Free round worms have a more complex body system compared to parasitic roundworms because they are independent and exist as a whole organism. Parasitic round worms are less complex because they are dependent on their hosts for survival.
C. by observing them in their habitats
Ex: The Galapagos Islands. Darwin went their to study the flora and fauna in their natural habitat.
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.
The physical properties of slime : its sticky , ropey & viscous .
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