Unicellular and Multicellular Organisms

•Organisms are living things

•There are many kinds of organisms in nature.

•Organisms can be divided into two groups, namely unicellular organisms and multicellular organisms.

Unicellular organisms

•Unicellula organisms are organisms that consist of one cell only (uni means one)•Unicellular organisms are also micro – organisms.•Micro organisms are very tiny organisms and can only be seen under the microscope

•These organisms usually live in the sea, rivers and lakes•Unicellular organisms carry out all the life processes such as movement, response, respiration, digestion, excretion, reproduction and growth.

Euglena

Amoeba

Paramecium

Examples of unicellular organisms

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Yeast

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Chlamydomonas

Multicellular organisms•Multicellular organisms are organisms that consist of many cells (multi means many)•Like unicellular organisms, multicellular organisms carry out all the processes of life.•Multicellular organisms are made up of many types of cells. Each type of cell has a different structure and carries out only specific functions.•Man is the most complex multicellular organisms.

Examples of multicellular organisms

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Hydra

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Earthworm

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Deer

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Spirogyra

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Mucor

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grass

Cell organization in the Human body

•Humans are multicellular organisms. There are million of cells in our body.•Cells in our body have different sizes and shapes and carry out various functions.•They are classified into many different groups. Each group 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 functions

Insert imageEpithelial cells

Insert imageReproductive cells

Insert imageMuscle cells

Insert imageNerve cells

Insert imageRed blood cells

Insert imageWhite blood cells

Insert 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 carry out various functions in the body.•Cells in our body work together at three levels of organization: the tissue level, the organ level and the system level.

Tissue level•Tissue is a group of similar cells working together as a unit.•There are four major types of basic tissue in the human body.

Major tissue group

Function Example/ location

Epithelial tissue

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•Covers the body and line surfaces of organs

•Blood vessels, skin and the lining of the digestive tract

Nerve tissue

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•Responds to stimuli and transmits impulses

•Brain and spinal cord

Connective tissue

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•Connects various sets of tissues •Provides support

•Blood, bone, fat cells, tendons, ligaments, cartilage in nose and in ear

Muscle tissue

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•Causes movement by contraction

•Heart, walls of the digestive tract, skeletal muscle

Organ level

•A few different types of tissues group together and form an organ. An organ perform a specific function

•For example, the small intestine which is an organ for the digestion and absorption of digested food, is made up of muscle tissue and epithelial tissue.

How cells combine to form tissues, and tissues combine to form organs

ImageMuscle cells

ImageMuscle tissue

ImageEpithelial and muscle tissues combine together to form the wall of an organ such as the small intestines

ImageEpithelial cells

ImageEpithelial tissue

•Organs are more complex than tissues.

•There are many organs in the human body. Heart, eyes, ears, lungs, liver, skin, kidneys and reproductive organs are examples of organs in the human body.

•Each organ carries out a particular function.

Organs in the human body

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Human body (organs)

Eye detects light

Nose detects smell

Lungcarries out

gaseous exchange

Brain Controls parts of

the body

Ear Detects sound

Skin Regulates body

temperature

Heart Pumps blood to all parts of the body

Stomach Digests food substance

System level•A group of organs which work together to perform a specific function forms a system.•For example, organs such as kidney, ureters, urinary bladder and urethra from excretory system.

Example of systems

Muscular system

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Controls body movement

Skeletal system

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Provide support and protects internal organs

Nervous system

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•Receives and evaluates information from the surroundings.•Controls and coordinates body’s activities.

Blood circulatory system

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•Bring nutrients and oxygen to cells•Removes dissolved wastes from the cells

Respiratory system

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•Supplies body with oxygen•Remove carbon dioxide from the body

Digestive system

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•Digests and absorbs food•Eliminates solid wastes

Reproductive system

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•Produce offspring•Ensures continuation of species

Excretory system

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•Removes wastes from the body

Organism level

•All systems in the body work together to produce an independent organism.

•These system do not work independently. They all cooperate with one another so that the human body functions as a whole

Organism in a human being

Insert imageEpithelial cells

Insert imageEpithelial tissue

Insert imageStomach (organ)

Insert imageDigestive system

Insert imageMuscle cells

Insert imageMuscle tissue

Insert imageSmall intestine

(organ)

•The organization of cells can be represented in the form of ladder of hierarchy.

cell

tissue

organ

system

organism

Simple Complex

Diffusion and Osmosis in Cells

Diffusion

•Diffusion is the movement of the molecules from the region of a higher concentration to the region of a lower concentration.

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•Where there is no difference in concentration, molecules diffuse in all directions at the same rate.•The rate of the net diffusion depends on the difference in concentration. The greater the concentration, more molecules will move from the high to the low concentration per unit time.•The transport of the oxygen and nutrients into cells and carbon dioxide and other waste materials out of the cells are done by diffusion.•Small ions such as sodium ion diffuse through the cell membrane.

Osmosis•Osmosis is the net movement of water molecules across a semipermeable membrane from a region of a higher water potential to a region of a lower water potential

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•Osmosis is important for the entry and exit of water to or from cells of all organisms. For example water moves through the cells of roots.•Besides, osmosis can also transport water across living tissues.