Science 8 Iii Partial 4 and Study Guie
Science 8 Iii Partial 4 and Study Guie
Science 8 Iii Partial 4 and Study Guie
Eight Grade
Excretion is biological function, by which the organism eliminates substances to keep the composition and
function of the organs of the body of living beings.
Do not confuse excretion with secretion, since secretion is the release of useful substances or hormones,
such as: saliva, gastric juices or milk.
Excretion in animals is the elimination of substances resulting after metabolism, carbon and nitrogen
compounds.
As a result of cellular metabolism, animals acquire energy and synthesize their organic matter, but waste
substances are also produced that may be toxic if they are not eliminated.
INVERTEBRATES WITH EXCRETORY SYSTEM.
Some invertebrates have an excretory system called nephridium; of which consist exist metanephridium and
photonephridium.
Protonephridium: Formed by the flame cells that mobilize by means of its cilia, water mineral salts and
ammonia towards the excretory tube.
Metanephridium: Consist of a tube surrounded by a capillary network that possesses glands with
vescicles and which usually pass waste outside of the organism.
Insects carry out excretation by means of the Malpighian tubules and the posterior intestine.
1. Make an album about the excretion system of invertebrates and vertebrates animals.
2. What is excretion?
This type of breathing is more complex and requires the presence of a respiratory organ capable of
transporting gases from the environment to the circulatory system and vice versa.
Terrestrial snails have an invagination called pallial cavity, which is much vascularized and acts as a
lung. In mollusks such as squid; oysters and clams, the gaseous exchange is performed by grills.
All mammals have pulmonary respiration, including aquatic ones like whales. The exchange of gases
or hematosis is performed at the level of the alveoli, which are surrounded by blood capillaries.
Insects breathe througth tracheas , which are smalls chitin tubes branched all over the body and
communicated abroad through some tiny holes called stigmata.These Branches are wet and therethe
cells are oxygenated.
10. How is breathing in Fish.?
Breathing is carried out through gills. In cartilaginous fish there are branchial archs, the first is smalls and
called spiracle
11. What is stomata?
Stomata or pneumatodes are formed by a pair of modified epidermal cells, stomatal cells or occlusive
cells, which are kidney –shaped.