Make sure you have understood everything in this section (Lessons A7, A8, A9, and A10).
Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
This is also a good time to visit your Section 3 Checklist to make sure you have completed all the recommended learning activities.

Unit A Section 3 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 section 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 the lessons of this section 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.

Monitoring ecosystems is important. By keeping track of various populations, one can see how an ecosystem changes over time. Counting all the plants or animals in an ecosystem is impossible, so samples are taken using various sampling techniques. Capture-recapture is a common technique used to count animals in an ecosystem. An average count of organisms, taken over time, can indicate whether that population is increasing or decreasing. It can also provide information about the general health of the ecosystem.
Invasive species have serious effects on the ecosystem they invade. Often, they affect the availability of resources. They alter the food web. In their original locations, invasive species evolved with other competitors, but those competitors are absent in the new ecosystem. Without them, the invaders outcompete native species. When resources are scarce, the invader has the advantage. The native species eventually becomes scarce and it may die out.

Animal invaders may have no natural predators in their new ecosystems. Or, similar to the Norway rat, they out-smart their predators. The invasive species can multiply quickly. They may wipe out entire populations of prey. Outcompeting and preying on native species reduces the biodiversity of the ecosystem. Reduced biodiversity weakens ecosystems.
Members of the same species compete with each other for limited resources. Animals might compete for mates, food sources, living space, and shelter from predators. Plants compete for living space, minerals, and sunlight. Even microbes compete with each other for living space and energy sources. Competition is more intense when a resource becomes scarce. Then, only the strongest members of a population survive.
Lynx and snowshoe hares have a predator-prey relationship. Hares eat small plants and grass in summer and small twigs in winter. The boreal forest where they live usually provides an abundant food supply. Hares have several litters every year so they reproduce at a fast rate. The only major factor that limits the hare population is predators. Hares have many predators but the lynx almost exclusively eats hares.

The hare population is abundant when few predators are present. Lynx, who eat them, increase in numbers because they now have plenty of food for themselves and their cubs. However, a larger lynx population eats more hares. The hare population goes down. Less food available means that the lynx population decreases in response. Less lynx now mean more hares and the cycle continues
Secondary succession is triggered when a forest ecosystem is disturbed. Fire removes trees and debris from the forest floor. It reduces plant matter to nutrient-rich ash. Sunlight can now reach the forest floor. Seeds and surviving roots have good growing conditions. Plants such as grasses and small herbs have a chance to grow. Insects and birds move into the new habitat. The small plants are later replaced by shrubs and fast-growing trees. Bird and insect populations change, and larger animals move in to eat berries and leaves. The grassy forest floor is perfect for their germination.

As succession proceeds, plant and animal species become more diverse and food webs grow more complex. Eventually, slow-growing trees sprout among the shrubs and smaller trees. Years later, they shade all the shorter plants. The animal population shifts again. Succession ends when a stable climax community is reached.