2. In which habitat do birds live?
Birds are terrestrial animals but the majority of them also explore the aerial environment by flying.
3. What adaptations for flight are present in birds?
The features of birds that allow them to fly are: wings attached to a well-developed pectoral musculature, pneumatic bones, less accumulation of feces in the bowels due to the absence of the colon, the absence of a bladder (no urine storage), an aerodynamic body and lungs with specialized air sacs.
4. What are pneumatic bones?
Birds have lightweight bones with internal spaces filled with air. These bones are called pneumatic bones. This feature reduces the density of body of the animal, facilitating flight.
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Respiration in Birds
5. How is the respiratory system of birds characterized?
Like reptiles and mammals, they carry out gas exchange through lungs.
The Avian Heart
6. How is the circulatory system of birds characterized?
Birds, like every vertebrate, have a closed circulatory system. Their heart is similar to the heart of mammals, as it has four chambers (two atria and two ventricles) and 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).
Excretion in Birds
7. Which type of nitrogen waste do birds produce? Why is this feature, in addition to being an adaptation to the terrestrial environment, also an adaptation to flight?
Birds are uricotelic, meaning that, like reptiles, they excrete uric acid. This substance needs less water to be eliminated and it helps to reduce body weight, making flight easier.
Similarities between Birds and Reptiles
8. What similarities are present in birds and reptiles regarding external coverage, reproduction and excretion?
Regarding external coverage, birds are similar to reptiles in that they present impermeable keratinized outside. Concerning reproduction, fertilization is internal in both and the embryo develops within a shelled egg. Regarding excretion, both excrete uric acid.
Reproduction in Birds
9. How do birds reproduce?
Birds, like every vertebrate, use sexual reproduction. Their embryos develop within shelled eggs containing extraembryonic membranes. Therefore, their embryonic development occurs outside the mother’s body.
Birds copulate. Fertilization is internal and occurs only before the female gamete is wrapped in the calcareous eggshell.
10. Is embryonic development in birds direct or indirect?
Embryonic development in birds is direct. There is no larval stage.
11. What are the main chemical compounds found in eggshells, whites and yolks, respectively?
The eggshell is basically made of calcium carbonate. The white, or albumen, is composed by albumin, a protein. The yolk is predominantly made up of lipids, but also contains proteins and vitamins.
Temperature Control in Birds
12. How different are reptiles and birds concerning their maintenance of body temperature? Are birds rare in polar regions?
Reptiles are heterothermic, meaning that they do not control their body temperature. Birds are the first homeothermic animals, as they are able to maintain a constant body temperature.
Many birds live in regions of intense cold. Penguins are an example of birds that live in polar region.
Diseases Caused by Birds
13. What are zoonoses? What are some examples of zoonoses transmitted by birds?
Zoonoses are human diseases transmitted by animals. Psittacosis, a bacterial disease, and histoplasmosis and cryptococcosis, which are fungal diseases, are examples of zoonoses transmitted by birds.
A Summary of Birds
14. The main features of birds. How can birds be described according to examples of representative species, basic morphology, skin, respiration, circulation, nitrogen waste, thermal control and types of reproduction?
Examples of representative species: 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 fertilization, shelled eggs with extraembryonic membranes.