STD 6 BASIC SCIENCE CHAPTER 1 CASKETS OF LIFE | PART 1 |

MAIN POINTS

1. MICROORGANISMS

2. TINY UNITS OF A BODY

"CELLS ARE BASIC STRUCTURAL UNIT OF A BODY"

MICROORGANISMS

2. ARE THERE ORGANISMS SMALLER THAN ANT ?

AN : YES, MOST OF THE ANIMALS THAT WE COME ACROSS ARE SMALLER THAN ANT . IN ADDITION TO THIS THERE ARE NUMBER OF INVISIBLE ORGANISMS IN THE SOIL,WATER AND IN THE AIR. THESE ORGANISMS ARE KNOWN AS MICROORGANISMS.

3. HOW CAN WE OBSERVE ORGANISMS THAT CANNOT BE SEEN BY THE NAKED EYE ?

AN : MICROORGANISMS CAN BE OBSERVED USING MICROSCOPE.

4.

PROCEDURE

1.SOAK THE HAY IN WATER FOR AT LEAST 1 OR 2 DAYS.

2.TAKE A DROP OF HAY-SOAKED WATER ON A GLASS SLIDE.

3.PLACE THE COVER GLASS PROPERLY.

4.OBSERVE IT THROUGH THE MICROSCOPE .

INFERENCE

THERE ARE MANY ORGANISMS ON THE EARTH THAT CANNOT BE SEEN BY THE NAKED EYE. THESE ORGANISMS ARE KNOWN AS MICROORGANISM.

TINY UNITS OF A BODY

5. WHAT ARE CELLS ?

AN : CELLS ARE BASIC STRUCTURAL UNITS OF A LIVING BODY.

6. WHAT ARE UNICELLULAR ORGANISMS?

AN : ORGANISMS HAVING ONLY ONE CELL IN THE BODY ARE CALLED

UNICELLULAR ORGANISMS.

Eg: AMOEBA, PARAMECIUM, EUGLENA

7. WHAT ARE MULTICELLULAR ORGANISMS?

AN : ORGANISMS THAT HAVE MORE THAN ONE CELL IN THE BODY ARE CALLED

MULTICELLULAR ORGANISMS.

Eg : PLANTS & ANIMALS

8. THE BODY OF UNICELLULAR ORGANISM IS TOO SMALL TO BE SEEN. WHY IS THE BODY OF AN ANT BIGGER THAN THAT OF UNICELLULAR ORGANISM?

AN : CELLS ARE TOO SMALL TO BE SEEN BY THE NAKED EYE. SO WE CAN NOT SEE THE UNICELLULAR ORGANISMS. THERE ARE THOUSANDS OF CELLS IN THE BODY OF AN ANT. SO, WE CAN SEE AN ANT.

9.

PROCEDURE

1. CLEAN THE MOUTH OF THE CHILD AND ADULT USING PURE WATER.

2. SCRATCH THE INNER SIDE OF THE CHEEK OF THE CHILD AND ADULT USING SEPARATE BRUSH.

3. TRANSFER THE PARTICLES FROM THE BRUSH TO THE DROP OF WATER TAKEN SEPARATELY ON THE SLIDE.

4. SPREAD IT PROPERLY AND ADD A DROPLET OF STAIN.

5. COVER PROPERLY WITH THE GLASS COVER.

OBSERVATION

ON CLOSE EXAMINATION YOU WILL FIND THAT THE CELLS OF THE ADULT AND THAT OF THE CHILD DO NOT DIFFER IN THEIR SIZE.

INFERENCE

THE CELLS DO NOT GROW IN ACCORDANCE WITH THE GROWTH OF THE BODY. THE DIFFERENCE IN THE NUMBER OF CELLS IS THE REASON FOR THE CHANGE IN SIZE.

10. HOW DOES THE BODY GROW WITHOUT BRINGING ABOUT ANY CHANGE IN THE SIZE OF THE CELLS?

AN : WHEN THE CELLS ATTAIN MATURITY, THEY DIVIDE REPEATEDLY CAUSING THE INCREASE IN NUMBER. THIS PROCESS CONTINUES AND THUS GROWTH TAKES PLACE.