Lab 10 Food Web BY-102 Zach Nolen

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

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

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

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

Owl video

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?

Review questions

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

How long do they live? In the wild: 1-5 years Protected environments: 20-25 years

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

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

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.

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.

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.

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

Potential Prey of Tyto alba Shrew Vole Mouse Bird Rat Insect

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.

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.

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.

Class findings

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?

Before You Leave Lab Clean up your work station.

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