CELL DIFFERNTIATION
Cell differentiation:
 Examples of animal body system:
 is the process by which cells develop from
reproductive system, digestive system,
simple into more complex forms in order to
excretory system and respiratory system.
perform a specific role.
 Examples of plant body system: root system
OR
and shoot system
 is the process by which cells undergo
structural modification and specialization
Organisms
to carry out specific functions in an
Comprise various systems that join together to
organism.
carry out specific function.
 Carry out all life processes such as excretion,
This process occurs after cell division.
nutrition, growth, or sensitivity.
Cell differentiation is also known as division of
labor within the organism.
Importance of Cell differentiation
1. Cell differentiation leads to a division of
labor.
 This cell specialization helps the body to
carry out all life processes at the same
time and more efficiently.
2. Enable organism to perform different tasks.
3. Leads to the formation of an organism
Cell organization
Cell organization is the arrangement of living
components in a cell.
 Each component called an organelle
Organelle is the structure that has a specific
function in the cell such as Mitochondria.
Cells are the smallest functional living unit and
the most basic part of living organism.
Tissue
This is the group of specialized cells that join
together to carry out a specific function.
 Examples of Animal tissues: Bones, muscles
epithelial tissues, nerve tissues and blood
tissues
 Examples of plant tissues: Xylem tissue,
phloem tissue.
Organ
This is a group of various tissues that join
together to perform a specific function.
 Examples of animal organs: stomach, brain,
liver, muscles, skin or eye
 Examples of plant organs: leaves, fruits,
roots or flowers
Organ system
Several different organs in the body may work
together to carry out a major function in the
body.
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An organism is a living thing which is a
complete entity, cellular organization can be as:
A) Unicellular organism
Sometimes termed as single cell an organism
made up of one cell.
In such organisms, only one cell carries all the
life processes such respiration and
reproduction.
Examples of such organisms are Amoeba,
Paramecium, Yeast, and bacteria
B) Multicellular organism
The organisms made up of more than one cell.
The cells have different functions and the
features that make them better suited to carry
out these functions. (Cell specialization or cell
differentiation)
Examples of such organisms are: Plant, Animal,
and spirogyra
Summary as
Some important organs and systems of a
mammalian body
System: Excretory system
Organs: Kidney, urethra, urinary bladder, skin,
liver and lungs.
Functions:
Removal of waste products or excess materials
from the body.
System: Digestive system
Organs: Stomach, intestine and digestive
glands.
Functions: Digestion of food and Absorption of
food and water.
System: Nervous system
Organs: Brain, spinal cord, nerves, sense
organs
Functions: Detection of stimuli/transmission
of impulses
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System: Circulatory system
Organs: Heart, blood vessels and lymphatic
vessels
Functions: Transport of nutrients, gases,
excretory products, hormones.
System: Respiratory system
Organs: Lungs. Gills, skin, trachea
Functions: Exchange of gases, removal of
carbon dioxide and uptake of oxygen.
Organs: Ovaries, uterus, testes
Functions: Production of gametes and new
individuals.
System: Endocrine system
Organs: Endocrine glands (e.g. pituitary gland,
Pancrease and thyroid)
Functions:
Production of gametes and new individuals.
System: Reproductive system
Level of cell organization
Organelle: Structure that has a
specific function
Cell: a basic unit of life.
Tissue: a group of cells working
together to perform a common
function.
Organ: Tissues working together.
Organ system: group of organs
working together.
Organism: The entire living being.
Specialized cells (Differentiated cells)
Specialized cells are cells that perform specific
functions.
 When cells differentiate, they change in size,
shape and acquire special features that
make them suited to perform their function.
 They have unique structures and features
that allow them to operate differently and
carry out their intended functions.
Examples of specialized animal cells include:

(b) Produce digestive enzymes which destroy
the microorganisms and immune the body
against further infections.
 Lymphocytes produce chemical substance
called antibodies
STRUCTURE OF A WHITE BLOOD CELL SEEN
UNDER MICROSCOPE
Blood cells, reproductive cells and nerve
cells.
Examples of specialized plant cells include:
Root hair cells, guard cells, xylem vessel and
palisade cells.
Specialized animal cells (Types of animal
cells)
1. Blood cells
There are three types of blood cells which are
specialized to perform specific functions
(A) White blood cells (leucocytes)
Are irregular-shaped nucleated cells
The role of white blood cells
(a) To protect body against pathogens.

The phagocytic white blood cells
engulf and destroy harmful foreign
bodies. (phagocytosis)
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Structure of white blood cell.
(B) Red blood cells (erythrocytes)
They lack nuclei and a biconcave in shape; (this
provide large surface area for transporting
oxygen from the lungs to various parts of the
body)
Filled with protein pigments called
Haemoglobin: which give them the red colour
Role of red blood cells
To transport oxygen from the lungs to the
tissues of the body.
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
Haemoglobin readily combines with oxygen
to form oxyhaemoglobin
STRUCTURE OF RED BLOOD CELL SEEN
UNDER THE MICROSCOPE
Function of Sperm
– To fertilize the female egg in order for
reproduction to take place.
(b) Ova
They are female gametes produced in the
ovaries.
 They are immobile round is shape.
(C) Platelets (thrombocytes)
They are the fragments of red blood cells which
have failed to form normally.
They contains enzymes called thrombokinase
and mineral salts of calcium ions.
DIAGRAM OF AN OVUM SEEN UNDER
MICROSCOPE
Function of Platelets
– To form blood clots – helps to prevent loss of
blood from the wounds.
2. Reproductive cells
Reproductive cells or gametes are responsible
for the transmission of hereditary traits (genes)
Also responsible giving rise to new individuals
(offspring)
Function of Ova
– Fertilized by male gamete in order for
reproduction to take place.
There are two types of gametes: male gametes
(sperm cells) and female gametes (ova)
Nerve cell
(a) Sperm cells
They are male gametes produced in the testes.
The mature sperms are mobile.

Nerve cells are also called neurons.
STRUCTURE OF SENSORY NERVE CELL SEEN
UNDER THE MICROSCOPE
They contain numerous mitochondria which
provide the necessary energy for rapid

locomotion.
The sperm cell has a tail which enables it to

swim to the egg.
Has a pointed head which enables it to
penetrate the egg.
STRUCTURE OF SPERM CELL SEEN UNDER
THE LIGHT MICROSCOPE
Function of nerve cells
– To detect the changes in the environment,
both internal and external to the body.
– To transmit or conduct nerve impulses
(messages) from/to the brain, spinal cord or
sense organs.
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Types of plant cells (Specialized plant
cells)
Function of Guard cells
To control the opening and closing of stomata.
The following are examples of specialized plant
cells:
(c) Xylem vessels
(a) Root hair cells
These cells absorb water and mineral salts from
– Xylem vessels are made up of hollow dead
cells with walls made of lignin.
the soil.
– Lignin is a tough rigid material that makes up
the wall of xylem vessels.
Role of the root hair
Helps to increase the surface area for
absorption of water and mineral salts from the
soil.
DIAGRAM OF ROOT HAIR CELL
Function of xylem vessels
(b) Guard cells

– Guard cells surround the stomata. (Singular:
Stoma)
Transport water and minerals from the root
to the leaves.

Support the plant in the form of wood.
– The inner walls of the guard cells are thicker
than the outer walls- this makes them expand
irregularly.
– When the guard cells expand, the stoma
opens.
– When they contract, the stoma closes.
– Stomata are the tiny pores used for gaseous
exchange and loss of excess water
STRUCTURE OF GUARD CELLS SHOWNG
(d) Palisade cells
– Palisade cells are found in the leaves contain
large amounts of chloroplasts.
– Chloroplasts are site for photosynthesis.
– They contain chlorophyll which traps sunlight
energy during photosynthesis
STRUCTURE OF PALISADE CELL AS SEEN
UNDER A LIGHT MICROSCOPE
STOMA
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+255713097337
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