Science Form 1 Chapter 2

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CHAPTER 2 Cell as a unit of life

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.

MICROSCOPE

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.

PLANT CELL AND ANIMAL CELL

SIMILARITIES BETWEEN PLANT AND ANIMAL CELL 

Have cell membrane – controls the movement of substances in and out of the cell



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)

DIFFERENCES BETWEEN PLANT AND ANIMAL CELL

2.2 UNICELLULAR AND MULTICELLULAR ORGANISMS 

Organism consists of living things which include microscopic of animals and plants (bacteria, viruses and fungus)



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

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 air and human body.

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

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

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 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

HUMAN CELLS AND ITS FUNCTIONS Send nerve impulses to the whole body

Carry oxygen from lungs throughout the whole body

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

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.

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 entire body 

THERE ARE SOME EXAMPLES OF HUMAN ORGANS AS SHOWN BELOW:

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 carry out life process normally and more efficiently



There are 10 main systems in a human body

SYSTEM AND ITS FUNCTIONS 

Digests food and absorb nutrient

 Transport oxygen and digested food to the body  Carries unwanted excretory materials to organs to be disposed from the body



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



Coordination of body activities , such as digestion and metabolism

SKELETAL SYSTEM 

Preserves the body shape



Provides support and protection to internal organs such as the heart, lungs and other organs

MUSCULAR SYSTEM 

Enables body movement



Muscles usually react as opposing pairs to produce movement

REPRODUCTION SYSTEM 

Produces offspring to continue the generation

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



Co-ordinates and control all activities in the body



Responds to the stimuli when the sensory organs receive impulses from brain

LYMPHATIC SYSTEM 

Body defense



Remove bacteria from the tissue

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 efficiently

2.4 THE HUMAN BEING– A COMPLEX ORGANISMS 

Human considered to be a complex organisms because they have various types of cells that form tissues, organs and systems. (cell specialisation)

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