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```					                            SNC2P Unit 1 Lesson 4

Student Instruction Sheet
Populations
Suggested time:      1 Hour

What’s important in this lesson:

A population is one important part of an ecosystem. Populations make up
communities or organisms where the action of each impacts others around it. You will
study populations in natural ecosystems and look at the ever growing human
population and the problems that arise.

Complete these steps:

1. Complete the diagnostic activity to refresh your memory of important terms.

2. Get a copy of the student handout for Unit 1 Lesson 1 and follow the instructions
to complete the activity. Have your teacher check this.

3. Complete the Assessment. You have 15-20 minutes to do this. Turn in to the
teacher.

4. Complete the Reflective Activity. Turn in to the teacher

Hand-in the following to your teacher:

1.   Diagnostic activity
2.   Lesson to be checked
3.   Assessment activity
4.   Reflective activity

Questions for the teacher:

Unit 1 Lesson 4 – Page 1
SNC2P Unit 1 Lesson 4

From the following definitions, choose the word that matches best. You can use
the glossary to help if necessary.

1. ____________________          The number of individuals in a given
area

2. ____________________          Birth rate

3. ____________________          Death rate

4. ____________________          The number of individuals of a given
species living in an area

5. ____________________          An artificial population, such as lab rats.

6. _____________________         A natural population, such as a field
dandelions.

7. _____________________         Organisms moving out of a given area.

8. _____________________         Organisms moving in to a given area

WORDS: Immigration, Mortality,         Open Population,      Closed
Population Natality, Emigration,         Density        Population

Unit 1 Lesson 4 – Page 2
SNC2P Unit 1 Lesson 4

Use Nelson Science 10 pgs. 77-79 or Nelson Science Concepts and Connections
pgs. 39-41 to answer the following questions

Limits on Populations

Field mice may have litters with ________ or more pups, and they can
reproduce every _______ weeks. After a pup is born, it takes only ________
weeks for a mouse to become sexually mature. In six months, a population of
______ mice could become a population of __________ mice. Mice have been
around for _________________ of years, so why is it that the field mice
population has not taken over different ecosystems?
The reason is that there are _____________________ on all populations.

Biotic Potential

Biotic potential is
________________________________________________________________
________________________________________________________________

Biotic potential is regulated by four factors:

Factor Affecting Biotic                         Description             Example
Potential

1

2

3

4

Limiting Factors

Any resource that is in short supply is a _______________ _____________ on a
population. Food, _______________, ____________________ and the
presence of pollution are all limiting factors.

Unit 1 Lesson 4 – Page 3
SNC2P Unit 1 Lesson 4

Factors that cause a population to          Factors that cause a population to
increase                                    decrease

Abiotic

Factors that cause a population to          Factors that cause a population to
increase                                    decrease

Biotic

Factors that Limit Populations

For example:
 What 2 factors will increase a fern population?

    What factors will cause a decline in the fern population?

Carrying Capacity

Populations fluctuate regularly due to an interaction of the many
________________ and _______________ limiting factors. However,
communities tend toward _____________________. Stability is achieved when
an ecosystem is in equilibrium, when none of the populations exceeds the
____________________ _____________________ of the ecosystem.

Unit 1 Lesson 4 – Page 4
SNC2P Unit 1 Lesson 4

The carrying capacity is _______________________________________.
________________________________________________________________.
The carrying capacity of an ecosystem depends on _______________________.

Density Dependent and Independent Factors

The _______________________ of organisms in an ecosystem is
important when considering the effects of some _____________________ and
____________________ factors. A population is called dense when:
________________________________________________________________
___.

Density-independent factors are:

.
     Give 2 examples of density-independent factors.
____________________________, ______________________________

Density-dependent factors are:

     Give 2 examples of density-dependent factors.
_____________________________, ______________________________

Unit 1 Lesson 4 – Page 5
SNC2P Unit 1 Lesson 4

A Population Study
Number of Organisms

700
600
500                                                       Rye Grass
400
Frogs
300
200                                                       Grasshoppers
100
0
1950   1952    1954     1956     1958     1960   1962
Year

1. Considering only the three organisms mentioned in the study, what food chain
probably exists among them?

2. Which members are producers and which are consumers?

3. In what year was the number of

a) producers greatest?

b) grasshopper population greatest?

c) frog population greatest?

4. Why did the grasshopper population reach a peak immediately after the rye
grass
peak?

5. Why was the frog population never as great as the grasshopper population?

Unit 1 Lesson 4 – Page 6
SNC2P Unit 1 Lesson 4

6. The population of which organism seems to control all of the population in this
food chain?

7. Why were all three populations nearly constant during the last five years?

8. The community was given an extra amount of fertilizer to make the rye grass
grow better and produce more seeds.

a) Which of the three populations will probably show an increase next year?

b) Which population will probably be the last to show an increase due to the

9.      What population would be affected if an insect killing chemical were

Unit 1 Lesson 4 – Page 7
SNC2P Unit 1 Lesson 4

Human Population

1. Plot the following
(estimated) data of
human population of the
world.

Year World
2.        Population in
3.        Billions
4.1700 0.7
5.1800 1.0
6.1900 1.8
7.1950 2.5
8.1975 3.2
9.2000 6.1
2. Draw a curve line
through the plotted points.

3. Determine the changes in the human population occurring between the
years:

a)   1700-1800

b)   1800-1900

c)   1900-2000

4. During which time interval is growth most rapid?

5. During which tie interval is growth slowest?

6. What do you think may happen to the human population if it continues to
increase?

7. How can each of the following factors be important in influencing human
population growth?

a) Crowding or available space

b) Food availability

c) Chemicals produced as waste

Unit 1 Lesson 4 – Page 8
SNC2P Unit 1 Lesson 4

It has been said that the human population is increasing by 145
individuals per minute. Should nothing be done to stop this growth
explosion? Write at least 5 points commenting on this statement.

Unit 1 Lesson 4 – Page 9
SNC2P Unit 1 Lesson 4

Part 1:             True or False. Correct False answers

1. All populations reach a stable state of equilibrium.

2. A forest fire is an example of a density dependent factor.

3. Carrying capacity is the maximum number of individuals that can be
supported in a population based on available resources.

3. Population sizes do not fluctuate.

4. Length of reproductive life refers to the number of offspring
produced by an individual.

5. Having sufficient food is an example of a biotic factor that causes a
population to increase.

6. A resource in short supply is an unlimiting factor.

Wolves were reintroduced into Yellowstone National Park in 1995
after the last Native wolf was killed in 1926. Read the following
excerpt from the Yellowstone National Park website and answer the
questions that follow:

“The annual census was taken and one estimate of the population size was one
third less than last year. With around 100 wolves, the park’s population is still
quite healthy by any standard. However, the seemingly sudden decline in
numbers would be alarming if most biological indications did not suggest this
would be natural. For much of the past ten years, the population has grown from
a few wolves brought from Canada to several hundred. Naturally, the population
will peak at some high level then decline to fluctuate moderately around a lower,
long-term population size. The peak occurred in about 2003 and since then the
pack sizes and total number of Yellowstone wolves has declined moderately.”

1. What might be a reason the wolf population grew tremendously in the first
few years after reintroduction?

2. List 3 possible causes for the decline in the wolf pack population.

Unit 1 Lesson 4 – Page 10
SNC2P Unit 1 Lesson 4

3. Why are the scientists not overly concerned with the decline?

4. Before reintroduction of the wolves, the elk population was destroying the
young aspen trees turning forests into fields. Explain what you think
happened to the following populations after wolf reintroduction. Give

Elk –

Aspen –

Wolf -

Unit 1 Lesson 4 – Page 11

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