Birds Review from
Biology Questions and Answers

Class Aves - Q&A Review

1. What are the main morphological features of birds?

Birds are animals that present aerodynamic bodies covered with feathers, anterior limbs transformed into wings, pneumatic bones and horny (corneous) beaks.

Image Diversity: birds avian body structure

2. In which habitat do birds live?

Birds are terrestrial animals but the majority of species also explore the aerial environment by flying.

3. What are flight adaptations present by birds?

Wings associated to a well-developed pectoral musculature, pneumatic bones, less accumulation of feces in the bowels due to the absence of the colon, absence of the bladder (no urine storage), aerodynamic body and lungs with specialized air sacs are all adaptations which enable birds to fly.

4. What are pneumatic bones?

Birds have lightweighted bones with internal spaces filled with air. These bones are called pneumatic bones. This feature reduces the corporal density of the animal facilitating the flight.

Image Diversity: pneumatic bones

5. How is the respiratory system of birds characterized?

Like reptiles and mammals, they make gas exchange through lungs.

6. How is the circulatory system of birds characterized?

Birds, like every vertebrate, have a closed circulatory system. The heart is similar to the mammalian heart, having four chambers (two atria and two ventricles) and with no mixture of venous and arterial blood. (In mammals, however, the aorta curves down to the left and in birds it curves down to the right).

Image Diversity: avian heart

7. Which is the type of nitrogen waste birds produce? Why does this feature, besides being an adaptation to the terrestrial environment, also mean an adaptation to flight?

Birds are uricotelic, i.e., like reptiles, they excrete uric acid. This substance needs less water to be eliminated and so it helps to reduce the body weight thus aiding in flight.

8. What similarities do birds and reptiles share regarding external coverage, reproduction and excretion?

Regarding external coverage, birds are similar to reptiles as they present impermeable keratinized coverages. Concerning reproduction, in both fecundation is internal and the embryo develops within a shelled egg. Regarding excretion, both excrete uric acid.

9. How do birds reproduce?

Birds, like every vertebrate, have sexual reproduction. Their embryos develop within shelled eggs containing extraembryonic membranes and outside the mother’s body.

Birds copulate. Fecundation is internal and it occurs only before the female gamete is involved by the calcareous eggshell.

10. Is the embryonic development in birds direct or indirect?

The embryonic development is direct, there is no larval stage.

11. What are the predominating chemical compounds respectively in eggshell, white and yolk?

The eggshell is basically made of calcium carbonate. The white, or albumen, is composed by albumin, a protein. The yolk is predominantly constituted of lipids but it also contains proteins and vitamins.

Image Diversity: avian egg

12. How different are reptiles and birds concerning the maintenance of body temperature? Are birds rare in polar regions?

Reptiles are heterothermic, i.e., they do not control their body temperature. Birds however are the first homeothermic animals, they are able to maintain their body temperature constant.

There are many birds that live in intense cold regions. Penguins are examples of birds that live in polar region.

13. What are zoonoses? What are some examples of zoonoses transmitted by birds?

Zoonoses are human diseases transmitted by animals. Psittacosis, a bacterial disease, hystoplasmosis and cryptococcosis, fungal diseases, are examples of zoonoses transmitted by birds.

14. Bird identity card. How are birds characterized according to examples of representing beings, basic morphology, skin, respiration, circulation, nitrogen waste, thermal control and types of reproduction?

Examples of representing beings: chickens, sparrows, parrots, ostriches, penguins. Basic morphology: aerodynamic body, feathers, pneumatic bones, horny beaks. Skin: impermeable keratinized, feathers, uropygial gland. Respiration: pulmonary. Circulation: closed and complete, heart with four chambers. Nitrogen waste: uric acid. Thermal control: homeothermic. Types of reproduction: sexual, internal fecundation, shelled eggs with extraembryonic membranes.

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