G10 Coord Biology Revision booklet Dec 2024 for mocks

Introduction to Biology and Coordinated Science

Adaptation for T IS International School of Toulouse: Overview of the biology syllabus, updated for the CAIE IGCSE for the academic years 2023-2025 and 2026-2028, focusing on foundational principles of biology and the interdisciplinary approach of coordinated science.

Characteristics of Living Organisms

MRS GREN:

Acronym summarizing the seven characteristics of living things:

  • Movement: Activity causing a change in position or place, which can be voluntary (in animals) or involuntary (in plants, like phototropism).

  • Respiration: Involves chemical reactions in cells, breaking down nutrients to release energy essential for cellular functions. It can be aerobic (with oxygen) or anaerobic (without oxygen), affecting energy yield.

  • Sensitivity: The ability of organisms to detect and respond to stimuli in their environment, crucial for survival. This includes responses to light, temperature, and chemical signals.

  • Growth: A permanent increase in size and mass, which involves cellular division and differentiation; it can occur throughout an organism's life or be restricted to certain phases.

  • Reproduction: The process by which organisms create offspring of the same kind, which can occur sexually (involving gametes) or asexually (without gametes, such as budding or binary fission).

  • Excretion: The removal of metabolic wastes from the body, important for maintaining homeostasis. Different organisms have specialized excretory systems.

  • Nutrition: The intake of materials for energy and growth, encompassing various feeding mechanisms, including autotrophic (self-feeding via photosynthesis) and heterotrophic (feeding on other organisms) modes.

Cell Structure:

All living organisms are composed of cells, which arise from existing cells through the process of division (cell division).

Typical Animal Cell Structures:

  • Cell Membrane: A selectively permeable barrier that regulates the movement of substances in and out of the cell.

  • Cytoplasm: The jelly-like fluid where cellular processes occur, containing organelles.

  • Nucleus: Contains genetic material (DNA) and controls cell activities.

  • Mitochondria: Known as the powerhouse of the cell, responsible for aerobic respiration and energy production.

  • Ribosomes: Sites for protein synthesis, translating mRNA into polypeptides.

  • Endoplasmic Reticulum:

    • Rough ER: Studded with ribosomes; involved in protein synthesis and processing.

    • Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.

Plant Cells Also Include:

  • Vacuoles: Large membrane-bound spaces in plant cells that maintain turgor pressure, store substances, and help in cellular waste management.

  • Cell Wall: A rigid outer layer providing structural support and protection, made primarily of cellulose.

  • Chloroplasts: Organelles containing chlorophyll, the site of photosynthesis where light energy is converted to chemical energy.

Cell Types and Levels of Organization

Differences Between Cell Types:

  • Animal Cells: Typically more flexible and lack rigid cell walls; contain typical organelles and are specialized for a variety of functions.

  • Plant Cells: Have distinctive organelles such as chloroplasts and a rigid cell wall, which support their structure; often larger than animal cells.

  • Prokaryotes (Bacteria): Unicellular organisms lacking a true nucleus; contain circular DNA, ribosomes, a cell wall, and are usually much smaller than eukaryotic cells.

Levels of Organization:

  1. Cells: Basic building blocks of life, each type specialized for specific functions.

  2. Tissue: A group of similar cells working together to perform a function; types include muscle, nerve, epithelial, and connective tissue.

  3. Organ: A structure composed of two or more tissue types that work together to carry out particular functions (e.g., heart, lungs).

  4. Organ System: Groups of organs that collaborate to perform complex functions for the body (e.g., cardiovascular system, digestive system).

Movement and Transport Across Membranes

Diffusion:

A passive process involving the movement of particles from an area of higher concentration to lower concentration until equilibrium is reached; plays a vital role in cellular processes.

Factors Affecting Diffusion:

  • Concentration Gradient: Greater differences drive faster diffusion.

  • Temperature: Higher temperatures increase kinetic energy, enhancing diffusion rates.

  • Surface Area: Larger surface areas promote greater diffusion.

Osmosis:

The specific diffusion of water through a selectively permeable membrane, from an area of high water potential (low solute concentration) to low water potential (high solute concentration), essential for maintaining cell turgor and overall homeostasis.

Active Transport:

An energy-dependent process where particles move against a concentration gradient, vital for nutrient uptake and maintaining cellular functions, often using ATP as the energy source.