CAROLINA. What s Eating You? Predator-Prey Kit Instructions Teamed with Teachers

Transcription

1 CAROLINA Teamed with Teachers Demo Kit Classroom Kit What s Eating You? Predator-Prey Kit Instructions

2 Adapted with permission from publications of the Wisconsin Fast Plants/Bottle Biology Program, University of Wisconsin, Madison, Wisconsin. Important Information: Read This First Students learn to cut plastic bottles, assemble them, and create an experimental system used to study the interactions of carnivorous plants and insect prey. This system is known as the Predator/Prey Column. It provides an environment in which the predator and prey can grow and develop and eventually come into contact with each other. The demonstration kit contains materials and instructions for creating one Predator/Prey Column. The classroom kit is designed for 6 groups of up to 4 students each. This gives a total of 6 predator/prey columns. Both kits use the same instructions. Make an overhead transparency of the instructions or photocopy them for each group (see pg. 6). Objectives Understand basic needs of organisms and how needs are met in a closed system. Learn basic culturing techniques needed to maintain a fruit fly culture. Study adaptations of some plants to a nutrient-poor environment. Observe predation in a closed environment and relate it to the natural world. Background Typically, when we think of a predator/prey relationship, we imagine the predator actively pursuing the prey, e.g., a fox chasing and catching a rabbit. There are other ways for organisms to capture food. In this kit a Venus flytrap is the predator and fruit flies are prey. In the predator/prey column, you will observe this interaction. Predators Venus flytrap The Venus flytrap is one type of carnivorous plant. In the wild, it is found in a small area of the coastal plain of the Carolinas. The flytrap lives in damp, boggy soil that is deficient in basic plant nutrients, such as nitrogen. The flytrap has some unusual adaptations that enable it to get 1999 Carolina Biological Supply Company Printed in USA 2

3 nutrients from other sources. Its leaves are modified into traps that catch insects and other small animals. The plant produces enzymes that digest the captured prey, and the flytrap uses the animals components as a source of nutrients. The flytrap has a small root system. The leaves are 2-lobed traps occurring in a basal rosette 2 6 inches in diameter. Plants growing in bright sunlight can develop a bright red color on the upper surface of the open traps. Plants grown in indirect sunlight or shade will more likely have green leaves. Each leaf lobe has three or more trigger hairs, or trichomes. If any two of these trigger hairs are touched in close succession, or if any one is touched twice in succession, the trap will close tightly. In nature, the plant produces a single flower stalk containing several white five-petalled flowers. Flowering takes place in May. The plant is selective in the food it traps. The traps do not close tightly on small insects that offer little nutrition, so these smaller insects can escape. Soon after being trapped, the prey dies, and glands inside the lobes secrete substances that digest the soft tissues in the insect. The digestion process lasts approximately 10 days. After digestion is completed, the trap opens slowly and the remains of the prey fall off or are blown away. Each trap may capture as many as four victims before it withers. The flytrap is in true danger of extermination. Even though the plant is protected by state law, its unique behavior makes it popular with plant collectors. Since the plant has a limited range, collection can drastically affect its population. In order to follow state-set guidelines, plants can only be collected for educational or scientific purposes, and the collector must have a special permit. Sundew Sundews are found in acid, boggy soils or damp soils deficient in nitrogen. They thrive in swampy areas where sphagnum moss is found. There are several different types of sundews. Most species are small plants. Each plant consists of a rosette (circle) of leaves that extends about 1 1 /2 inch in diameter. Typically, the rounded end of the leaf contains many stalked glands or tentacles. Additional glands attach directly to the stalk. A tentacle consists of a tapering stalk topped by a bright red, oval gland. Each gland is covered with a highly viscid, clear fluid. The fluid remains present even in bright sunlight, giving the plant its name. The flower is small but interesting. A fully opened blossom 3

4 measures about 1 /2 inch across. Each plant usually bears a single flower stalk with several blossoms. Blossoms open one at a time. Sundews have a unique method for trapping food. The trap of the sundew works very slowly and catches only small insects. Even prey as tiny as an ant can sometimes escape. Once captured, the animal will struggle to escape, but nearby tentacles bend toward it. More and more tentacles bend toward the victim over time. The bending response continues in a widening circular pattern until the victim is covered by the fluid-bearing glands. Finally, the leaf folds over until it is cup-shaped. After a few days the prey is digested, the non-chitinous parts are absorbed, the leaf reopens, and remains of the victim fall off or are blown away. The fluid serves to absorb and digest prey. It also helps in receiving and transmitting stimuli. Other glands located on the surface of the leaf also absorb nutrients. The insect-snaring mucilage has been demonstrated to be antiseptic, inhibiting bacterial action. Prey Fruit Fly The prey, or victim, in this predator-prey column is the fruit fly. It has been chosen for its rapid life cycle (about 2 weeks) and the fact that it can be easily raised in captivity. There are four stages to the life cycle of the fruit fly. These include egg, larva, pupa, and adult. The flies spend approximately 8 days in the egg and larval stages and another 6 days in the pupal stage. Then, the adult flies emerge. 4 Classroom Tips If you are using the classroom kit, these hints may help you. Divide students into 6 groups. Each group should be given 3 2-liter plastic soda bottles, 1 6-inch ruler, 1 bag of potting mix, fruit flies (groups share the 2 vials provided and each group removes flies from the vial as they are needed), culture medium (the class shares the bag, and each group gets medium as needed), 1 vial, 1 foam plug, 1 1-oz cup with lid, 1 flytrap, 1 sundew, scissors (groups share scissors, teacher may choose to provide additional scissors or make cuts for students), 1 set of instructions (photocopied). You should make a 1-inch cut in all the bottles before the students make cuts with scissors. This will serve as an entrance area and decrease the

5 chance that students cutting will cause the bottles to collapse. Extra bottles should be collected to replace those cut incorrectly. Students follow instructions on pg. 6 to construct the Predator/Prey Column. Materials Demonstration Kit ( ) Classroom Kit ( ) plastic ruler 6 plastic rulers bag of potting mix 6 bags of potting mix culture of fruit flies 2 cultures of fruit flies small bag of fruit fly small bag of fruit fly culture medium culture medium 3 culture vials 6 culture vials 3 foam plugs 6 foam plugs 1-oz cup with lid 6 1-oz cups with lids Venus flytrap plant 6 Venus flytrap plants sundew plant 6 sundew plants pair of scissors 2 pairs of scissors plastic tray and lid for holding 2 plastic trays and lids for bottles steady while cutting them holding bottles steady while cutting them Materials not supplied 3 2-L plastic bottles (collect extras) roll transparent tape soda lid, punched permanent marker or wax pencil for designating cutting locations Velcro Materials not supplied 18 2-L plastic bottles (collect extras) 6 rolls transparent tape (or share fewer) 6 soda lids, punched 6 permanent markers or wax pencils for designating cutting locations Velcro 5

6 Preparation of Bottle Pieces Instructions Note: You may wish to cut all the bottles before using this lab activity with younger children, or you may provide a lab instrument safety lesson before allowing students to make the desired cuts. It may work best if you make the first cut with a razor knife and then let students finish the cuts with scissors. 1. Collect three 2-liter plastic soda bottles before starting this lab. 2. Clean and dry bottles. Remove all labels and plastic bases. (Let hot tap water sit for a minute or two in a bottle before you remove the label. This will soften the waxy glue.) 3. Bottle #1: Make a cut 2 cm above the shoulder curve. (This leaves a tapered end at the top of cylinder A. Cut 1 cm below the curve on the bottom of the bottle. (This leaves a tapered end at the bottom of the cylinder). A B C 4. Bottle #2: Make a cut 0.5 cm below the shoulder curve. (This leaves a straight edge on bottle piece B). Cut the bottom of bottle #2 6 cm above the curve. (This leaves a straight edge on bottle piece C). Place the bottle cap (with a punched hole) on bottle part B. 5. Bottle #3: Cut the bottom of the third bottle 9 10 cm above the bottom curve. (This leaves a straight edge on bottle piece D.) D 6

7 6. Pictured below are bottle pieces needed to construct the Predator/Prey column. A B C D Construction of the Predator-Prey Column 1. Use bottle pieces A and B. Invert B so that it can be pushed upward into piece A. You need to work piece B back and forth to push it in until the outer and inner edges touch. Once the edge of A and B are in contact with each other, use 1-inch strips of transparent tape to hold the two together. (Be sure the punched or drilled bottle cap has been placed on piece B). 2. Set A and B into bottle base D as shown below. If the fit is snug, remove piece D and add the 1-oz cup with fruit as illustrated. Add Velcro to the bottom of the cup and to the bottom of bottle piece D. Stick the two together. Put some fruit in the cup. Next get some flies from the fruit fly vial and put them into the bottom of the base. Quickly place piece A back over them to seal them in. Use 1-inch strips of transparent tape to tape around the bottom at the area where pieces A and D touch. 3. Place a small piece of tape over the opening on top of the bottle cap. Add soil mixture to the bottle until it reaches the cap of the bottle. Make an indentation in the soil on one side of the bottle cap and 7

8 plant the Venus flytrap. (Plant it deep enough to bury the root system.) Make an indentation in the soil on the other side of the bottle cap and plant the sundew. Remove the tape from the bottle cap and quickly invert bottle piece C over the top of A. Use 1-inch strips of transparent tape to seal around the area where the two pieces touch. Suggested Extension Activities A Predator/Prey Column can allow for close study of various life forms. You may want to have students create their own versions of these miniature ecosystems. Students may explore questions such as the following: Why is predation important to an ecosystem? How do predators and prey relate to one another in a closed, controlled ecosystem? How do the methods predatory animals use to get food compare to those of predatory plants? Additional Activities Students can design and build a fruit fly trap for capturing prey. Students can design a chamber for culturing fruit flies. Students can create several chambers and design an experiment for determining the effects of varying degrees of light on life in the chamber. Students can collect other forms of prey, introduce them into the system, and judge how the carnivorous plant reacts. (Observe the time period until prey is trapped, how long until it is digested, and what percentage of the prey escape or die naturally). Related topics to which the predator-prey column can apply: food webs, ecosystems, adaptation, selection, niche, habitat, behavior, life cycles. To order call: (US and Canada) (International) For technical help call: Carolina Biological Supply Company 2700 York Road, Burlington, North Carolina CB