Biology Half-Yearly Notes

1.04 Groups of Living Things

  • Kingdoms Overview: Commonly split organisms into four out of five kingdoms.

    • Protoctista: Microscopic creatures, e.g., protozoa and algae (plant-like organisms).

    • Fungi: Includes mushrooms, toadstools, and molds.

    • Plants:

      • Includes simpler plants like mosses and liverworts, ferns, conifers, and flowering plants.

      • Characteristics:

        • Mosses: Do not have proper roots.

        • Ferns: Produce spores.

        • Conifers: Trees with needle-shaped leaves; produce cones.

        • Flowering Plants: Have flowers and produce seeds.

        • Differentiation in flowering plants:

          • Monocotyledons: Parallel leaf veins.

          • Dicotyledons: Network of leaf veins.

1.08 Animals

  • Classification:

    • Vertebrates: Animals with backbones.

    • Invertebrates: Animals without backbones.

      • Includes coelenterates (like jellyfish), flatworms, molluscs (like snails), arthropods (insects, arachnids, crustaceans), and annelids (segmented worms).

    • Chordates:

      • Categories include: bony fish, amphibians, reptiles, birds, and mammals.

      • Key distinctions:

        • Scales on fish, hair on mammals, feathers on birds.

        • Young mammals feed on mother's milk.

1.07 In and Out of Cells

  • Diffusion:

    • Molecules are in constant motion.

    • Demonstrated by ink in water: Ink spreads as its molecules move.

    • Diffusion leads to molecules moving from areas of high concentration to low.

  • Cellular Exchange:

    • Blood vessels facilitate diffusion of food and oxygen into cells and removal of carbon dioxide.

    • Active transport:

      • Plants absorb minerals against concentration gradients using energy.

Osmosis

  • Definition:

    • Special type of diffusion involving water molecules through a semi-permeable membrane.

  • Experiment: Shows how water moves from weaker to stronger sugar solutions.

  • Function in Plants:

    • Water moves through plant cells via osmosis, aiding in nutrient transport and cellular turgidity.

1.08 Cell Division by Mitosis

  • Mitosis Overview:

    • Process by which cells divide, producing genetically identical daughter cells.

    • Stages of mitosis:

      • Chromosomes appear and align in the cell.

      • Chromosomes separate to opposite ends and the cell divides.

  • Purpose:

    • Creates new cells for growth and replaces damaged tissues.

    • Asexual reproduction in organisms like amoebas occurs via mitosis.

1.09 Cell Division by Meiosis

  • Meiosis Process:

    • Produces gametes (sex cells) necessary for sexual reproduction.

    • Reduces chromosome number by half, creating diversity among offspring.

  • Sexual Reproduction:

    • Fusion of male and female gametes creates a zygote.

    • Genetic variation arises from combining chromosomes from both parents.

2.03 Chromosomes and Genes

  • Inheritance:

    • Characteristics inherited through chromosomes and their genes (made from DNA).

    • Genes paired during fertilization influence traits (e.g., eye color).

  • Dominant and Recessive Genes:

    • Dominant genes overshadow recessive genes in trait expression.

    • Example: Black hair dominates blond hair.

3.05 Transport and Support in Plants

  • Transport System:

    • Comprised of xylem and phloem.

      • Xylem carries water/minerals from roots to leaves.

      • Phloem distributes glucose from leaves.

  • Support Mechanism:

    • Xylem provides structural support to plants due to thick walls.

3.06 Transpiration

  • Definition:

    • Loss of water vapour through leaves, primarily from stomata.

  • Transpiration Stream:

    • Water evaporated from leaves is replaced by the upward flow from roots through xylem.

  • Adaptation in Dry Climates:

    • Cacti minimize water loss through specialized structures and reduced stomata.