Which of the following terms best describes the structure that is a common passageway for air and food, and where does gas exchange occur?

Here are the answers to the questions:

11) The pharynx is the space at the back of the mouth that serves as a common passageway for both air and food, leading to the airway (larynx/trachea) and the esophagus.

• C. Pharynx

12) Gas exchange, where oxygen enters the bloodstream and carbon dioxide leaves it, occurs in the tiny air sacs within the lungs called alveoli.

• C. Alveoli

13) The nephron is the microscopic structural and functional unit of the kidney, responsible for filtering blood and forming urine.

• C. Nephron

14) In the food chain: Grass (Producer) -> Rat (Primary Consumer) -> Snake (Secondary Consumer) -> Eagle (Tertiary Consumer). The snake is at the 3rd trophic level and is a secondary consumer (which can be represented as the 2nd feeding level if producers are 0, primary 1, secondary 2).

• A. 3, 2

15) According to the 10% rule of energy transfer in an ecological pyramid: * Producers: $70,000 \text{ Kcal}$ * Primary Consumers: $10\%$ of $70,000 \text{ Kcal} = 7,000 \text{ Kcal}$ * Secondary Consumers: $10\%$ of $7,000 \text{ Kcal} = 700 \text{ Kcal}$ * Tertiary Consumers: $10\%$ of $700 \text{ Kcal} = 70 \text{ Kcal}$ Based on this, the primary consumers would have $7,000 \text{ Kcal}$.

• B. The primary consumers would have a total of $7000 \text{ Kcal}$ energy

16) Biomass refers to the total mass of living organisms (plants, animals, microorganisms) in a given area or ecosystem.

• B. The total mass of living organisms in an ecosystem

17) In nitrogen fixation, atmospheric nitrogen ($\text{N}_2$) is converted into ammonia ($\text{NH}_3$) or other nitrogenous compounds. This process involves nitrogen combining with hydrogen.

• B. Hydrogen

18) The process where water vapor in the air cools and changes back into liquid water droplets is called condensation. This is how clouds form.

• A. Condensation

Instruction III: Fill in the blank space with appropriate words to complete the statements.

19) Tiny sacs in the lungs where gas exchange takes place are called alveoli.
20) A wave of involuntary muscle contractions that moves food through the digestive system is called peristalsis.