1. Predator and Prey & Population Growth
Population Notes
Predator and Prey
&
Population Growth

2. 1. Predator Prey Relationships
Learning Objectives
Be able to describe the relationship between predators and their prey.
Be able to explain the shape of a predator – prey graph.

3. 6. Animals that eat other animals
Populations of animals are often limited by the amount of food.
What are animals that eat other animals called?
predators
What are the animals that predators eat called?
prey
To do: Define the words Predator and Prey and give an example of each.

4. 12. The Lynx and the Snowshoe hare
This is the most common example of the predator prey relationship.

5. 15. Predator–prey graph
Question: In all of the examples provided who has a larger
Population: Predators or Prey? Explain your answer.
There are always more prey than predators.
The prey always increases before the predators do.

6. 16. Predator–prey graph
This population data comes from fur trapping records.
How are the populations linked?

7. estimated population size (thousands)
17. Predator–prey graph
How does the lynx population depend on the number of snowshoe hares?
Take a closer
look at this part
of the graph.
150
snowshoe
hare
lynx
100
estimated population size (thousands) 50
1800
1820
1840
1860
1880
1900
time (year)

8. 18. Predator–prey graph section
Why does the peak for the lynx population always come after the peak for the number of snowshoe hares?
150
snowshoe
hare
lynx
For the populations
to survive, there will always be more hares than lynxes.
100
estimated population size (thousands) 50
1850
1855
1860
1865
time (year)

9. An ecologist has been studying the moose and wolf population on an island off the coast of Washington. Over the period of 1955 through 1999 she has seen many fluctuations, or changes, in the population numbers. Here is a table of the information she put together:

10. A key for the different populations
On a separate piece of graph paper, you will need to make a graph of the ecologist’s information. You need to include:
A title for the graph
A key for the different populations
Units and label for the Y-axis (the vertical one) – this will be the population #s
Units and label for the X-axis (the horizontal one) – this will be the year
Year
Moose Population
Wolf Population
1960 13 22
1963 16 21
1966 20
1969 29 18
1972 32
1975 30 40
1978 23 39
1981 51
1984 25
1987 27 17
1990 42
1993 31 19
1996 57 12
1999

11. ANSWER THE FOLLOWING QUESTIONS:
WHICH ANIMAL IS A PREY? WHICH ANIMAL IS A PREDATOR?
AS MOOSE POPULATION INCREASES, WHAT HAPPENS TO THE WOLF POPULATION?
WHY DID THE MOOSE STARTED DECREASING AFTER 1975?
DESCRIBE THE PATTERN BETWEEN THE WOLF POPULATION IN RELATION TO THE MOOSE POPULATION.

12. POPULATION
BIOLOGY

13. What do you think this map represents?

14. Ecosystem → Communities → Populations → Organisms
4.1 Population Dynamics
Ecology can viewed through several hierarchical "levels of organization.
Ecosystem → Communities → Populations → Organisms

15. Limiting factors—biotic or abiotic factor that prevents population growth
A. Physical factors -- temperature, water, light, soil acidity
B. Biological interactions --competition, predation, symbiosis
C. Geographical barriers – Mountains, deserts, oceans (Humans sometimes transport species past these barriers)

16. Population Density
Population density is total population size per unit of area.
Carrying capacity is the maximum number of organisms that can be supported in a given habitat. K

17. Exponential growth (J-shaped curve)-- Assumes no limitations on resources.
Some species have brief periods of exponential growth, followed by population crashes.

18. Logistic growth (S-shaped curve)—Has a carrying capacity (K) due to limited resources (food, light, space, water).
Logistic growth often has an "overshoot" phase, followed by fluctuations in population.

19. Population Growth
Exponential vs. Logistical Growth

20. Limits on Population Growth
Density Dependent Limits
Predation
Competition for food & water
Shelter
Parasitism & Disease
Density Independent Limits
Weather/ Climate
Human Activity
Natural Disaster
Water and shelter are
critical limiting factors in
the desert.
Fire is an example of a
Density independent
Limiting factor.