Lesson 2.1 - Population Growth and Decline 

The population of mice in Alberta exploded in 2004.  The mosquito population was very low in Edmonton during the summer of 2004.  The white-tail deer population in zone 510 was at an all time high in 2004.  The population of walleye was down to all time lows in many Alberta lakes that year. 

What caused these large changes in the populations?  Is it just food supply, predators, habitat, and disease?  Are other factors possible that you have not thought about? 

Read all the information on pages 258 and 259 in your textbook. Then, answer the following questions.

 

Question 1. How many factors determine the size of a population at any given time?  What are these factors and what do they mean?

Question 2. What factors affect the birth rate?

Question 3. What factors affect the death rate?

Question 4. How does immigration affect the size of the population?

Question 5. How does emigration affect the size of the population?

Question 6. What are common reasons for immigration and emigration?



Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. How many factors determine the size of a population at any given time?  What are these factors and what do they mean?

There are four factors that determine the size of a population at any given time:

        1. birth rate: the number of young produced by a population over a period of time
        2. death rate: the number of individuals that die over a period of time
        3. immigration: organisms move into an area
        4. emigration: organisms move out of an area

Question 2. What factors affect the birth rate?

The factors that affect the birth rate are

        1. environmental conditions
        2. nutrition
        3. population density
        4. number of young produced by the female in a year (This may sound like the definition of birth rate, but there is a difference.  The females of some species are able to produce very few young in a year although, in other species, females may produce thousands of young in a year.)  

Question 3. What factors affect the death rate?

The factors that affect the death rate are

        1. predation
        2. disease
        3. competition for food
        4. the environmental conditions (This is important although this was not mentioned in the reading.  For example, if it is a very dry spring and summer, the death rate of animals that eat grasses will increase because of a lack of food.) 

Question 4. How does immigration affect the size of the population?

Immigration always increases the size of the population because individuals are moving into the area.

Question 5. How does emigration affect the size of the population?

Emigration always decreases the size of the population because individuals are moving out of the area.

Question 6. What are common reasons for immigration and emigration?

Some common reasons for immigration and emigration are

        1. food supply
        2. population density
        3. habitat quality

 


Go to the next page to continue Lesson 2.