Predator and Prey & Population Growth Population Notes Predator and Prey & Population Growth

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.

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.

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

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.

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

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)

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)

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:

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

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.

POPULATION BIOLOGY

What do you think this map represents?

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

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)

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

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

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.

Population Growth Exponential vs. Logistical Growth

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.