Hello Everyone! My name is Zahra Ghacemi. I am a biologist. Today we are going to determine the normal heart rate of Daphnia magna. A Daphnia is a water flea. It is a crustacean that lives in lakes or freshwater. It is also an excellent food source for fish. Their size is between 2 mm to 5 mm in length. The Daphnia was placed in water in the depression slide and observed under the scanner objective lens of the compound microscope. So, let’s see what we see under the microscope. This is incredible, and I hope you’re so excited as we are. The reason we have chosen Daphnia is because it has a transparent body. This is its compound eye. These are its antennae. These are abdominal legs. Intestine. And the heart, as you see here, is located at the back of its body. So, three drops of water have been added to Daphnia. Count the heartbeats once you hear the beep sound. Pause this video, record your result, and then click play. How to calculate heartbeats per minute or bpm? You need to multiply the number of heartbeats counted in 15 seconds by 4. For example, if the number of beats counted in 15 seconds is 20, you need to multiply this number by 4 to have beats per minute. And be aware, the Daphnia’s heart was beating much faster than this number. This was just an example. Watch this video again, count the heart rate two times more in 15 seconds, and then calculate the average Daphnia heart rate per minute, and complete your data sheet. Thank you for watching this video. I hope you find it helpful.