·
In this topic of IBDP Biology, we will learn about cell differentiation.
Organelle
- Membranous sacs or other structures inside a cell.
- They separate different metabolic reactions inside the cell.
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.
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.
Tissue
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:
Organs
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.
Organ system
- 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
