cell as a unit of life form 1

8/12/2019 Cell as a Unit of Life Form 1

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CELL AS A UNIT OF LIFE

UNDERSTANDING CELLS

Parts of Microscope and Their Functions


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Technique in Using a Microscope A microscope is used to examine specimens which are too small to be seen with thenaked eye. It is a very delicate and expensive instrument. It must be used with great careso as not to demage it.

Do 1. Use both hands when carrying a microscope - one hand hold the limb and the otherto support the base.

2. Place the microscope down gently on the table in an upright position.

3. Always keep the stage and other parts of the microscope dry.


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4. Always clean the lenses with tissue paper only to avoid scratching them.

5. Always start viewing a specimen with the low power objective lens. Change to thehigh power lens if necessary.

6. Use the fine adjustment knob for focusing when viewing with the high powerobjective lens.

Don't 1. Don't repair the microscope; report any demage to your teacher.

2. Don't view slides which are wet; wipe te slides with tissue paper.

3. Don't use the high power objective lens without covering the specimen with a coverslip.

4. Don't squint down the microscope; view the specimen with both eyes open.

Technique in Mounting a Slide on a Microscope for Viewing .1. Place the microscope in a well-lit place such as in front of a window.

2. Fit in the eyepiece for the microscope.

3. Fit in the low power objective lens and turn it to position.

4. Look down the eyepiece and adjust the mirror so that a bright view is obtained. (Makesure the diaphragm is open if there is one.)

5. Place the prepared slide on the stage so that the specimen to be viewed is in the middleof the hole on the stage.

6. Placing your eye level with the stage, slowly lower the objective lens until it is veryclose to the slide.

7. Looking down the eyepiece, turn the coarse adjustment knob t owards you (raisingthe objective lens) until the specimen is in focus.

8. Change the objective lens to a medium of high power if necessary. Use the findadjustment for the high power objective lens.

Technique in Mounting a Specimen on a Slide. 1. Place the specimen in the middle of a clean slide.

2. Place a drop of water on the specimen.

3. With the help of your fingersand a long needle, gently lower a cover slip on thespecimen. Do not trap any air bubbles!

4. Use a piece of filter papaer to wipe away any water around the cover slip. The slide isnow ready for viewing.

5. If you wish to stain the specimen:


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a) place a drop of iodine solutiion or methylene blue solutiion at one end of the cover slip.

b) use a strip of filter papaer at the other end of the cover slip to draw the solutionacross the specimen, using the irrigation technique.

1. Generally, Each animal cell is made up of cel l protoplasm (cytoplasm and nucleus)and cel l memb rane.

2. The protoplasm is a semi-solid or jelly-like substance.

3. The nucleus is the oval or round seen in the centre of a cell.

4. Surrounding the nucleus is the cytoplasm.

5. The cytoplasm is thinner and more watery than the nucleus. The cytoplasm is definedas the material between the cell membrane (plasma membrane) and the nucleusenvelope.


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1. Typical plant cells are rectangular in shape.


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2. The plant cell has a rigid cell wall . A cell wall is made up of cellulose which is a formof carbohydrate.

3. There are regions in the plant cell which do nt contain cytoplasm. These arecalled vacuoles. Vacoules contain cell sap which is a very dilute solution ofsugar and salt in water.

4. In very young cells, the vacuoles may not be seen. But as the cell grows older, moreand more vacuoles are formed.

5. Chloroplast builds chlorophyll, a green pigment, only found in plant cells.


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1. The function of cell structures are shown in the table and figure below:


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Table: Function of cell structures

2. The function of cell structures can be illustrated as shown in figure below:

An overview of the comparison of animal and plant cells is shown below:


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Unicellular and Multicellular Organisms

1. A living thing (plant or animal) is called an organ i sm.

2. A living thing which can only be seen under a microscope is called a m ic roorgan i sm.

3. Microorganism are found everywhere such as in the air, water, soil, on plants and in ourbody.

4. Examples of microorganisms are:a) bacteriab) viruses.c) algaed) yeastse) amoeba


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Examples of microorganisms

1. An organism which consists of only one cell is called a unicel lu lar organism .

2. Unicellular organisms are usually found in water (ponds, lakes, rivers and sea) or onmoist areas (tree trunks and in the soil).

3. They are usually very active and are always moving about.

4. Each of them can carry out all the life processes that large organisms do such asmoving about, feeding and respiring.

5. Some unicellular organisms are animals such as amoeba, paramecium andplamodium. Some are plants such as euglena, chlamydomonas and pleurococcus.

6. Unicellular organisms which are microscopic in size are also calledunicellular microorganisms.


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1. Some organisms consist of many cells. They are mu lt icel lu lar organism s.

2. Most organisms are multicellular including large plants and animals.

3. Multicellular organisms which are microscopic in size are referred to asmulticellular microorganisms.

4. Most multicellular microorganisms live in water such as spirogyra (plant) and hydra(animal)

5. Multicellular organisms have different types of cell, each type serving a differentfunction.


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1. Unicellular and multicellular organisms carry out all the life processes in order tolive, although they may be very small.

2. Unicellular and multicellular organisms:a) moveb) need foodc) need aird) growe) reproducef) give out waste substancesg) are sensitive


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Organisation Of Cells In The Human Body

1. All organisms including human beings are built from basic units called cel ls .

2. The simplest organism such as an amoeba consists of only one cell, but is able to carryout all the life processes.

3. Cells are microscopic and can only be seen under a microscope.

4. The human body has different types of cell with each type carrying out a differentfunction.

5. Some examples of cells in the human body are shown below:


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6. Some functions carried out by cells are explained in the table below.

Cells and their functions

1. A group of simillar cells performing the same function forms a t i ssue.

Two types of tissue

2. The human body is built of four main types of tissue.


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1. An organ is made up of a group of different tissues which carry out a specific function.

Example:The leg is an organ formed from different types of tissue (see figure) to perform the samemain function, that is to move the body from place to place.

2. Figure in the below shows the main organs in the body and their functions.


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1. A sys t em consists of a group of organs working together to carry out the samefunction.

2. Figure in the below shows the main organs in some of the systems in the human body.


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Some of the system in the human body

3. The main functions of the different systems are given below.


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The main functions of different systems.

1. The different systems form an organism such as a human being.

2. The different systems in the body function and co-ordinate their activities so that thebody functions as one whole.

3. The human body is organised as shown in the figure below:


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Organisation if the human body


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Human Are Complex Organisms

1. Human are complex made up of thousands of individual systems. Some of the majorsystems are the blood circulatory system, the skeletal system, the digestive system, thenervous system and the respiratory system.

2. The human body is a complex system of cells most of which are grouped into organsystems that have specialised functions. These systems can best be understood in termsof the essential functions they serve, deriving energy from food, protection against injury,internal coordination and reproduction.

3. Humans are unique among Earth's life forms as they have language and thought.

4. Humans have a better developed brain than other life forms. Human are able to createand learn from experience that far exceeds any other species. Humans can use this abilityto create technologies and literary and artistic works on a vast scale, and to develop ascientific understanding of themselves and the world.

5. Humans are endowed with intelligence which enables them to think rationally anddifferentiate right from wrong.

6. Humans are also unique in their profound curiosity about themselves.

cell as a unit of life form 1

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