CAIE IGCSE Biology Notes Flashcards

Characteristics and Classification of Living Organisms

• MRS GREN: Acronym representing the seven characteristics of living organisms:
  • Movement: Change of position or place.
  • Respiration: Chemical reactions that break down nutrient molecules, releasing energy.
  • Sensitivity: Ability to detect and respond to environmental changes.
  • Growth: Permanent increase in size and dry mass.
  • Reproduction: Production of offspring (either genetically identical or different).
  • Excretion: Elimination of metabolic waste products.
  • Nutrition: Intake of materials for energy, growth, and development.

Classification of Organisms

• Purpose: Organisms classified by shared features to show evolutionary relationships.

• Taxonomic Hierarchy:

  • Sequence: Kingdom → Phylum → Class → Order → Family → Genus → Species.
  • Mnemonic: King Philip, Come Over For Good Soup.

• Binomial Nomenclature: Naming system consisting of genus and species. Format: Genus species (e.g., Homo sapiens).

  • Genus is capitalized, species is not, and both are italicized or underlined.

Features of Organisms

• Five Kingdoms:

  • Animals: Multicellular, ingestive heterotrophs. (e.g., cats, ladybirds)
  • Plants: Multicellular, photosynthetic autotrophs with cell walls (cellulose) and chloroplasts. (e.g., oaks, cacti)
  • Fungi: Heterotrophic, can be unicellular or multicellular, and have cell walls (not cellulose). (e.g., yeast, mushrooms)
  • Prokaryotes: Unicellular organisms without a true nucleus. (e.g., E. coli, Salmonella)
  • Protists: Mostly unicellular with a nucleus, some multicellular. (e.g., Amoeba, seaweed)

• Vertebrates and Invertebrates:

  • Vertebrates have backbones; invertebrates do not.

Types of Vertebrates

Classification of Plants

• Types:
  • Ferns: Do not have flowers or seeds, reproduce via spores.
  • Flowering Plants: Have flowers and seeds.
  • Monocotyledons: One seed leaf, parallel veins.
  • Dicotyledons: Two seed leaves, branching veins.

Viruses

• Non-Living Organisms: Viruses do not carry out the seven life processes.
• Structure: Contain genetic material (RNA or DNA) and a protein coat.

Cell Structure and Organisation

• Eukaryotic Cells: Contain a nucleus and other organelles (e.g., mitochondria, ribosomes).
• Prokaryotic Cells: Lack a true nucleus, e.g., bacterial cells.
• Cell: Basic unit of life, can be specialized.
  • Tissue: Group of similar cells performing a function.
  • Organ: Group of tissues working together.
  • Organ System: Group of organs working together.

Movement Into and Out of Cells

Diffusion

• Definition: Movement of particles from high to low concentration.
• Factors Affecting Diffusion: Concentration gradient, temperature, surface area.

Osmosis

• Definition: Movement of water through a semi-permeable membrane from high to low water potential.
• Cell Conditions:
  • Hypertonic: Cell shrinks; high solute outside.
  • Isotonic: No change; equal solute.
  • Hypotonic: Cell swells; low solute outside.

Active Transport

• Definition: Movement against a concentration gradient using energy.
• Transport Mechanism: Carrier proteins in the membrane.

Biological Molecules

• Carbohydrates: Composed of Carbon, Hydrogen, Oxygen (CHO).
• Proteins: CHON(S), made from amino acids.
• Lipids: CHO, contain fatty acids and glycerol.

Food Tests:

Enzymes

• Characteristics: Biological catalysts that speed up reactions but are not consumed in the process.
• Enzyme Action: Lower the activation energy required for reactions.
• Factors Affecting Enzyme Activity:
  • Temperature: Optimal at ~37 °C (human body); too high leads to denaturation.
  • pH: Enzymes have optimal pH ranges.

Plant Nutrition

Photosynthesis

• Equation: $6CO2 + 6H2O + light + chlorophyll ightarrow C6H{12}O6 + 6O2$.

Mineral Requirements

• Nitrate Ions: For amino acid production.
• Magnesium Ions: For chlorophyll production.

Human Nutrition

• Balanced Diet: Proper proportions of nutrients (carbohydrates, fats, proteins, vitamins, minerals, and water).
• Deficiency Diseases:
  • Vitamin C: Scurvy.
  • Iron: Anaemia.

Circulatory System

• Components: Heart, blood vessels (arteries, veins, capillaries).
• Types:
  • Single/Double Circulation: Single (fish), Double (mammals).

Heart Structure

• Chambers: Right atrium, right ventricle, left atrium, left ventricle.
• Function: Pumps blood; oxygenated and deoxygenated blood separation ensured by septum.

Diseases and Immunity

• Pathogens: Organisms causing disease; transmitted through direct or indirect contact.
• Body Defenses: Include mechanical and chemical barriers.
• Active Immunity: Body produces antibodies after exposure or via vaccination.
• Passive Immunity: Temporary immunity (e.g., breast milk).
• Example Disease: Cholera caused by Vibrio cholerae, treated by rehydration and antibiotics.