1.      Compare whales and dolphins with humans. What do they have in common, what are the
differences?



                                                          similarities


                                                       differences


whales dolphins









humans









2.      Go quickly through the whole text and mark a borderline between the facts and the
hypotheses. Then highlight the words that indicate a certain degree of uncertainty.


3.      The following statements are either true or false.

Whales and dolphins

§  can spend half an hour underwater without breathing

§  sleep 1/3 of the day

§  preferably sleep along the surface without any movement


Language focus

4.      What other systems besides the respiratory system do you know?

5.      Paragraph 3: find the words that mean

§  possible or reasonable

§  capable of life or normal growth and development


6.      Word formation

                                               Verb

                                                                                                      Noun

                                                                                                              Adjective

                                                                                                                          Adverb


                                                       oxygen




                                                       difference




                                                       breath





                                                                 conscious



                                                       mammal






                                                                            presumably

                                            be aware of






                                                                 respiratory


solve






                                                                 viable





7.      Complete the sentences (based on the article)


§  Mammals are ........-blooded animals, reptiles are .........-blooded.

§  Most mammals give birth to …….. young.

§  Human beings and other mammals breathe ………… (3x)

§  They have to ………. decide when to breathe.

§  ………… brains need to enter an unconscious state from time to time.


Do whales and dolphins sleep?


1. Whales and dolphins are mammals, so in a lot of ways, they are just like human beings. Among
other things, they have similar bone structure, are warm-blooded and give birth to "live young."
The biggest differences between these animals and human beings are related to our respective
environments. Whales and dolphins have a unique respiratory system that lets them spend long
periods of time (sometimes 30 minutes or longer) underwater, without taking in any oxygen.

2. On land, human beings and other mammals breathe involuntarily: If we don't make a decision to
breathe or not to breathe, our body will take in air automatically. Because of their undersea
environment, whales and dolphins must be conscious breathers: They have to actively decide when to
breathe. Consequently, in order to breathe, they have to be conscious. This presents a problem,
since mammalian brains need to enter an unconscious state from time to time in order to function
correctly (see How Sleep Works to find out why this might be).

3. There's plenty of time for a dolphin to catch a catnap between trips to the ocean surface, of
course, but this isn't a viable option. When you're a conscious breather, it's just not feasible to
be completely unconscious -- what if you don't wake up in time? The solution for whales and
dolphins is to let one half of the brain sleep at a time. In this way, the animal is never
completely unconscious, but it still gets the rest it needs.

4. Scientists have studied this phenomenon in dolphins, using electroencephalography. In this
process, electrodes hooked up to the head measure electricity levels in the brain. The resulting
electroencephalograms (EEGs) of dolphin brains demonstrate that in the sleep cycle, half of the
dolphin's brain does indeed "shut down" while the other half is still active. Researchers have
observed that dolphins are in this state for approximately eight hours a day.

5.We can't really know what this rest state feels like, but we can make a good guess. It is
probably something like the semi-conscious state we experience as we begin to fall asleep. We're
pretty close to unconsciousness, but are aware enough of our surroundings to wake up completely if
we need to.

6. And where do dolphins and whales sleep? They could probably sleep anywhere, but it makes sense
that they would do it near the surface of the ocean so they can come up for air easily. It's not
uncommon to see dolphins "logging," swimming slowly along the surface, with very little movement.
Presumably, these are dolphins at rest.


                        http://science.howstuffworks.com/question643.htm      Accessed Dec.4, 2017


Student A

3. There's plenty of time for a dolphin to catch a catnap between trips to the ocean surface, of
course, but this isn't a viable option. When you're …………………….. breather, it's just not feasible to
be completely unconscious -- what if you don't wake up in time? The solution for whales and
dolphins is ……………………..……………………... In this way, the animal is never completely unconscious, but it
still gets the rest it needs.

Student B

Scientists have studied this phenomenon in dolphins, using ……………………... In this process, electrodes
hooked up to the head measure electricity levels in the brain. The resulting electroencephalograms
(EEGs) of dolphin brains demonstrate that in the sleep cycle, half of the dolphin's brain does
indeed "shut down" while the other half is still active. Researchers have observed
……………………..……………………..