Biology Class 8th

Biology, Class 8th

Cell: The Basic Unit of Life

• A cell is the smallest unit of life that can exist independently.
• Cell structure:
  • Cell wall: outermost layer, provides protection and shape.
  • Cell membrane: semi-permeable membrane, regulates what enters and leaves the cell.
  • Cytoplasm: jelly-like substance inside the cell membrane, contains organelles.
  • Nucleus: control center of the cell, contains DNA.

Tissue

• A group of similar cells performing a specific function.
• Types of tissues:
  • Epithelial tissue: covers the body surface, forms glands.
  • Connective tissue: provides support, connects, and binds organs.
  • Muscular tissue: helps in movement, contraction, and relaxation.
  • Nervous tissue: helps in transmission of nerve impulses.

Nutrition in Plants

• Autotrophic nutrition: plants prepare their own food through photosynthesis.
• Photosynthesis: process by which plants convert light energy into chemical energy.
• Ingredients for photosynthesis:
  • Light
  • Water
  • Carbon dioxide
  • Chlorophyll (green pigment)

Respiration in Organisms

• Breathing: process of taking in oxygen and releasing carbon dioxide.
• Respiration: process of breaking down glucose to release energy.
• Types of respiration:
  • Aerobic respiration: occurs in the presence of oxygen.
  • Anaerobic respiration: occurs in the absence of oxygen.

Transportation in Plants

• Transportation: movement of water, minerals, and food throughout the plant.
• Xylem: transports water and minerals from roots to leaves.
• Phloem: transports food from leaves to other parts of the plant.

Reproduction in Plants

• Modes of reproduction:
  • Vegetative propagation: reproduction through stems, roots, and leaves.
  • Sexual reproduction: reproduction through flowers, fruits, and seeds.
• Parts of a flower:
  • Sepals: protect the bud.
  • Petals: attract pollinators.
  • Stamen: produce pollen.
  • Carpels: contain ovules.