Tracking Changes in Photoperiod Around the Globe

Mystery Class Update: March 7, 1997

Joan Berger

Challenge Question #1:

"How do seasonal changes in photoperiod affect your animal's food web?"

Generally, the longer the photoperiod, such as in spring and summer,the more food that will be available. This is because the added sunlight and heat in spring and summer make plants grow, and the plants provide food for plant-eating animals, and these plant-eating animals can then be available as food for animals which prey on them. Also, the added sunlight and heat warm the air and thaw frozen soil and lakes, making other foods such worms, insects and fish available too. On the other hand, the shorter the photoperiod, such as in fall and winter, the less food that will be available. The reduced amount of sunlight and heat means fewer plants are available for plant-eating animals, and fewer worms, insects and fish too, and therefore less food is available for animals that prey on these food sources.

Two schools responded to this Challenge Question, and their answers do a nice job of showing how seasonal changes in photoperiod affect the food web. As a class, read their thoughts and discuss their conclusions.

From: MINNESOTA
Our fourth grade class in White Bear Lake, MN came up with some answers. The heat and light determine what kind of food there is for the animal to eat. The amount of light and amount of darkness effects how long the animals have time to eat.
Kelsey and Ashley and Elizabeth
Jon P. Mares (jpmare@wbl.whitebear.k12.mn.us)

From: ONTARIO
Four species groups answered this question:
1. Bald Eagles
Seasonal changes and photoperiod can injure and help our animal. In the winter the ice freezes and the days are shorter and the Bald Eagle can't find one of its favourite prey--fish. In the summer the days are longer and warmer, so the Bald Eagles live well, as they have access to their food. In the spring the eagle usually mates, then that's when their is a big demand for food, and that's when there is a lot of food available for the eagle.
Andrew Beatty, Scott McKenzie gr. 5

2. Humpback Whales
During the winter, the whales migrate south to warmer waters to have their babies. After they give birth in the summer, they migrate north to colder waters to feed on the krill. When the days get longer, the whales know that summer is coming and they migrate north. When the days get shorter (and colder), they migrate south to have their babies in warm waters.
Dustin Crowe & Deanne McIntosh gr.5

3. Caribou
In the spring time when the snow finally begins to melt, temperatures can drop and may re-freeze, making it impossible to dig for food. In the summer, it can be a bad time of year for the caribou because not just the adult wolves need to be fed, but their pups too.So more caribou die because of the warmer temperatures/long photoperiod.
Doug McKenzie gr.5

4. Monarch Butterflies
The monarch eats goldenrod and milkweed. When the frost starts (less photoperiod --fall) coming in, these plants die off, so the butterfly has nothing to eat in Canada. To add to its problems, it's too cold (less photoperiod) for them. So they migrate to Mexico, where it is warmer. They come back when the weather gets warmer (spring) and the milkweed and goldenrod are starting to bloom again. They feed here in Canada all summer, then the cycle starts again (fall-spring & spring-fall).
Shannon Mitchell & Lee Taylor gr. 5
Bobcaygeon Public School
Bobcaygeon, Ontario
44.536 N, 78.544 W
kevin adams (bob1@knet.flemingc.on.ca)

Now, back to this week's sunrise and sunset times from Mrs. Berger's class. Remember, this information was recorded on Monday, the same day you collected your sunrise/sunset data.

Journey North Mystery Class
Sunrise/Sunset Data

Data For: Monday, March 3, 1997

**"A storm blew the rest of the broken-up ice in the sound out to sea allowing access to pods of Orca and Minke whales."

From Mrs. Berger's Class
Roslyn Public Schools
Roslyn, New York
Visit theEast Hills School WEB site

The Next Mystery Class Update Will Be Posted on March 14, 1997