Science 10
Immigration, Births, Emigration, and Death
A population’s size is determined by four factors: immigration, emigration, birth and
death.

Immigration: movement of individuals into a population from another
population.

Emigration: Movement of individuals out of a population into another
population.

Birth: increase in the number of individuals in a population.

Death: Decrease in the number of individuals in a population when individuals
die.
Population growth is based on available resources
Types of Population Growth
1. Exponential Growth
 Occurs when a population size increases dramatically over a period of
time.
 Appears as a Jshaped curve
 Example: Human
population on
Earth.
 This type of
growth may occur
when a species
moves to a
previously
uninhabited area.
2. Logistic Growth
 Occurs when populations face limited resources.
 Begins with a period of slow growth, followed by exponential growth,
then eventually the growth levels off.
 Appears as an S-shaped curve.
 Initially, there is lots of resources and the population size increases,
eventually the resources deplete and the population growth levels off
at the size the environment can support.
Science 10
Carrying Capacity
The carrying capacity is the maximum number of individuals of a particular
species that the environment can support. The environment determines how many
individuals of the species can be supported based on natural changes and supply of
resources.
The actual size of a population is usually higher or lower than the carrying
capacity.
Science 10
Assignment on Limiting Factors, Immigration,
Emigration, and Carrying Capacity
1. Read the information and data below. Answer the three questions about the graph. (Each worth 1
mark)
Science 10
Use the graph below (fig. 14.13) to answer the following questions:
2. Describe what happened to the moose population in 1994. Using the data on the graph, explain why
this happened. (2 marks)
3. Describe the individual trends of the wolf and moose populations given by the graph. (2 marks)
4. How does the wolf population on Isle Royale affect the carrying capacity of the moose population? (1
mark)
***NOTE:
Density Dependent limiting factors are the factors that are affected by the number of individuals in a
given area, i.e. disease. Density Independent limiting factors are factors that limit a population’s growth
no matter what the size or density the population is, i.e. fire.
Science 10
5. The graph in fig. 14.13 shows density dependent factors. List two density independent factors that
would have an effect on the population of the moose. (2 marks)
6. A population of algae in a pond is limited by the amount of sunlight that strikes the pond’s surface. Is
sunlight a density dependent or density independent factor? (1 mark)
7. In 1944, 29 reindeer were introduced to St. Matthew Island off the coast of Alaska. At the time, the
island was covered with lichens. Plenty of good food allowed the reindeer herd to grow at an exponential
rate. By the summer of 1963, the island population had grown to 600 reindeer. Over the winter, large
amounts of snow fell on the food resources (which were depleting because of the large herd). In the
spring of 1964, only 50 reindeer remained.
a) What two factors caused the population to crash? (2 marks)
b) What would have eventually happened to the reindeer herd if the winter had not made
foraging so difficult? Explain. (2 marks)
8. The graph below shows the growth of bacteria with two different food sources. The bacteria use two
food sources: lactose and glucose. The bacteria prefer to use glucose.
I indicates growth using glucose. II indicates growth using lactose.
Science 10
a) What is happening to the population of bacteria between hour 3 and 4? Why is this trend occurring?
(hint: remember bacteria prefer glucose) (2 marks)
b) What are the limiting factors for the population of bacteria? Are the limiting factors density dependent
or density independent? (2 marks)
c) After 8 hours of growth, what do you think will happen to the bacteria population? Why? (2 marks)
9. Use the graph below to answer the following questions.
a) What are some possible reasons why people immigrate to Canada? (2 marks)
b) What are some reasons why people emigrate from Canada? (1 mark)
c) Are there more people immigrating or emigrating to Canada? (1 mark)
Science 10
10. The construction of logging roads has led to increased access to wilderness areas, thereby leading to
an increase in the number of hunters. Speculate what you think would happen to the elk population in the
area of construction? If the elk population has been effected, speculate what would happen to the
animals that prey on elk. (4 marks)