One end product of the light reaction in photosynthesis is Oxygen.

1. One end product of the light reaction in photosynthesis is Oxygen.

2. Higher animals need an internal transport system for two main reasons:

• They have a large body size, meaning diffusion alone is too slow and inefficient to transport nutrients and oxygen to all cells and remove waste products.
• They have a high metabolic rate, requiring a constant and rapid supply of substances like glucose and oxygen, and efficient removal of metabolic wastes.

3. a) When environmental temperatures are low, the body conserves heat by vasoconstriction (narrowing of blood vessels) in the skin. This increases blood pressure, leading to increased blood flow to the kidneys, which filter more blood and produce more urine. Additionally, less water is lost through sweating, so more water is excreted via urine.

4. It is important to use dry mass in ecological studies because it represents the actual organic matter (biomass) of an organism or population, excluding variable water content. Wet mass includes water, which can fluctuate significantly and does not accurately reflect the amount of energy or organic material present.

5. a) The formula for magnification is:

$$\text{Magnification} = \frac{\text{Drawing length}}{\text{Actual length}}$$

b) Step 1: Identify the given values.
The diagram is one and a half times the real size, so the magnification is 1.5.
The drawing length is $3 \text{ cm}$.