1. Lab 10 Food Web
BY-102
Zach Nolen

2. What is a food chain? The order of who eats who Examples:
Seeds → Grasshopper → Mouse → Owl

3. What about a Food Web?
Interconnection of several food chains to form more complex relationships.

4. Trophic Levels
Are based on the position that an organism holds in a food chain.

5. Food Sources Classification Food Source Examples Producer
Produce their own from sunlight
Plants
Grass
Herbivore
Eat producers
Beetles
Grasshoppers
Carnivore
Eat other animals
Owls
Shrews
Omnivore
Eat other animals and producers
Field mice
Birds
Decomposer
Only dead organic matter
Mushrooms
Bacteria

6. Owl video

7. Try to answer the following questions.
Where do they live?
How long do they live?
Where do they hunt?
How many owlets do they have?
When do the owlets hatch?
Why are owls such good hunters?
How are owl pellets formed?
Describe the digestive process of the barn owl.
Number and name(s) of stomach(s), etc…
What dangers do barn owls face?

8. Review questions

9. Where do they live? Tyto alba (Barn Owl) Habitat Barns Silos
Hollowed trees

10. How long do they live? In the wild: 1-5 years
Protected environments: years

11. How many owlets do they have?
Average clutch size is 4-7 owlets

12. When do the owlets hatch?
Eggs are laid 2 days apart and hatch in 2 day intervals

13. Describe the digestive process of the barn owl.
2 stomachs
Glandular stomach – secretes digestive enzymes to separate the fleshy portions of prey from the bones, hair, and fur.
Muscular stomach – further breaks down fleshy portions of food.

14. How are owl pellets formed?
Prey is swallowed whole
Reached gladular stomach. Fleshy portion passes to next stomach.
Hair, feathers, and bones remain in glandular stomach.

15. How are owl pellets formed?
Fleshy portion is further broken down by muscular stomach and nutrients are absorbed.
Waste matter (uric acid) is excreted.
Hair, feathers, and bones are compacted into a bolus in the glandular stomach and regurgitate.

16. What dangers do barn owls face?
Harsh weather conditions
Busy railways and motorways
Loss of habitat
Drowning in water troughs
Loss of suitable nesting sites

17. Potential Prey of Tyto alba
Shrew
Vole
Mouse
Bird
Rat
Insect

18. What is a dichotomous key?
A tool that allows easy identification of items.
Key provides 2 choices at a time
Think of these as a “choose your own story” where your choices affect the final outcome.

19. Dissecting Owl Pellets
Open foil wrapping
Gently find a place to start your dissection
Use tweezers, probes, and your hands to separate the bones from the hair and feathers.

20. Dissecting Owl Pellets
After you have found as much as possible, use the dichotomous key on page 111 to identify any skulls that you found.
If you did not find any skulls, use the key on page 112 to match the bones that you found.

21. Class findings

22. Review Questions What is a food chain?
What is the difference between a food chain and a food web?
What is the scientific name for the barn owl?
How are owl pellets formed?

23. Before You Leave Lab
Clean up your work station.

24. Before Next Lab
Complete all sections of lab manual for final lab manual check
Complete Study guide 3 (Optional)
Study for test