Diet
Regular exercise and a balanced diet are needed to keep the body healthy.
Insufficient food leads to a person being underweight and prone to illness.
Too much food and not enough exercise leads to a person being overweight and get other illnesses.
Nutrient
Carbohydrates- Source of Energy
Fats- Source of Energy + for insulation
Proteins- for Growth and repair, Building cells in our body
Mineral ions + Vitamins - For healthy functioning of the body
Imbalanced Diet- Causes a person to be malnourished,
Too little food - underweight
Too much food - overweight
May also lead to deficiency diseases
Exercise
Metabolic rate Speed in which chemical reactions happen in our body.
Affected by:
- Proportion of muscle and fat in the body
- Amount of exercise
- A higher muscle : fat ratio = higher Metabolism
- Exercising= higher Metabolism
Receptors are groups of specialized cells that detect changes in the environment called stimuli.
Cells
Sensory neurones carry signals from receptors to the spinal cord and brain
Synapses are where two neurones meet.
Reflex actions
Stimulus > receptor > sensory neurone > relay neurone > motor neurone > effector.
An effector produces the response e.g muscles, glands.
Reflex actions are rapid and does not require us to think.
Control in the human body
Control of internal conditions-
Salt content is also controlled to protect cells from having too much water entering or leaving them, we lose ions through sweat and urine.
Blood sugar levels is controlled, to provide cells with a constant supply of energy. It is controlled by insulin and the release and storage of glucose is controlled.
Thyroid gland produces thyroxine - controls rate of metabolism
Menstrual cycle
FSH produced in the pituitary gland and causes an egg to mature + stimulates the ovaries to release oestrogen.
Oestrogen is secreted by the ovaries. Stops FSH being produced and stimulates the pituitary gland to release LH which triggers ovulation ( release of egg)
Day 1-4 Menstruation
Contraceptives
Fertility treatments
In vitro fertilisation
Control in Plants
Sensitivity in plants
Phototropism- light
This allows shoots to grow upwards towards the sun and roots to grow downwards towards the soil + water.
Auxins
In shoots, auxin mores towards the shaded side increasing the grow on the shaded side so the plant bends towards the lighter side.
In roots, Auxin moves to the shaded side but it slows down grown so it grows towards the shaded side.
Geotropism
In shoots, bottom side has more auxin and grows faster so the shoot bends upwards.
In roots the bottom side has more auxin and the side grows slower so it bends downwards.
Plant hormones can be used as weed killers or rooting powders
Rooting powders contain growth hormones to make stem cuttings develop roots more quickly
Environmental Changes
Changes can be cause by living factors e.g. change in a predator, food source or a competitor, or non living factors e.g. change in temperature or rainfall.
If prey population grows predator numbers will increase as there is an increase in food supply.
Indicators of pollution
Water pollution is caused by discharge of harmful substances into river, lakes and seas.
We can measure rainfall using a rain gauge. Depth of rain is measured consistently.
Energy in Biomass
The sun is the ultimate source of energy.
Consumers take energy by eating other organisms.
Producers - Plant
Energy transfer
Decaying processes
Decay is a process that digests food or waste matter and recycles materials.
Factors that affect decay are:
The carbon cycle
Organisms return carbon dioxide in the atmosphere by respiration.
When organisms eat a plant the carbon becomes part of the fats and protein in the animal.
Genes
Darwin's theory of evolution
He has wrote a book called On the Origin of Species which explained his ideas.
His theory states that evolution happens by natural selection
Different organisms can be classified by their similarities and differences.
Lamarck developed an alternative theory of evolution.
Mutation causes changes in genes.
Peppered moths
Before the industrial revolution in Britain, peppered moths were mostly pale as they were camouflaged against pale birch trees they rest on.
Pollution then blackened the birch trees with soot.
Other factors that affect health include:
Inherited factors e.g. blood cholesterol level
Pathogens
Bacteria
Microscopic living cells which can multiply rapidly in the body.
They release toxins that make us feel ill.
Diseases caused by Bacteria include: Food poisoning, cholera and typhoid.
Viruses
They are smaller than bacteria and have a protective protein coat that surrounds a genetic material.
They reproduce inside host cells and damage them when they do this.
They multiply inside the host cell and filling and burst it opens passing out into the blood.
Diseases caused by viruses include: Flu, colds, measles, mumps and rubella.
White blood cells
They can either ingest pathogens, destroying them
Or
Produce antibodies to destroy specific pathogens
Produce antitoxins to counteract the toxins released by pathogens
Lymphocytes release antibodies bind to antigens on pathogens which clumps them or damage/destroy them
Each lymphocyte produces a specific type of antibody which fit in a certain antigen.
When a lymphocyte releases the correct antibody, they reproduce very quickly and make many antibodies.
Phagocytes ingest pathogens.
Vaccination
Causes body to produce enough white blood cells to protect against a pathogen.
Antibiotics are effect against bacteria but do not work for viruses.
Vaccines contain:
Live pathogens which are harmless
Harmless fragments of the pathogens
Dead pathogens
These all act as antigens,
They stimulate white blood cells to produce antibodies against the pathogen.
If the person gets infected with the real pathogen, their body can respond faster.
Hygiene
In the 19th century, Ignaz Semmelweiss realised the doctors should wash their hands before examining patients which greatly reduced the number of deaths
Medicines
Painkillers relieve the symptoms of diseases but don’t kill pathogens E.g. Paracetamol.
Antibiotics kill bacteria or stop their growth, does not work against viruses, Penicillin was the first antibiotic discovered by Alexander Fleming.
Antibiotic resistance
Bacteria strains can develop resistance to antibiotics, this happens because of natural selection.
In a large population of bacteria,
Antibodies kill individual pathogens of the non-resistant strain
Resistant individual pathogens survive and reproduce.
Population of resistant pathogens increases
MRSA is a one of them. To avoid this happening we should avoid the unnecessary use of antibiotics and complete the full course of prescription given by the doctor.
Growing micro-organisms
We can investigate actions of antibiotics and disinfectants using cultures of micro-organisms (Population of micro-organisms that have been grown for a purpose)
Important that cultures are not contaminated by other micro-organisms so sterile conditions are needed:
Petri dishes, agar jelly must be sterilised
Inoculating loops sterilised (passed through Bunsen burner flame)
Safety
Dangerous to incubate cultures close to 37 degrees Celsius as it might allow growth of pathogens harmful to health. Max used in schools is 25 degrees Celsius. Higher temperatures are used industrially to speed it up.
Nerves and Hormones
The nervous system- allows the body to respond to changes in the environment coordinated by the Central nervous system (Brain and spine)
Reflex actions are faster responses to stimuli and involves the spine.
They are located in sense organs:
Eye has light receptors
Ears have sound receptors and also sense position of the head
Tongue has chemical receptors which detects chemicals in food
Nose has chemical receptors which detect chemicals in the air
Skin has touch receptors and detect pressure, pain and temperature
Neurones are nerve cells, which allows electrical impulses to travel.
Relay neurones carry messages from one part of the CNS to the other.
Motor neurones carry signals from CNS to effectors.
Signals cross this gap using chemicals, one neurons releases the chemical in the gap and it diffuses and the next neurone transmit and electrical signal.
When a receptor is stimulated it sends a signal to the central nervous system where the brain coordinates the response. But in a reflex action, it does not involve the brain.
Hormones are chemical substances that regulate processes in the body.
They are secreted by glands and travel through the bloodstream to their targeted organ.
Homeostasis is the maintenance of a constant internal environment.
Water in the body has to be controlled to protect cells from either too much water entering or leaving.
Water is lost through breathing, sweating and urine.
Hypothalamus in our brain detects water in blood, they make the pituitary gland to release more or less ADH depending on the water level in our blood. We produce More ADH if we have too little water in our blood. ADH reduces kidney blood water levels so we excrete less water in our urine ( more concentrated urine).
Adrenal gland produces adrenaline - prepares for rapid activity increases heart rate and level of sugar in the blood
Pancreas produces insulin which controls blood sugar level.
Testes produces testosterone which causes the changes at puberty and stimulates sperm production
Ovary produces oestrogen which causes changes at puberty and controls the menstrual cycle.
Monthly recurring process which the lining of the uterus is prepared for pregnancy. if pregnancy does not happen, the lining is shed at menstruation.
4- 14 Lining of uterus builds up
Day 14 egg released
14-28 lining maintained
The pill (oral contraceptive) reduces the chance of mature eggs being produced, it contains oestrogen or progesterone and inhibits the production of FSH.
+
Allows couples to choose time to start a family
-
Side effects include changes in wright, mood and blood pressure, Progesterone has less side effects
Helps women becoming pregnant, fertility drugs contain FSH and LH
It does not always work and multiple conceptions sometimes occur ( twins/ triplets)
Increases risk in pregnancy and may lead to premature babies.
Egg is fertilised outside the womb and planted in her uterus,
ethical concerns (designer babies)
Tropism is growth in response to a stimulus
Auxin is a plant hormone produced in stem tips and roots and controls direction of growth.
Plant grow towards water in soil and light from the sun.
Positive tropism where plants grow towards stimulus
Negative tropism where plants grow away from stimulus
geotropism- gravity
Shoot- Positive phototropism/ Negative geotropism
Root- Negative phototropism/ Positive geotropism
Made at tip of roots and shoots and can diffuse to other parts of the root or shoot.
They change the rate of elongation controlling how long they become.
Cells in shoots grow more
Cells in roots grow less.
Weed killers contain growth hormones that cause weeds to grow too quickly and die, it is absorbed in larger quantities in weeds than other plants. so wanted plants stay healthy
Drugs
Drugs are substances that change chemical reactions in the body.
Medical drugs relieve diseases and illness.
Recreational drugs are used for pleasure.
Developing new drugs
- Drugs are tested using computer models and human cells growth in the laboratory. (Many substances fail this test as they damage the cell or don’t work)
- Drugs that pass the first stage are tested on animals. They are monitored carefully for any side effects.
- Drugs that passed the animal test are used in clinical trials. They are tested on healthy volunteers to check if they are safe. Low doses are used at the beginning and further clinical trials are done to find the optimum dose for the drug.
Double blind trials
People feel better from a drug because they have taken a medicine called a placebo effect.
Double blind trials are used to minimise the placebo effect.
Some people are given the drug whilst others are given a placebo.
A placebo does not contain the drug.
Doctors and patients are both not told which have taken the placebo or drug until the trial is over.
Thalidomide is medical drug that caused an unexpected and serious damage to unborn babies.
First developed as a sleeping pill, it was thought to be useful for easing morning sickness but hasn’t been tested for use in this way.
It was found to have damaged the development of unborn babies, it lead to babies born very short or incompletely formed. More than 10,000 babies were affected around the world.
Thalidomide was banned and drug testing was made more rigorous than before.
Thalidomide is used as a treatment for leprosy and bone cancer now.
Alcohol and nicotine are legal recreational drugs.
Alcohol is a depressant so it slows down signals in the nerves and brain.
It is addictive and long term effects of alcohol include damages to the liver and brain and it is often the cause of weight gain. Small amounts of alcohol can be relaxing but large amounts lead to aggression and sometimes unconsciousness.
Nicotine is found in tobacco smoke
100,000 people die each year from smoking related illnesses.
It is addictive.
It increases the risk of heart diseases and strokes
Premature birth
Lung cancer, mouth + throat cancer
It deposits tar in the lung.
Illegal drugs
Heroin and cocaine are very addictive, they damage the heart and circulatory system, and cannabis can cause mental illness in some people.
Recreational drugs can damage health indirectly (people spending less money on food to buy drugs)
Injecting drugs through a syringe can lead to HIV.
Adaptations
Adaptations help organisms survive in the habit.
Organisms compete with each other for limited resources which includes water and space.
Plants also compete with each other for lights and minerals.
Ecological words
Environment- all the conditions that surround living organism
Habitat- the place where organism lives
Population- the amount of a single species that live in habit
Community- all the populations of different organisms that live in habitat
Ecosystem- community and its habitat
Competition
Organisms will die if they are unsuccessful in competing for resources
Resources that animal compete include water, food and space
Plants compete for water space and mineral salts
Cold climates
Plants in the Arctic grows very close to the ground and have small leaves this helps them to conserve water
Polar bears are adapted for survival in the Arctic they have white fur as camouflage from prey
They have a thick layer of fat and fur for insulation
They have a small surface area to volume ratio which minimises heat loss
Hot climates
Camels have large flat feet to spread their weight on the sand
They have thick fur on the top of the body for shade and thin fur elsewhere to allow easy heat loss
A larger surface area to volume ratio which maximises heat loss
They have the ability to go for a long time without water
Desert plants
Cacti has to stems that can store water
Widespread root systems that can collect water from a large area.
Cacti have spines instead of leaves. These minimise the surface area and reduce water loss by transpiration. The spines also protect the cacti from animals that might eat them.
Extremophiles
They are organisms that live in very extreme environments which would kill most other organisms
Extreme conditions include
High temperature
High concentrations of salt in the water
High pressures.
Changes in the environment may affect distribution and behaviour of organisms.
Growing predator numbers will reduce the number of food supply so it can no longer sustain the predator population and number of predator goes down.
Most common source of air pollution is the burning of fossil fuels. Lichens can be used as air pollution indicators.
Lichens are plants that grow on places such as rocks or tree bark.
They are very good at absorbing water and nutrient to grow.
Air pollutant dissolved in rainwater make it more acidic and damages lichens preventing them from growing.
Bushy lichens need really clean air
Leafy lichens can survive a small amount of pollution
crusty lichens can survive in more polluted air
Many aquatic invertebrate animals cannot survive in polluted water so their numbers can indicate how polluted the water is.
Clean- mayfly larva
Low- fresh water shrimp
high- water louse
Very high- rat tailed maggot, sludge worm
Temperature can be measured using a normal thermometer.
Food Chains
A food chain shows what eats what in a particular habitat.
A pyramid of biomass shows the mass of living material at each stage.
The amount of biomass decrease from one stage to the next.
Plants absorb some of the light from the sun and turns this into chemical energy stored as sugar during photosyntheses.
Primary consumers - Herbivores
Secondary consumers - Carnivores
Predators - animals that kill for food
A prey is an animal that a predator feed on
Scavengers feed on dead animals
Decomposers feed on dead and decaying organisms.
Not all energy is transferred to the next organism it decreases from one to the next.
Some energy goes into growth and production of offspring. This energy becomes available to the next stage.
Others are used up e.g.
Energy released through respiration used for movement and processes. This is lost as heat to the surroundings
Energy is lost in waste material such as faeces
Microorganisms cause decay by releasing enzymes that break down compounds which are absorbed by their cells.
Bacteria and fungi are the main groups of decomposers.
Moisture
Temperature
Amount of oxygen available
Substances released during decay are used by plants for growth.
Plants remove carbon dioxide by photosynthesis, the carbon becomes part of protein, fats and carbohydrates in the plant.
Remains of dead animal and plants have carbon that are transferred to microorganisms and detritus feeders
Genetic information
Offsprings resemble parents as genetic information are pass from the parents
Chromosomes and genes
Chromosomes are found in the nucleus of cells and contains many genes.
A gene is a section of a DNA which carries coding for a particular protein.
Different genes control the development of different characteristics of organisms.
Variation
Genetic
Inherited variation- offsprings carry half of their inherited features from each parent.
Environmental factors
Climate, diet, accidents and lifestyle can cause changes in animals and plants.
E.g Eating too much causes you to be heavier.
Reproduction
Sexual reproduction produces offspring that are not identical
Asexual reproduction produces offspring that are genetically identical to their parents
Sex cells are called gametes.
Male have sperm
Female have eggs or ova.
Fertilisation is when a sperm and egg fuse together, genetic information is mixed from both parents.
Gametes contain 23 chromosomes and when they fuse they contain 46 chromosomes which is what a normal cell has.
Asexual reproduction only needs one parent offsprings are clones.
Asexual reproduction mostly happen in plants
Artificial cloning in plants
This allows us to produce a lot of identical new plants.
Cuttings
A branch from the parent is cut off.
Its lower leaves removed and the stem planted.
Plant hormones are often used to encourage new roots to develop.
The cutting is often covered in a clear plastic bag to keep it moist and warm.
Roots develop and a new plant is produced.
Tissue culture works with tiny tissues from the parent plant.
Sterile agar jelly with plant hormones with lots of nutrient allows it to grow into a plant.
Artificial cloning in animals.
Allows features of an animal to be reproduced several times.
Embryo transplant
A developing embryo is removed from a pregnant animal.
Cells are separated and grown for a while and transplanted into host mothers.
Adult cell cloning
Nucleus is removed from an unfertilised cell egg.
A Nucleus is removed from an adult body cell and injected into the empty egg cell.
An electric shock is applied to make the egg cell begin to divide to form an embryo.
The embryo continues to grow and develop.
Dolly the sheep is the first animal to be cloned using this method.
Genetic modification.
it modifies a gene in an organism for unique features.
DNA from an organism can be cut using certain enzymes.
The gene can be removed and placed into a gap in the DNA of another organism.
E.g. New genes can be transferred to crop plants to make them resistant to herbicides.
GM can be useful in many cases but some people think it is unethical as it has limitless possibilities. Some say that they may harm humans.
Evolution
It caused controversy and was only gradually accepted.
It conflicted with religious views
He did not have enough evidence but is not supported by evidence from fossils and by rapid changes that can be seen to occur in organisms.
Individuals in a species have a large range of variation as they have a difference in their gene.
Individuals with characteristics more suited for the environment are more likely to survive and reproduce.
Genes of these individuals pass down to offsprings.
Individuals poorly adapted are less likely to survive and reproduce.
Evolutionary trees are used to represent relationships between organisms.
Characteristics used by an organism becomes stronger, one that is not used eventually disappears. Features of an organism is improved as use is passed to its offsprings.
A rapid change in a species may happen if the environment changes.
Moths with a mutant black colouring were easily spotted and eaten by birds.
The white variety had an advantage and were more likely to survive and reproduce
Mutant black moths were now camouflaged and pale moths were more vulnerable to predators.
Black moths were more likely to survive and reproduce and is far more numerous in urban areas.