Be sure to write about what you are learning in the lab section of your notebook. You will be expected to answer questions about the lab activity during the lab self test and lab quiz. It helps to have your text and coloring books open beside you for support.

Predators

Predators are animals which capture, kill and consume other organisms which are called prey. The prey organism can be of any type. Predators are classified by the type of prey they cconsume.

Carnivores

Predators that eat other animals are called carnivores. There are two types of carnivores: attackers and ambushers. Attackers or pursuing carnivores "run down" their prey. They are highly active with acute senses for detecting and capturing prey. Ambushers or sit-and-wait carnivores remain in one place and wait for prey to come to them. They must remain perfectly still and are often camlouflaged so that prey animals will not see them until it is to late. Some ambushers rush out of hiding to grab their prey but some are actually attached to the bottom and to get a meal their prey must blunder into them. These attached ambushers are often slow to move and lack sense organs.

Sea Anemones
Sea anemones are ambush carnivores that eat small crustaceans that swim into them unsuspectingly. They creep slowly along the bottom on their pedal disc and have a series of tentacles that surround their mouths. The tentacles are armed with stinging cells called nematocysts and are used to capture prey. Each nematocyst acts as a tiny harpoon that injects poison and paralyzes the prey. The tentacles move the helpless prey into the mouth.
Experimental Set Up: We filled a small glass dish with seawater and placed a small anemone in the dish. We set the dish under a dissecting microscope and focused on the anemone's oral disc and tentacles. We adjusted the magnification so that the entire anemone was visible and filled the feild of view. We observed the anemone until it spread its tentacles and appeared comfortable with its new surroundings. Then we added some brine shrimp and photographed the anemone feeding.
Observations: How do you think the anemone reacted when a brine shrimp swam into it? How do you think the anemone detected its food? What can the anemone do to improve its chances of capturing prey?

Saprophages

Saprophages are organisms which consume dead and decaying organic matter. The source of the organic matter is the bodies or parts of previously living organisms. Saprophages are classified by the types of organic matter they consume.

Scavengers

Scavengers are animals that eat the corpses of animals or plants. They are often active animals with acute senses. To find the rare corpse a scavenger must search over relatively large areas and detect their food from a distance. They must locate their food quickly before other scavengers beat them to it.

Mud Snails
Mud snails are scavengers that live in mudflats near shore. They have a long extensible siphon that is used to conduct water into their shell cavity which contains their gills and a sense organ called an osphradium. They spend a great deal of their time buried in the mud with their siphons sticking out into the seawater. When they detect a corpse they will leave the mud and crawl to it to feed.
Experimental Set Up: We filled a small glass bowl with seawater, placed some mud snails in it, and allowed the snails to crawl in the bowl and get use to their surroundings. We placed the bowl under a dissecting microscope and adjusted the position of the bowl and the magnification so that the snails could be plainly seen. We placed a small piece of mussel flesh in the bowl on the side opposite the snails and photographed the snails feeding on the mussel flesh.
Observations: How do you think the mud snail fed? How might the mud snail detect its food?

Detritivores

Detritivores are animals that eat organic fragments called detritus. Detritus is formed when dead plants and animals are broken down into tiny bits. The detrital particles are often mixed with sediments and must be collected by the detritivore. Detritivores remove detritus from sediments in different ways. Deposit feeding detritivores swallow the sediments, digest the organics and pass the undigestible sediment as feaces. Selective deposit feeders pick the detritus out of the sediments and eat it.

Hermit Crabs
Hermit crabs are selective deposit feeders. They will move over the sediments and pick up detrital particles and place them in their mouth parts. The mouth parts are used to remove any remaining sediments before the detritus is swallowed.
Experimental Set Up: We filled a small glass bowl with seawater, placed some seasoned gravel in the bottom, and put some hermit crabs into the bowl. We placed the bowl under a dissecting microscope and adjusted the position of the bowl and the magnification so that the crabs could be plainly seen. We photographed the crabs.
Observations: What do you think the hermit crab used to transfer detritus to its mouth? How might the hermit crab detect its food? Compare the method of feeding of the hermit crab to that of the mud snail.