Unicellular and Multicellular Organisms•Organisms are living things•There are many kinds of organisms in nature.•Organisms can be divided into two groups, namelyunicellular organisms and multicellular organisms.
Unicellular organisms•Unicellula organisms are organisms that consist ofone cell only (uni means one)•Unicellular organisms are also micro – organisms.•Micro organisms are very tiny organisms and can onlybe seen under the microscope•These organisms usually live in the sea, rivers and lakes•Unicellular organisms carry out all the life processessuch as movement, response, respiration, digestion,excretion, reproduction and growth.
Examples of unicellular organismsImageYeastImageChlamydomonas
Multicellular organisms•Multicellular organisms are organisms thatconsist of many cells (multi means many)•Like unicellular organisms, multicellularorganisms carry out all the processes of life.•Multicellular organisms are made up of manytypes of cells. Each type of cell has a differentstructure and carries out only specific functions.•Man is the most complex multicellularorganisms.
Examples of multicellular organismsImageHydraImageEarthwormImageDeerImageSpirogyraImageMucorImagegrass
Cell organization in the Human body•Humans are multicellular organisms. There aremillion of cells in our body.•Cells in our body have different sizes and shapes andcarry out various functions.•They are classified into many different groups. Eachgroup of cells carry out a special function.
The types and functions of human cells•There are many types of cell in our body•Each type of cell performs only one specific function.•This characteristics is known as specialization of cells.
Different types of cell and their functionsInsert imageEpithelial cellsInsert imageReproductivecellsInsert imageMuscle cellsInsert imageNerve cellsInsert imageRed blood cellsInsert imageWhite blood cellsInsert imageEpithelial cell
The organization of cells in the human body•Most organisms are made up of many cells.•They have different shapes and sizes, and carryout various functions in the body.•Cells in our body work together at three levels oforganization: the tissue level, the organ level andthe system level.
Tissue level•Tissue is a group of similar cells working togetheras a unit.•There are four major types of basic tissue in thehuman body.Major tissue group Function Example/ locationEpithelial tissueInsert image•Covers the body and linesurfaces of organs•Blood vessels, skin andthe lining of the digestivetract
Nerve tissueInsert image•Responds tostimuli andtransmitsimpulses•Brain andspinal cordConnective tissueimage•Connects varioussets of tissues•Provides support•Blood, bone, fatcells, tendons,ligaments, cartilagein nose and in earMuscle tissueimage•Causes movementby contraction•Heart, walls of thedigestive tract,skeletal muscle
Organ level•A few different types of tissues group togetherand form an organ. An organ perform a specificfunction•For example, the small intestine which is anorgan for the digestion and absorption ofdigested food, is made up of muscle tissue andepithelial tissue.
How cells combine to form tissues, and tissuescombine to form organsImageMuscle cellsImageMuscle tissueImageEpithelial and muscletissues combine togetherto form the wall of an organsuch as the smallintestinesImageEpithelial cellsImageEpithelial tissue
•Organs are more complex than tissues.•There are many organs in the human body.Heart, eyes, ears, lungs, liver, skin, kidneysand reproductive organs are examples oforgans in the human body.•Each organ carries out a particular function.
Organs in the human bodyInsert imageHuman body(organs)Eyedetects lightNosedetects smellLungcarries outgaseous exchangeBrainControls parts ofthe bodyEarDetects soundSkinRegulates bodytemperatureHeartPumps blood to allparts of the bodyStomachDigests foodsubstance
System level•A group of organs which work together to perform aspecific function forms a system.•For example, organs such as kidney, ureters, urinarybladder and urethra from excretory system.Example of systemsMuscular systemInsert imageControls body movementSkeletal systemInsert imageProvide support andprotects internal organs
Nervous systemInsert image•Receives and evaluatesinformation from thesurroundings.•Controls and coordinatesbody’s activities.Blood circulatorysystemInsert image•Bring nutrients and oxygento cells•Removes dissolved wastesfrom the cells
Respiratory systemInsert image•Supplies body with oxygen•Remove carbon dioxidefrom the bodyDigestive systemInsert image•Digests and absorbs food•Eliminates solid wastes
Organism level•All systems in the body work together to produce anindependent organism.•These system do not work independently. They allcooperate with one another so that the human bodyfunctions as a whole
Organism in a human beingInsert imageEpithelial cellsInsert imageEpithelial tissueInsert imageStomach (organ)Insert imageDigestivesystemInsert imageMuscle cellsInsert imageMuscle tissueInsert imageSmall intestine(organ)
•The organization of cells can be representedin the form of ladder of hierarchy.celltissueorgansystemorganismSimple Complex
Diffusion and Osmosis in CellsDiffusion•Diffusion is the movement of the molecules fromthe region of a higher concentration to the region ofa lower concentration.Insert image
•Where there is no difference in concentration,molecules diffuse in all directions at the samerate.•The rate of the net diffusion depends on thedifference in concentration. The greater theconcentration, more molecules will move from thehigh to the low concentration per unit time.•The transport of the oxygen and nutrients intocells and carbon dioxide and other wastematerials out of the cells are done by diffusion.•Small ions such as sodium ion diffuse throughthe cell membrane.
Osmosis•Osmosis is the net movement of water moleculesacross a semipermeable membrane from a regionof a higher water potential to a region of a lowerwater potential•Insert image
•Osmosis is important for the entry and exitof water to or from cells of all organisms. Forexample water moves through the cells ofroots.•Besides, osmosis can also transport wateracross living tissues.
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