THE EGG OF GALLUS GALLUS DOMESTICUS (DOMESTIC FOWL)
THE EGG OF GALLUS GALLUS DOMESTICUS (DOMESTIC FOWL).
Habitat:
- coop
Classify the egg/or type of egg.
- Cleidoic egg (Egg covered with a calcareous shell)
Mode of reproduction of the organism that produces the egg
- Sexual with oviparity.
- Internal fertilization
What is the ecological significance of a cleidoic egg?
- It is capable of full development on land
Two groups of organisms that produce this type of egg
- Birds
- reptiles
Two classes of organisms that produce a cleidoic egg
- Class Aves
- Class Reptilia
Class Aves
Characteristics
- Presence of feathers,
- Presence of wings
- Presence of horny scales on legs
- Presence of a horny beak, but no teeth
Class Reptilia
Characteristics
- Presence of dry, horny epidermal scales covering the skin.
- Presence of two pairs of limbs with claws
- Presence of homodont dentition
- They lay cleidoic eggs, capable of full development on land
- Absence of the external ear
Observable features
- Calcareous shell
- Blunt end
- Pointed end
- Air space between the shell membranes at the blunt end
- Yolk
- Albumen
- Double shell membranes
Features of interest
- Hard calcareous shell for mechanical protection
- Porous shell / semi-permeable shell for gaseous exchange
- Shell membranes are semipermeable for gaseous exchange
- Shell prevents evaporation /desiccation
- Yolk stores food as nourishment for the developing embryo
- Albumen provides water to the yolk and food for the embryo and absorbs shock
- Air space for gaseous exchange
ADAPTIVE FEATURES
- Hard calcareous shell for mechanical Protection and preventing evaporation/desiccation
- Porous shell / semi-permeable shell for gaseous exchange
- Shell membranes provide a moist surface for gaseous exchange
- Yolk stores food as nourishment for the developing embryo
- Albumen provides water to the yolk and food for the embryo.
- Air space stores air for gaseous exchange
What are the functions of the shell?
- Protection against mechanical injury
- Prevents evaporation
- Exchange of gases
- Provision of food
Economic importance of egg
- Source of food/ protein
- Reproduction
- Employment/source of income
- Food reserve
Albumen: Protein
Yolk: vitamins, protein, and fats
Classes of food in egg
- Proteins
- Vitamins
- Fats
Importance of protein to the human body
- Growth, repair, and replacement:
- Enzyme formation, e.g., ptyalin
- Hormone formation, e.g., insulin
- Structural materials such as cartilage, tendons, nails, feathers, horn, claws, beak etc.
- Formation of antibodies.
- Energy sources in the absence of carbohydrates and lipids
- Formation of haemoglobin
Importance of vitamins to the body
- They maintain the metabolic activity of the body
- They maintain good health of the body
- They build the body
Experiment to test for protein in the lab:
-
Millon’s Test
Method:
- Add 1cm³ of Millon’s reagent to 1cm³ of the sample of food solution in a test tube.
- Warm the mixture.
Observation:
- A white precipitate is formed on the addition of the reagent.
- The precipitate turns red on heating.
Conclusion:
- Protein is present.
