Cells and Organisation of Living Things -1

Living Things and Cells

• Characteristics of Living Organisms (MRS H GREN)

  • Movement: Changes in position or location.

  • Respiration: Chemical processes that release energy from food.

  • Sensitivity: Detection and response to stimuli.

  • Homeostasis: Regulation of internal conditions.

  • Growth: Increase in size and mass.

  • Reproduction: Production of offspring to ensure species survival.

  • Excretion: Removal of metabolic waste.

  • Nutrition: Obtaining food for energy and growth.

Cell Structures and Functions

• Key Cell Structures

  • Nucleus: Control center containing DNA.

  • Cytoplasm: Site for chemical reactions.

  • Cell Membrane: Controls movement of substances in and out of the cell.

  • Cell Wall: Provides structural support (found only in plant cells).

  • Mitochondria: Site of aerobic respiration, releases energy.

  • Chloroplasts: Site of photosynthesis (found only in plant cells).

  • Ribosomes: Protein synthesis.

  • Vacuole: Storage of substances and structural support (large in plant cells).

Comparison of Plant and Animal Cells

• Similarities

  • Both contain a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.

• Differences

  • Plant cells have a cell wall, chloroplasts, and large central vacuoles, while animal cells do not.

Levels of Organization in Organisms

• Hierarchy: Organelles → Cells → Tissues → Organs → Organ Systems → Organism

  • Example:

  • Organelles: Mitochondria, nucleus

  • Cells: Muscle cells, nerve cells

  • Tissues: Muscle tissue

  • Organs: Heart

  • Organ Systems: Circulatory system

  • Organism: Human

Using Microscopes

• Microscope Parts:

  • Eyepiece, Objective Lens (varying magnifications), Stage, Coarse Adjustment, Fine Adjustment, Light Source.

• Observing Cells:

  • Method to prepare plant and animal cells.

  • Example: Onion cell preparation using iodine as a stain.

  • Example: Cheek cell preparation using methylene blue stain.

• Drawing Cells:

  • Accurate representations showing structure and function of visible organelles.

Classifying Living Things

• Five Kingdoms:

  1. Animals

  2. Plants

  3. Fungi

  4. Protoctists

  5. Prokaryotes (Bacteria)

• Key Features:

  • Eukaryotic: Organisms with a true nucleus (animals, plants, fungi, protoctists).

  • Prokaryotic: Organisms without a nucleus (bacteria).

Summary of Microbial Life

• Pathogens: Organisms that cause disease.

• Bacteria: Microscopic unicellular organisms with cell walls.

  • Helpful (Lactobacillus in yogurt making).

  • Harmful (food poisoning, cholera).

• Viruses: Non-living entities that require a host cell for replication; cause diseases such as influenza and HIV.

• Examples of Pathogenic Organisms: Bacteria, viruses, fungi, and protoctists (e.g., Plasmodium causing malaria).

Specialised Cells

• Adaptations for Function:

  • Sperm Cells: Tail for swimming, genetic material for reproduction.

  • Red Blood Cells: Biconcave shape for oxygen transport, lacks nucleus to maximize hemoglobin space.

  • Root Hair Cells: Increased surface area for absorption of water and nutrients.

    

Fungi and Protoctists

• Fungi:

  • Example of multicellular (mushrooms) and unicellular (yeasts).

  • Use saprotrophic nutrition (extracellular enzyme secretion).

    

• Protoctists:

  • Diverse group, many unicellular.

  • Examples: Amoeba has animal-like features, Chlorella is plant-like.

Conclusion: Understanding Cells and Life Processes

• Integration of Concepts:

  • Cells are the fundamental units of life, organized into more complex structures serving specific functions in multicellular organisms.

  • Recognition of similarities and differences among organisms enables classification and understanding of ecological roles.