Week Three
Lesson 3: Diet & The Food Chain
S4L1. Obtain, evaluate, and communicate information about the roles of organisms and the flow of energy within an ecosystem.
This is the story of Demetrious the dragonfly...
One cool cloudy morning, an elegant red colored dragonfly flew around Lake Lori. It neared the water, and perched on a water lily, ready to lay her eggs. One by one, she laid her eggs in the still water right beneath the water lily, and then quickly flew off. A season later, the little eggs started to hatch, and little larvae began to appear in the water. That day, Demetrious entered the world. He was just a tiny little larva, and quickly swam with his siblings to the waterweeds below them. Swimming around in the waterweeds, Demetrious saw many other creatures. Little ones, big ones, shiny ones, and ones that even tried to eat his brothers and sisters! They were called Fish.
Demetrious started to become hungry, and needed to eat. He darted around in the water staying close to the waterweeds so he wouldn't get eaten. He ate tiny water beetles and mosquito larvae. Every few days, Demetrious became a bigger and bigger nymph. He started to eat bigger creatures like tadpoles, worms and even some small fish. He hunted and played every day with his siblings... he really liked Lake Lori. But sometimes, he would go to the water's surface beneath the edge of a water lily and peer out into the world above thinking, "I wonder what it's like up there?"
One day, Demetrious's body started to hurt a lot. It was time for him to molt! He decided to
climb and perch onto a reed above the waterweeds. He looked up into the sky, as the back of his skin split into two. He was a majestic red color, with tones of light purple. His light, transparent wings glinted in the sunlight. Demetrious had become a dragonfly! He fluttered and pumped his wings and leaped into the air. It took him quite some time to build strength in his wings, but eventually, he did.
Being quick and agile, he zipped through the air. "Woo hooo!" said Demetrious. He was having so much fun. But soon, he became tired and perched on a cattail. His stomach rumbled... he was hungry. Taking flight again, he looked around Lake Lori and spotted some mosquitoes and gnats nearby. Speeding through the air, with his long legs, making a basket-like shape, he snatched up a mosquito that buzzed and struggled in Demetrious's grip. Demetrious flew back to his reed, and enjoyed his little meal. Soon after, he flew off, catching more mosquitoes, gnats and even some cicadas, until he was full. The sun was setting, and he decided to rest in the safety of the reeds.
The next morning, Demetrious woke up and began his day. When he was out hunting that afternoon, a bird dove at him and tried to eat him! Demetrious quickly sped away from the Swallow and took cover, hiding in a bush. The brown bird soon gave up, as it was too sluggish to catch the agile dragonfly. Emerging out from the bush to continue hunting, he soon heard a buzzing noise behind him. It was a bee! This bee was faster than the bird, and chased Demetrious around Lake Lori. He dipped and swerved, trying to throw the bee off, almost running straight into a spiderweb! Luckily he avoided the bee and the spiderweb, and flew down to perch onto a water lily. Suddenly, something lunged at him! A frog! He flew off again, deciding to rest in the cover of some arrowheads. He shuddered... spiders, bird, bees and frogs! Today was not his lucky day. Everything wanted to eat him! But Demetrious went on with his day, and made up for the meals he had lost earlier.
A couple of months went by, and Demetrious was growing old. He hunted and flew everyday to catch his food and dodge his enemies. It was a bright sunny day, so Demetrious just wanted to perch on a cattail, sunbathe and rest. He started to get hot though, so he flew and skimmed the surface of Lake Lori to cool off. He sometimes even met his other brothers and sisters again, as some of them had split off, and some of them had stayed at Lake Lori like Demetrious. Feeling exhausted, he caught and ate a couple more mosquitoes and sat at the base of some reeds. Then he closed his eyes, and passed away. Demetrious the dragonfly had a full life.
What do dragonflies eat?
- The diet of a dragonfly can depend on its stage of life.
- During it's stage as a nymph, they eat other aquatic organisms such as mosquito larvae, water spiders, tadpoles, water beetles, and some tiny fish
- Mosquitoes, gnats, cicadas, ants, flies, moths, and most other flying insects are part of an adult dragonfly's diet. They can eat hundreds of mosquitoes in one day!
What are their predators?
- Adult dragonflies have to dodge all sorts of predators like: reptiles, fish, frogs, arthropods, bees, and even some birds.
- But dragonflies are highly agile, and some species have skin that can change to blend into the environment, so their predators have to work hard to catch them.
- Some carnivorous plants such as Sundew, also eat dragonflies.
- Predators of nymphs include ducks, fish, and amphibians like toads and newts.
What is a food chain?
- The food chain is a network/series of organisms that are each dependent on another as a source of food. It starts from producer organisms, and ends at apex predators or decomposer species. This chain shows how the organisms are related to each other by the food they eat.
What is a food web?
- A food web is the a natural system of interconnecting food chains. It consists of all food chains in one ecosystem. Organisms in food webs are divided into something called trophic levels. The first level is made up of producers, which are autotrophs that can make their own food and do not depend on other organisms for nutrition. (ex. plants) The next level would be consumers, then primary, secondary, & tertiary consumers, with detritivores and decomposers on the last level.
What is the difference between them? How are they related?
- Well, food webs connect many food chains, and they can support chains that are long/complex or short/simple.
- Food chains only follow the movement of one path of energy as animals find food.
- Food webs show how plants & animals are connected in several ways in order to help them all survive.
- Click here to see some examples of how the food web and food chain work!
How do dragonflies contribute to the food chain?
- Dragonflies are actually considered apex predators of invertebrates.
- They are top predators in the aquatic food web, but actually reside in a lower spot on the main food chain, since they are insects.
- They serve as food for several creatures, such as frogs, and eat/control pests, like mosquitoes.
- Without dragonflies, the population of gnats, mosquitoes and other pesky flying insects would be very high.
Click below to watch a short clip of Dragonfly Power!
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