Multicellular organisms have a number of levels to the organism. The cells within the organism have their own functions and work as a team for the organism to benefit, this makes the cells become dependent on one another.
The organisms are in 5 levels to its organisation starting simply and becoming complex. Each of these levels have different levels of organisation. The levels go:
Level 1 cells
Level 2 tissues
Level 3 organs
Level 4 organ systems
Level 5 organisms
Level one is the cell, this is the simplest living thing with germs and bacteria being smaller than cells and they cannot live by themselves. For the bacteria to live it must go into a cell and take part of its function to survive, this damages the cell it is using. Within a cell a macromolecule can form, these are called organelles, these arte surrounded by membranes. The organelles are small structures that live within a cell, these are mitochondria and chloroplast. The mitochondria create energy whereas chloroplast use the energy from sunlight and make sugars. All organisms are made of cells, however some are single celled and some are multicellular. The cells that are single celled are prokaryotic and multicellular are eukaryotic.
Level 2 is the tissues, these are made from the cells that have a common structure and function, and these will work together for specific tasks, cells can produce blood and bone. The tissues are grouped in 4 different types; epithelial tissue, muscle tissue, nerve tissue and connective tissue. These all have different roles which they execute. The epithelial cover the surface of the body and lines a number of parts to the body, the muscular tissue creates physical force to move the body and create heat for the body, nervous tissue has the job of identifying changes within the body and responds by sending impulses, lastly the connective tissue has a number of roles, it protects, binds and supports organs in the body along with storing fat as energy which provides immunity. The tissues in the body develop from 3 different germ layers, these are ectoderm, endoderm and mesoderm, these different layers create epithelial tissue but only mesoderm layers create connective and muscular tissue and ectoderm only produces nervous tissue.
...(download the rest of the essay above)