cell as a basic unit of life
DESCRIPTION
SCIENCE FORM 1 CHAPTER 2TRANSCRIPT
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CHAPTER 2 Cell as a unit of life
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2.1 WHAT IS A CELL?
� A cell is the basic unit of life.
� Its size is too small to be seen with the naked eye.
� We need an instrument called a microscope to
observe cells.
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MICROSCOPE
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THE FUNCTIONS OF MICROSCOPE’S PARTS
Part Function
Eyepiece To magnify the image formed by he objective
lens.
Objective lens To magnify the image of the object.
Stage clip To hold the microscope slide in position.
Adjustment knob To get a sharper focus of the object.
Diaphragm To control the amount of light entering the
objective lens.
Stage To support the microscope slide.
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PLANT CELL AND ANIMAL CELL
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SIMILARITIES BETWEEN PLANT AND
ANIMAL CELL
� Have cell membrane
– controls the movement of substances in
and out of the cell
Have nucleus � Have nucleus
– control all activities of a cell
� Have cytoplasm
– it’s a jelly like-substance fluid filled with cell
sap (where chemical processes take place)
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DIFFERENCES BETWEEN PLANT AND
ANIMAL CELL
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2.2
UNICELLULAR AND MULTICELLULAR ORGANISMS
� Organism consists of living things living things which
include microscopic of animals and plants
(bacteria, viruses and fungus)
� A life process is a process conducted by all living � A life process is a process conducted by all living
things to enable them to survive in the world
� Life process conducted by multicellular
organisms are more complex compare to a
unicellular organisms
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UNICELLULAR ORGANISMS
� Organisms that consist of only one cell are called
unicellular organisms.
� These organisms usually live in water. Some of
them such as bacteria and yeast can even live in them such as bacteria and yeast can even live in
air and human body.
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UNICELLULAR ORGANISMS THAT
PHOTOSYNTHESIZE
� Unicellular organisms such as euglena and
chlamydomonas which consists of chloroplasts
can produce food by themselves through the
process of photosynthesis
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MULTICELLULAR ORGANISMS
� Multicellular organisms are complex organisms
that made up of many cells.
� Multicellular organisms have many types of
different cells with its special function. This
caused them to have a huge size in shape
Hydra Spirogyra Mucor
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2.3
ORGANISATION OF CELLS IN THE HUMAN BODY
� Human body is the most complex multicellular
organism. It has about 60,000 billion of cells
� The cells differ by its size, shape and structure
to enables it to perform a particular functionto enables it to perform a particular function
� A speciallised cell is a cell that performs only one
specific function in order to carry out and
maintain the stability of a huge processes
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HUMAN CELLS AND ITS FUNCTIONS
Carry oxygen from lungs
throughout the whole body
Send nerve impulses to the whole
body
Form the outer layer of skin Form the outer layer of skin
to protect the body surface
Fertilises the ovum in sexual
reproduction
Allows movement
Found in bones and functions in
the support system of the body
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TISSUES
� A tissue is a group of similar cells that carry out
the same function. Example,
Tissues Function
Epithelium
tissue
to protect the tissues beneath it
Muscle tissue Made up of muscle cells that contracts and relaxes
to enable movements of body
Nervous
tissue
Carry massages from one part of the body to
another
Connective
tissue
To connect and join several tissues together for
support and
protect the organs and body.
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ORGANS
� When different tissues co-operate to carry out a
certain function is called an organ
� For example, heart is an organ formed of muscle
tissues and connective tissues that co-operate to
carry out the function of blood circulation to the carry out the function of blood circulation to the
entire body
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THERE ARE SOME EXAMPLES OF HUMAN ORGANS
AS SHOWN BELOW:
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SYSTEMS
� A group of different organs that co-operate to
perform a certain function of life process is
known as the systems
� The body systems as a whole enable human to � The body systems as a whole enable human to
carry out life process normally and more
efficiently
� There are 10 main systems in a human body
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SYSTEM AND ITS FUNCTIONS
� Digests food and
absorb nutrient
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�� Transport oxygen
and digested food to
the body
�� Carries unwanted �� Carries unwanted
excretory materials to
organs to be disposed from the body
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� Inhales oxygen into
the body and exhales
carbon dioxide out of
the body
� During respiration, the
exchange of oxygen
and carbon dioxide
gases occur in the alveolus
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� Coordination of
body activities ,
such as digestion
and metabolism
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SKELETAL SYSTEM
� Preserves the body
shape
� Provides support and
protection to internal protection to internal
organs such as the
heart, lungs and other
organs
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MUSCULAR SYSTEM
� Enables body
movement
� Muscles usually react
as opposing pairs to as opposing pairs to
produce movement
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REPRODUCTION SYSTEM
� Produces offspring to
continue the generation
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EXCRETORY SYSTEM
� Dispose waste from the
body
� Lung − carbon dioxide
and water vapour
� Skin − Urea, mineral
salt and water
� Kidney − Urea, mineral
salt and water
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� Co-ordinates and control
all activities in the body
� Responds to the stimuli
when the sensory
organs receive impulses
from brainfrom brain
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LYMPHATIC SYSTEM
� Body defense
� Remove bacteria from
the tissue
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ORGANISMS
� All systems in the body works together to perform a
life process that produce an independent organism
� Cell organisation allows different types of work in
body to work more smoothly and efficientlybody to work more smoothly and efficiently
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2.4 THE HUMAN BEING– A COMPLEX ORGANISMS
� Human considered to
be a complex
organisms because
they have various
types of cells that form types of cells that form
tissues, organs and
systems. (cell
specialisation)