Chap 5: Cell Diversity

Cell Diversity

Cell Diversity

The differences that exist between plant/microbial/animal cells

Tissue

A group of similar cells adapted to carry out the same function

Plant tissues

Dermal tissue, Vascular/Transport Tissue

Types of vascular tissue

Xylem tissue, Phloem tissue

Types of xylem tissue

Xylem tracheids, xylem vessels

Dermal Tissue

This is a singular layer of cells surrounding plant parts. E.g. the epidermis. Found covering leaves, stems, and roots. Its function is to protect the plant, a cuticle prevents the loss of water

Appearance of Epidermis

Has living, rectangular walls, a slightly thickened cell wall, and sometimes a water-proof cuticle present on the surface

Xylem tracheid

Long, tapering cells with hollow sides at maturity. These overlap and allow water to pass from tracheid to tracheid through pits/holes in the walls. Found in coniferous trees, e.g. Pine

Xylem Vessel

Tubular structures with cells end to end. Wider than tracheids, and end walls break down to form continuous tube. Have pits on side walls, and efficient at transporting water. Found in flowering plants.

Function of xylem tissue

Transports water and minerals up a plant from roots. Gives mechanical support when turgid with water.

Phloem tissue

Living vascular tissue (due to companion cells), walls of sieve tubes are made of cellulose, and there is no lignin present. Found in vascular bundles of roots, stems, leaves, and flowers

Function of phloem tissue

Carries food, i.e. glucose from the leaf to other plant parts.

Animal tissue types

Epithelial, connective, muscular, nervous tissue.

Connective Tissue

This is a number of cells spread out in a ‘matrix’ produced by connective cells. This tissue type joins and supports other body structures.

Connective Tissue example

Blood. A matrix of red blood cells, white blood cells, and platelets floating in a plasma liquid.

Bone. Hollow, and needs to be filled with calcium, phosphorus, and vitamin D.

Nervous Tissue

This is a tissue composed of nerve cells, or neurons. Neurons are adapted to carry impulses to and from the brain/spinal cord.

Types of Neurons

Sensory neurons, Motor neurons

Sensory Neurons

Carries impulses from a sense organ/sensory cell up towards the central nervous system, the brain and spinal cord.

Motor neurons

Carries response impulses back from the Central Nervous System to an effector, a muscle or gland.

Tissue Culture

This is the growth of tissues on an artificial medium outside an organism. Taken from plant or animal.

Tissue Culturing in Plants

Micropropagation, of a carrot. Growth of large numbers of plants from a small plant cell/tissue pieces. Cells are taken from a mature organism and placed in a petri dish in agar jelly/a nutrient medium. This is placed in an incubator at 25degrees Celsius for a number of days. Now known as a callus.

Tissue culturing in animals

Skin grafting. This can be used to replace burnt skin. Previously skin would be taken from a healthy body part. Human cells are taken, placed on a special medium, and grown into sheets of human cells that grow as single layer tissues.

Organs

An organ is a structure composed of a number of tissues that work together to carry out one or more functions. E.g. Heart, Leaf.

Animal organ

Heart. Made of all four tissue types. Cardiac tissue. Outer membrane of pericardium is made of epithelial tissue. Blood/blood vessels made of connective tissue. Controlled by nervous tissue. This pumps blood around the body.

Plant organ

Leaf. Three tissue types found, dermal in epidermis, vascular (xylem and phloem) in vascular bundles, ground tissue. The process of photosynthesis occurs here.

Organ Systems

An organ system consists of a number of organs working together to carry out one or more functions. E.g. skeletal, muscular, reproductive.

Digestive System

Consists of mouth, oesophagus, stomach, small intestine, large intestine, and anus (in association with the liver and pancreas). Takes in food, breaks it down, transfers digestive nutrients to circulatory system.

Urinary System

Consists of 2 kidneys, bladder, two ureter tubes and one urethra. Removes waste from the body and controls composition of many chemicals in the blood.