers and to stimulate growth.

• Using Hormones

• In women

Many women use the contraceptive pill to prevent pregnancy and otehr women use hormones to plan pregnancy.

Sometimes these treatments can help older women to become pregnant and it may also involve the use of egg donors or hormones to produce extra eggs.

• In plants

Plant hormones can be used by farmers and gardeners to kill unwanted plants or encourage roots to grow on cuttings.

Some hormones are also used to encourage fruit to ripen.

However if used incorrectly they can damage more useful plants.

• Developing New Medicines

Large numbers of substances have to go through stages of testing to see whether they might cure a disease or relieve symptoms.

The first stage is testing on cells and tissues or organs. If they pass they are tested on animals, healthy volunteers and finally paitients.

Healthy people are given very low doses of the drug to find out if it is safe.

In some trials placebos are used where half the people are given the drug and half have the placebo, thsi is to see whether the drug actually has an effect on the people testing it.

In a double-blind trial neither the doctors or the paitients know who has the drug.

Thalidomide was developed as a sleeping pill however doctors found it could help with morning sickness, the problem was it had not been tested for this purpose and some babies were born with limb abnormalities.

It is now used to treat leprosy but is never given to pregnant women.

• How effective are medicines?

Statins are drugs which lower the amount of 'bad cholestrol' in blood, they are given to people to be taken daily. 

Trials have shown that these have lowered the risk of heart disease and strokes by 40%.

Some people take drugs not persrcibed by doctors such as herbal remedies.

The only way to check whether natural substances are better than perscribed is to conduct a double-blind trial.

• Drugs

Drugs have to be tested over long periods of time to check that they do not carry any side effects.

Recreational drugs are used for pleasure. Heroin and Cocaine are addictive and illegal, although Cannabis is not as bad it is still illegal and some people think it leads to 'harder drugs'.

• Legal and Illegal Drugs

Medicinal drugs are developed to control disease or help people that are suffering and are mostly only available when perscribed by a doctor.

Recreational drugs are used for pleasure and have effects on the brain, nervous system and heart. 

As these drugs affect the nervous system they are 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.

There are many health problems associated with legal recreational drugs such as alcoholic poisioning and lung cancer.

Some drugs used for medicinal purposes can be used illegally such as stimulants used by sports people.

• Does Cannibis lead to hard drugs?

There is evidence that cannabis can cause mental illness and teenagers that smoke cannabis increase their risk of depression.

Cannabis is an illegal drug which must be bought from dealers.

This brings cannabis into contact with hard drugs such as heroin.

Nearly all heroin user have previously smoked cannabis.

• Drugs in Sport

Steroids build up muscle mass and other drugs may increase stamina.

Strong pain killers are banned because the athlete may avoid the injury if they do not feel it.

Many performance drugs are expensive therefore those who can afford them have an unfair advantage. Also people think it is un-ethical.

• Adapt and Survive

To survive organisms are required to have adaptations which allow them to get all the materials required by them from their surroundings.

Plants need: light, carbon dioxide, water, oxygen and nutrients.

Animals need: food, water and oxygen.

Different organisms need different adaptations as these allow them to survive in specific habitats, or when the conditions are extreme.

Plants have adaptated to obtain light as they need it for photosynthesis.

Different animals have different mouth parts depending on their diet (carnivore) or (herbivore).

Most organisms live below 40 degress celsius so their enzymes work.

Extremeophiles are organisms that can live in conditions where enzymes would usually not work.

• Adaptation in Animals

If animals were not adapted to their surroundings they would die.

Animals in cold climates have different adaptations to those in hot/dry climates.

Cold

• Thick fur
• Fat under the skin
• Camouflaged colour
• Bigger volume to surface area ratio

Hot/Dry

• Hunt at night
• Long eyelashes
• Camouflaged colour
• Smaller volume to surface area ratio

• Adaptation in Plants

Plants need to collect and conserve water as it can be lost as water vapour or through the stomata.

Water can be collected by an extensive root system.

Water can be conserved in a swollen stem or through having small, waxy leaves.

Also plants have adapted to have thorns, poisionous chemicals and warning colours to put animals off.

• Competition in Animals

Animals compete for food, water, space, mates and breeding sites.

Predators compete with prey as they want to eat them however prey have to compete with eachother to be the one that doesn't get eaten.

Some animals may be poisionous or camouflaged to avoid being eaten.

• Competition in Animals

Animals compete for water, food, space, mates and breeding sites.

Predators compete with prey as they want to eat them however prey have to compete with eachother to be the one that doesn't get eaten.

Some prey may be poisionous or camouflaged to avoid being eaten.

• Competition in Plants

All plants compete for water, nutrients and light.

For example smaller plants may struggle if they are growing close to a tree who takes all the light, also plants with deep roots can reach water unlike shallow rooted plants.

Some plants may use the wind, other animals or mini explosions to disperse their seeds so they don't compete with themsleves.

• How do you survive?

Some animals and plants have special adpations which make them successful competitors.

• Female Fig Wasps - Specially shaped heads for getting into fig flowers and ovipositors to deposit eggs deep inside the flower.
• Star-Nosed Moles - Sensitive to touch and smell.
• Venus Fly Traps - Sweet, sticky nectar and are red inside.

• Measuring Environmental Change

Non-living factors which might affect change include: temperature, rainfall, light and oxygen levels.

Living factors may include: new predator, disease, new food or habitats.

Lichens indicate the level of air pollution especially sulphur dioxide, the more species the cleaner the air. Freshwater invertebrates detect water pollution, the wider the range the cleaner the water. Equipment can also be used to measure factors of change and pollution.

• Pyramids of Biomass

Biomass is the mass of living material in plants and animals.

A pyramid of biomass represents the mass of organisms in each trophic level, this is better than a pyramid of numbers because the insects may feed of a bush however they have a smaller mass than a bush.

Plants begin the food chain because they gain their energy from the sun which they convert to chemical energy. The chemical energy is then passed on through the chain as the plants get eaten.

• Energy Transfers

There is always energy lost between each stage in the food chain, therefore not all the energy taken in by an organsim is used by it for growth.

Not all the food can be digested so some is lost as faeces or urine.

Some of the biomass is used for respiration whidh releases energy fro living processes, this includes movement whereby the more movement an organism does the more energy it uses therefore there is less for growth.

If animals need to maintain a constant temperature some of the energy is used for this.

Most of the energy released in repiration is eventually released to the environment.

• Decay Processes

All organisms take up nutrients if they were never released the nutrients would run out.

Detritus feeders start the process of decay by eating dead animals or plants and producing waste materials. 

Decay organisms then break down the waste.

Decay organisms are known as decomposers. Decay happens faster if it is warm and wet, also many decomposers need oxygen for respiration.

All the materials from the waste and dead organisms are recycled, returning the nutrients back into the soil.

Humans can recycle waste using compost heaps.

• The Carbon Cycle

The recycling of carbon requires photosynthesis and respiration.

The steps are:

• Photosynthesis removes CO2 from the atmosphere.
• Green plants and animals respire, returning the CO2 back into the atmosphere.
• When humans burn trees CO2 is released into the atmosphere.
• Animals eat green plants and build the carbon into their bodies.
• When plants or animals die the microorganisms release CO2 through respiration.
• A stable community recycles all of the nutrients it takes up.

• Recycling Organic Waste

Waste vegetables, peelings, grass cuttings and clippings all contain organic waste, therefore it can be recycled.

Organic waste can be composted in several ways.

The most efficient methods allow the waste to be mixed with oxygen and moisture. They also allow energy to escape by heating the surroundings.

Gardeners may add worms and layers of garden soil to composters to speed up the process.

• Inheritance

The nucleus of the cell contains thread-like structures called chromosomes.

These chromosomes carry the genes.

In the nucleus of gametes (sex cells) there is only a single set of chromosomes, therefore teh nucleus of male and female sex cells conatin only one set of genes.

The genetic information is passed onto offspring durijng reproduction. Where two sets of genes are inherited from the parents.

Different genes control the development of different characteristics within offspring.

In most body cells the chromosomes are in pairs, one set from the mother and one set from the father.

• Types of Reproduction

Asexual Reproduction

• Does not involves the fusion of gametes.
• All the genetic information comes from one parent.
• All the offspring are identical to the parent therefore there is no variation.
• Produces clones.

Sexual Reproduction

• Involves the fusion of gametes.
• The offspring are similar to both parents but are not identical therefore there is variation.
• Random mixing of genes leads to variation.
• Some characteristics may give offspring a better chance of survival.

• Genetic and Environmental Diffences

Differences in the characteristcis of individuals may be due to:

• Differences in the genes they have inherited
• The conditions in which they have developed
• A combination of both these genetic and environmental causes.

Genes are the most important factor in controlling the appearance of an individual.

Plants may be affected by lack of light, nutrients or space to grow. The weaker plants may have the same genes as healthier plants but they cannot grow aswell because they have less nutrients.

Human development may be affected during pregnancy from factors such as if the mother smokes or drinks alcohol.

Once they are born too little or too much food can also alter the characteristics of animals.

• Cloning

Individuals that are genetically identical to their parents are known as 'clones'.

It is much more difficult to clone animals than it is to clone plants.

In plants the process can be cheap and effective, the plants can be cloned by taking cuttings and growing them.

Taking small groups of cells from part of a plant and growing them under special conditions (tissue culture) is more expensive. However it can produce large numbers of rare/top quality product.

Embryo transplants are used to clone animals. In this process an embryo with unspecialised cells is splint into smaller groups of cells. Each group is implanted into a host animal where it can develop.

Sometimes animals or plants are genetically modified to produce useful substances before they are cloned.

• Adult Cell Cloning

In adult cell cloning the nucleus of an adult cell replaces the nucleus of an egg cell.

First the nucleus is removed and placed inside the empty egg cell.

The new cell is given an electric shock which causes it to start to divide. This forms an embryo.

Once the embryo has developed into a ball of cells it is inserted into the womb of a host mother.

Dolly the sheep was produced by adult cell cloning in 1997.

• Genetic Engineering

Genetic engineering involves changing the genetic make-up of an organism.

Genes can be transferred into cells of animals, plants or microorganisms in the early stage of their development.

A gene is cut out of the chromosome using enzymes it is then put into the chromosome of a different organism.

The genes may be put into the same species to give it a desired characteristic.

Sometimes genes are put into different species such as the gene that produces insulin from humans can be put into bacterium therefore large quantities can be produced.

New genes can be transferred to crop plants.

Crops with changed genes are caused genetically modified plants.

GM plants may be insect or herbicide resistant.

• Making choices about Technology

Advantages

• Cloning cattle can produce herds with useful characteristics.
• Adult cell cloning makes copies of the best animals.
• Genetic disorders could be cured by transferring genes.
• Several medical drugs have been produced by genetic engineering.
• GM crops are insect and herbicide resistant.

Disadvantages

• Farmers need to buy new GM seed every year.
• Some people are concerned about accidentally introcuding genes.
• Insects which are not pests may be affected by GM crops.
• Many people worry about eating GM crops and the effects on human health.
• Many people argue about whether the process is ethical or not.

• Theories of Evolution

Scientists believe life on Earth began about 3 billion years ago.

Before the 18th century there were few scientific ideas about evolution so theories developed.

Jean-Baptiste Lamarck suggested that characteristics which develop over an organisms life will be passed on to offspring. For example if the parents built up muscle in the gym this would be passed on to offspring.

Charles Darwin suggested the theory of 'natural selection'. Whereby very small changes in organisms took place over a very long time, all organisms in a species vary and so some are more likely to survive.

Those that are best adapted survive and pass on the advantageous gene.

• Accepting Darwin's Ideas

Darwins theory was ony gradually accepted for several reasons:

• The theory challenged religious views about the creation of life.
• Many scientists could not find sufficient evidence therefore they did not trust the theory.
• Darwin could not explain why there was a variety in organiss or hwo inheritance worked. Now we know this was due to genes which were only found out about 50 years later.
• Darwin tried to show how different birds had different adaptations depending on their surroundings howver he could not explain why the offspring inherited these useful adpatations.

• Natural Selection

Most organisms produce large numbers of offspring.

Individual organisms show a wide range of variation because of differences in their genes.

All the organisms in a population will compete for the same things however only those who are specially adapted will survive and reproduce.

The genes that have enabled them to survive are passed onto their offspring.

Sometimes a gene accidentally changes in the form of a mutation. If this mutation makes the organism more adpated to the environment then it will be passed on to the offspring.

Mutations are particularly important as sometimes only those with the mutation can survive because they are immue to diseases which kill those without the mutation.