Pearson Edexcel International GCSE in Biology (4BI1) Exhaustive Study Guide

Overview of the International GCSE in Biology

• The Pearson Edexcel International GCSE in Biology is a linear qualification, meaning all examinations are taken at the end of the course of study.

• The specification is designed for use in schools and colleges and is valid for examinations from June 2019.

• The qualification focus is on key biology theory and includes relevant, engaging content equivalent in standard to Pearson's regulated GCSE in Biology.

• Subject specific features include bolded statements with a 'B' reference, which signify content found only in the Biology specification and not in the International GCSE in Science (Double Award).

• The curriculum is organized into five main topics:

  • The nature and variety of living organisms.

  • Structures and functions in living organisms.

  • Reproduction and inheritance.

  • Ecology and the environment.

  • Use of biological resources.

Characteristics and Variety of Living Organisms

• Living organisms share several essential characteristics:

  • Nutrition: They require nutrients for energy and growth.

  • Respiration: They release energy from food through chemical reactions.

  • Excretion: They remove toxic waste products from their bodies.

  • Response: They react to stimuli in their environment.

  • Movement: They can change position or place.

  • Control of internal conditions: They maintain a stable internal environment (homeostasis).

  • Reproduction: They produce offspring.

  • Growth and development: They increase in size and complexity.

• Eukaryotic Organisms

  • Plants: Multicellular organisms with cellulose cell walls. They contain chloroplasts for photosynthesis and store carbohydrates as starch or sucrose. Examples include flowering plants like maize (a cereal) and peas or beans (herbaceous legumes).

  • Animals: Multicellular organisms without cell walls or chloroplasts. They possess nervous coordination, can move between locations, and often store carbohydrate as glycogen. Examples include humans (mammals) and the housefly or mosquito (insects).

  • Fungi: Organisms incapable of photosynthesis. Their bodies are typically structured as a mycelium of thread-like hyphae containing multiple nuclei. Their cell walls are made of chitin. They utilize saprotrophic nutrition, secreting enzymes onto food and absorbing the products. Examples include yeast (single-celled) and Mucor.

  • Protoctists: Microscopic single-celled organisms. Some, like Amoeba, resemble animal cells, while others, like Chlorella, possess chloroplasts like plants. A pathogenic example is Plasmodium, the cause of malaria.

• Prokaryotic Organisms

  • Bacteria: Microscopic single-celled organisms with a cell wall, cell membrane, cytoplasm, and plasmids. They lack a nucleus, containing instead a circular chromosome of DNA. Examples include Lactobacillus bulgaricus (used in yogurt production) and Pneumococcus (the pathogen causing pneumonia).

• Pathogens and Viruses

  • Pathogens are agents that cause disease and may include fungi, bacteria, protoctists, or viruses.

  • Viruses are non-living particles smaller than bacteria. They are parasitic, reproducing only inside living cells, and infect all types of organisms. They lack cellular structure, possessing a protein coat and a core of DNA or RNA. Examples include Tobacco Mosaic Virus (causes leaf discoloration), Influenza virus (causes flu), and HIV (causes AIDS).

Structures and Functions in Living Organisms

• Levels of Organisation: Organisms are structured hierarchically: organelles, cells, tissues, organs, and systems.

• Cell Structure: Key organelles and structures include the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes, and vacuole.

• Specialisation (B): Cell differentiation is critical for the development of specialized cells. There are distinct advantages and disadvantages to using stem cells in medicine.

• Biological Molecules

  • Elements: Carbohydrates, proteins, and lipids (fats and oils) contain carbon, hydrogen, and oxygen. Proteins also contain nitrogen.

  • Structure: Large molecules are constructed from smaller units: starch and glycogen from simple sugars, proteins from amino acids, and lipids from fatty acids and glycerol.

  • Enzymes: Act as biological catalysts in metabolic reactions. Their function is affected by temperature and pH levels, which can alter the shape of the active site.

• Movement of Substances: Substances move into and out of cells via diffusion, osmosis, and active transport. Rate factors include surface area to volume ratio, distance, temperature, and concentration gradient.

Nutrition and Energy Flow

• Flowering Plants

  • Photosynthesis: The conversion of light energy into chemical energy. The balanced equation is $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$.

  • Factors affecting rate: Carbon dioxide concentration, light intensity, and temperature.

  • Mineral requirements: Magnesium ions for chlorophyll and nitrate ions for amino acids.

• Human Nutrition

  • A balanced diet includes carbohydrates, proteins, lipids, vitamins ($A$, $C$, and $D$), mineral ions (calcium and iron), water, and dietary fibre.

  • The alimentary canal includes the mouth, oesophagus, stomach, small intestine (duodenum and ileum), large intestine (colon and rectum), and pancreas.

  • Food movement: Peristalsis moves food through the gut.

  • Digestion: Starch is digested to glucose by amylase and maltase; proteins to amino acids by proteases; lipids to fatty acids and glycerol by lipases.

  • Bile: Produced by the liver and stored in the gall bladder; it neutralizes stomach acid and emulsifies lipids.

Gas Exchange, Transport, and Excretion

• Respiration: Living organisms produce ATP via respiration. ATP provides energy for cells. Aerobic respiration requires oxygen ($C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$), while anaerobic respiration occurs without oxygen.

• Human Gas Exchange: The thorax includes the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli, and pleural membranes. Alveoli are adapted for gas exchange by diffusion.

• Plant Transport: Xylem transports water and mineral ions from roots to leaves. Phloem (B) transports sucrose and amino acids. Transpiration is the evaporation of water from plant surfaces.

• Human Transport: Blood consists of red blood cells, white blood cells, platelets, and plasma.

  • Red blood cells: Transport oxygen using haemoglobin; they have a biconcave shape and no nucleus.

  • Immune System: Phagocytes ingest pathogens; lymphocytes release antibodies. Vaccination (B) stimulates memory cell production.

• Excretion: Organs of excretion include the lungs (carbon dioxide), kidneys (urine), and skin (sweat).

  • The Nephron (B): Parts include the Bowman’s capsule, glomerulus, convoluted tubules, loop of Henle, and collecting duct. Functions involve ultrafiltration and selective reabsorption of glucose and water.

  • ADH (B): Regulates water content in the blood.

Coordination and Response

• Homeostasis: The maintenance of a constant internal environment, such as body water content and temperature.

• Nervous System: Consists of the central nervous system (CNS) - the brain and spinal cord - and peripheral nerves. Responses involve a stimulus, receptor, and effector.

• The Eye: Functions as a receptor to focus on objects and respond to light intensity.

• Hormones: Key hormones include adrenaline, insulin, testosterone, progesterone, and oestrogen. Additional hormones (B) include ADH, FSH, and LH.

Reproduction and Inheritance

• Plants: Use insect-pollinated or wind-pollinated flowers. Asexual reproduction occurs naturally via runners or artificially via cuttings.

• Humans: Fertilization involves the fusion of a male gamete (sperm) and a female gamete (egg) to form a zygote ($46$ chromosomes in diploid cells, $23$ in haploid gametes).

• Genetics:

  • The genome is the entire DNA of an organism.

  • DNA (B): A double helix with paired bases ($A-T$ and $C-G$). RNA (B) is single-stranded and contains Uracil ($U$) instead of Thymine.

  • Mitosis: Division of a diploid cell to produce two genetically identical cells for growth and repair.

  • Meiosis: Division to produce four genetically different haploid gametes.

  • Natural Selection: Darwin's theory explains evolution; mutation is a rare, random change in genetic material.

Ecology and Human Impact

• Ecosystem Trophic Levels: Producers, primary consumers, secondary consumers, tertiary consumers, and decomposers. Approximately $10\%$ of energy is transferred between levels.

• Cycles:

  • Carbon cycle: Includes respiration, photosynthesis, decomposition, and combustion.

  • Nitrogen cycle (B): Involves nitrogen-fixing, nitrifying, and denitrifying bacteria.

• Pollution: Sulfur dioxide and carbon monoxide are air pollutants. Greenhouse gases include water vapour, $CO_2$, nitrous oxide, methane, and CFCs.

Use of Biological Resources

• Food Production: Glasshouses, fertilizers, and pest control increase crop yield. Yeast is used in bread making, and Lactobacillus in yogurt production.

• Genetic Modification: Restriction enzymes cut DNA at specific sites; ligase joins DNA pieces. Vectors (plasmids/viruses) insert recombinant DNA into cells.

• Cloning (B): Micropropagation produces identical plants. Mammalian cloning (e.g., Dolly the sheep) involves transferring a diploid nucleus into an enucleated egg cell.

Assessment Information

• Biology Paper 1 (Code 4BI1/1B)

  • Weighting: $61.1\%$ of the total qualification.

  • Total Marks: 110 marks.

  • Duration: 2-hour written examination.

  • Content: Assesses core content (unbolded).

• Biology Paper 2 (Code 4BI1/2B)

  • Weighting: $38.9\%$ of the total qualification.

  • Total Marks: 70 marks.

  • Duration: 1-hour and 15-minute written examination.

  • Content: Assesses all content, including bolded 'B' statements.

• Grading: Awarded on a scale of $9$ to $1$, with $9$ being the highest.

Command Word Taxonomy

• Calculate: Obtain a numerical answer with working.

• Describe: Give an account of something without necessarily justifying it.

• Explain: Provide a justification or reasoning for a point.

• Evaluate: Review information and bring it together to form a supported conclusion.

• State what is meant by: Provide the meaning of a specific term.

• Suggest: Propose a solution based on knowledge in a novel context.

• Determine: The answer must contain a quantitative element from the stimulus.