I'm writing biology paper 1 Zimsec O level which topics do I need to know ?

for Zimsec O Level Biology Paper 1, you need to have a strong understanding of these core topics:

• Characteristics and Classification of Living Organisms: Understanding the seven life processes (movement, respiration, sensitivity, growth, reproduction, excretion, nutrition) and the principles of classification (kingdoms, phyla, classes, orders, families, genera, species).
• Cell Structure and Organisation: Differences between plant and animal cells, functions of organelles (nucleus, cytoplasm, cell membrane, cell wall, chloroplasts, mitochondria, vacuoles). Also, the difference between prokaryotic and eukaryotic cells.
• Movement of Substances: Diffusion, osmosis, and active transport – their definitions, examples, and importance in living organisms.
• Nutrition:
  • Plants: Photosynthesis (raw materials, products, conditions, balanced equation, limiting factors).
  • Animals: Types of feeding, human digestive system (structure and function of organs, enzymes, balanced diet, malnutrition).
• Respiration: Aerobic and anaerobic respiration (equations, sites, products, energy release, practical applications).
• Transport:
  • Plants: Water and mineral uptake, transpiration, transport of manufactured food.
  • Animals: Human circulatory system (heart, blood vessels, blood components and their functions).
• Excretion: Removal of metabolic waste products, focusing on the human urinary system (kidneys, nephrons).
• Coordination and Response:
  • Nervous System: Structure and function of neurons, reflex arc, brain, sense organs (eye, ear).
  • Endocrine System: Hormones (e.g., insulin, adrenaline) and their roles.
• Reproduction:
  • Asexual and Sexual Reproduction: Advantages and disadvantages.
  • Plants: Structure of a flower, pollination, fertilization, seed and fruit formation, germination.
  • Humans: Male and female reproductive systems, menstrual cycle, fertilization, pregnancy, birth control.
• Growth and Development: Cell division (mitosis), stages of human development.
• Inheritance and Variation: Basic genetics (genes, alleles, dominant/recessive, genotype/phenotype, monohybrid crosses), DNA, mutations, natural selection.
• Ecology: Ecosystems, food chains, food webs, energy flow, nutrient cycles (carbon, nitrogen), human impact on the environment (pollution, conservation).
• Diseases and Immunity: Types of diseases (infectious, non-infectious), pathogens, modes of transmission, body's defense mechanisms, immunity (natural, artificial, active, passive).

Focus on definitions, diagrams, functions, and practical applications for each of these areas.