OCR GCSE Biology Revision
GCSE Biology A (Gateway) · Specification J247 · England
Revising for OCR 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 OCR course so you only revise what's on your exam.
OCR GCSE Biology topics
B1 Cell level systems
Cells are the fundamental units of life. Eukaryotic cells, found in animals, plants, fungi, and protists, are complex, possessing a true nucleus to house genetic material and membrane-bound organelles like mitochondria and chloroplasts. In contrast, prokaryotic cells, such as bacteria, are simpler and smaller. They lack a nucleus, with their DNA free in the cytoplasm, often in a circular plasmid. They also lack membrane-bound organelles. Ribosomes are present in both cell types, but are generally smaller in prokaryotes. This distinction is crucial for understanding different life forms.
B2 Scaling up
Organisms are organised in a hierarchical way, from simple to complex. It starts with specialised cells, which group together to form tissues. Different tissues then work together to create organs, like the heart or stomach. Several organs coordinating their functions form an organ system, such as the digestive system. Finally, all organ systems work together to make a complete multicellular organism. This organisation allows for complex life.
B3 Organism level systems
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. This process does not require energy and happens naturally due to the random motion of particles. It's crucial for the movement of substances like oxygen into cells for respiration, and carbon dioxide out of cells. The concentration gradient, temperature, and surface area all affect the rate of diffusion. A steeper gradient, higher temperature, and larger surface area increase the rate.
B4 Community level systems
An ecosystem is a community of living organisms (biotic factors) interacting with their non-living surroundings (abiotic factors), such as sunlight, water, and soil pH. A habitat is the specific place where an organism lives, providing the conditions and resources it needs to survive. For example, a pond is an ecosystem, while the muddy bottom of the pond is a habitat for worms. Understanding how these factors interact is crucial for studying the flow of energy and the cycling of materials within a community, impacting populations and biodiversity.
B5 Genes, inheritance and selection
Inheritance is the passing of genetic information from one generation to the next. Genes, located on chromosomes, carry this information. Alleles are different forms of a gene. We inherit one allele from each parent for every gene. This combination determines our characteristics. Variation arises from both genetic factors (like mutations and sexual reproduction) and environmental factors. Understanding inheritance helps explain why offspring resemble their parents but are not identical.
B6 Global challenges
Biodiversity refers to the variety of living organisms on Earth, including genetic diversity, species diversity, and ecosystem diversity. It is crucial for maintaining stable ecosystems, providing resources, and regulating environmental processes. Human activities such as deforestation, habitat destruction, pollution, and climate change are leading to a rapid decline in biodiversity. This loss impacts food webs, nutrient cycles, and the availability of essential resources, posing significant global challenges for both current and future generations. Protecting biodiversity is vital for ecological balance.
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Topic summaries are ScienceForge originals, not official OCR material. Check the official OCR specification for the definitive content list.