Cycling Matter & Changes in Ecosytems

1. Cycling Matter & Changes in Ecosytems Warden Ave PS – Grade 7 Science

2. Learning Goals By the end of this section we will be able to… • Describe and define the phrase “cycling of matter” • Explain some changes that result from the cycling of matter • Define and explain competition in an ecosystem • Describe and define sustainability in an ecosystem

3. Cycling Matter Picture this: You leave half a sandwich under your bed for 2 weeks. When you finally realise it’s there and you clean it up, you find mould on it. GROSS, right?!! This is the result of decomposers breaking down the organic matter (living things) into abiotic elements so that they can be reabsorbed by biotic elements. This is the first step in the cycling of matter.

4. Cycling Organic Matter Organic matter is broken down remains of plants and animals in the environment. The cycling of this is a series of steps that allows abiotic elements (like oxygen and nitrogen) to be use over and over again. By breaking down organic matter, producers are able to reuse these materials and continue the food web process we learned about earlier.

5. Changes due to the Cycling of Matter Ecosystems are constantly changing from year to year, season to season. Plants grow, sprout fruit or leaves and die. Animals build nests, reproduce and then abandon their nests. The cycling of matter is continuous, just like the energy transfer in a food web. Over time an ecosystem can change due to these various factors, but the cycling of matter is constantly going on.

6. Limiting Ecosystems All ecosystems rely on a balance of biotic and abiotic elements. The population of biotic elements is limited by factors such as food, predators, climate and amount of suitable habitat. These are an ecosystems limiting factors.

7. Why Ecosystems Change Ecosystems are constantly affected by many factors. For example, if an area suffers from a drought, the number of producers likely decreases. As a result, the number of primary and secondary consumers will also decrease, as they won’t have enough producers to eat. The reverse is also true, so that if an area has heavy rainfall, it’s number of producers and consumers will increase. Change is always happening in ecosystems. Usually this is a result of the natural flow of living things. However, some changes occur due to a change in competition orbioinvasion.

8. Change in Competition Just like any competition like a race or American Idol, species also compete. All living things compete with all other living things for resources to survive. Things like food, water and habitat are all up for grabs in an ecosystem. An ecosystems balance is created through this competition. If another element is introduced, like adding a new predator, that can change the competition and throw off an ecosystems balance.

9. Bio-invasion To understand bio-invasion, one must first understand the three types of species that can exist in an ecosystem:

10. Bio-invasion (cont’d) In short, bio-invasion is when a an invasive species takes over an existing ecosystem and kills off native species. This can dramatically change an ecosystem and can result in the disappearance of certain parts of food webs.

11. Sustainability Ecosystems must be able to keep themselves alive. Humans must help this process by being aware and acting consciously to avoid over-influencing an ecosystem. Sustainability is the ecosystem’s ability to continue existing. Human’s role is to aid this along.

12. Questions and Notesfrom the Textbook Page 47 – Questions # 1 & 7 Page 54 – Questions # 1, 5, & 7