biology homework

Bio 1101 - Homework 8

Population Ecology

Introduction: The ability to interpret graphs and tables is a necessary skill in science but also finds use in everyday life. In articles or textbooks you are likely to find graphs and tables.

Understanding the article’s message depends heavily on being able to interpret many different types of graphs and tables. In science tables are used to provide information. Frequently one quantity in a table depends upon or is related to another. Data from tables can be graphed

to aid interpretation. Graphs give a visual representation of the data that helps to reveal regularities and patterns.

Ecological Studies of Wolves and Moose on Isle Royale: If you were to travel on Route 61 to the farthest reaches of Minnesota and stand on the shore of Lake Superior looking west, on a clear day you would see Isle Royale. This remote, forested island sits isolated and uninhabited 15 miles of the northern shore of Lake Superior, just south of the border between Canada and the USA. If you had been standing in a similar spot by the lake in the early 1900s, you may have witnessed a small group of hardy, pioneering moose swimming from the mainland across the open water, eventually landing on the island. These fortunate moose arrived to find a veritable paradise, devoid of predators and full of grass, shrubs, and trees to eat. Over the next 30 years, the moose population exploded, reaching several thousand individuals at its peak. The moose paradise didn't last for long, however.

Lake Superior rarely freezes. In the 1940s, however, conditions were cold and calm enough for an ice bridge to form between the mainland and Isle Royale. A small pack of wolves found the bridge and made the long trek across it to the island. Once on Isle Royale, the hungry wolves found their own paradise - a huge population of moose. THe moose at eaten most of the available plant food, and many of them were undernourished. These slow-moving starving moose were easy prey for the wolves.

The Isle Royale Natural Experiment: The study of moose and wolves on Isle Royale began in 1958 and is thought to be the longest runnign study of its kind. The isolation of the island provides conditions for a unique natural experiment to study the predator-prey system. Isle Royale is large enough to support a wolf population, but small enough to allow scientists to keep track of all the wolves and most of the moose on the island in any given year. Apart from occassionaly eating beaver in the summer months, the wolves subsist entirely on a diet of moose. This relative lack of complicating factors on Isle Royale compared to the mainland has made the Island a very useful study system for population ecologists.

Fore more information visit: http://www.isleroyalewolf.org/

1. At what point during the study did ecologists observe the greatest moose population?

What was the size of population?

What was the size of the wolf population during this time?

2. Based on the data in the graph, describe the patterns observed for the moose and wolf populations.

3. What would happen to the wolf population if the moose population decreases? Why?

4. Originally, there were no wolves on Isle Royale. What do you think would happen to the moose population if the wolves died out?

5. What other factors may have influence changes in the two populations over the last five decades?

Moose population? Wolf population?