Photosynthesis as an endothermic reaction

Overview

Producers, biomass and why animals depend on photosynthetic organisms, the word and balanced symbol equations for photosynthesis, why it is endothermic, chlorophyll in chloroplasts, where the raw materials come from, and how a plant uses the glucose and oxygen it makes.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a producer in an ecosystem?

   Model answer

   A producer is an organism that makes its own food from simple substances using light energy, forming the start of a food chain.

2. 2

   What is meant by biomass?

   Model answer

   Biomass is the mass of living material present in an organism or in a group of organisms.

3. 3

   Nearly all the living material on Earth can be traced back to plants and algae. Explain why.

   Model answer

   They trap light energy and use it to build glucose, which becomes new living material that all other organisms ultimately depend on.

4. 4

   Apart from land plants, name two kinds of organism that act as producers.

   Model answer

   Algae, including the phytoplankton in oceans and lakes, and photosynthetic bacteria.

5. 5

   Explain why animals depend on photosynthetic organisms for their food.

   Model answer

   Animals cannot make their own food, so they must obtain it by eating producers or by eating other animals that ate producers.

6. 6

   Suggest what would happen to the total biomass of an ecosystem if all its producers died.

   Model answer

   Total biomass would fall at every feeding level, because no new food or stored energy would enter the ecosystem.

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