Ecosystems Organisms need resources to stay alive. Plants need light, water, carbon dioxide, oxygen, warmth and mineral ions. Animals need oxygen, food, water and shelter. Organisms are continually interacting with the environment to in ecosystems to form communities,...
Efficiency of Exchange and Transport in Organisms Organisms need to transport substances in and out for a range of reasons. Oxygen, glucose and water are needed for respiration and to carry around substances, while urea, carbon dioxide and excess salts must be...
Hormones The hormonal system is response system in humans that uses chemical messengers called hormones, which are carried by the blood so take time to move around the body from the endocrine gland in which they are produced, to send messages. The pituitary gland...
Photosynthesis Photosynthesis is the process by which plant gain biomass, and therefore photosynthetic organisms are the main produces of food. It is an endothermic reaction where energy transferred by sunlight reaches the chloroplasts, and carbon dioxide and water...
Health and Disease Health is defined as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity (World Health Organisation). Communicable Diseases are caused by a disease-causing organism called pathogens, such as...
Reproduction Most animals and plants reproduce sexually, involving the fertilisation of a female sex cell with a male sex cell, while other organisms can reproduce asexually to produce clones. Reproduction Advantages Disadvantages Sexual Combines...
The Theory of Evolution by Natural Selection In the Galapagos Islands in 1835, Charles Darwin noticed how different mockingbirds were suited to aspects of the island and came up with the idea that species best suited to the environment will survive and reproduce....
Growth and Repair The Cell Cycle has two parts: interphase and mitosis. During interphase, the cell haves extra sub-cellular parts and DNA replication occurs. Mitosis is the production of two diploid daughter cells, each with identical sets of chromosomes in the...
Cells All organisms are made of cells. Eukaryotic cells are complex and include plant and animal cells, while prokaryotic cells are simple and unicellular, i.e. bacteria. These cell types contain different structures: Specialised Cells are adapted to their functions....
The menstrual cycle has four stages Stage 1: Day 1 is when the bleeding starts. The uterus lining breaks down and is released. Stage 2: The lining of the uterus builds up again, from day 4 to day 14, into a thick spongy layer of blood vessels ready to receive the...
Sex determination Women have two X chromosomes and men have one X and one Y. The 23rd pair of chromosomes is called the sex chromosomes. When making sperm, the X and Y chromosomes are drawn apart in the first division in meiosis. There’s a 50% chance each sperm cell...
Monoclonal antibodies Monoclonal antibodies: many identical antibodies. These were invented for making large quantities of antibodies for identifying particular substances. A lymphocyte can divide over and again to make identical clones of itself. However, once it...
The kidneys The Kidneys help maintain the internal environment by: Filtering the blood Reabsorbing all the sugar Reabsorbing the dissolved ions needed by the body Reabsorbing as much water as the body needs Releasing urea, excess salts and excess water as urine. Blood...
Biological rhythms Biological rhythms that happen across one day are circadian rhythms. For example, in human brains there is a timing mechanism called a biological clock which regulates the things that occur in our body over a 24 hour period and can be influenced by...
A GM future Genetically modified maize, soya and cotton are widely grown in both developed and developing countries. Many of these have a gene that makes them resistant to an herbicide. This means crops are not damaged by the chemical but the weeds growing with them...
Photoperiodism This is controlled by plant genes. The way in which living organisms respond to changes in day length. An example of this is deciduous trees as they lose their leaves in winter as the days become shorter. The plants use the change in day length to help...
Plant defences Plants can be attacked by insects or pathogens. If this happens to crops, crop yield can be severely reduced as the plants are eaten, which will increase the price of the crop in the long run. As a result, plants can produce chemicals to protect the...
Microorganism growth Much is done to keep numbers of bacteria in milk as low as possible; the milking equipment is sterilised, the cow’s udders are washed before milking and most milk is cooled rapidly to slow the growth of bacteria. It is then pasteurised. If...
Vaccines Edward Jenner founded the idea of vaccination. He realised that people who got cowpox didn’t get smallpox. In 1796 Jenner took pus from a cowpox blister and rubbed it into the skin of an 8-year-old boy. He got a mild fever but that was all. He did the same...
White blood cells There are two types of white blood cells. Phagocytes and Lymphocytes. They both get rid of pathogens. Phagocytes get rid of pathogens by phagocytosis: Step 1: encounters foreign body or pathogen Step 2: engulfs the foreign body or pathogen Step 3:...
Enzyme Technology Meat contains fibres which are tough if you don’t beat it to break up the fibres. Pineapple juice, which contains enzymes that tenderise the meat, is sometimes added to meat in recipes to break down the protein fibres. Yoghurt production The...
Breeding plants Unfortunately, as the human population grows many people all over the world do not have enough food. The World Health Organisation has said there is a ‘global food security crisis’. Global food security: the ability to produce enough food in the future...
Biofuels Our increasing population also needs more energy for industry, transport and other uses. However, most people agree we need to reduce our use of fossil fuels. Replacements for them are biofuels. Biofuels are fuels that are made from biomass (plants, animals...
Enzymes in digestive system Three main types of digestive enzyme: Protease (digests proteins) Carbohydrase (digests carbohydrates) Lipase (digests fats) Digesting carbohydrates Food like bread and pasta are full of large carbohydrates. They simplest carbohydrates are...
Probiotics and prebiotics Functional foods are eaten by people in order to make themselves healthier. Probiotics These contain live bacteria such as Lactobacillus and Bifidobacteria which are ‘friendly’. They are similar to those found naturally in the gut and produce...
Biotechnology Biotechnology: using living organisms (especially microorganisms) to produce useful products (e.g. food, medicines) or to provide people with services (e.g. waste management, water purification). Biomolecule: a chemical or substance produced by a living...
Fermenters Modern biotechnology often involves big steel vessels, called fermenters, in which microorganisms are grown. Inside these fermenters, the microorganisms are provided with exactly the right conditions to encourage them to grown and produce the substances we...
Microorganisms for food In the early 1960s, scientists were looking for cheap sources of protein. They tried cultivating bacteria, fungi and other kinds of microorganisms. Fusarium was the successful fungus found. It is sold commercially as QuornTM. Fusarium is made...
Factors affecting yoghurt making Yoghurt is made from milk by bacteria such as Lactobacillus bulgaricus. The bacteria live on the sugars in the milk. They convert lactose into lactic acid as they aspire anaerobically (glucose à lactic acid) A variety of factors affect...
The heart The heart consists of four chambers and four major blood vessels. Deoxygenated blood goes to the right side and oxygenated blood into the left side. The two sides of the heart are completely separated by the muscular septum. ...
The Digestive System Food contains a lot of large, insoluble molecules that need to be broken down into smaller soluble molecules. This is so they can be absorbed and used by the body. Digestion is the process of breaking down food which takes place in the organ...
Villi These absorb the soluble molecules of food. There are millions of villi covering the interior of the small intestine. Villi massively increase the surface area of the small intestine so more diffusion of substances can take place. Each villus has a good network...
Plant transport systems Plants have two specialised tissue: xylem and phloem which carry minerals, salts and water up and down the plant. Xylem tissue consisting of long dead cells that die and form hollow tubes. These tubes also give support to the plant. Xylem...
Growth Growth in an organism is the increase in the number of cells and cell size. There are three ways growth can be measured: Size: height, width, length, circumference Wet mass: the mass of the organism including all the water in the body. It can vary from day to...
Fossils and evolution Fossils are the preserved traces of organisms that lived millions of years ago. Fossils are formed in 3 ways: A buried organism in soft material such as clay decays and leaves a cast/imprint of the organism. Footprints can be preserved this way....
Cells make up tissues, organs and systems Tissue: a tissue (e.g. muscle tissue) is a group of similar cells that work together to carry out a particular function. Organ: An organ is a group of different tissues that work together to perform a particular function....
Photosynthesis This is the process for plants that produces their ‘food’. Also needs sunlight and chlorophyll. Plants need to respire as well as photosynthesise. Photosynthesis is their way of getting glucose (which is stored as starch) for respiration. Chloroplasts...
Osmosis Osmosis: The movement of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential. Osmosis is a special type of diffusion as it only involves water particles. In the context of a partially...
Clones Clones are individuals which are genetically identical. Making plant clones – bit of leaf, stem or root is planted to form a clone of the original plant – is far easier than cloning animals. Clone: These are individuals that genetically identical. Stages in the...
Microscope Magnification Microscopes have improved greatly over the past 350 years. The best modern light microscopes can magnify specimens more than 1500 times. As a result, we can observe very small structures inside cells. For example, we can see inside bacterial...
The Human Genome Project This is thousands of scientists collaborating to find every single human gene. Human DNA is made up of about 25,000 genes curled up to form 23 chromosomes. If the scientists work together, they can share resources and reduce costs. The...
Genetic engineering Scientists can now remove a gene from one organism and insert it into the DNA of another. This is called genetic engineering. This technique produces a genetically modified organism. Benefits of genetic engineering Reducing vitamin A deficiency...
Plant cells and animal cells Even though they belong to different organisms, plant and animal cells have some features in common: Cell Membrane – separates the contents of the cell and its surroundings. It controls the movement of substances like glucose, oxygen and...
Human activity and the Environment Rapidly growing population The population of the world is growing exponentially which means it is growing very quickly. This is mostly due to modern medicine, making people live longer and more babies to survive at birth. It is also...
The Discovery of DNA structure It was in 1962 when James Watson and Francis Crick along with Maurice Wilkins were awarded a Nobel Prize for discovering the structure of DNA. In the 1950s, in London, Rosalind Franklin and Maurice Wilkins used X-Ray photography to study...
Physical and Chemical barriers These are both harnessed by the body to stop pathogens getting in. Physical barriers Skin: Outer layer skin cells contain keratin which makes the skin very effective at protecting against microorganisms. If damaged, blood clots can seal...
Food webs Interdependence: When organisms in an area depend on each other for food. All organisms require food to survive. Some organisms are producers and make their own food, such as green plants, and the rest get their food from other organisms. They are either...
Indicator species An indicator species is an organism whose presence, absences or abundance reflects a specific environmental condition. Indicator species can signal a change in the biological condition of a particular ecosystem and thus may be used to diagnose the...
The Carbon Cycle • The Carbon Cycle: A sequence of processes by which carbon moves from the atmosphere, through living and dead organisms, into sediments and into the atmosphere again. • The only way carbon dioxide is removed from the atmosphere is by photosynthesis –...
The Nitrogen Cycle The Nitrogen Cycle: A sequence of processes by which nitrogen moves from the atmosphere through living and dead organisms, into the soil and back to the atmosphere. There are four main types of bacteria involved in the Nitrogen Cycle: Decomposer...
Ethics and organ transplants If an organ is severely damage it can be replaced by a donated natural organ. Many people die every year waiting for transplants so the doctors need to decide carefully who to operate on. There is a shortage of organ donors in the UK. Some...
Infectious diseases Pathogens are microorganisms that cause disease. They include bacteria, protozoa, fungi and all viruses. Pathogens are spread in different ways: Water: Water may contain bacteria such as those that cause cholera. Food: Food may contain food...
The Nervous System A stimulus is a change in the environment that you may need to react to. We have five sense organs: eyes, ears, nose, tongue and skin. They all contain different receptors which are groups of cells sensitive to a stimulus. They change stimulus...
Tropisms Tropism: a growth movement in response to a stimulus. Plants grow towards or away from stimuli. A growth movement towards a stimulus is called a positive tropism. A growth movement away from a stimulus is called a negative tropism. Light; phototropism...
Reflexes Reflexes have to be quick and they are so because they are automatic. The message of a reflex does not go up the brain which is why they are involuntary. Many reflexes occur naturally such as accommodation and sneezing but some can be learned e.g. conditional...
Insulin and Diabetes Insulin and glucagon control blood sugar levels. Insulin reduces glucose in the blood and glucagon converts glycogen (a store of glucose in the liver) back into glucose. Glucose is added into the body through foods containing carbohydrates....
Uses of plant hormones Selective weedkillers Artificial auxin is used as a selective weedkiller as it makes plants with broad leaves, like dandelions and daisies grow out of control and die. This means plants with narrow leaves, such as wheat and grass, are...
Effects of alcohol Short term effects Alcohol slows down reactions because it is a depressant. Being drunk can lead to blurred vision (making it more difficult to do simple tasks) and can lower inhibitions – people may do things they normally wouldn’t. The more...
Drugs A drug is a chemical substance that changes the way in which the body works, including our behaviour. Some drugs particularly affect the central nervous system and change our psychological behaviour. There are different types of drugs: Narcotic: is a drug that...
Punnett squares and family pedigrees Specific genetic disorders Genetic disorders are diseases which are caused by faulty alleles. The allele for sickle cell anaemia is recessive so two copies are needed to suffer from the illness. Sickle Cell Anaemia is bad as the...
Hormones and Nerves Hormones and Nerves Hormones Hormones are chemical messengers which travel the blood to activate target cells. Hormones are released directly into the blood stream and are carried around the body until they reach their target organ/cells. The...
Homeostasis Conditions in our body need to be maintained and controlled so cells can function properly. For example: Osmoregulation: This is the regulation of water content. A balance needs to be kept between water gained and water lost. Thermoregulation: This is the...
Adaptions Deep under the surface of the sea, conditions are hard to live in. Food is scarce due to lack of sun, thus lack of photosynthesis, and thus organisms survive on scraps that sink down from above. Some animals have adapted to living in the deep ocean: Some...