CCEA GCSE Biology Revision
GCSE Biology · Northern Ireland
Revising for CCEA GCSE Biology? Below is every topic in the course, in specification order, with a short summary. Sign up free to get the full notes, quizzes, flashcards and exam questions for each one — filtered to the CCEA course so you only revise what's on your exam.
CCEA GCSE Biology topics
1 Cells
Cells are the fundamental building blocks of all living organisms. They are the smallest units of life that can carry out all life processes, such as respiration, growth, and reproduction. Organisms can be unicellular (like bacteria and yeast), consisting of a single cell, or multicellular (like plants and animals), made up of many specialised cells working together. Understanding cell structure and function is crucial for comprehending how living things survive and interact with their environment. Different types of cells have evolved to perform specific roles within an organism.
2 Photosynthesis and plants
Photosynthesis is the fundamental process by which green plants, algae, and some bacteria convert light energy into chemical energy, in the form of glucose. This vital reaction takes place in the chloroplasts, specifically within the chlorophyll pigment. The overall word equation is: Carbon dioxide + Water → Glucose + Oxygen. Light energy is essential to drive this endothermic reaction. Glucose is used for energy, growth, and storage, while oxygen is released as a byproduct, crucial for aerobic respiration.
3 Nutrition and health
A balanced diet provides the body with all the essential nutrients in the correct proportions for growth, repair, and energy. It includes carbohydrates for energy, proteins for growth and repair, and fats for concentrated energy and insulation. Vitamins and minerals are vital for various bodily functions, while fibre aids digestion. Water is crucial for transport, temperature regulation, and chemical reactions. Eating a variety of foods ensures all these components are obtained, supporting overall health and preventing deficiency diseases. Energy requirements vary with age, gender, and activity level.
4 Enzymes and digestion
Enzymes are biological catalysts, which are proteins that speed up the rate of biochemical reactions without being used up themselves. They are essential for all life processes, including digestion, respiration, and synthesis of new molecules. Each enzyme has a specific 3D shape, crucial for its function. This shape includes an active site, a region where specific substrate molecules bind. Without enzymes, metabolic reactions would occur too slowly to sustain life. Their efficiency is remarkable, allowing reactions to happen millions of times faster than they would spontaneously.
5 Breathing and respiration
The human respiratory system is designed for gas exchange. Air enters through the nose or mouth, passes down the trachea, which is kept open by C-shaped cartilage rings. The trachea branches into two bronchi, one for each lung. Inside the lungs, the bronchi further divide into smaller bronchioles, which terminate in tiny air sacs called alveoli. The diaphragm and intercostal muscles facilitate breathing by changing the volume of the chest cavity, creating pressure differences that draw air in and push it out.
6 Nervous system and hormones
The nervous system is a complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body. It allows us to sense, interpret, and respond to our environment, as well as control internal body functions. It's broadly divided into the Central Nervous System (CNS), which includes the brain and spinal cord, and the Peripheral Nervous System (PNS), comprising nerves that branch out from the CNS.
7 Ecological relationships and energy flow
An ecosystem is a community of living organisms (biotic factors) interacting with their non-living environment (abiotic factors) in a specific area. Examples of biotic factors include plants, animals, fungi, and bacteria. Abiotic factors include sunlight, water, temperature, soil pH, and mineral availability. All these components are interconnected, and changes in one can affect the entire system. Understanding these interactions is key to studying ecology.
8 Osmosis and plant transport
Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane. This is a passive process, meaning it does not require energy. Water potential is influenced by the concentration of solutes; pure water has the highest water potential. Cells gain or lose water depending on the water potential gradient with their surroundings.
9 DNA, genes and chromosomes
DNA, or deoxyribonucleic acid, is a double helix polymer made of repeating units called nucleotides. Each nucleotide consists of three components: a deoxyribose sugar, a phosphate group, and a nitrogenous base. There are four types of nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). The two strands of the helix are held together by weak hydrogen bonds between complementary base pairs: A always pairs with T, and C always pairs with G. This complementary base pairing is crucial for DNA's function in replication and protein synthesis.
10 Cell division and genetics
Mitosis is a fundamental process of cell division in eukaryotic cells, resulting in two identical daughter cells from a single parent cell. This process is crucial for growth, tissue repair, and asexual reproduction. It involves several distinct phases: prophase, metaphase, anaphase, and telophase, followed by cytokinesis. During mitosis, chromosomes are accurately replicated and segregated, ensuring that each new cell receives a complete set of genetic material. Understanding mitosis is key to grasping how multicellular organisms develop and maintain their bodies.
11 Reproduction
Reproduction is the process by which living organisms produce offspring. There are two main types: asexual and sexual. **Asexual reproduction** involves only one parent and produces genetically identical offspring (clones). It is common in bacteria, some plants (e.g., runners, cuttings), and simple animals (e.g., budding in hydra). It's efficient as it doesn't require a mate, but offers no genetic variation. **Sexual reproduction** involves two parents, usually producing offspring that are genetically unique. This involves the fusion of male and female gametes (sex cells) during fertilisation. While more complex, it leads to genetic variation, which can be advantageous for species survival in changing environments.
12 Variation and selection
Variation refers to the differences within a species. There are two main types: continuous and discontinuous. Continuous variation shows a range of phenotypes, like height or weight, and is often influenced by multiple genes and the environment. Discontinuous variation falls into distinct categories, such as blood groups or flower colour (e.g., red or white, not shades in between), and is primarily controlled by one or a few genes with minimal environmental influence. Understanding these differences is crucial for studying inheritance.
13 Health, disease, defence mechanisms and treatments
Diseases can be classified as communicable (infectious) or non-communicable. Communicable diseases are caused by pathogens such as bacteria, viruses, fungi, and protists. These microscopic organisms can be transmitted in various ways, including direct contact (e.g., skin-to-skin), indirect contact (e.g., contaminated surfaces), airborne droplets (e.g., coughing), waterborne (e.g., contaminated drinking water), and vector-borne (e.g., insects). Understanding transmission routes is crucial for preventing the spread of infections and implementing effective control measures, like hand hygiene and vaccinations.
14 The circulatory system
The human circulatory system is a vital transport network. It consists of three main components: the heart, blood vessels, and blood. The heart acts as a muscular pump, propelling blood throughout the body. Blood vessels, including arteries, veins, and capillaries, form a closed network of tubes. Blood itself is a fluid tissue composed of plasma, red blood cells, white blood cells, and platelets. Together, these components ensure the efficient delivery of oxygen and nutrients and the removal of waste products.
15 Microorganisms and biotechnology
Microorganisms are tiny living organisms, too small to be seen with the naked eye. They include bacteria, fungi (like yeast), viruses, and protozoa. While some are pathogens causing disease, many are beneficial. They play crucial roles in ecosystems, such as decomposition and nutrient cycling, and are harnessed in various industrial processes, including food production and medicine. Understanding their diverse characteristics is key to appreciating their impact.
More CCEA GCSE Science
Topic summaries are ScienceForge originals, not official CCEA material. Check the official CCEA specification for the definitive content list.