You’ve had a few days to think about it, but if you want another look at the questions close your eyes and click.
1. Cacti have all sorts of tricks for surviving in deserts. (A bit like penguins.)
- They don’t have leaves, which means less surface area to lose water through. Instead the outer surface of the stem has chlorophyll and photosynthesises for their energy, which is why they are green.
- They have a waxy coating to protect them from water loss.
- They store water very quickly when it is around. In fact that pleated shape many of them have is to allow them to expand easily and hold more.
- The prickles are mostly to protect them from animals, since they’re an important food and water source in deserts. However many have adapted so they also form a sun cover and stop the stems from getting burnt. They also work to catch rain or dew when it happens and channel it down to the roots, which is very similar to the Australian thorny devil lizard.
- Rather than being woody, they are supported by the water they hold. This is just like what happens with the water daisies we played with a while ago. When they have less water they can’t be supported and bend over, this is actually good because it means more of them is shaded and out of the sun.
- They have very wide root systems to catch as much rain as possible. When it is wet they grow little roots off the main network, then let them die when it dries out again.
2. There are some stations in the Atacama desert that have never recorded rain – in over 400 years. It is considered the driest place in the world and has an average of 0.1 mm of rain per year. Unfortunately an average is fairly useless in cases like this because it tends to rain in one hit then nothing for years. Or centuries.
The area has been arid for millennia, there are identified river beds that seem to have been dry for 12,000 years. Some areas ‘failed’ the life test NASA used on Mars, although there is actually microbial life there. Fogs from the Pacific ocean do support some life, and there was even a snowfall just a couple of months ago.
3. There are many desert frog species, most of them use a combination of behavioural and physical adaptations to survive.
- Almost all desert frogs and toads burrow while waiting for the rain. Most of them create a type of waterproof shell for themselves, either by secreting a covering or even shedding layers of skin.
- They generally have specialised feet to help them burrow.
- While in the burrow their metabolism is slowed right down.
- They develop extremely quickly. When a thunderstorm or rain happens they dig out and find puddles then gorge on all the insects that are also celebrating the rain. Some species can go from egg to froglet in only two weeks before the puddle dries up. Hopefully they’ve had enough to eat to get them through to the next rain.
4. The two big mountain ranges of the world have serious deserts associated with them – the Atacama desert runs along the Andes and the Himalayas are south of the enormous deserts of central Asia, particularly the Taklamakan desert. Both of these mountain ranges are from tectonic plate subduction and are still growing. They have created deserts thanks to their rain shadows.
Moisture rich air sweeps towards the mountain ranges. As it gets to them it has to go higher and gets colder. Colder air cannot carry as much water, so it produces rain. This is one of the reasons for the Amazon and Indian rainforests. By the time any prevailing winds make it over the high mountains, they have lost most of their moisture. This happens on all sorts of scales, but the Andes and Himalayas are so large they have affected the weather of continents.
Most of the deserts of western North America are also due to rain shadows, including the Mojave, Nevada and Utah and the Great Plains of Canada.
5. The photo is definitely a Tasmanian Tiger or Thylacine. Before dingos arrived around 4000 years ago they were found throughout Australia, but the dingos out-competed them and eventually confined them to Tasmania. In spite of its name and appearance, Thylacines were marsupials like kangaroos. The last known wild thylacine was shot in 1930, the last one in captivity died in 1936. This one is a mummy found on the Nullarbor plain. Embarrassing note for Australians: I can’t be the only one who assumed ‘Nullarbor’ was an Aboriginal word. It isn’t, it comes from Latin and means ‘no trees.’
The interesting desert-related bit about it is that it is a beautifully preserved natural mummy. When it was first found in the 1960s people thought it must be recent because it was in such good condition and there was great excitement at the idea of a surviving population. However it has been dated to between 4,000 and 5,000 years old.
Desert mummies are relatively common and include humans as well as animals. Bacteria and other decomposers need water to live, in desert conditions bodies can dry before they rot. Deserts are often salty from evaporated water, this is another preservative and helps to set colours. Some of the most famous desert mummies are the Tarim mummies, Caucasian people living in the middle of Asia.
Here is a recording of the last known Thylacine. Notice how wide the jaws open and the stiff tail like a kangaroo. They also put their hind feet down at times, showing the resemblance even more.
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