Eduqas GCSE Biology Revision
GCSE Biology · England
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Eduqas GCSE Biology topics
1 Cells and movement across membranes
All living organisms are made of cells. There are two main types: prokaryotic (bacteria) and eukaryotic (animals, plants, fungi, protists). Eukaryotic cells have a nucleus and other membrane-bound organelles, while prokaryotic cells do not. Key organelles in eukaryotic cells include the nucleus (contains genetic material), mitochondria (site of aerobic respiration), ribosomes (protein synthesis), and cytoplasm (where most chemical reactions occur). Plant cells also have a cell wall, chloroplasts, and a permanent vacuole.
2 Respiration and the respiratory system
Aerobic respiration is the process by which cells release energy from glucose using oxygen. It occurs primarily in the mitochondria. The word equation for aerobic respiration is: Glucose + Oxygen → Carbon Dioxide + Water (+ Energy). This energy is used for processes like muscle contraction, maintaining body temperature, and active transport. It's a highly efficient way to produce ATP, the immediate energy currency of the cell, and is vital for sustained activity in most living organisms. Understanding this process is key to comprehending how living things power their lives.
3 Digestion and the digestive system
The digestive system is a long, muscular tube called the alimentary canal, stretching from the mouth to the anus. Its primary function is to break down large, insoluble food molecules into smaller, soluble molecules that can be absorbed into the bloodstream. This process, known as digestion, involves both mechanical and chemical breakdown. Organs like the stomach, small intestine, and large intestine play crucial roles, aided by accessory organs such as the liver, pancreas, and salivary glands, which produce digestive juices containing enzymes.
4 The circulatory system
The human heart is a muscular pump responsible for circulating blood throughout the body. It is divided into four chambers: two atria (upper chambers) and two ventricles (lower chambers). The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs. The left side receives oxygenated blood from the lungs and pumps it to the rest of the body. Valves ensure unidirectional blood flow, preventing backflow. The septum divides the left and right sides, preventing mixing of oxygenated and deoxygenated blood.
5 Plants and photosynthesis
Photosynthesis is the fundamental process by which green plants and some other organisms convert light energy into chemical energy. The overall word equation is: carbon dioxide + water $\xrightarrow{\text{light energy}}$ glucose + oxygen. The balanced symbol equation is: 6CO$_2$ + 6H$_2$O $\xrightarrow{\text{light energy}}$ C$_6$H$_{12}$O$_6$ + 6O$_2$. This reaction takes place primarily in the chloroplasts of plant cells, specifically in the chlorophyll-containing structures. Glucose is used for energy, storage, or building materials, while oxygen is released as a byproduct.
6 Ecosystems, nutrient cycles and human impact
An ecosystem is a community of living organisms (biotic components) interacting with their non-living environment (abiotic components). Biotic factors include producers (plants), consumers (animals), and decomposers (bacteria, fungi). Abiotic factors include sunlight, water, temperature, soil pH, and mineral availability. These components are interconnected, and a change in one can affect the entire system. Understanding ecosystems helps us predict the impact of human activities on the environment and develop conservation strategies.
7 Classification and biodiversity
Classification is the process of grouping living organisms based on their shared characteristics. Historically, organisms were grouped into kingdoms, but modern classification uses a hierarchical system called Linnaean classification: Kingdom, Phylum, Class, Order, Family, Genus, Species. Organisms are identified by a binomial naming system, consisting of their Genus and species (e.g., *Homo sapiens*). This system helps scientists worldwide communicate clearly about species and understand evolutionary relationships.
8 Cell division and stem cells
Mitosis is a type of cell division that produces two genetically identical daughter cells from a single parent cell. It's essential for growth, repair of damaged tissues, and asexual reproduction. Before mitosis, the cell's DNA is replicated, so each chromosome consists of two identical sister chromatids. The process involves stages like prophase, metaphase, anaphase, and telophase, ensuring equal distribution of genetic material.
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, forming the 'sugar-phosphate backbone'. The 'rungs' of the ladder are formed by pairs of nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). A always pairs with T, and C always pairs with G, held together by weak hydrogen bonds. This complementary base pairing is crucial for DNA replication and protein synthesis.
10 Variation and evolution
Variation refers to the differences between individuals within a species. These differences can be **inherited** (genetic) or **environmental**. Genetic variation arises mainly from **mutations**, which are changes to the DNA sequence, and from **sexual reproduction**, which shuffles existing genes through meiosis and random fertilisation. Environmental variation comes from differences in conditions such as diet, exercise, or climate. Understanding variation is crucial as it provides the raw material for natural selection and evolution. Both types of variation contribute to an individual's **phenotype** (observable characteristics).
11 Response and regulation
The nervous system coordinates our actions and responses. It's divided into the Central Nervous System (CNS) – the brain and spinal cord – and the Peripheral Nervous System (PNS), which includes all other nerves. Neurones (nerve cells) transmit electrical impulses. Sensory neurones carry impulses from receptors to the CNS, relay neurones connect sensory and motor neurones within the CNS, and motor neurones carry impulses from the CNS to effectors (muscles or glands).
12 Kidneys and homeostasis
The kidneys are vital organs in the excretory system, playing a crucial role in maintaining homeostasis, the body's stable internal environment. They filter blood to remove metabolic waste products, primarily urea, which is a toxic byproduct of protein metabolism. Beyond waste removal, kidneys regulate water balance, ensuring the body has the correct amount of fluid. They also control the concentration of salts and ions in the blood, which is essential for nerve and muscle function. This constant regulation helps maintain stable blood pH, blood pressure, and red blood cell production.
13 Microorganisms and their applications
Microorganisms 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. They are found almost everywhere: in the air, soil, water, and on and inside living organisms. While some can cause disease, many are beneficial and play crucial roles in ecosystems and industrial processes. Understanding their diversity and characteristics is fundamental to their application.
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 reproduce rapidly and produce toxins. Viruses are even smaller, needing a host cell to replicate. Fungi can be single-celled (like yeast) or multicellular, causing diseases like athlete's foot. Protists are single-celled eukaryotic organisms, often parasites, responsible for diseases like malaria. Understanding these different types of pathogens is crucial for developing effective treatments and prevention strategies. Each type has unique characteristics that dictate how they spread and cause harm.
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