Cells
(Division of Labour)
Chapter 24
In this chapter, you will learn…
• that cells of similar structures are
organised into tissues
• that several tissues may make up an
organ
• that organs are organised into systems
• to explain the significance of division of
labour
Unicellular Organisms
Paramecium
Amoeba
Unicellular Organisms
• Paramecium
– Microscopic organism
– Found on surface of water
(eg: pond, river)
– Has hair surrounding the
body for movement
– Has a mouth
Unicellular Organisms
• Amoeba
– Often found at bottom of ponds
or under rocks
– Does not move fast
– No arms, legs, eyes, mouth
– Eats by surrounding its prey with
its body
– Lives only for 2 days
– Reproduce by spliting itself into
2 new amoebas
Multicellular Organisms
• Have many different cells
• Different cells perform different
functions
• Examples
– Plants
– Humans
Cells in a Human
• Examples
– Red blood cell (transport
oxygen)
– Nerve cell (have nerve fibres
to transmit signals to and from
the central nervous system)
Cells in a Plant
• Examples
– Root hair cell
– Leaf guard cell
From cells to tissues
• Tissue
– Group of similar cells that are
specialised to perform a particular
function
Tissues in a Human
• Epithelial tissue
– Covering or lining tissue
to protect structure
beneath it
Connective tissue
– Joins, stores or
supports all parts of an
organism
Tissues in a Human
• Muscle tissue
– Cause movement
• Nerve tissue
– Carry messages
from one part of
body to another by
conducting
electrical signals
Tissues in a Plant
• Epidermal tissue
– Protects plant against
injury and losing too
much water
• Vascular tissue
– Transports materials
within a plant
Tissues in a Plant
• Photosynthesis tissue
– Carries out photosynthesis in a
plant
From Tissues to Organs
• Organ
– Group of specialised tissues that
are gathered in a certain part of the
body to perform a particular
function together
Organs in a Human
• Examples
– Skin
– Lungs
– Heart
Organs in a Plant
• Examples
– Leaves
– Stem
– Roots
– Flowers
From Organs to Systems
• System
– Different organs working together
to perform a major function in an
organism
Main Organ Systems in a Human
•
•
•
•
•
Respiratory system
Digestive system
Blood circulatory system
Skeletal system
Muscular system
Respiratory System
Nasal Passage
Pharynx
Larynx
Trachea
Bronchioles
Alveoli
Bronchus
Respiratory System
• Respiration
– Process in which cells release energy from
the food we eat
– Oxygen is required
– Carbon dioxide is removed
Respiratory System
• Mechanics of
breathing
Exhalation
Inhalation
Digestive System
Mouth
Pharynx
Oesophagus
Liver
Stomach
Large Intestine
Small Intestine
Villi
Digestive System
• Digestion
– Process in which large, insoluble food
substances are broken down into
smaller, soluble food substances for
absorption into blood
Blood Circulatory System
Blood Circulatory System
• Transports nutrients, gases, water and
hormones to different parts of the body
• Include red blood cells, white blood
cells, heart, blood vessels
Red blood cells
White blood cells
Skeletal System
Skeletal System
•
•
•
•
Supports our body
Gives us shape
Protects our organs
Enables movement
Muscular System
Deltoid
Pectoralis major
Biceps brachi
Gluteus maximus
Rectus femoris
Gastrocnemius
Muscular System
• Enables movement by
contraction and relaxation of
muscles
• 3 muscle types:
– Skeletal muscles
– Smooth muscles
– Cardiac muscles
Other systems in Human
• Reproductive System
- Produces sex cells (sperm, ovum)
- For reproduction
• Nervous System
- Consists of the brain, spinal cord and nerves
found throughout our body
- Controls and coordinates functions
throughout our body
- Enables us to respond to changes around us
Male Reproductive System
Urinary bladder
Vas deferens
Prostate gland
Urethra
Seminal vesicle
Epididymus
Penis
Testis
Female Reproductive System
Fallopian tube
Uterus
Urinary bladder
Vagina
Anterior View
Sagittal
View
Fallopian tube
Uterus
Ovary
Vagina
Nervous System
Cerebrum
Corpus
callosum
Thalamus
Hypothalamus
Midbrain
Pons
Medulla
oblongata
Spinal cord
Cerebellum
Plant Transport System
From Systems to Organisms
• Organism
– Made up of different systems
working effectively in a
coordinated manner
The Human Body
- An organism
CELLS
TISSUES
ORGANS
SYSTEMS
ORGANISM
Division of Labour
• Each cell in a multicellular organism
does not perform all the bodily
functions.
• Each type of cell specialises in
performing one particular function.
• Different functions in a multicellular
organism can be performed at the
same time by division of labour.
Division of Labour
• Division of labour
– Sharing different functions in an
organism among its cells, tissues,
organs and systems
– Ensures smooth running and
effective working of the different
parts in an organisms as well as the
organism as a whole