EDEXCEL INTERNATIONAL GCSE (9–1) BIOLOGY Notes

EDEXCEL INTERNATIONAL GCSE (9–1) BIOLOGY

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Course Structure

  • Unit 1: Organisms and Life Processes
    • Life Processes
    • The Variety of Living Organisms
  • Unit 2: Animal Physiology
    • Breathing and Gas Exchange
    • Food and Digestion
    • Blood and Circulation
    • Coordination
    • Chemical Coordination
    • Homeostasis and Excretion
    • Reproduction in Humans
  • Unit 3: Plant Physiology
    • Plants and Food
    • Transport in Plants
    • Chemical Coordination in Plants
    • Reproduction in Plants
  • Unit 4: Ecology and the Environment
    • Ecosystems
    • Human Influences on the Environment
  • Unit 5: Variation and Selection
    • Chromosomes, Genes and DNA
    • Cell Division
    • Genes and Inheritance
    • Natural Selection and Evolution
    • Selective Breeding
  • Unit 6: Microorganisms and Genetic Modification
    • Using Microorganisms
    • Genetic Modification
  • Appendices
    • Appendix A: A Guide to Exam Questions on Experimental Skills
    • Appendix B: Command Words
    • Glossary
    • Index

About This Book

  • Designed for students following the Edexcel International GCSE (9–1) Biology specification and the Edexcel International GCSE (9–1) Science Double Award specification.
  • Content clearly indicates what is in the Biology examinations and not in the Double Award specification.
  • Includes explanations, worked examples, and exercises.
  • Describes methods for carrying out required practicals.
  • Language graded for speakers of English as an additional language (EAL).
  • Advanced Biology-specific terminology highlighted and defined in the glossary.
  • Includes a list of command words.
  • Features Progression icons and Skills tags.

Assessment Overview

  • Paper 1
    • Paper code 4BI1/1B and 4SD0/1B
    • Biology and Science Double Award.
    • 61.1%
    • 110 marks
    • 2 hours
    • January and June examination series
  • Paper 2
    • Paper code 4BI1/2B
    • Biology
    • 38.9%
    • 70 marks
    • 1 hour 15 mins
    • January and June examination series
  • Assessment Objectives:
    • AO1: Knowledge and understanding of biology (38%–42%)
    • AO2: Application of knowledge and understanding, analysis and evaluation of biology (38%–42%)
    • AO3: Experimental skills, analysis and evaluation of data and methods in biology (19%–21%)
  • Students may be tested on their ability to:
    • Solve problems in a practical context.
    • Apply scientific knowledge in practical questions.
    • Devise and plan investigations, using scientific knowledge when selecting techniques.
    • Demonstrate experimental methods, including safe techniques.
    • Make observations and measurements with precision and record them methodically.
    • Identify independent, dependent and control variables.
    • Analyze and interpret data to draw conclusions.
    • Communicate findings using appropriate language and graphs.
    • Assess the reliability of an experimental activity.
    • Evaluate data and methods, considering factors affecting accuracy and validity.
  • Calculators are permitted in the examinations (excluding those with QWERTY keyboards or text retrieval).

Unit 1: Organisms and Life Processes

  • All living organisms are composed of microscopic units known as cells.
  • Cells grow, reproduce, and generate more organisms.
  • Chapter 1: Structure and function of cells, and essential life processes.
  • Chapter 2: Diversity of living things and classification into groups based on features.

Unit 1: Life Processes - Chapter 1

  • All living organisms are composed of cells.
  • Simplest organisms: single cells.
  • Complex organisms: millions of cells.
  • Multicellular organisms: hundreds of different cell types with different structures.
  • Cells are specialized to carry out particular functions.
  • Basic features are the same in all cells.
  • Eight life processes:
    • Nutrition: plants make their own food, animals eat other organisms.
    • Respiration: release energy from their food.
    • Excretion: get rid of waste products.
    • Respond to stimuli: sensitive to changes in their surroundings.
    • Move: muscles in animals, slow growth movements in plants.
    • Control internal conditions: maintain a steady state inside the body.
    • Reproduce: produce offspring.
    • Grow and develop: increase in size and complexity.
  • Most cells contain parts such as the nucleus, cytoplasm and cell membrane.
  • Some cells have structures missing, for instance red blood cells are unusual in that they have no nucleus.
  • Living material that makes up a cell is called cytoplasm.
  • Organelles are structures within the cytoplasm (details seen under an electron microscope).
  • Nucleus:
    • Largest organelle.
    • Controls cell activities.
    • Contains chromosomes (46 in human cells) which carry genes.
    • Genes determine which proteins the cell can make.
    • DNA remains in the nucleus.
    • Instructions for making proteins are carried to the cytoplasm.
    • Proteins are assembled on ribosomes.
  • Enzymes:
    • Control chemical reactions in the cytoplasm.
  • Cell membrane:
    • Thin layer ('skin') on the cell surface.
    • Boundary between cytoplasm and the outside.
    • Partially permeable: some chemicals can pass into the cell and others can pass out.
    • Selectively permeable: controls the movement of some substances.
  • Mitochondrion (plural mitochondria):
    • Found in the cytoplasm of all living cells.
    • Carry out some reactions of respiration.
    • Release energy that the cell can use.
    • Most of the energy from respiration is released in the mitochondria.
  • Plant cells contain the cell wall, permanent vacuole and chloroplasts.
  • Cell wall:
    • Layer of non-living material outside the cell membrane.
    • Made mainly of cellulose.
    • Helps the cell keep its shape.
    • Porous, so it is not a barrier to water or dissolved substances.
    • Called freely permeable.
  • Vacuole:
    • Large central space surrounded by a membrane.
    • Permanent feature of the cell.
    • Filled with cell sap, which is a store of dissolved sugars, mineral ions and other solutes.
    • Watery liquid within the vacuole.
  • Chloroplast:
    • Cells of the green parts of plants, especially the leaves, contain chloroplasts.
    • Absorb light energy to make food in photosynthesis.
    • Contain a green pigment called chlorophyll.
    • Cells from non-green parts of plants have no chloroplasts.
  • Enzymes are biological catalysts.
    • They speed up a reaction without being used up themselves.
    • Cells contain hundreds of different enzymes, each catalysing a different reaction.
    • The activities of a cell are controlled by enzymes.
    • genes → proteins (enzymes) → catalyse reactions.
    • Necessary because temperatures inside organisms are low to allow life to go on.
  • Metabolic reactions:
    • The chemical reactions taking place in a cell are metabolic reactions.
    • The sum of all the metabolic reactions is known as the metabolism of the cell.
    • The function of enzymes is to catalyse metabolic reactions.
  • Secretion:
    • Secretion is the release of a fluid or substances from a cell or tissue.
  • Extracellular enzymes:
    • In the intestine enzymes are secreted onto the food to break it down.
    • These are called extracellular enzymes, which means they function ‘outside cells’.
    • Digestive enzymes are extracellular.
  • Intracellular enzymes:
    • Most enzymes stay inside cells and carry out their function there; they are intracellular.
  • Substrate:
    • The molecule that an enzyme acts on is called its substrate.
  • Active site:
    • Each enzyme has a small area on its surface called the active site.
    • The substrate attaches to the active site of the enzyme.
  • Lock and key model:
    • The substrate fits into the active site of the enzyme like a key fitting into a lock.
    • Just as a key will only fit one lock, a substrate will only fit into the active site of a particular enzyme.
    • This is known as the lock and key model of enzyme action.
    • It is the reason why enzymes are specific, i.e. an enzyme will only catalyse one reaction.
  • Optimum temperature means the ‘best’ temperature, in other words the temperature at which the reaction takes place most rapidly.
  • Kinetic energy is the energy an object has because of its movement. The molecules of enzyme and substrate are moving faster, so they have more kinetic energy.
  • From 40 °C upwards, the heat destroys the enzyme. We say that it is denatured.
  • Denaturing changes the shape of the active site so that the substrate will no longer fit into it.
  • Denaturing is permanent – the enzyme molecules will no longer catalyse the reaction.
  • The pH around the enzyme is also important. The pH inside cells is neutral (pH 7) and most enzymes have evolved to work best at this pH.
  • The pH at which the enzyme works best is called its optimum pH.

Unit 1: Life Processes - Cell Energy, Movement, Cell Division (Biology Only)

  • Respiration:
    • A cell needs a source of energy in order to be able to carry out all the processes needed for life.
    • It gets this energy by breaking down food molecules to release the stored chemical energy that they contain.
    • Respiration happens in all the cells of our body.
  • Aerobic respiration:
    • Oxygen is used to oxidise food.
    • Carbon dioxide (and water) are released as waste products.
    • The main food oxidised is a sugar called glucose.
    • glucose + oxygen → carbon dioxide + water (+ energy)
    • C<em>6H</em>12O<em>6+6O</em>2→6CO<em>2+6H</em>2OC<em>6H</em>{12}O<em>6 + 6O</em>2 → 6CO<em>2 + 6H</em>2O (+ energy)
    • Happens in the cells of humans and those of animals, plants and many other organisms.
    • Takes place gradually, as a sequence of small steps, which release the energy of the glucose in small amounts.
    • Each step in the process is catalysed by a different enzyme.
    • The later steps in the process are the aerobic ones, and these release the most energy.
    • They happen in the mitochondria of the cell.
  • ATP – adenosine triphosphate or ATP:
    • ATP is composed of an organic molecule called adenosine attached to three phosphate groups.
    • Transfers energy between the process that releases it (respiration) and the processes in a cell that use it up.
  • Anaerobic respiration:
    • Cells can respire without using oxygen.
    • In anaerobic respiration, glucose is not completely broken down, so less energy is released.
    • It can occur in situations where oxygen is in short supply.
    • Two important examples of this are in yeast cells and muscle cells.
  • Anaerobic respiration in Yeast cells:
    • glucose → ethanol + carbon dioxide (+ some energy)
    • The ethanol from this type of respiration is the alcohol formed in wine- and beer-making.
    • The carbon dioxide is the gas that makes bread dough rise.
  • Anaerobic respiration in Muscle cells:
    • glucose → lactate (+ some energy)
    • The volume of oxygen needed to completely oxidise the lactate that builds up in the body during anaerobic respiration is called the oxygen debt.
  • Diffusion is the net movement of particles (molecules or ions) from a region of high concentration to a region of low concentration, i.e. down a concentration gradient.
  • Active transport is the movement of substances against a concentration gradient, using energy from respiration.
  • Osmosis in cells is the net movement of water from a dilute solution to a more concentrated solution across the partially permeable cell membrane.
  • 'Adapted’ or ‘an adaptation’ means that the structure of a cell or an organism is suited to its function.
  • Multicellular organisms like animals and plants begin life as a single fertilised egg cell, called a zygote.
  • Mitosis:
    • This divides into two cells, then four, then eight and so on, until the adult body contains countless millions of cells.
    • First of all the chromosomes in the nucleus are copied, then the nucleus splits into two.
    • So that the genetic information is shared equally between the two ‘daughter’ cells.
    • The cytoplasm then divides (or in plant cells a new cell wall develops) forming two smaller cells.
  • Differentiation:
    • As the developing embryo grows, cells become specialised to carry out particular roles.
    • This specialisation is also under the control of the genes, and is called differentiation.
  • Cells with a similar function are grouped together as tissues.
  • A collection of several tissues carrying out a particular function is called an organ.
  • Organ system:
    • In animals, jobs are usually carried out by several different organs working together.
    • The digestive system consists of the gut, along with glands such as the pancreas and gall bladder. The function of the whole system is to digest food and absorb the digested products into the blood.
  • Stem cell:
    • A stem cell is a cell that has the ability to divide many times by mitosis while remaining undifferentiated.
    • Later, it can differentiate into specialised cells such as muscle or nerve cells.
  • Embryonic stem cells are found in the early stage of development of the embryo. They can differentiate into any type of cell.
  • Adult stem cells are found in certain adult tissues such as bone marrow, skin, and the lining of the intestine. They have lost the ability to differentiate into any type of cell but can form a number of specialised tissues.
  • The use of stem cells to treat (or prevent) a disease, or to repair damaged tissues is called stem cell therapy.

Unit 1: Variety of Living Organisms - Chapter 2

  • There are more than ten million species of organisms alive on Earth today.

  • Biologists classify organisms, putting them into groups.

  • Members of each group are related by common ancestry and reflect similarities of structure and function.

  • The five major groups of living organisms are plants, animals, fungi, protoctists and bacteria.

  • Plants:

    • Flowering plants, mosses and ferns.
    • Multicellular.
    • Cells contain chloroplasts, carry out photosynthesis.
    • Cell walls made of cellulose.
    • Make organic compounds as a result of photosynthesis.
    • Store the carbohydrate starch.

  • Animals:

    • Sponges, molluscs, worms, starfish, insects, crustaceans, fish, amphibians, reptiles, birds and mammals.
    • Multicellular.
    • Cells never contain chloroplasts.
    • Gain nutrition by feeding on other animals or plants.
    • Cells lack cell walls.
    • Store carbohydrate in their cells as a compound called glycogen.

  • Fungi:

    • Mushrooms, toadstools, moulds, yeasts.
    • Cells of fungi: cell walls are not composed of cellulose, and never contain chloroplasts.
    • Mushroom or toadstool, called a fruiting body.
    • Fine thread-like filaments called hyphae.
    • The whole network called a mycelium.
    • Moulds feed by absorbing nutrients from dead material.
    • Saprotrophic nutrition: digestion takes place outside of the organism.
    • Enzymes secreted out of cells are called extracellular enzymes.

  • Protoctists:

    • 'Dustbin kingdom’.
    • Mixed group of organisms that don’t fit into the plants, animals or fungi.
    • Microscopic single-celled organisms.
    • Protozoa: Amoeba
    • Algae- have chloroplasts and carry out photosynthesis.

  • Eukaryotic Organisms:

    • Eukaryotic’ means ‘having a nucleus’ – their cells contain a nucleus surrounded by a membrane, along with other membrane bound organelles, such as mitochondria and chloroplasts.

  • Prokaryotic Cells:

    • Simpler cells, which have no nucleus, mitochondria or chloroplasts.
    • Prokaryotic’ means ‘before nucleus’.
    • The main forms: bacteria.
    • Bacteria are small single-celled organisms.

  • Bacteria:

    • Cells are much smaller and have a much simpler structure than those of eukaryotic organisms.
    • Three basic shapes of bacteria: spheres, rods and spirals.
    • Surrounded by a cell wall protecting the bacterium and keeps the shape of the cell. Cell wall are not made of cellulose but a complex compound of sugars and proteins called peptidoglycan.
    • Bacterium has no nucleus: genetic material (DNA) is in a single chromosome, loose in the cytoplasm, forming a circular loop.
    • Contain a form of chlorophyll in their cytoplasm, and can carry out photosynthesis.
    • Important decomposers, recycling dead organisms and waste products in the soil and elsewhere.
    • Used by humans to make food, such as Lactobacillus bulgaricus.

  • Pathogens: organisms that cause disease.

  • Viruses:

    • All viruses are parasites, and can only reproduce inside living cells. The cell in which the virus lives is called the host.
    • Much smaller and simpler than bacterial cells.
    • Are not made of cells. A virus particle is very simple. It has no nucleus or cytoplasm, and is composed of a core of genetic material surrounded by a protein coat DNA, or a similar chemical called RNA.
    • Viruses do not feed, respire, excrete, move, grow or respond to their surroundings. They only ‘reproduce’ but can in a parasitic manner.
    • Biologists do not consider viruses to be living organisms. A virus reproduces by entering the host cell and taking over the host’s genetic machinery to make more virus particles.

Unit 2: Animal Physiology

  • Physiology: branch of biology that looks at how living things function, studying the workings of an organism at different levels from cells, tissues and organs through to the whole organism.
  • Knowledge of the body is essential in understanding how to treat it when it goes wrong.

Unit 2: Breathing and Gas Exchange - Chapter 3

  • Cells get energy by oxidising foods such as glucose, during the process called respiration.
  • If cells are to respire aerobically, they need a continuous supply of oxygen from the blood.
  • Carbon dioxide from respiration needs to be removed from the body.
  • In humans, these gases are exchanged between the blood and the air in the lungs.
  • Difference between respiration and breathing:
    • Respiration: oxidation reaction that releases energy from foods such as glucose.
    • Breathing: mechanism that moves air into and out of the lungs, allowing gas exchange to take place.
    • Lungs and associated structures are often called the ‘gas exchange system’.
  • Structure of the Gas Exchange System:
    • Lungs are enclosed in the chest or thorax by the ribcage and a muscular sheet of tissue called the diaphragm.
    • Two sets of muscles called intercostal muscles join each rib to the next.
    • Diaphragm separates the contents of the thorax from the abdomen.
  • Trachea - windpipe splits into two tubes called the bronchi, one leading to each lung.
  • Each bronchus divides into smaller and smaller tubes called bronchioles, eventually ending at microscopic air sacs, called alveoli.
  • Walls of trachea and bronchi: rings of gristle or cartilage keep them open when we breathe in.
  • Pleural membranes separate the inside of the thorax from the lungs forming an airtight seal.
  • Pleural cavity between membranes: filled with pleural fluid acts as lubrication.
  • Keeping the airways clean:
    • Trachea and larger airways are lined with cells that secrete mucus or have cilia keep airways clean.
    • Cilia beat backwards and forwards, sweeping the mucus and trapped particles out towards the mouth. One of the effects of smoking is that it destroys the cilia and stops this protection mechanism from working properly.
  • Ventilation of the Lungs:
    • Moving air in and out of the lungs.
    • Requires a difference in air pressure moving high to low.
    • Ventilation depends on the fact that the thorax is an airtight cavity.
    • Movements of the ribs and the diaphragm bring about ventilation.
    • When we breathe, we change the volume of our thorax, which alters the pressure inside it.
    • Air enters the lungs (inhalation).
    • Difference in pressure forces air out of the lungs (exhalation).
    • Changes in volume and pressure during ventilation.
  • Gas exchange in the Alveoli:
    • Lungs absorb oxygen into the blood and remove carbon dioxide from it.
    • Happens in the alveoli, structure brings the air and blood very close together, over a very large surface area= 60m2, which is bigger than the floor area of an average classroom!
    • Have a thin layer of fluid lining the inside
    • Moist surface before it passes through the alveolar wall into the blood.
    • Diffusion of oxygen and carbon dioxide takes place between the air in the alveolus and the blood in the capillaries. Oxygenated blood is pumped to the lungs by the heart.
  • The Effects of Smoking:
    • Upsets conditions that would otherwise support gas exchange.
    • Smoking is linked to and causes diseases of the lungs are now a proven fact. Smoking is associated with lung cancer, bronchitis and emphysema along with being a contributing factor to coronary heart disease and ulcers.
    • Destroys lungs protection of mucus and cilia and makes lining of the wall secretion worse causing irritation of bronchia.
    • Smoker’s cough.
  • Emphysema:
    • Affects lung by breaking down the surface area and kills 20000 British people annually.
    • Smoke damages the walls of the alveoli, which break down and fuse together again, forming enlarged, irregular air spaces.
  • Lung cancer:
    • Strongly linked carcinogens due to cigarette and chemicals from Tabasco as well as nicotine.
    • Increase likelihood death in individuals of cancer from lungs the more cigarettes/Tabasco smoked is how tumors develop.
    • In smoke contain more than 7000 chemicals more than 60 and known to cause cancer. Carbon monoxide is the chemical.
    • Carbon Monoxide combines with haemoglobin at a faster rate than O2 causing lack of oxygenated blood. Cause heart disease and pregnant women to deprive fetus from oxygen.
    • Over a billion smokers exist.
    • Worldwide roughly 31 per cent of men and 80 per cent of women are smokers.
  • Giving up/Withdraw from smoking uses e-cigarettes, nicotine gum/patches, and medicine support in withdrawal.

Unit 2: Food and Digestion - Chapter 4

  • Food is essential for life because nutrients help with energy for our bodies and materials for our bodies function.
  • Balanced Diet:
    • Carbohydrates: fuel source.
      • Glucose: C6H12O6 carbohydrate and hydrate.
      • Fructose: found in lactose, fruits. Sucrose from plants such as cane sugar. Fiber important and has “roughage”.
    • Lipids: insulate, and found in plant oils (e.g. Olive oil) also comes from Beef, and has fatty acids that has an oily structure and glycerol.
      • Saturated fats and cholesterols.
    • Proteins: help with recovery and growth.
      • Amino acids are involved that support functions and proteins. ( e.g. sulfur, c,h, and 20 sub units).
      • Keratin are proteins and Hemoglobin are subunits and 10 have to be amino acids and 70g for dialy intake.
    • Minerals: calcium( bones and teeth). iron(carries oxygen), phosphorus(teeth and bones) ,sodium, chloride , magnesium, sodium.
    • Vitamins: (milk) support body functioning an example lacking of vitamin D causes rickets. Another one vitamin A, light sends retinal info.
      • Main example vitamin C, keeps sells functioning correctly and sticks skin, tissue lining in side skin. B group helps with cell functioning correctly and are thiamine , riboflavin and niacin.
    • Food test that you can do
      • Chemical test can find of a food has lipid , glucose proteins and starch. Example adding a iodide to the food you are testing, it mean the food has starch in it.
    • Food energy that a body has it can be found on label. and the food has contents can be found also (kj= carbs 17 grams protein yield 18grams and 39 lipid).