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Chapter 7: Cell Diversity
Leaving Certificate Biology
Higher Level
Tissue
• Tissue: group of similar cells with a shared
function
Tissues
• Plant tissue: meristematic tissue divides to
ultimately give rise to three types of plant tissue:
– Dermal tissue: covering layer of tissue functions in protection
– Vascular tissue: functions in transport:
• Xylem (water & minerals)
• Phloem (glucose and amino acids)
– Ground tissue: bulk of plant, comprising the
tissue between the dermis and vascular tissues functions in photosynthesis, storage, and
support
Tissues
• Animal tissue: four main categories:
1. Epithelial tissue: covering layer of tissue for the outside
of body and on internal organs and cavities within body functions in protection, absorbing, and/or secretion
depending on location, e.g. skin, kidney and gland
tubules, blood vessels (capillaries, arteries, veins) and
mucous membranes of the respiratory and digestive
systems
2. Connective tissue: sparsely located cells in a matrix
secreted by those cells - functions in binding together
and supporting other tissues, e.g. blood, cartilage,
adipose, bone, tendons and ligaments
Tissues
• Animal tissue (continued):
3. Muscular tissue: long excitable cells (muscle fibre)
capable of generating movement - functions in creating
movement of limb and appendages (striated muscle)
aswell as in digestion (smooth muscle) and pumping
blood around the body (cardiac and smooth muscle)
4. Nervous tissue: excitable cells (called neurons)
consisting of a cell body, dendrites and axons (which
can be up to a metre long!) - functions in sensing stimuli
and transmitting signals from one part of the body to the
other
Organ
• Organ: group of tissues that carry out a
particular function
– Examples of animal organs: heart; lungs;
kidneys
– Examples of plant organs: leaf; flower; stem
Organ system
• Organ system: group of organs that carry
out a number of linked functions
– Examples of animal organ systems:
circulatory system
– Examples of plant organ system: root system
Tissues
• Tissue/Cell Culture: the growth of cells in a nutrient
medium outside a living organism
– It is possible to grow individual cells or groups of living
cells (tissues) in artificial (in vitro), sterile growth
medium (containing a large mixture of many nutrients –
including glucose, amino acids, hormones, minerals,
vitamins, and antibiotics to prevent microorganisms
taking hold)
Tissues
• Tissue Culture: Process: e.g. plant breeding:
– Take a very small piece of tissue of interest from plant,
e.g. carrot tissue, and placed in nutrient culture medium,
where the cells begin to divide to form a small plantlet
which continues to grow – eventually forming a new
plant which will be planted in soil when strong enough
Plant Breeding
Root of
carrot
plant
Transverse
section of Small plantlet
root
develops from
Small
fragments
Fragments
cultured in
nutrient
medium
the dividing
cells
Cells begin to
divide
Adult
plant
Plant cultured on agar
medium and later
transferred to soil