The cell is the simplest bit of living thing or matter that exist independently. We always see this in unicellular organisms which will show all the necessary characteristic of a living things. Namely respiration, nutrition, excretion, movement, irritability, growth and reproduction.
Cell can exhibit different type of size or shape. Some may be square or round in shape while some is rectangular or star like shap. They always range extremely from tiny bacteria cells which is about (1pm) which can only be seen with a powerful microscope to the large York cell of hen egg (100mm).
FORMS IN WHICH LIVING CELLS EXIST
Unicellular plant like protists
The word chlamydomonas is a unicellular organism in which is also a motile with cup shaped chloroplast. it is also a free living autotroph that carry out specific activities of a living organism. Protoplasm is therefore always complex since it can only perform all the function of a living organism
Chlamydomonas cell often receive light and starch grain will appear in their cytoplasm, which will indicate the ability to produce food. This grain always disappear if they are kept in the dark.
chlamydomonas
Chlamydomonas cell always move around by using their whip like flagella. They are always sensitive or adapt to their surrounding. For example they move from a dimly lit region to a region of more light in it.
Chlamydomonas cell always get rid of excess water that get through them from the surrounding by means of contractile vacuoles, which is filled up with water and empty it to the exterior continuously.
structure,occurrence,reproduction
Little chlamydomonas cell always grow until they become large in size. Then they will reproduce by sexual or asexual methods.
Unicellular Animal-like Protists
Amoeba is know as the smallest unicellular organism that is heterotrophic. It always take in complex food, and also digest it in a food vacuole that use the solution food for it own activities and also for it growth by also getting rid of undigested food material. It is most sensitive to the presence of food in its own environment. The following features help it to obtain food:
amoeba
- Ability to move by using pseudopodia
- Ability to capture food by using pseudopodia and by ingesting it into its body in the food vacuole.
- Sensitivity within organic substance in it own environment.
Amoeba get rid of excess water that enter its cell by using a contractile vacuole. The amoeba cell always grow to a certain size before it stop growing, and it will start reproducing by dividing to form two daughters cells.
feeding in amoeba
Paramecium is also a unicellular organism. It is more complex than that of amoeba, which Celia that assist it to move,strain food and also waft food into the gullet. It has a specific mouth in which food pass through and a fixed anal pore for passing out undigested food. Food vacuole have this special structure for locking itself while feeding. There is present of sensory cilia which help it to move to area where is much food. Posterior and Anterior contractile vacuole with this radiated channel draining through them and also help in getting rid of excess water from the body.
paramecium