Observing Daphnia. Student Resources 1.4 Observing Daphnia, Pages 1 and Counting Daphnia Populations Inquiry Focus Observe

Size: px

Start display at page:

Download "Observing Daphnia. Student Resources 1.4 Observing Daphnia, Pages 1 and Counting Daphnia Populations Inquiry Focus Observe"

Margery Hines
6 years ago
Views:

1 Observing Daphnia Observing Daphnia, Page 1 30 minutes Pairs Observe the daphnia in your cup. List two ways you can tell the adults from the babies: 1 Babies are smaller. 2 Babies are brownish. How do daphnia move? They move in all directions using their antenna. Turn an empty cup upside-down. Use a dropper to catch several large adult daphnia. Put them on the bottom of the cup. Tell what the daphnia look like. Students should accurately describe the size, shape, color, structures, and other characteristics of daphnia. 16 AQUARIUM HABITATS SECTION 1 OBSERVING DAPHNIA Student Resource 1.4, Page 1 (p. 16) Observing Daphnia, Page 2 Use the dropper to put five large adult daphnia in the vial. Pick ones that you think will have babies. Observe the vial with a magnifier to be sure there are only five adults and no babies. Put today s date in the first date box. Record the number of adults and babies in your vial. Use a for adults and b for babies. s Number of adults and babies 5 a 0 b a b a b a b a b a b Predict what will happen to the daphnia population. The population will get larger as babies are born. Objectives Students observe daphnia with and without a magnifier. Students set up a test vial to study changes in a daphnia population. Materials For each pair 1 dropper 1 cup (large) containing aged *water and daphnia 1 empty cup 2 magnifiers 1 vial containing aged *water 1 vial lid For the teacher 1 cup (large) containing aged *water and daphnia 1 dropper 1 empty cup 1 lamp with light bulb *Not provided in kit Student Resources 1.4 Observing Daphnia, Pages 1 and Counting Daphnia Populations Inquiry Focus Observe In Advance Each pair of students will need one vial and one large cup. Number the vial lids consecutively, and fill each vial three-fourths full of aged water. Fill each cup half full of aged water. Just before students begin this activity, pour some daphnia into each cup of aged water. Do not use a dip net with the daphnia, as they cannot survive out of water. Draw an adult daphnia. Show what is inside it. AQUARIUM HABITATS SECTION 1 OBSERVING DAPHNIA 17 Student Resource 1.4, Page 2 (p. 17) 1. Distribute materials. Make copies of Student Resource 1.4, Observing Daphnia, Pages 1 and 2, and distribute to students. Give each pair the materials listed above. 2. Students observe daphnia without magnifiers. Have students observe the daphnia without using a magnifier. Ask: How can you tell the babies from the adults? (The babies are tiny and move rapidly.) SECTION 1 OBSERVING DAPHNIA 7

Observing Daphnia (continued) Have students estimate the number of adults and babies in their cup. Tell students that daphnia, also called water fleas, live in freshwater habitats.

2 Observing Daphnia (continued) Have students estimate the number of adults and babies in their cup. Tell students that daphnia, also called water fleas, live in freshwater habitats. Have students observe and describe how the daphnia move. A Viewing platform 3. Students use magnifiers to view daphnia. Turn a cup upside-down, and show students how to put a drop of water with one large daphnia in the indentation on the cup s bottom. Explain that you have made a viewing platform to use with the magnifier. Have students capture one large daphnia in a dropper and place the daphnia with some water on an inverted cup. Have students observe the daphnia with magnifiers. Counting Daphnia Populations Vial Numbers / Time start 5a 0b 18 AQUARIUM HABITATS SECTION 1 OBSERVING DAPHNIA Student Resource Page 1.5 (p. 18) end Key: a = adults; b = babies STUDENT RESOURCE 1.5 INFORMATION SHEET 4. Students record observations. Have students record their observations on the Observing Daphnia Resource page. Tell them to wait until the next activity to draw the daphnia. 5. Prepare for population study. Have students use the dropper to carefully transfer five large daphnia with eggs from the cup to the vial. Tell them to check the vial to make sure it does not contain any baby daphnia. If it does, have them use the dropper to remove the babies and put them back in the cup. Direct students to put the numbered lid securely on the vial. Students should record the number of daphnia in the vial on the Observing Daphnia Resource page. 6. Record the class daphnia population. Make a transparency of Student Resource 1.5, Counting Daphnia Populations, and project it for the class. Write the date and time in the first box of the first column. Ask each pair of students to report the number of daphnia in their vial. Write each pair s population on the transparency, using the following key: a for adult, and b for baby. This first entry should be 5a/0b. Tell students they will be counting their daphnia populations twice a day for the next three days. 7. Students predict population changes. Ask: What do you think will happen to the population of daphnia in your vial? (The population will increase as babies are born.) Have students write their predictions on the Observing Daphnia Resource page. 8 EXPERIENCE SCIENCE

3 Observing Daphnia (continued) 8. Maintain the vials. Keep the vials at room temperature, preferably near a lighted lamp or direct sunlight. Adult daphnia can produce eggs and give birth every four days. The first babies will be born in about two hours, so you should begin Section 2 on the same day, if possible. Assessment Lead students to think about the needs of living things. Ask: What do daphnia need to survive? (food, water, air, space, warm temperature) Daphnia Body Parts STUDENT RESOURCE 1.6 INFORMATION SHEET Observing Daphnia with a Microscope Cells Eye Mouth Antenna Esophagus Heart Food tube Eggs 30 minutes Objectives Students use a microscope to observe daphnia. Students describe daphnia structures and behavior. Small Groups Legs Filter hairs Compound eye with optic nerve Cells Carapace (shell) Anus Student Resource 1.6 (p. 19) Babies are born live AQUARIUM HABITATS SECTION 1 OBSERVING DAPHNIA 19 Materials For each group 1 depression microscope slide with single daphnia and aged *water 1 *microscope For the teacher *algae water * video/microscope projection system (optional) *Not provided in kit Student Resources 1.4 Observing Daphnia, Page 2 from Investigate Daphnia Body Parts Inquiry Focus Communicate Teaching Tip As an alternative to several microscopes, you could use a video/ microscope projection system to project the daphnia to the entire class on a television screen. In Advance Prepare one depression slide for each pair of students, as follows: Use a dropper to capture one large daphnia with eggs. Put it with a drop of water on the center of the slide. Daphnia are easier to observe when they are moving slowly in water. Remove excess water from the slide to slow the daphnia, leaving only enough water to keep it alive. SECTION 1 OBSERVING DAPHNIA 9

4 Observing Daphnia with a Microscope (continued) 1. Students use microscopes to observe daphnia. Have each group of students observe the daphnia with a microscope. If you do not have microscopes use magnifiers. 2. Students discuss observations. Make a transparency of Student Resource 1.6, Daphnia Body Parts, and project it for the class. Ask: What do you see inside the daphnia? (Daphnia have a clear shell, or carapace, that is separated at the legs and abdomen so that food and water can enter and babies can be born.) A Daphnia Safety Review how to handle and use a microscope and glass slides with students. Teaching Tip Throughout this activity, add drops of aged water to the slides as needed. Daphnia cannot live without water. 3. Students observe daphnia s eyes. Ask: How many eyes does the daphnia have? (one) Explain that the eye has 18 lobes and 3 muscles that constantly rotate it. Daphnia can only see light, not movement. Point out the optic nerve. 4. Students describe daphnia movement. Point out the antennae, which are attached to the daphnia s head. Ask students to describe the antennae. (They are jointed, forked, and hairy.) Ask: How do the antennae help the daphnia move? (The antennae move in all directions, jerking the daphnia through the water.) 5. Explain daphnia reproduction. Have students find the brood pouch above the digestive tube. Tell students to count the eggs (brown spheres) in the pouch. Tell them that the eggs hatch inside the daphnia; this may happen as you watch. The babies (oval gray shapes) begin moving their antennae, pushing to get out of the parent. Point out that the shell is open along the lower edge. Healthy daphnia may have babies every four days and they can carry as many as 40 eggs. Usually, however, they carry three to six eggs. In a poor environment, they stop producing eggs. 6. Discuss male and female daphnia. Tell students that all the daphnia the class has are probably females. Explain that daphnia reproduce asexually, with only one parent. Only when their environment gets cold or unhealthy do daphnia produce male and female babies. They reproduce (mate), producing eggs with hard shells. These eggs overwinter on the bottom of the pond and hatch in the spring. This may happen in your classroom if you try to raise daphnia. You will see two huge dark eggs in the daphnia. This means there are males in the water and mating has occurred. 10 EXPERIENCE SCIENCE

5 Observing Daphnia with a Microscope (continued) Observing Daphnia, Page 2 Use the dropper to put five large adult daphnia in the vial. Pick ones that you think will have babies. Observe the vial with a magnifier to be sure there are only five adults and no babies. Put today s date in the first date box. Record the number of adults and babies in your vial. Use a for adults and b for babies. s Number of adults and babies 5 a 0 b a b a b a b a b a b Predict what will happen to the daphnia population. The population will get larger as babies are born. Draw an adult daphnia. Show what is inside it. Drawing should resemble the diagram on the Daphnia Body Parts Resource Page. Student Resource 1.4, Page 2, from Investigate 2 AQUARIUM HABITATS SECTION 1 OBSERVING DAPHNIA Students observe daphnia eating. Add a drop of algae water to each group s slide. Let students observe the daphnia eating the algae. Ask: How do daphnia eat? (Daphnia have 10 pairs of legs that constantly move, circulating water and food into the mouth.) Point out the dark line in the daphnia s body. Tell students that this line is the digestive tube. When the daphnia have digested their food, they eliminate waste through the anus with a thrust of their long, bumpy abdomen. 8. Students describe daphnia cells. Have students adjust the microscopes to a stronger magnification. Tell them to focus on the daphnia s face and view the cells. Ask: What do the cells look like? (tiny rectangles) Remind students that all living things are made of cells. 9. Students observe a daphnia s heart. Point out the daphnia s heart on the diagram, along the back near the brood sack. Ask: What is the heart doing? (It is beating or pumping blood.) Tell students that the heart pumps blood all through the daphnia s body. The blood then reenters the heart and picks up oxygen. Healthy daphnia are orange; this is a sign that their habitat has lots of oxygen. Clear daphnia are not as healthy. 10. Students draw daphnia. Distribute students copies of the Observing Daphnia, Page 2 Resource page. Have students add drawings of the daphnia and label its body parts. Assessment Ask: How do daphnia use their antennae and their legs? (They use their antennae to move through the water. They use their legs to move water and food into the mouth.) SECTION 1 OBSERVING DAPHNIA 11

Daphnia Anatomy Teacher Resource

Grade Level 5-12 Objectives Daphnia Anatomy Teacher Resource 1. The student will identify daphnia as an important link in a food web. 2. The student will identify the anatomy of a daphnia. 3. The student