The alveoli are the functional unit of the lungs and are the principal respiratory surface of higher animals like amphibians, reptiles, birds, and mammals. Each alveoli are composed of very thin epithelial cells and the alveolar lining is approx 1 cell thick, this thin surface allows gaseous exchange between the blood and air present within the lungs. The alveoli are richly supplied with blood capillaries and it is between these capillaries and the alveolar membrane the exchange of gases occurs by diffusion. The diffusion of gases is driven by the variations of partial pressures of oxygen and carbon dioxide between the alveolar space and blood. The partial pressure of oxygen (pO2) is 104 mm of Hg, which is higher than the pO2 in deoxygenated blood (40 mm of Hg), thus it allows oxygen to diffuse from the alveolar space into the blood, on the contrary, the pCO2 in the deoxygenated blood is (45mm of Hg) which is higher than the alveolar space where pCO2 is 40 mm of Hg thus it helps the CO2 to diffuse out of the blood into the alveolar space to be released during expiration.

The pH of pure water is 7(neutral) at room temperature. Pure water is neutral, neither acidic nor basic in nature.

CLASS - AMPHIBIANS

General characteristic features are

1. They can live in both aquatic and terrestrial habitats

2. Body is divided into Head, Trunk, and Tail(present only in some), Neck absent.

3. Tympanum represents the ear.

4. Cloaca is a common opening for alimentary and urogenital tracts.

5. Respiration takes place in the Lungs, Gills, and Skin.

6. They are cold-blooded (Poikilothermic), having three-chambered hearts.

7. Mesonephric kidney, mostly ureotelic.

8. External fertilization and indirect development.

Classification - 2 Subclasses

1. Stegocephalia

2. Lissamphibia

The spleen is the largest lymphatic organ of the body, the size of the spleen is around 12 cm(5 inches), located on the left side under the ribs above the stomach. Spleen filters and stores the blood and produces Lymphocytes and RBC during embryonic stages. Spleen has a large reservoir of erythrocytes.

The Liver is the largest secretary gland in a human body.

Imagine cell as a sphere. The boundary of the sphere called cell membrane is made up of phospholipid bilayer which is called "sea" in the question. Phospholipid bilayer separates the cytoplasm from outside environment because of their non polar nature. What role proteins are playing in the cell membrane? Cell has to interact with the environment to get the survival signals, nutrients like biomolecules glucose, amino acids etc and many important ions like Na+, K+, Ca2+, Mg2+ so protein play an important role here. Protein have both polar and non polar regions so they can stay inside the phospholipid bilayer well just like ice bergs in the sea. 

Vision of cockroach is mosaic vision due to the presence of compound eyes. Omatidium of compound eye producing its own independent image of the object seen by the cockroach

An earthworm has five arches/hearts that are segmented and pump blood throughout its body.

Systema naturae & Species planetarium

The end product of ornithine cycle is urea.