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Living Things - Food Chains and Ecosystems

Grade 4IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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An ecosystem consists of all the living (biotic) things and non-living (abiotic) factors like sunlight, temperature, and H2OH_2O interacting in a specific area.

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Producers are organisms, mainly plants, that make their own food through photosynthesis using CO2CO_2, H2OH_2O, and sunlight to produce glucose (C6H12O6C_6H_{12}O_6).

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Consumers are living things that cannot make their own food and must eat other organisms. They are categorized as primary (herbivores), secondary (carnivores/omnivories), and tertiary consumers.

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Decomposers, such as fungi and bacteria, break down dead organic matter and return essential nutrients like Nitrogen (NN) and Phosphorus (PP) back into the soil.

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A food chain shows the flow of energy from one organism to another, always beginning with energy from the Sun.

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A food web is a complex network of many interconnected food chains within an ecosystem, showing that most organisms have more than one food source.

📐Formulae

6CO2+6H2O+light energy→C6H12O6+6O26CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2

Sun→Producer→Primary Consumer→Secondary Consumer\text{Sun} \rightarrow \text{Producer} \rightarrow \text{Primary Consumer} \rightarrow \text{Secondary Consumer}

💡Examples

Problem 1:

Identify the roles of each organism in the following food chain: Grass→Grasshopper→Frog→Snake\text{Grass} \rightarrow \text{Grasshopper} \rightarrow \text{Frog} \rightarrow \text{Snake}.

Solution:

Grass: Producer; Grasshopper: Primary Consumer; Frog: Secondary Consumer; Snake: Tertiary Consumer.

Explanation:

The Grass uses H2OH_2O and sunlight to produce energy. The Grasshopper eats the grass (herbivore), the Frog eats the grasshopper (carnivore), and the Snake eats the frog (apex predator in this chain).

Problem 2:

What would happen to the population of frogs if the number of snakes in the ecosystem suddenly decreased?

Solution:

The population of frogs would likely increase.

Explanation:

Since snakes are the predators of frogs, fewer snakes mean fewer frogs are being hunted. However, this might eventually lead to a decrease in grasshoppers because there would be more frogs eating them.

Problem 3:

During photosynthesis, what gas do plants take in from the atmosphere and what gas do they release?

Solution:

They take in CO2CO_2 and release O2O_2.

Explanation:

Plants absorb Carbon Dioxide (CO2CO_2) to create sugar (C6H12O6C_6H_{12}O_6) and release Oxygen (O2O_2) as a byproduct which humans and other animals need to breathe.