Answer:
Oxygen enters the lungs through the trachea, which branches into two tubes called the bronchi, which lead to the lungs.
Answer:
The correct answer would be D.Alveolar sacs are surrounded by thin capillaries where gases can be exchanged.
Alveoli are tiny sacs which form the site of gas exchange in the lungs.
The features of alveoli which help in gas exchange are:
- They increase the surface area in the lungs thus, more space is available for gas exchange.
- They have very thin walls, as thin as the thickness of a single cell only.
- They are surrounded by a bunch of thin capillaries which exchange gases with alveoli.
Answer:
Many human and physical factors affect population distribution and population density across the world. Physical factors that affect population density include water supply, climate, relief (shape of the land), vegetation, soils and availability of natural resources and energy.
Answer:
If cells do not work together, the organism would die.
Explanation:
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