The Energy Flow: Food Chains and Food Webs
The Energy Flow: Food Chains and Food Webs
At the end of this lesson, you are expected to:
Identify producers, consumers (primary, secondary, tertiary), and decomposers in a food chain.
Explain how energy flows from one trophic level to another.
Construct simple food chains using examples relevant to the Philippines.
Interpret food chains to understand the relationships between organisms in an ecosystem.
Imagine you are in a lush garden. You see a buzzing bee collecting nectar from a flower. A small bird then swoops down and eats the bee. Later, a larger bird spots the small bird and catches it for a meal.
Think about this:
Where did the bee get its energy?
Where did the small bird get its energy?
Where did the larger bird get its energy?
This simple story shows how energy moves from one living thing to another. In this lesson, we will explore these "journeys of energy" through something called food chains!
Welcome, young scientists! Today, we embark on an exciting journey to understand how energy travels through the amazing world of living things. Everything that lives needs energy to grow, move, and survive. But where does this energy come from, and how does it get passed around? The answer lies in food chains.
What is a Food Chain?
A food chain is like a simple map that shows who eats whom in nature. It’s a way to see how energy is transferred from one organism to another. Think of it as a line of dominoes falling – when one is knocked over, it knocks over the next, and so on. In a food chain, energy is passed along this line.
The Main Players in a Food Chain:
Every food chain has different roles, or trophic levels, that organisms play. Let's meet them:
Producers: The Energy Makers
Who they are: Producers are usually plants, algae, and some bacteria. They are called "producers" because they produce their own food using energy from the sun.
How they do it: They use a magical process called photosynthesis. During photosynthesis, they take sunlight, water from the soil, and carbon dioxide from the air to create their own food (sugars) and release oxygen, which we breathe!
Why they are important: Producers are the foundation of almost every food chain on Earth. Without them, there would be no energy to pass on to other living things.
Example: In the Philippines, think of the seaweed (like lato or gulaman dagat) that grows in our oceans. These seaweeds use sunlight to make their own food. Another example is the rice plant, a staple food for many Filipinos. Rice plants capture energy from the sun to grow.
Consumers: The Energy Eaters
Consumers are living things that cannot make their own food. They have to consume or eat other organisms to get the energy they need. There are different types of consumers:
a. Primary Consumers (Herbivores): The Plant Eaters Who they are: These are animals that eat only producers (plants). They are also called herbivores. How they get energy: They get energy by eating leaves, fruits, seeds, or roots of plants. * Example: In the Philippines, a carabao eats grass. A grasshopper eats leaves. A butterfly sips nectar from flowers. All these animals are primary consumers because they eat plants.
b. Secondary Consumers (Carnivores/Omnivores): The Meat/Plant Eaters Who they are: These are animals that eat primary consumers. They can be carnivores (eating only meat) or omnivores (eating both plants and animals). How they get energy: They get energy by eating herbivores. * Example: A frog eats grasshoppers. A chameleon eats insects. A small fish might eat seaweed or small aquatic plants. These are secondary consumers. If an animal eats both plants and other animals, like a pig that eats roots and also insects, it's an omnivore and can be a secondary or even tertiary consumer depending on what it eats.
c. Tertiary Consumers (Carnivores/Omnivores): The Top Eaters Who they are: These are animals that eat secondary consumers. They are usually at the top of the food chain. They can also be carnivores or omnivores. How they get energy: They get energy by eating other animals that have already eaten plants or other animals. * Example: A snake eats a frog. A hawk eats a snake. In our oceans, a tuna might eat smaller fish that ate plankton. These are tertiary consumers.
d. Quaternary Consumers (Apex Predators): The Ultimate Top Eaters Who they are: Sometimes, there's a fourth level of consumers, called quaternary consumers. These animals eat tertiary consumers and are often at the very top of the food chain, with no natural predators. Example: A shark eats a tuna. A Philippine eagle eats a snake or a monkey. These are apex predators.
Decomposers: The Nature's Recyclers
Who they are: Decomposers are tiny living things like bacteria and fungi (mushrooms are a type of fungus).
How they do it: When plants and animals die, decomposers break down their bodies. They "decompose" the dead material, returning important nutrients back into the soil and water.
Why they are important: They are nature's clean-up crew! They recycle dead organic matter, making nutrients available for producers to use again. This keeps the cycle of life going.
Example: When a fallen leaf or a dead insect is on the ground, tiny bacteria and fungi work to break it down, returning its building blocks to the earth.
Putting It All Together: Building a Food Chain
A food chain shows the flow of energy. We use arrows to show the direction the energy is moving. The arrow always points from the organism being eaten to the organism that eats it.
Let's look at a simple food chain from the Philippines:
Example 1: A Marine Food Chain
Phytoplankton (tiny ocean plants) → Zooplankton (tiny ocean animals that eat phytoplankton) → Sardines (small fish that eat zooplankton) → Tuna (larger fish that eat sardines) → Shark (a top predator that eats tuna)
Let's break this down:
Phytoplankton: These are the producers. They make their own food using sunlight in the ocean.
Zooplankton: These are the primary consumers (herbivores) because they eat the phytoplankton.
Sardines: These are the secondary consumers (carnivores) because they eat the zooplankton.
Tuna: These are the tertiary consumers (carnivores) because they eat the sardines.
Shark: This is a quaternary consumer or apex predator because it eats the tuna.
See how the energy from the sun, captured by phytoplankton, travels all the way up to the shark?
Example 2: A Terrestrial (Land) Food Chain
Grass → Grasshopper → Frog → Snake → Eagle
Let's break this down:
Grass: The producer.
Grasshopper: The primary consumer (herbivore) that eats grass.
Frog: The secondary consumer (carnivore) that eats the grasshopper.
Snake: The tertiary consumer (carnivore) that eats the frog.
Eagle: The quaternary consumer or apex predator that eats the snake.
The 10% Rule: Energy Loss at Each Step
Now, here’s a very important thing to remember: when energy is transferred from one trophic level to the next, a lot of it is lost! Organisms use most of the energy they consume for their own life processes – like moving, growing, and staying warm.
Scientists have found that only about 10% of the energy from one level is actually passed on to the next level. The other 90% is used up or lost as heat.
Imagine a producer (like grass) has 1,000 units of energy.
The primary consumer (grasshopper) that eats the grass will only get about 100 units of energy (10% of 1,000).
The secondary consumer (frog) that eats the grasshopper will get about 10 units of energy (10% of 100).
The tertiary consumer (snake) that eats the frog will get about 1 unit of energy (10% of 10).
The quaternary consumer (eagle) that eats the snake will get only about 0.1 units of energy (10% of 1).
This is why food chains usually don't have more than 4 or 5 levels. There simply isn't enough energy left to support more levels! This also explains why there are usually fewer large animals (like eagles) than smaller animals (like grasshoppers) in an ecosystem.
Why are Food Chains Important?
Understanding food chains helps us see:
How energy flows: It shows us the path energy takes from the sun to all living things.
Interdependence: It shows how all living things are connected. If one part of the food chain is removed or affected, it can impact all the other parts. For example, if all the frogs disappeared, the grasshopper population might increase, and the snake population might decrease because they have less food.
Balance in Nature: Food chains help maintain the balance in an ecosystem.
Guided Practice: Build Your Own Food Chain!
Let's practice building a food chain together. I will give you a list of organisms found in a Philippine forest. Your task is to arrange them in the correct order to form a food chain, using arrows to show the flow of energy.
Organisms:
Mango Tree (fruit)
Eagle
Insects
Snake
Instructions:
Identify the producer. Which organism makes its own food?
Identify the primary consumer. Which organism eats the producer?
Identify the secondary consumer. Which organism eats the primary consumer?
Identify the tertiary consumer. Which organism eats the secondary consumer?
Arrange them in order using arrows (→) to show the direction of energy flow.
Your Answer: ________________ → ________________ → ________________ → ________________
(Check your answer below!)
Answer: Mango Tree → Insects → Snake → Eagle
Interactive Activity: Food Chain Charades!
Let's play a game! I will give you a role (producer, primary consumer, secondary consumer, tertiary consumer, or decomposer). You will act out what your role does in a food chain. For example:
Producer: Stand still, reach your arms up like you're soaking up the sun.
Herbivore: Pretend to munch on leaves.
Carnivore: Pretend to hunt and eat another animal.
Decomposer: Pretend to break down something on the ground.
We can even create a "living food chain" where each of you represents an organism, and you connect yourselves with a string or by holding hands to show the energy flow.
Independent Practice: Philippine Food Web Snippet
A food web is like many food chains connected together. It shows that most animals eat more than one type of food.
Look at the organisms below, which are found in the Philippines. Draw a simple food web by connecting at least 4 of them with arrows showing the flow of energy. Make sure to label each organism with its role (Producer, Primary Consumer, Secondary Consumer, Tertiary Consumer).
Organisms:
Algae (producer in water)
Small fish (eats algae)
Crab (eats small fish and algae)
Larger fish (eats small fish and crabs)
Sea otter (eats crabs and larger fish)
Draw your food web here:
(Remember: Arrows point from the food to the eater!)
Think about what you ate for breakfast or lunch today. Can you trace the energy in your food back to the sun?
If you ate rice (a producer), the energy came directly from the sun through photosynthesis.
If you ate pork (from a pig), the pig ate plants (like corn or rice), so the energy in the pork originally came from the sun, captured by those plants.
If you drank milk, the cow that produced the milk ate grass, which got its energy from the sun.
Even if you ate fish, the fish ate smaller organisms that ultimately relied on producers like algae or phytoplankton.
Every meal you eat is a part of a food chain, showing the incredible journey of energy from the sun to you! Understanding food chains helps us appreciate where our food comes from and how important each living thing is in the environment.
A food chain shows how ________ moves from one living thing to another.
Organisms that make their own food using sunlight are called ________.
Organisms that eat other organisms are called ________.
Animals that eat only plants are called ________.
Animals that eat other animals are called ________.
When an organism dies, ________ break them down and return nutrients to the soil.
Only about ________ percent of energy is transferred from one trophic level to the next.
The arrows in a food chain show the direction of ________ flow.
Observe Your Surroundings: Go outside to your backyard, a park, or even look at plants in a pot. Can you identify a producer? Can you see any insects or birds that might be consumers? Try to imagine a simple food chain that might exist there.
Create a Poster: Draw a food chain using organisms found in the Philippines. Include at least four levels (producer, primary consumer, secondary consumer, tertiary consumer). Label each organism with its role and use arrows to show energy flow. You can draw it or print pictures and paste them.
Discuss with Family: Talk to your family about the food you eat and try to trace the energy back to the sun. Ask them what their favorite Filipino dishes are and see if you can identify the producers and consumers in those meals.
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