Life Sciences Term 2

PLANT AND ANIMAL TISSUES

PLANT TISSUES

• Plant tissue is categorized into two main groups:
  • Meristematic tissue
  • Permanent tissue

MERISTEMATIC TISSUE

• Definition: Actively dividing tissue where new cells are continually formed by mitosis.
• Characteristics: Cells are undifferentiated and do not yet perform a specific function.
• Types:
  • Apical meristem
  • Lateral meristem

PERMANENT TISSUE

• Definition: Tissue that is already differentiated to perform a specific function.
• Types Include:
  • Epidermis
  • Parenchyma
  • Sclerenchyma
  • Collenchyma
  • Vascular tissue

PERMANENT TISSUE DETAILS

• Epidermis:

  • Location: Outer layer around roots, stems, and leaves.
  • Basic Structure:
  • Brick-shaped, single-layered cells
  • Transparent, lacking chloroplasts
  • No intercellular air spaces
  • Covered by a waxy cuticle that prevents moisture loss.
  • Function: Protects underlying tissues from injury and desiccation; allows sunlight to enter for photosynthesis.

• Parenchyma:

  • Location: Abundant in stem, leaf, and root.
  • Basic Structure: Large cells with thin walls and abundant intercellular spaces. Stem and leaf parenchyma contain chloroplasts.
  • Function: Stores food and water, produces carbohydrates through photosynthesis, allows gaseous exchange, provides rigidity with cell sap.

• Sclerenchyma:

  • Location: Found in leaves, stems, and fruits.
  • Basic Structure: Cells with evenly thickened walls and small lumens.
  • Function: Provides mechanical support to the plant.

• Collenchyma:

  • Location: Present in young, growing herbaceous plants.
  • Basic Structure: Cells with unevenly thickened walls, thickened at the corners.
  • Function: Serves as strengthening tissue and provides mechanical support.

• Vascular Tissue:

  • Location: Found in the roots, stems, and leaves.
  • Xylem:
  • Components: Consists of xylem vessels and tracheids.
  • Function: Transports water and dissolved minerals from the roots to the rest of the plant.
  • Phloem:
  • Components: Comprised of sieve tubes and companion cells.
  • Function: Transports organic nutrients from the leaves to the rest of the plant.

ANIMAL TISSUES

• Animal tissues include four main types:
  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nerve tissue

EPITHELIAL TISSUE

• Definition: Specialized to form linings that cover both internal and external surfaces.
• Characteristics: Cells are tightly packed with minimal intercellular spaces.
• Types Include:
  • Squamous epithelium
  • Cuboidal epithelium
  • Columnar epithelium
  • Ciliated epithelium

CONNECTIVE TISSUE

• Definition: Binds, supports, or surrounds other tissues or organs.
• Types Include:
  • Areolar connective tissue
  • Dense connective tissue
  • Cartilage
  • Bone
  • Blood

CONNECTIVE TISSUE DETAILS

• Cartilage:

  • Location: Found between bones (e.g., vertebrae), in joints, and in structures like ears and noses.
  • Types: Hyaline, fibrous, and elastic cartilage.
  • Basic Structure: C-shaped cartilage rings in the trachea; tough rubbery matrix (chondrin); fluid-filled spaces (lacunae) housing cartilage cells (chondrocytes).
  • Function: Acts as a shock absorber in joints, prevents friction, provides flexibility and structure.

• Bone:

  • Location: Forms the endoskeleton of vertebrates.
  • Basic Structure: Contains a hard matrix of calcium phosphate and carbonate, Haversian canals for blood vessels and nerves, and is encased by a fibrous membrane (periosteum).
  • Function: Provides support and shape; mineral storage; blood cell formation in red bone marrow.

• Blood:

  • Location: Found in blood vessels (arteries, veins, and capillaries).
  • Basic Structure: Watery yellow fluid (plasma) containing red blood corpuscles (erythrocytes), white blood corpuscles (leucocytes), and blood platelets (thrombocytes).
  • Function: Transports nutrients, waste products, hormones, and plays a role in temperature regulation and immunity.

MUSCLE TISSUE

• Definition: Composed of specialized cells that allow movement through contraction.
• Types of Muscle Tissue Include:
  • Skeletal muscle: Striated and under voluntary control.
  • Cardiac muscle: Involuntary and striated, found only in the heart.
  • Smooth muscle: Non-striated and involuntary, found in organs.

NERVE TISSUE

• Definition: Composed of neurons that transmit nerve impulses.
• Location: Forms the brain, spinal cord (central nervous system), and peripheral nervous tissue.
• Basic Structure: Neurons consist of a cell body, dendrites (which conduct impulses toward the cell body), and axons (which carry impulses away).
• Types of Neurons Include:
  • Sensory neurons: Transmit impulses from receptors to the CNS.
  • Motor neurons: Transmit impulses from the CNS to effectors (muscles and glands).
  • Interneurons: Connect sensory and motor neurons in the brain and spinal cord.

APPLICATION OF INDIGENOUS KNOWLEDGE SYSTEM AND BIOTECHNOLOGY

INDIGENOUS KNOWLEDGE

• Definition: Knowledge acquired by communities through interaction with their environment.

BIOTECHNOLOGY

• Definition: The use of living organisms or biological systems in industrial processes, including food processing, antibiotics production, and genetic manipulation of crops.

TRADITIONAL BIOTECHNOLOGY

• Indigenous medicinal plants are used by over 60% of South Africans, especially traditional healers.
• Examples:
  • Devil’s claw
  • African potato

MEDICAL BIOTECHNOLOGY

• IMMUNITY:
  • Definition: Body's defense mechanism against pathogens (viruses, bacteria, protozoans, fungi).
  • Types of Immunity:
  • Natural immunity: External barriers (skin, mucus, fever, inflammation).
  • Acquired immunity: Developed through various means including maternal transfer of antibodies and vaccines.

VACCINES AND IMMUNISATION

• Definition: Vaccination is administering a vaccine to develop immunity to a disease. Vaccines typically contain a dead or weakened form of a pathogen.

ANTIBIOTICS

• Definition: Chemical substances that kill pathogenic bacteria but not viruses; most are derived from fungi.

BLOOD GROUPS AND TRANSFUSIONS

• Blood groups include A, B, AB, and O:
  • Universal donor: Blood group O
  • Universal recipient: Blood group AB
• Transfusion: Transfer of blood; incompatible groups lead to agglutination and can be fatal.

CLONING AND STEM CELL RESEARCH

• Cloning: The process of creating genetically identical replicas of molecules, cells, or organisms.
• Stem cells: Undifferentiated cells that can develop into any specialized cell.
  • Sources: Human embryos, umbilical cord, placenta.
  • Applications: Development studies, tissue replacement, disease treatment (e.g., diabetes, leukemia, Alzheimer's).