Chpt. 8 Cell Diversity

Cells are not identical - they diversify their structure to suit their function!!!!!!!

TissuesA Tissue is a group of similar cells that are modified to carry out the same function.

Tissue Types

Animal Tissue:Four main types of animal tissue (two of which we will study in more detail):

Epithelial – covers internal and external surfaces of the body.

Connective

Muscular – capable of contraction found in muscles and internal organs.

Nervous

Animal Tissue:Connective Tissue:• Consists of a number of cells spread out in a matrix that is produced by the connective cells.• Connective tissue joins and supports other body structures.

Animal Tissue:Nervous Tissue:• Nervous tissue is composed of nerve cells called neurons.• Neurons are adapted to carry impulses to and from the brain and spinal cord.

Tissue Types

Plant Tissue:Four main types of plant tissue (two of which we will study in more detail):

Dermal Vascular Ground Meristematic

Plant Tissue:Dermal tissue:• A single layer of cells that surrounds the different parts of a plant e.g. one type of dermal tissue – epidermis

• Location – epidermis found as a covering on leaves, stems and roots.

• Appearance – epidermis cells are living, rectangular cells. Sometimes a layer called a cuticle is found on its outer surface.

• Function – protect the plant. - presence of a cuticle prevents water loss from the

plant.

Plant Tissue:Vascular Tissue:• Transports materials around a plant.

• Consists of two types of cells:- xylem- phloem

• Xylem: - transports water and minerals around the plant. - provide support (woody plants)

• Phloem: - transports food from the leaves to the other parts of the plant.

Plant Tissue:

Plant Tissue:

Tissue Culture• Tissue culture is the growth of tissues in or on an artificial medium outside an organism.

• The tissue sample is removed from a plant or animal and grown in glassware ( in vitro) or in a bioreactor under carefully controlled conditions.

• Sterile conditions are essential in tissue culture. This involves the prevention of the growth of micro-organisms in the bioreactor, such as bacteria and yeast, as these would produce waste products which contaminate the container and often kill the desired cells.

• Growth is by mitosis and produces a cluster of identical offspring - a clone.

Conditions necessary for Tissue growth

• Oxygen• Nutrients• Growth factors and hormones• Correct pH• Optimum temperature• Sterile conditions• Freedom from competition

Applications of Tissue Culture

Micropropagation Monoclonal Antibodies

Micropropagation:this is the growth of large numbers of plants from very small plant pieces.

• Desirable plant cells obtained

• Cells grown on controlled culture medium

• Form callus (clump of similar cells)

• Growing conditions changed to promote callus growth

• Over time callus forms a plant embryo and then a young plant

• Once large enough young plant can be planted out

Benefits of micropropagation:

• Produces exact copies

• Quickly produces mature plants

• Doesn’t need pollinators or seeds

• Producing plants that are disease resistant and virus free

• Inexpensive method of producing large number of similar plants.

Monoclonal Antibodies (MAB’s) and Cancer Research:

• Antibodies are special proteins that react with one particular chemical – called an antigen.

• Cancer cells produce special antigens that are not produced by any other normal body cells.

• Tissue culture can be used to produce special antibodies, MAB’s, that will react with the antigens on cancer cells

Benefits of monoclonal antibodies:

• MAB’s will not join to normal cells.

• May change colour on reacting with cancer antigens allowing the presence of cancerous cells to be detected.

Organs

An organ is a structure composed of a number of tissues that work together to carry out one or more functions

Examples of Plant Organs:Leaf – Dermal tissue, vascular tissue, ground tissue - all of these tissues combine so that the leaf can carry out photosynthesis. Root – anchorage and absorptionStem – support and transportFlower – reproduction Seeds – reproduction

Organs

Examples of animal organs:Heart – muscular tissue, epithelial tissue, connective

tissue, nervous tissue - combined all of these tissues allow the heart to

carry out its function i.e. pump blood

StomachIntestineLiverLungsSkin

Organ Systems

All the organ systems combine to form the organism.

Animal organ systems:Circulatory system: - consists of heart, blood vessels, blood,

lymph vessels, lymph. - function transport materials, fight infection

Digestive system: - consists of mouth, oesophagus, stomach, small intestine, large intestine and anus. - function to take in, break down and transfer digested food into circulatory system.