Science by Email 6 July 2012

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	6 July 2012
News: Did dinosaurs generate their own heat? By Patrick Mahony Endothermic or ectothermic? Recent research suggests that dinosaurs may have been able to generate their own body heat. How do you keep warm when it's cold? Warm jumpers, central heating and electric blankets are just some of the useful things humans have invented to keep away the cold. However, one of the best ways we keep warm isn't something that was invented, but something we are born with: an endothermic metabolism. Humans are endotherms. This means human bodies are able to generate their own heat to keep warm. Other endotherms include mammals, birds and some types of fish and reptiles. The opposites of endotherms are ectotherms. Most reptiles, fish and insects are ectotherms. They can't generate their own body heat, instead drawing heat from the surrounding environment. Being an endotherm has its advantages and disadvantages. For example, endotherms typically grow quickly and at a fairly constant rate, due to their more stable metabolism. However, maintaining a constant body temperature requires eating a relatively large amount of food. Ectotherms, on the other hand, often have fluctuating rates of growth, but don't have to eat as much as endotherms. Dinosaurs were reptiles, and for many years were thought to be ectotherms. Some evidence included the observation of rings in their fossil bones, like rings in a tree trunk. These rings indicate fluctuating rates of growth once thought only to occur in ectotherms. However, recent research on mammal bones shows similar rings. In fact, the rings in the dinosaur fossils were more similar to the rings in mammal bones than those of modern reptiles. As all mammals are endotherms, this suggests that dinosaurs may have kept themselves warm on the inside – like us! More information Study suggests dinosaurs not cold-blooded Endotherm Careers link Paleontologist – career profile
You will need your hands and a cold day.   Place your cold hands against your cheeks.   Try breathing on your hands - does your breath feel warm or cold?   Tuck your hands under your armpits. How does it feel?   Try this: Cold hands   You will need Your hands Cold weather What to do After you've been outside on a cold day, hold your hands against your cheeks. Are your hands colder or warmer than your cheeks? Try breathing on your hands – does your breath feel warm, or cool? Hold your hands under your armpits. Does this feel warmer or cooler than your breath? After your hands have warmed up, repeat this activity. Do you observe anything different? What's happening? Our bodies maintain a constant temperature of around 37 °C. This temperature is called the 'core body temperature'. The actual temperature in different parts of the body can vary. The temperature in your extremities, such as your hands and toes is lower than the core temperature in your torso. Your breath and armpits typically feel warm because of this slight temperature difference. When you get cold, the blood vessels constrict, reducing the blood flow to the extremities. The temperature of your hands drops further and they become more sensitive to heat. This is why your breath feels warmer on cold hands than on warm ones. Applications It's important that our bodies maintain a relatively high temperature. Hypothermia occurs when the body's core temperature drops below 35 °C. When this occurs, the body's metabolism and functions begin to fail. If it is not treated, hypothermia can be fatal. Frostbite occurs when skin is exposed to extreme cold. Blood flow is restricted to such an extent that cells begin to freeze and die. Extremities are more likely to be affected. Both frostbite and hypothermia can be prevented by wearing warm clothing and limiting exposure to cold conditions. By Patrick Mahony Try another handy Science by Email activity More information How our bodies keep warm View the online version Quiz questions 1. What is the coldest temperature ever recorded on the Australian mainland: a) -13°C; b) -23°C or c) -33°C? 2. What are the branches of a snowflake called? 3. When water freezes, does it expand or contract? 4. Using high levels of nitrogen fertiliser can lead to rises in emissions of which greenhouse gas? 5. According to recent research, how many biogeographic regions are there in Antarctica? Did you know? Applying pressure to ice lowers its melting point. When the pressure is removed, it refreezes. This phenomenon is called regelation. Websites   Read it! Frank Hurley was a photographer on some of the earliest expeditions to Antarctica. Read his story and see some of his work in this article. See it! Do you know what an aurora is? Check out this gallery and learn about this beautiful atmospheric phenomenon! Quiz answers 1. b) -23°C. It was recorded at Charlotte Pass in the Snowy Mountains. 2. The branches on a snowflake are called dendrites. 3. Water expands when it freezes. 4. Using high levels of nitrogen fertiliser can lead to rises in nitrous oxide emissions. 5. The research, from a collaboration including the Australian Antarctic Division, divided Antarctica into 15 distinct biogeographic regions. Science by Email is a CSIRO publication. bankmecu is a proud partner of Science by Email. Editor: Jasmine Leong| Manage your subscription | FAQ

 

 

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