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

Trachea

Bronchus

Larynx

Bronchioles

Alveoli

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

Villi

Mouth

Liver

Pharynx

StomachLarge Intestine

Small Intestine

Oesophagus

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

DeltoidPectoralis 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

Penis

Seminal vesicle

Epididymus

Testis

Female Reproductive System

Sagittal View

Anterior View

Fallopian tube

Ovary

Uterus

Vagina

Uterus

Vagina

Fallopian tube

Urinary bladder

Nervous System

Cerebrum

Corpus callosum

Cerebellum

Thalamus

Hypothalamus

Midbrain

Pons

Medulla oblongata

Spinal cord

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