Biology Exam Revision Notes

Variety of Living Organisms

• Characteristics of Living Organisms

  • Understanding the traits that define life.
  • Major characteristics include:
  • Growth: Organisms grow and develop.
  • Reproduction: Ability to reproduce and pass on genetic information.
  • Responsiveness: Reaction to environmental stimuli.
  • Metabolism: Chemical processes that convert food into energy.
  • Homeostasis: Maintaining a stable internal environment.

• Types of Organisms

  • Plants, Animals, and Fungi:
  • Plants: Autotrophic organisms that perform photosynthesis.
  • Animals: Heterotrophic organisms that consume other organisms.
  • Fungi: Saprotrophic organisms that decompose organic matter.

• Protoctists, Bacteria, and Viruses:

  • Protoctists: Simple eukaryotic organisms (e.g., amoebae).
  • Bacteria: Prokaryotic microorganisms that can be beneficial or pathogenic.
  • Viruses: Non-living entities that require a host to replicate.

Structure and Function of Living Organisms

• Levels of Organisation

  • Organisms organized from cells to tissues, organs, and systems.

• Cell Structure

  • Key components of cells include:
  • Cell membrane, nucleus, mitochondria, ribosomes.

• Biological Molecules

  • Carbohydrates, Proteins, Lipids, and Nucleic Acids:
  • Essential macromolecules for life processes.
  • Carbohydrates: Energy source (e.g., glucose).
  • Proteins: Structural components and enzymes.
  • Lipids: Energy storage and membrane formation.
  • Nucleic Acids: DNA and RNA, carriers of genetic information.

• Enzymes

  • Biological catalysts that speed up chemical reactions.
  • Key factors affecting enzyme activity: temperature, pH, substrate concentration.

Transport Mechanisms in Cells

• Diffusion

  • Movement of molecules from high concentration to low concentration.

• Osmosis

  • Specific type of diffusion involving water through a semipermeable membrane.

• Active Transport

  • Movement of substances against a concentration gradient, requiring energy (ATP).

Nutrition and Digestion

• Photosynthesis

  • Process by which plants convert sunlight into chemical energy.
  • Equation: $6CO<em>2 + 6H</em>2O + light <br /> ightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2$

• Nutrition in Humans

  • Importance of a balanced diet including carbohydrates, proteins, fats, vitamins, and minerals.

• Digestive System

  • Key organs: mouth, esophagus, stomach, intestines.
  • Enzymes involved: amylase (carbohydrate digestion), protease (protein digestion), lipase (fat digestion).
  • Bile: Aids in the digestion of fats.

Respiration and Gas Exchange

• Cellular Respiration

  • Process of converting glucose into energy (ATP), involving glycolysis, the Krebs cycle, and the electron transport chain.
  • Equation: $C<em>6H</em>{12}O<em>6 + 6O</em>2 <br /> ightarrow 6CO<em>2 + 6H</em>2O + ATP$

• Gas Exchange in Plants and Humans

  • Plants exchange gases through stomata.
  • Humans exchange gases in the alveoli of the lungs.

Transport Systems

• Transport in Plants

  • Xylem: Transports water and minerals.
  • Phloem: Transports sugars produced in photosynthesis.

• Circulatory System in Humans

  • Comprises the heart, blood vessels, and blood.
  • Types of Blood Vessels: Arteries, veins, capillaries.

Reproduction and Inheritance

• Types of Reproduction

  • Sexual and asexual reproduction.

• Genetics

  • Overview of chromosomes, DNA, genes, and inheritance patterns (monohybrid inheritance and sex determination).

Ecology and Environment

• Ecosystems

  • Interactions between living organisms and their environment.
  • Biodiversity: Variety of life in an ecosystem.

• Food Chains and Trophic Levels

  • Description of energy flow through ecosystems, organized in trophic levels: producers, consumers, and decomposers.