Cell Diversity

Tissue: group of similar cells modified to carry out the same functions

Two types: simple (one cell type), complex (more than one cell type)

Four types of plant tissue: dermal, vascular, ground, meristematic

1. Dermal tissue - surrounds and protects plants, cells rectangular and living e.g. epidermis (also has cuticle a waterproof layer on surface that prevents water loss)
2. Vascular tissue – transports materials, 2 types

• Xylem: hollow tubes, transports water & minerals from roots-stem-leaves. Also forms wood in trees
• Phloem: transports food from leaves to other parts of plant, plant made up of tube-like structures

Four types of animal tissue: epithelial, connective, muscular, nervous.

1. Connective tissue – cells spread out in matrix, joins & supports other body structures e.g. bone, cartilage, blood (red blood cells, white blood cells, platelets suspended in matrix called plasma)
2. Nervous tissue – made up of neurons (nerve cells) – carry electrical impulses to & from brain and spinal cord

Tissue Culture: the growth of cells in or on a sterile nutrient medium outside an organism

Tissue culture - group of cells

Cell culture – isolated cells

In vitro – growth outside body

In vivo – growth inside body

• Conditions necessary for tissue culture: absence of contaminating organisms, food vitamins and minerals, substances (e.g. hormones) to stimulate growth

Applications of tissue culture:

1. Micropropagation: growth of large number of plants from small parts of a plant – advantage = produces genetically identical plants, inexpensive and fast
2. Cancer research: special antibodies (monoclonal antibodies-MABs) tell if cells are cancerous
3. Skin grafts: stem cells from bone marrow & umbilical cord to grow new skin

Organ: a structure composed of a number of tissues that work together to carry out one or more functions

E.g. root, stem, leaf, flowers, seeds, fruits, stomach, brain, liver, kidney, heart

Example of plant organ - leaf (has 3 types of plant tissues: dermal, vascular, ground)

Example of animal organ – heart

1. Walls of heart – muscular tissue (cardiac tissue)
2. Membrane – pericardium (epithelial tissue)
3. Blood & numerous blood vessels (connective tissue)
4. Controlled by neurons

Organ system: number of organs working together to carry out one or more functions

• Organ systems combine to form an organism

E.g. circulatory system - heart, blood vessels, blood, lymph vessels, lymph

Function: transport materials around body & fight infection

E.g. digestive system - mouth, oesophagus, stomach, small intestine, large intestine, anus.

Function: take food in, break it down & transfer digested food into circulatory system which carries it to all cells in the body

Biological organisation: cell – tissue – organ – organ system – organism

E.g. red blood cell – blood – heart – organ system – organism