Section 2: Energy Flows and Cycles in Ecosystems

Key Ideas   Unit Checklist

  Unit A: Section 2 - Introduction

Figure A.S.1.1 – The Canadian arctic is beautiful but harsh.
Figure A.S.1.2 – An arctic fox begins to lose its white winter fur when spring arrives.

Life Thrives in the Canadian Arctic
 
The Canadian arctic is one of the harshest climates in the world. Summers are short but warm and the sun shines all day and night. Winters are dark and very cold. Few trees can survive here. Only during a few weeks in summer is it warm enough for plants to grow. Many of them burst into bloom.  For a short while, food is plentiful for organisms such as the arctic hare. It nibbles on the tender new growth of shrubby willows, saxifrage, and short grasses. It builds fat stores for the harsh winter quickly. In turn, the hare is food for arctic wolves, arctic foxes, snowy owls, and sometimes humans. The Inuit are part of the arctic ecosystem. They must rely on the their knowledge of the plants and animals that live here to survive.
Most of the year, the arctic is completely frozen, but a surprising number of organisms thrive even in winter. They are specially adapted to the rapidly changing conditions. Their relationships make life possible in the far north.
Figure A.S.1.3 – The arctic hare is an important part of the arctic ecosystem. 

Each organism has an important role in survival. The arctic hare is part of a complex food web that includes many organisms. In this section, you will learn more about the surprising roles organisms have in ecosystems and how energy in those systems flows and cycles.

 Watch More

Arctic Food Web

Watch this video to see how parts of the arctic food web work. You might be very surprised to see the very small arctic fox stealing food from a polar bear or climbing on cliffs to steal eggs and hunt birds.

  Connections

Connections: Aboriginal Culture
>> Storytelling

The Inuit have a rich tradition of storytelling. Elders share stories about all aspects of life with the younger generation.

 The Inuit live closely with animals, including the arctic hare. Many of these familiar animals become characters in their stories. For example, “Light and Dark” tells the myth of how night and day came to exist:

A talk between a fox and a hare has been remembered:

"Taaq, taaq, taaq! Darkness, darkness, darkness!" said the fox. It liked the dark when it was going out to steal from the caches of the humans.

"Ulluq, ulluq, ulluq! Day, day, day!" said the hare. It wanted the light of day so that it could find a place to feed.

And suddenly it became as the hare wished it to be; its words were the most powerful. Day came and replaced night, and when night had gone, day came again. And light and dark took turns with each other.

- Rasmussen 1931
Canadian Museum of Nature

  Words to Think About:

Check out the word cloud below. It pictures the important words that you are going to learn in this section. Watch for these words, and combinations of these words, as you read. When you see them highlighted, you can click on them to learn more about what the word means. You can also visit the course glossary and read definitions for all of these words.

Lessons in This Section

Lesson A4: Producers, Consumers, and Decomposers
Key Question – How do organisms provide food for other organisms?

Lesson A5:  Energy Flow in Ecosystems
Key Question – How does energy flow through food chains and food webs?

Lesson A6:  Ecosystem Cycles
Key Question – How do water and carbon cycle through an ecosystem?
Reading and Materials for This Section

Science in Action 7
Reading: Pages 26–46

Materials Lists for Unit:

  Try It!

Learn More about the Arctic Hare

The arctic hare has many predators. The species would die out if it were not so good at avoiding being eaten.

Instructions

Visit the following websites to learn more about the arctic hare. As you explore, make a list of ways the hare avoids its predators. Think about how it hides, how it gets away, and how it senses a predator is nearby. After you complete your research, try to answer the questions that follow.

National Geographic: Arctic Hare
http://www.canadiangeographic.ca/article/animal-facts-arctic-hare
Wikipedia article: Arctic Hare
https://en.wikipedia.org/wiki/Arctic_hare

Arctic Hare - adaptations for survival in the far north
http://www.saskschoolsinfo.com/arctic/Ahare.html

Cool Critters: Arctic Hare
http://bit.ly/arctic_hare
Questions:

Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.

The colour of the hare’s coat helps it blend into its surroundings. In winter, it is as white as the snowy landscape. In summer, it is as brown as the bare ground and rocks. These colour changes make the hare more difficult to see, and predators do not notice it quickly.
The hare has long strong hind legs that help it to run very fast. In fact, it can outrun foxes and wolves. It can hop easily over obstacles as it runs away. Its feet are large and very furry. They act as snowshoes, so its feet do not sink into the snow. The closely-related snowshoe hare has large furry feet for the same reason.
Arctic hares stay in loose groups. Some rest and feed while others stand guard. When a predator comes near, they scatter in all directions. This behaviour confuses the predator, making catching one more difficult. Baby hares know instinctively to stay very still when a predator is near. This helps them remain hidden -- and safe.
The hare’s eyes are located on the sides of its head so it can see an approaching predator from any direction. Often, the hare stands on its hind feet so it can look around for predators.
If hares were easy to catch, very few would survive predation. The hare species could go extinct.
If the hare were impossible to catch, predators that rely on it for food would suffer. Some of the predator species might go extinct. The health of this food web relies on a balance of prey and predator species.