1. How can food webs change?

2. Unit Standards
5.L.4B.1
Analyze and Interpret data to explain how organisms obtain their energy and classify organisms as producers, consumers (including herbivore, carnivore, and omnivore), or decomposers (such as Fungi, Bacteria insects and molds).
5.L.4B.2
Develop and use models of food chains and food webs to describe the flow of energy in an ecosystem.
5.L.4B.3
Construct explanations for how organisms interact with each other in an ecosystem (including predators and prey, and parasites and hosts).
5.L.4B.4
Construct scientific arguments to explain how limiting factors (including food, water, space, and shelter) or newly introduced organisms can affect an ecosystem.

3. How can food webs change?
    
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How can food webs change?
Living things in a food web depend on one another. Suppose the population of one organism in a food web changes.

4. How can food webs change?
    
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How can food webs change?
Population- all the members of a single type of organism in an environment

5. How can food webs change?
When one population in a food web changes, all of the other populations in the food web can also be affected.
This is what happened in the ocean’s kelp forest. Kelp is a type of seaweed.

6. How can food webs change?
Kelp forests are home to thousands of ocean creatures.
Some kelp forests have been greatly changes by just one animal, the sea otter.

7. How can food webs change?
Sea otters eat several animals in their ocean food web. They eat sea stars, sea urchins, mussels, crabs, and large fish.
The kelp forest were almost destroyed when the sea-otter population changes about 200 years ago.

8. How can food webs change?
In the 1800s, too many sea otters were hunted for their fur.
Without the sea otter to help control the size of the sea urchin population, the kelp forests almost disappeared
Without sea otters, fewer sea urchins were eaten.
Soon too many sea urchins were being born.
Smaller fish could not survive, because sea urchins ate their supply of kelp.
These fish were food for sea stars and crabs.
The sea stars and crabs began to die out.
Muscles also depended on kelp to stay alive.
meant less crabs & large fish that depended on muscles for food.
After a while, even decomposers could not survive.

9. How can food webs change?
In the 1900s, many countries agreed to stop hunting sea otters. The kelp-forest food web became balanced again. Now, new food-web changes are putting kelp forests in danger again.