CHAPTER 6- TISSUES

1. Cells and Organisms

• Unicellular organisms: Only one cell performs all life functions (e.g., Amoeba).
• Multicellular organisms: Made of many cells, each specialized for a particular task. For example:
  • Muscle cells: Help in movement.
  • Nerve cells: Transmit signals.
  • Blood cells: Transport oxygen, food, hormones, and waste.
  • Plant tissues (e.g., vascular tissues): Transport water and food.

2. Tissues in Multicellular Organisms

• Cells that are similar in structure and function are grouped together to form a tissue.
• Examples of tissues: Blood, phloem, and muscle tissue.

3. Differences Between Plant and Animal Tissues

• Plants:
  • Stationary and don’t move.
  • Have more supportive tissues (e.g., dead cells) to stand upright.
  • Growth occurs in specific regions (e.g., meristematic tissues).
  • Divided into meristematic tissues (for growth) and permanent tissues (for specific functions).
• Animals:
  • Move and consume more energy.
  • Mostly made of living tissues.
  • Growth is uniform, not restricted to specific areas.
  • More complex organ systems compared to plants.

4. Types of Plant Tissues

• Meristematic Tissue: Found in growing regions of the plant (e.g., tips of roots and stems).
  • Apical meristem: Increases the length of roots and stems.
  • Lateral meristem: Increases the girth (width) of stems and roots.
  • Intercalary meristem: Found near nodes (growth regions between leaves and stems).
  • Cells in meristematic tissue are active, have thin walls, no vacuoles, and divide rapidly to form new cells.
• Permanent Tissue: Formed from meristematic tissue after it differentiates (changes into specialized cells).
  • Simple permanent tissues: Made of similar cells, like:
    • Parenchyma: Stores food, has intercellular spaces, and can have chlorophyll for photosynthesis.
    • Collenchyma: Provides flexibility (e.g., in tendrils or stems of climbers).
    • Sclerenchyma: Strengthens plants, e.g., in the husk of coconuts (cells are dead with thickened walls).

5. Epidermal Tissue in Plants

• Epidermis: Outermost protective layer of plants.
  • Usually a single layer of cells.
  • Has a waxy coating to reduce water loss.
  • In roots, epidermal cells have hair-like structures for absorbing water.
  • Stomata: Pores in leaves for gas exchange and transpiration (water loss through evaporation).
• Cork: Formed by a secondary meristem in older plants, provides protection and prevents water loss.

6. Extra Knowledge for Competitive Exams:

• Function of tissues: Specialization allows efficient function, as each tissue focuses on one task (e.g., transport, support, protection).
• Growth patterns: In plants, growth happens in certain regions due to meristematic tissue, while animals grow uniformly across their bodies.
• Adaptations: Plants have thick epidermal tissues or waxy coatings to prevent water loss, which is critical in dry habitats like deserts. This adaptation helps them survive harsh conditions.
• Transpiration: Important for cooling the plant and drawing water up from roots to leaves. It also helps with nutrient transport.

1. Complex Tissues in Plants:

• Xylem:
  • Responsible for transporting water and minerals in plants.
  • Composed of tracheids, vessels, xylem parenchyma, and xylem fibers.
  • Tracheids and vessels are tube-like and have thick walls. They transport water and are often dead when mature.
  • Xylem parenchyma stores food.
  • Xylem fibers provide structural support.
• Phloem:
  • Transports food (mainly sugars) from leaves to other parts of the plant.
  • Made up of sieve cells, sieve tubes, companion cells, phloem fibers, and phloem parenchyma.
  • Sieve tubes are tube-like structures with perforated walls.
  • Most phloem cells are living, except for phloem fibers.
• Complex Permanent Tissues:
  • Tissues made of more than one type of cell working together to perform a specific function.
  • Examples include xylem and phloem, both conducting tissues that form a vascular bundle.

2. Animal Tissues:

• Muscular Tissue:
  • Composed of muscle fibers responsible for movement.
  • Muscle contractions allow the movement of body parts and organs (e.g., heart, digestive system).
  • Muscle cells have special proteins that allow contraction and relaxation.
• Blood:
  • Blood is a type of connective tissue that transports substances like oxygen, nutrients, and waste products.
  • It contains red blood cells (RBCs), white blood cells (WBCs), and platelets, suspended in plasma.
• Epithelial Tissue:
  • Covers organs and forms protective barriers.
  • It has different types based on structure and function, such as:
    • Squamous epithelium: Thin, flat cells forming linings like the skin and blood vessels.
    • Columnar epithelium: Tall cells found in places where absorption occurs, like the intestines.
    • Ciliated columnar epithelium: Has hair-like structures (cilia) that move substances, such as mucus in the respiratory tract.
    • Cuboidal epithelium: Cube-shaped cells found in the kidneys and glands.
    • Glandular epithelium: Specialized for secretion.
• Connective Tissue:
  • Connective tissues include blood, bone, cartilage, ligaments, and tendons.
  • They support and connect different parts of the body. For example:
    • Bone: Strong tissue supporting the body and anchoring muscles.
    • Cartilage: Smoothens joint surfaces, providing flexibility (found in ears, nose, etc.).
    • Ligaments: Connect bones to bones, allowing flexibility.
    • Tendons: Connect muscles to bones and enable movement.
• Muscular Tissue Types:
  • Striated Muscle: Voluntary muscles attached to bones. These muscles have light and dark bands (striations).
  • Smooth Muscle: Involuntary muscles found in the digestive tract and blood vessels. These muscles have no striations and are spindle-shaped.
  • Cardiac Muscle: Involuntary muscles in the heart, responsible for rhythmic contractions. They are cylindrical, branched, and uninucleate.
• Nervous Tissue:
  • Composed of neurons (nerve cells) that transmit electrical signals.
  • Neurons have a cell body, an axon (long part), and dendrites (short branches).
  • Neurons transmit signals from the brain to other body parts, allowing us to respond to stimuli.

3. Summary of Tissues:

• Plant Tissues:
  • Two main types: Meristematic (growing) and Permanent (mature) tissues.
  • Permanent tissues are further classified into simple (e.g., parenchyma) and complex (e.g., xylem and phloem) tissues.
• Animal Tissues:
  • Four main types: Epithelial, Connective, Muscular, and Nervous.
  • Each type has specialized cells and functions that contribute to the overall functioning of the body.

Additional Knowledge:

• Meristematic Tissue:
  • Found at the tips of roots and stems, where it is responsible for plant growth. It is made of actively dividing cells.
• Tissue Repair:
  • Tissues like areolar connective tissue help repair and support damaged tissues.
• Adaptation in Muscles:
  • Muscular tissue is specialized for movement, and different types of muscles (striated, smooth, and cardiac) are adapted to specific functions such as voluntary and involuntary actions, and heart contractions.

Competitive Exam Tips:

• Xylem and Phloem are common questions related to plant tissues. Remember the key differences:
  • Xylem: Transports water and minerals; made of dead cells.
  • Phloem: Transports food; mostly made of living cells.
• Types of Muscle Tissues:
  • Striated (voluntary): Skeletal muscles that help in voluntary movement.
  • Smooth (involuntary): Found in internal organs, controlling movements like peristalsis.
  • Cardiac: Found in the heart, pumps blood continuously.
• Types of Connective Tissues: Be familiar with their locations and functions:
  • Bone: Hard matrix, supports the body.
  • Cartilage: Flexible, supports joints.
  • Blood: Fluid, transports materials in the body.

THESE ALL ARE THE NOTES OF CHAPTER 6 SCIENCE. AND AFTER SOME TIME YOU GET IMPORTANT QUESTIONS HERE. *#THANKS FOR VISITING, VISIT AGAIN#* 😊