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SUBJECT: BIOLOGYÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
TOPIC: RESPIRATORY SYSTEM
CONTENT:
(a) Types of respiratory systems:
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- (i) Body surface respiration
- (ii) Coetaneous/Cutenous respiration
- (iii) Gills
- (iv) Trachea system
- (v) Lungs.
(b) Mechanisms of respiratory system:
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- (i) Higher animals
- (ii) Lower animals
- (iii) plants
- (iv) Mechanisms of gaseous exchange through the stomata of plants.
SUB-TOPIC 1: TYPES OF RESPIRATORY SYSTEMS
Note: that respiration is one of the characteristics of living things we discussed in our basic classes, in this process, oxygen is taken in while carbon iv oxide is given out. The two basic types of respiration are; aerobic and anaerobic respiration.
Respiratory system refers to all the parts or organs and cells responsible for respiration process that take place in the organism.
Respiration is simply a biochemical process in which energy is liberated from food substances (mainly simple sugars) in the mitochondria of living cells with the aid of enzymes in the absence or presence of oxygen.
The production of water, carbon iv oxide, alcohol or other organic substances is just incidental to the basic process. Respiration is achieved through the mouth, nose, trachea, lungs and diaphragm. The system functions to obtain oxygen for use by the body and to eliminate the carbon iv oxide. It works in conjunction with the circulatory system.
In animals, the structures associated with respiration include the following organs:
- Body surface (amoeba, paramecium, earthworm,).
- Lung books (spider,)
- Gills (tadpole, molluscs, fish).
- Trachea (man, insects,)
- Lungs (reptiles, man, birds, goat, and other mammals etc)
In plants, the stomata and Lenticels are the main respiratory structures for gas exchange by diffusion. Gas exchange in animals depends on their respiratory medium (whether it is air or water) and the nature of their respiratory surfaces. For aquatic animals, the respiratory medium is water, as for terrestrial animals, the medium is air. Amphibians and some fishes use both air and water as their media of exchange.
The exchange of gases with the respiratory medium by animals is called breathing. The respiratory surface provides a boundary between the body and respiratory medium. The cells in this surface are epithelial in nature (have thin wall) and have large surface area. This enhances diffusion.
BODY SURFACE RESPIRATION
This is the simplest type of respiration found mainly in unicellular organisms and some multi-cellular organisms such as Annelids (earthworms), Platyhelminthes (flatworms), sponges, toads, and frogs. Respiration occurs by diffusion. In unicellular organisms, the exchange of gases takes place at the respiratory surfaces. Gases are dissolved in water before they are diffused across the cell membrane. Organisms that respire through their body surface possess moist skin. Breathing, it is a visible, mechanical, muscular action, which enables an animal to quicken the rate of gas exchange between itself and its environment.
GILLS
The gill is found in large aquatic organisms such as tadpole, aquatic snails and fishes. Gills are highly branched and vascularised, i.e., they are richly supplied with blood capillaries. Gills may be external or enclosed. External gills may be sea slugs and amphibian larvae, whereas in enclosed gills are found in water snails and crustaceans.
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