Lesson A9: Survival in Ecosystems

Key Ideas   Unit Checklist

  Video Lesson

Ecosystems change naturally. Often, organisms are able to adapt to the changes to survive. Watch this video for examples of how organisms survive ecosystem change.

  Lesson A9: Survival in Ecosystems


A Year in the Life of a Columbian Ground Squirrel

Summers are brief and winters are long and harsh in Jasper National Park. The Columbian ground squirrel has no time to waste. When the days warm in early May, the squirrel wakes from a long hibernation. It is thin and weak. It must eat, breed, and give birth. Much precious time is spent avoiding predators. Grizzly bears, badgers, weasels, and hawks are on the prowl for food.
Reading and Materials for This Lesson

Science in Action 7
Reading: Pages 57–60

Materials:
No other materials are needed for this lesson.

The alpine meadow habitat of the Columbian ground squirrels is exploding with life. Colourful spring flowers, birds, and insects are everywhere. For a few months, life is easy. The squirrel nibbles on juicy young leaves. In a few months, seeds and grainsare plentiful. The squirrel is enormously fat by now. It struggles to stay cool on hot July days. In September, the first winter snow storm howls. The squirrel does not notice. It is deep underground in its burrow, hibernating. It hibernates for about eight months – until spring arrives.

Figure A.3.9.1 – A Columbian ground squirrel rests for a moment on a warm lichen-covered rock.
Figure A.3.9.2 – A Columbian ground squirrel checks for predators in an alpine meadow.
Dueling Sea Anemones

If you ever walk along the rocky beaches on Vancouver island, look down. You will see little green structures that look like flowers waving in the water. They are not flowers or even plants. They are anemones submerged in tide pools. It looks like they live a peaceful life but life is far from pleasant for them.

These animals are voraciously hungry all the time, and food is limited. They cannot chase their prey. They must let it come to them because they are stuck in one place attached to rock. They use tiny poisonous darts in their tentacles to kill any prey that comes too close. This means that location is everything. A tide pool where lots of food is present is highly sought-after real estate.

Anemones turn on each other to get a good spot on a rock. These anemones have special club-like structures stuffed with poisonous darts. When another anemone invades its territory, it will club it with its poisonous club. Eventually, someone backs down and moves on. However, one or both anemones often are injured seriously in such attacks. The violence is worth it when a prime food-rich location is at stake.


Figure A.3.9.3 – This sea anemone has found a prime location in a tide pool. Surrounding it are purple sea urchins.
Figure A.3.9.4 – Anemones live in tide pools along Vancouver Island’s rocky beaches.

 Watch More

Sea Anemones Battle for Survival

It is a slow-motion battle for life and death when two sea anemones clash over territory on a rock.

Cnidarians: Anemones Fight from Shape of Life on Vimeo.


Sea Anemone vs Sea Star

In this video, an anemone has even more tricks up its sleeve. A sea star can smell a nearby anemone, and that means dinner time. It will try to wrap its body around the anemone and release its digestive enzymes over it.

As you will see in this video, the anemone wants no part of being dinner. It spends several minutes stinging and attacking this sea star. When that attack does not work, it detaches itself and swims to safer territory. 



Purple Martin Condos

Purple martins are native to North America. These large swallows nest in cavities such as cliff face crevices, abandoned woodpecker holes, and hollow trees. They are amazing aerial acrobats. They dive and swoop to catch dragonflies, moths, butterflies, house flies, and horseflies. Both members of each bonded pair must feed their fast-growing chicks.

Two invasive bird species pose a constant threat to purple martins. House sparrows often evict purple martins from their nests and use them for their own young. Starlings are even more aggressive. They raid purple martin nests and kill the chicks inside. Because cavity-type nesting sites are rare, the gentle purple martin often loses the battle for them.

Many people build special condos for purple martins. Multiple wood cavities within a single structure offer these social birds ideal homes to raise their young. The condos give them a chance against their non-native aggressors.

To learn more about purple martin condos, click here to Explore with Elsie.



  Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.

Unit A Lesson 9 Self-Check

Instructions


Complete the following 6 steps. Don't skip steps – if you do them in order, you will confirm your understanding of this lesson and create a study bank for the future.

  1. DOWNLOAD the self-check quiz by clicking here.

  2. ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.

  3. COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.

  4. REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.

  5. SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.

  6. CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!


Self-Check Time!
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Self-Check Quiz Answers

Click each of the suggested answers below, and carefully compare your answers to the suggested answers.

If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.

Females of the same species compete for mates so they can reproduce. The members of the species compete for limited resources such as food, shelter, water, and the best spaces to live. Both the anemone and the purple martin compete for limited living spaces. When the Columbian ground squirrel wakes from hibernation, males start immediately to compete for females with whom to mate. Plants also compete for water, sunlight and minerals. They do not compete for food because they make their own. Tiny bacteria and other organisms compete for living space and for energy sources.
If two species must compete for the same resource, one species usually wins. It will claim the resource, and the other species must find a new resource elsewhere. A study of two species of parameciums shows this effect.

Populations of each species were raised in test tubes. Each tube contained a broth of bacteria. Bacteria is food of parameciums. Both species thrived in their separate test tubes. However, when they were mixed into one test tube, the growth rates of both species slowed. Eventually, one species declined in number and disappeared. The other species, meanwhile, grew to the limit of its food supply. Food is a limiting factor for any population of organisms.
Not necessarily will one of the species always die out if two species compete for the same resource. For example, four species of warblers often live together in spruce forests. All these birds eat the same insects. We might expect them to compete with each other. These species can thrive together in the forest because each species claims a different part of the spruce tree as its habitat. One species captures insects under the bark. Another species catches insects while flying. A third species looks for insects among the needles. A fourth species forages for insects on the forest floor. The four warbler species eat the same food, but they find it in different locations. This means they do not compete directly with each other for the same food, and all four species can live together. Think about how this arrangement might change if the insect population were reduced.
Surprisingly, interspecies competition often increases diversity in the long term. Closely related species often migrate into different habitats to avoid competition. The warblers in the response to Question 3 are an example. If food becomes scarce, the warblers might begin to look elsewhere from their spruce habitat. When they are in new habitats, each species will adapt to its new unique resources. Over time, the differences between the species likely will increase. This process increases species diversity. Species further avoid competition by becoming more different from each other over time. One species might learn to prefer large flying insects while another begins to prefer tiny aphids, for example. One or more warbler species might move away from spruce trees completely.  Eventually, the warblers could evolve into four very different species.
Population A is the prey and population B is the predator. We can determine this by considering some clues.
  • Population A is a larger number of individuals. We know that, typically, a food chain has more prey individuals than predator individuals.
  • Population B always increases just after population A increases. This means that when more prey are available, the food chain can support more predators. As prey are eaten and begin to grow scarce, the predator population dwindles also because less food is available.
  • Both populations cycle. Their numbers go up and down over time. However, as we can see here, they are kept in balance by each other. Fox and rabbit populations in an area often have this cyclic relationship. Wolves and deer also tend to follow this cyclic rule.