WJEC GCSE Biology Revision
GCSE Biology · Wales
Revising for WJEC 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 WJEC course so you only revise what's on your exam.
WJEC GCSE Biology topics
1 Cells and movement across membranes
All living organisms are made of cells, the basic units of life. There are two main types: prokaryotic and eukaryotic. Prokaryotic cells (like bacteria) are simpler, lacking a nucleus and membrane-bound organelles. Eukaryotic cells (like plant and animal cells) are more complex, containing a nucleus to house genetic material and various organelles like mitochondria, chloroplasts (plants), and ribosomes. Understanding these fundamental structures is crucial for comprehending cell function and processes like movement across membranes.
2 Respiration and the respiratory system
Aerobic respiration is the release of energy from glucose using oxygen. It occurs primarily in the mitochondria of cells. The word equation is: Glucose + Oxygen → Carbon Dioxide + Water + Energy It's a highly efficient process, producing a large amount of ATP (adenosine triphosphate) which is the immediate energy source for cellular activities. This energy is vital for processes like muscle contraction, active transport, and maintaining body temperature. Without sufficient oxygen, aerobic respiration cannot occur efficiently.
3 Digestion and the digestive system
Digestion is the process of breaking down large, insoluble food molecules into smaller, soluble molecules that can be absorbed into the bloodstream and used by the body. This is a vital process as large molecules like carbohydrates, proteins, and fats cannot pass through cell membranes. The digestive system involves both **mechanical digestion** (physical breakdown, e.g., chewing) and **chemical digestion** (enzymatic breakdown). It's a continuous tube called the alimentary canal, along with accessory organs that produce digestive juices.
4 The circulatory system
The circulatory system is a vital transport network in the body, primarily responsible for moving blood, nutrients, hormones, and gases to and from cells. It also plays a crucial role in waste removal and maintaining body temperature. This system is comprised of three main components: the heart, blood vessels (arteries, veins, and capillaries), and blood. In humans, it is a closed double circulatory system, meaning blood passes through the heart twice for each complete circuit of the body, ensuring efficient oxygen delivery.
5 Plants and photosynthesis
Photosynthesis is the fundamental process by which green plants, algae, and some bacteria convert light energy into chemical energy, stored in glucose. This vital reaction uses carbon dioxide from the atmosphere and water absorbed by roots. It releases oxygen as a byproduct, which is essential for most life on Earth. Chlorophyll, the green pigment found in chloroplasts, absorbs the light energy required to drive this endothermic reaction. Without photosynthesis, there would be no food source for most ecosystems, and the atmosphere would lack sufficient oxygen.
6 Ecosystems, nutrient cycles and human impact
An ecosystem comprises all the living organisms (biotic factors) and non-living components (abiotic factors) interacting in a specific area. Biotic factors include producers (plants, algae), consumers (herbivores, carnivores, omnivores), and decomposers (bacteria, fungi). Abiotic factors include light intensity, temperature, water availability, soil pH, and oxygen levels. Organisms are interdependent, forming complex food webs where energy and nutrients flow. Understanding these interactions helps predict how changes in one part of the ecosystem can affect others, such as the impact of a new predator or a drought.
7 Classification and biodiversity
Classification is the process of arranging organisms into groups based on their shared characteristics. This helps scientists to identify, name, and study the vast diversity of life on Earth. The traditional system uses a hierarchical structure, moving from broad categories to more specific ones. Early classification was based on observable features, but modern methods incorporate genetic and biochemical evidence, leading to more accurate evolutionary relationships.
8 Cell division and stem cells
Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus. It is essential for growth, repair of damaged tissues, and asexual reproduction. Before mitosis begins, the cell duplicates its DNA during interphase. The process then involves several stages: prophase, metaphase, anaphase, and telophase, followed by cytokinesis which divides the cytoplasm. This ensures genetic continuity between parent and daughter cells.
9 DNA and inheritance
DNA, or deoxyribonucleic acid, is a double helix structure, often described as a twisted ladder. Each side of the ladder is made of alternating sugar (deoxyribose) and phosphate molecules. The 'rungs' are formed by pairs of nitrogenous bases: Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C). These base pairs are held together by weak hydrogen bonds. This specific pairing rule is crucial for DNA replication and genetic information storage.
10 Variation and evolution
Variation refers to the differences between individuals of the same species. These differences can be *continuous* (e.g., height, weight, hair colour) or *discontinuous* (e.g., blood group, eye colour). Continuous variation is often influenced by both genes and environment, while discontinuous variation is usually controlled by a few genes and unaffected by the environment. Understanding variation is key to comprehending how species can change over time through evolution.
11 Response and regulation
The nervous system coordinates responses to stimuli. It consists of the Central Nervous System (CNS) – brain and spinal cord – and the Peripheral Nervous System (PNS) – all other nerves. Neurons transmit electrical impulses. Sensory neurons carry impulses from receptors to the CNS, relay neurons connect neurons within the CNS, and motor neurons carry impulses from the CNS to effectors (muscles or glands) to produce a response. This allows for rapid communication and coordinated actions.
12 Kidneys and homeostasis
Homeostasis is the maintenance of a constant internal environment in the body, despite changes in external conditions. Key factors regulated include body temperature, blood glucose levels, and water potential. Kidneys play a vital role in osmoregulation, maintaining water balance, and excretion, removing metabolic waste products like urea. This ensures cells function optimally.
13 Microorganisms and their applications
Microorganisms, or microbes, are tiny living organisms that are too small to be seen with the naked eye. They include bacteria, fungi (like yeast and mould), viruses, and protozoa. While some are pathogens causing diseases, many are beneficial and play crucial roles in ecosystems, industry, and even our own bodies. They are found almost everywhere, thriving in diverse environments from soil and water to extreme temperatures and our digestive tracts.
14 Disease, defence and treatment
Pathogens are microorganisms that cause infectious diseases. These include bacteria, viruses, fungi, and protists. Bacteria are single-celled organisms that can multiply rapidly and produce toxins, e.g., *Salmonella*. Viruses are much smaller, non-living particles that replicate inside host cells, e.g., flu virus. Fungi can cause skin infections like athlete's foot, while protists are single-celled eukaryotes that can cause diseases like malaria. Understanding pathogen types is crucial for effective treatment and prevention strategies.
More WJEC GCSE Science
Topic summaries are ScienceForge originals, not official WJEC material. Check the official WJEC specification for the definitive content list.