Cell Organisation

Brief Account

1. There are two category of organisms:
-unicellular organism
-multicellular organisms

2. Unicellular organisms are organisms with just one cell, for example Amoeba and Paramecium.

3. Unicellular organisms are small and simple animals which are able to carry out vital functions within a single cell.

4. Unicellular organisms can feed, respire, excrete, move and respond to stimuli, grow and reproduce.

5. Unicellular organisms does not have any organs or systems thus it depends largely on its cellular components.

6.Most spesies of Amoeba are free-living in fresh water environment.

7. Table shows the components of Amoeba sp. and their roles in carrying out life processes in Amoeba sp.

8.Amoeba sp is a holozoic organisms which feeds on microscopic organisms such as bacteria.

9.Figure shows the process of phagocytosis in Amoeba sp.

10. Amoeba sp reproduces asexually by binary fission. If the environment is favourable. However,when the environment is not conducive , it forms spore.


Why is that a Paramecium sp. which lives in the ocean does not possess a contractile vacuole where as a similar Paramecium sp. which lives in fresh water must have such a cytoplasm organelle?

Because salt water go's through them instead of inside them so they dont need to expel salt water

In 2006- SPM Paper 2, there was a question like this:

9(b)Multicellular organisms like humans, need specific transport sysrems as compared to unicellular organisms like Amoeba sp., which do not need a transport system.

Give an evaluation of the above statement based on the physical features of the organisms with the following physiological processes:

* Respiration
* Nutrition

* Excretion [10 marks]

1. The question need you TO EVALUATE. ..(The highest level of skills in Bloom Taxonomy)
2. Look at some of the keywords of the question.
3. You have to be able to compare THE PHYSICAL FEATURES of BOTH ORGANISMS: Unicellular and Multicellular!!!
4. But of course with respect to 3 processes asked:
RESPIRATION
NUTRITION
EXCRETION
5. Dont forget MARKS ALLOCATED is 10 marks
...So how lengthy you should write?
..Write your answer using paragraph by paragraph NOT BULLETED like I do..
..I do it in bullet forms so that it is easier for you to locate the points/Facts required.

SUGGESTED ANSWER:
· The physical features of multicellular organism are big size and the TSA/V ratio is small
· So the rate of diffusion of substances into and out of the body cells is low
· Cells in the inner part of the body are not in direct contact with the surroundings
· Whereas the physical features of unicellular organism are small size and the TSA/V ratio is big
· So the exchange of substances between organism and surrounding occurs easily
· Body cell is directly in contact with surrounding
[ 4 marks maximum given ]

· As for multicellular organism, they need a specific gas exchange surface/organs such as lungs to exchange oxygen and carbon dioxide
· whereas unicellular do not need specific organ since gas exchange can takes place by simple diffusion through the plasma membrane.
[ 1+1]...RESPIRATION

· Multicellular organism needs digestive system to bring in food from surroundings into alimentary canal, digest then absorbed.
· Digested food then transported to the body cells by blood and lymphatic system
( Any ONE)

· Whereas in unicellular organism, it does not need transport system because food is directly taken in through membrane cells by phagocytosis
· Then digested by intracellular enzymes (in the vacuole)
(ANY ONE) [ 1+1 ]..NUTRITION

· Multicellular organism needs transport system to take excretory waste /urea from liver to the kidney
· Excretory waste is then taken out from kidney /excretory organs.
(Any one)
· Whereas in unicellular organism excretory waste are directly eliminated from body cells to the surroundings through the cell membrane
· Excretory waste is excreted out in contractile vacuole.
( Any one) [ 1+1 ]..EXCRETORY

.......................So Total Marks = 10 marks...
..So you see how beautifully written the essay is!!!
It includes all the FACTS required by the Marking Scheme..And definitely you will score full marks if you write such..

TIPS:
To produce good essay answer, you have to understand the task of the question..Dont forget to take note of all the important keywords in the question which might give you an idea to write about what..
And of course, you must know the subject content well as to discuss it correctly.
..and for the last minute students...understanding and memorising the marking schemes could do a bit of help to you..(If such question ever being asked again...)

Cell specialization and organization in multicellular organisms

1.A multicellular organism is an organism which consists of more than one cell.

2.These cells grow, change shape and differentiate to carry out specific function.

3. Cells of a multicellular organism differentiate and undergo specialization in order to perform their task efficiently.

4. Cells may become specialized in transport: example, red blood cell, which is biconcave disc-shaped and very flexible in order to move easily along the narrow blood capillaries.

5.Table shows some of the specialized human cells and their function.

6. Diagram shows some of the specialized plant and animal cells and their function

http://www.livingscience.co.uk/year7/cells/specialised%20cells.gif

7. Cells of the same type which carry out a common function are organized into tissues.

8. A tissue is a group of similar cells which are specialized to perform a particular function. There are four primary tissue types in the human body: epithelial tissue, connective tissue, muscle tissue, and nerve tissue.

9. Muscle tissue is the most abundant tissue in the body. It is a specialized tissue that can contract. Muscle tissue contains the specialized proteins actin and myosin that slide past one another and allow movement. Examples of muscle tissue are contained in the muscles throughout the body.

Types of muscles tissue
http://www.purchon.com/biology/muscles.htm

http://www.nvo.com/jin/homepage10/

10. There are three types of muscle tissues: smooth muscle, skeletal muscle, and cardiac muscle.

11. Table shows the type of muscle tissue and where can be found in the body.

http://www.human-body-facts.com/muscular-system.html

12. The cells of epithelial tissue pack tightly together and forms a continous sheets that serve as lining of all internal and external body surfaces.

13. Epithelial tissue serve as membranes lining organs and helping to keep the body's organs separate, in place and protected.

14. Some examples of epithelial tissue are the outer layer of the skin, the inside of the mouth and stomach, and the tissue surrounding the body's organs.

15. Table shows different function of epithelial tissue in relation with its location.

Epithelial tissue
http://www.nvo.com/jin/homepage6/

16. When different type of tissue group and work together, they form an organ of the body. The stomach, for example is an organ which is composed of smooth muscle tissue, loose connective tissue, nervous tissue, blood and columnar epithelium

17. Several organs working in conjunction form organ systems. An example of a system is the circulatory system, which is composed of heart, blood vessels, and blood.

Happy Revising..