Year 9 Biology Summer Exam Revision Notes

Living organisms share characteristics: nutrition, respiration, excretion, response, movement, control of internal conditions, reproduction, growth, and development.

Eukaryotic Organisms:
- Plants: Multicellular, chloroplasts for photosynthesis, cellulose cell walls, store carbohydrates as starch/sucrose (e.g., maize, peas).
- Animals: Multicellular, no chloroplasts, no cell walls, nervous coordination, movement, store carbohydrate as glycogen (e.g., humans, insects).
- Fungi: Not photosynthetic, mycelium of hyphae, chitin cell walls, extracellular digestion (saprotrophic nutrition), store carbohydrate as glycogen (e.g., Mucor, yeast).
- Protoctists: Microscopic, single-celled; some animal-like (Amoeba), some plant-like (Chlorella); pathogenic example is Plasmodium (malaria).
Prokaryotic Organisms:
- Bacteria: Microscopic, single-celled, cell wall, membrane, cytoplasm, plasmids, circular DNA, some photosynthetic, feed off living/dead organisms (e.g., Lactobacillus, Pneumococcus).
Pathogens:
- Include fungi, bacteria, protoctists, or viruses.
Viruses:
- Non-living, parasitic particles, protein coat, DNA or RNA (e.g., tobacco mosaic virus, influenza virus, HIV).

Levels of Organization: Organelles, cells, tissues, organs, systems.
Cell Structures: Nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes, vacuole.
Biological Molecules:
- Elements: Carbohydrates (C, H, O), proteins (C, H, O, N), lipids (C, H, O).
- Structure: Starch/glycogen from simple sugars, protein from amino acids, lipid from fatty acids and glycerol.
- Enzymes: Biological catalysts; activity affected by temperature and pH.
Movement of Substances: Diffusion, osmosis, active transport; affected by surface area to volume ratio, distance, temperature, concentration gradient.
Nutrition (Humans):
- Balanced Diet: Carbohydrate, protein, lipid, vitamins, minerals, water, dietary fibre.
- Components: Vitamins A, C, D, calcium, iron.
- Alimentary Canal: Mouth, oesophagus, stomach, small intestine (duodenum, ileum), large intestine (colon, rectum), pancreas.
- Digestion: Amylase/maltase (starch to glucose), proteases (proteins to amino acids), lipases (lipids to fatty acids and glycerol).
- Bile: Produced by liver, stored in gall bladder; neutralizes stomach acid, emulsifies lipids.
- Small Intestine: Adapted for absorption (villi).
Respiration:
- Produces ATP (energy for cells).
- Aerobic Respiration:
- Word equation and balanced chemical symbol equation required.
- Anaerobic Respiration:
- Word equation for plants and animals required.

Terms: Population, community, habitat, ecosystem, biodiversity.
Factors: Abiotic and biotic factors affect population size and distribution.
Trophic Levels: Producers, primary, secondary, tertiary consumers, decomposers.
Food Chains/Webs: Pyramids of number, biomass, energy transfer.
Energy Transfer: Approximately 10% transferred from one trophic level to the next.