Chapter 4, Problem 1CT

During the day, algae carry out both photosynthesis and respiration, but at night they can only perform respiration. Small, isolated tide pools on rocky shores often have thick growths of seaweeds, which are algae. Would you expect the amount of oxygen in the water to differ between night and day? How?

Summary Introduction

To determine: Whether the amount of oxygen in the water differs between night and day. 

Introduction: Photosynthesis is a process in which the green plants and algae obtain their nutrients using solar energy, carbon dioxide, and water. This process takes place in chloroplast where the chlorophyll molecules are present. The end product of the light reaction is the formation of ATP and NADPH. Respiration is the biological process that involves the production of energy usually by the intake of oxygen and release of carbon-dioxide.

Explanation of Solution

Algae are the group of organisms that are found on terrestrial areas and in aquatic and marine areas as well. They carry out both photosynthesis and respiration during day time. However, they cannot perform photosynthesis at night time.

Yes, the amount of oxygen in the water differs between day and night. The oxygen dissolved in the water decreases sharply during the night time.

Summary Introduction

To determine: The reason how the amount of oxygen in the water differs between night and day.

Introduction: Photosynthesis is a process in which the green plants and algae obtain their nutrients using solar energy, carbon dioxide, and water. This process takes place in chloroplast where the chlorophyll molecules are present. The end product of the light reaction is the formation of ATP and NADPH. Respiration is the biological process that involves the production of energy usually by the intake of oxygen and release of carbon-dioxide.

Explanation of Solution

Algae are the group of organisms that are found on terrestrial areas and in aquatic and marine areas as well. They carry out both photosynthesis and respiration during day time. Brown algae are the most complex and largest algae. These are multicellular and mostly marine. This type of algae is very common where there are cold water currents. The olive or brown color is due to the presence of carotenoids in their plastids. Seaweeds are mostly the brown algae. There is absence of true organs or tissues in the brown algae, unlike plants.

The amount of oxygen dissolved in the water differs between day and night. During night, the concentration of oxygen in water decrease sharply. This is because the seaweeds (marine algae) cannot perform photosynthesis (the process by which sunlight is used by the cell to convert carbon dioxide and water into glucose and oxygen) at night time. They carry out only respiration in night time. Thus, the oxygen becomes limited during night.