This document discusses unicellular and multicellular organisms. Unicellular organisms, like yeast and amoeba, consist of a single cell and carry out all life processes within that one cell. Multicellular organisms, like humans, are made of many different cell types that combine to form tissues and organs and work together in organ systems. The human body contains trillions of cells organized into tissues, organs, and four main organ systems - integumentary, skeletal, muscular, and nervous - that all work cooperatively to form a living organism.

1. 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.

2. 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.

3. Euglena

4. Amoeba

5. Paramecium

7. Examples of unicellular organisms
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Yeast
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Chlamydomonas

8. 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.

9. 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

10. 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.

11. 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.

12. Different types of cell and their functions
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Epithelial cells
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Reproductive
cells
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Muscle cells
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Nerve cells
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Red blood cells
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White blood cells
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Epithelial cell

13. 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.

14. 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

15. 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

16. 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.

17. How cells combine to form tissues, and tissues
combine to form organs
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Muscle cells
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Muscle tissue
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Epithelial and muscle
tissues combine together
to form the wall of an organ
such as the small
intestines
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Epithelial cells
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Epithelial tissue

18. •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.

19. Organs in the human body
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Human body
(organs)
Eye
detects light
Nose
detects smell
Lung
carries 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

20. 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

21. 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

22. 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

23. Reproductive system
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•Produce offspring
•Ensures continuation of
species
Excretory system
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•Removes wastes from the
body

24. 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

25. Organism in a human being
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Epithelial cells
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Epithelial tissue
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Stomach (organ)
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Digestive
system
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Muscle cells
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Muscle tissue
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Small intestine
(organ)

26. •The organization of cells can be represented
in the form of ladder of hierarchy.
cell
tissue
organ
system
organism
Simple Complex

27. 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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28. •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.

29. 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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30. •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.