Lesson 5.1 - Human Impact on Populations

You have learned much about the effects of biotic and abiotic limiting factors on populations.  How do people affect other populations?  Do we only affect populations that we use for food?  Or do we affect populations in other ways too? 

Read Human Impact on page 268 in your textbook.  Also check the Internet Connect site on page 268.

Question 1. What are exotic species?

Question 2. Why are humans usually responsible for the introduction of exotic species to an ecosystem?

Question 3. Name six exotic species that have been introduced into Canada.

Question 4. Why is it that an exotic species can cause serious damage to an ecosystem?

Question 5. Why do humans continue to introduce exotic species when the potential for serious damage to the ecosystem can occur?

Question 6. What are invasive plants?

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. What are exotic species?

Exotic species are plants and animals that are foreign to an ecosystem.

Question 2. Why are humans usually responsible for the introduction of exotic species to an ecosystem?

Humans are the only species that can travel almost anywhere on the planet.  Humans can also transport plants and animals with them.  People have brought new species intentionally into new ecosystems, often without regard for laws and regulations.

Question 3. Name six exotic species that have been introduced into Canada.

Six exotic species introduced to Canada are purple loosestrife, Atlantic salmon, chestnut blight, English sparrows, sea lamprey, and Norway rats.

Question 4. Why is it that an exotic species can cause serious damage to an ecosystem?

Exotic species often have no natural predators.  The species can then reproduce very quickly and take over from natural species.  All species higher up the food chain suffer as a result, and some may become extinct.  Cross-breeding is yet another possible way that the ecosystem can be damaged.

Question 5. Why do humans continue to introduce exotic species when the potential for serious damage to the ecosystem can occur?

Humans often do not understand the consequences of their actions.  People who like a certain plant or animal may bring it home unaware of the danger.  Others smuggle the exotic species because of greed and profit.  Think about how easy it would be for you to introduce an exotic species into a lake.  All you need is a boat that you use for fishing.  You fish in one lake, take your boat out, and pull it to the next lake with your truck.  You put the boat in the new lake and go fishing again.  Did you see what you just did?  Likely not.  There was some water trapped in the motor, boat, and trailer.  In that trapped water were many organisms such as plant seeds, insects, and even small fish.  When you drive your boat around the lake, some of these organisms might be released into the water and begin to reproduce.  You have just introduced exotic species into the lake, which may cause great damage.

Question 6. What are invasive plants?

Invasive plants are exotic plants that have the ability to compete with and replace native plants.  They can take over an ecosystem.

 


Go to the next page to continue Lesson 5.