In this topic of IBDP Biology, we will learn about cell differentiation.

• Membranous sacs or other structures inside a cell.
• They separate different metabolic reactions inside the cell.

• The smallest living unit;
• They may live independently,
  • Carry out all life processes in one cell.
  • • All prokaryotes
    • Some protoctists, eg Amoeba and Paramecium
    • Some fungi – yeast.
•  Or they may be part of a multicellular organism.

• When it comes to IBDP Biology, they contain many specialised cells.
• Perform different activities.
• Division of labour
• All cells rely on each other.
• Each cell may only carry out a few of the essential life processes.
• Differentiation occurs initially after fertilisation:
  • Stem cells created by mitosis, forming a blastocyst.
  • An embryo forms:
    • Complex chemical signalling processes switch on or off genes in cells in certain locations.
    • Cells differentiate into groups of similar specialised cells.

When it comes to IBDP Biology, a group of cells of a common origin, structure and function.

Animal examples

• Epithelial tissue:
  • Simple cells arranged in single or multilayered sheets.
  • The cover the internal and external surface of the body of an organism.
  • They often form exchange surfaces in the body, with capillaries providing the blood supply.
  • Capillary walls are made of a type of epithelium called endothelial cells.
  • Examples: skin, lining the intestinal tract, walls of alveoli, and nephrons in the kidney.

• Connective tissue:
  • Adds support and structure to the body
  • Includes bone, cartilage, fat and blood.
• Muscle tissue
• Nerve tissue

Plant examples:

• Epidermal tissue:
  • Outer single-layered group of cells covering a plant, especially the leaf and young tissues including stems and roots.
  • The epidermis serves several functions:
    • Protection against water loss – secretion of waxy cuticle by upper epidermis in leaves
    • Regulation of gas exchange – guard cells.
    • Absorption of water and mineral nutrients – root hair cells
• Vascular tissue:
  • xylem and phloem.
• Packing tissue - Parenchyma:
  • Close-packed cells
  • Large central vacuoles, which allows the cells to store and regulate ions, waste products and water.
  • They form:
    • The cortex and roots and stems.
    • The mesophyll of leaves

When it comes to IBDP Biology, one or more types of tissues, interacting as a structural, functional unit; it carries out a specific physiological function.

Human examples – heart, stomach, lungs, kidneys

Eg heart contains:

• Muscle tissue - myocardium
• Connective tissue attaches epithelium to myocardium
• Epithelial tissue surrounds the heart and lines the chambers
• Nervous tissue for regulation of the heart beat

Plant example – the leaf contains:

• Epidermal tissue - upper and lower epidermis.
• Packing tissue – palisade and spongy mesophyll.
• Vascular tissue – xylem and phloem in veins.

• When it comes to IBDP Biology, two or more organs whose specific functions are integrated in the performance of a specific task.
• Human examples: nervous, musculoskeletal, reproductive, excretory
• Eg circulatory system:

• Heart – provides the force to move the blood.
• Blood vessels – carry the blood:
  • Arteries to tissues
  • Capillaries through tissues and enable exchange
  • Veins from tissues to heart

• Eg respiratory system: Lungs, Bronchi, Trachea
• Eg digestive system:
  • Salivary glands
  • Oesophagus
  • Stomach
  • Small intestine
  • Pancreas
  • Large intestine

This is the end of this topic

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