1. the Sahara
1: The Sahara covers large parts of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and Tunisia.
2: The climate of the Sahara has undergone enormous variations between wet and dry over the last few hundred thousand years.
3: On February 18, 1979, snow fell in several places in southern Algeria, including a half-hour snowstorm that stopped traffic in Ghardaïa, and was reported as being "for the first time in living memory

2. People and animals Horned Vipers Dromedary Camels
The names in common is : Mohamed. The animals that are really common are :
Horned Vipers
Dromedary Camels
And some more but that two are the most common in the dessert of Sahara

3. Alaska
It is one of the most coldest countries of the world. There is a program that some people pass with the lorry to give some things throw Alaska and they suffer a lot
Alaska's economy is dominated by the oil, natural gas and fishing industries, resources which it has in abundance. Tourisms also a significant part of the economy

4. People and animals
The polar bears are really important because that ere the animals that are in the Alaska there are more but what you more see.
There are penguins to but you see more polar bears tan penguins the penguins are really funny how they walk and slice throw the snow like sqees

5. amazona
There in the amazone is cold and warm normaly humid there is one of the most rare countries that i have ever seen by the weather because it is always changing one day is cold one day is warm another day it is humid or Misti

6. Extreme environments 
conclusion
I think in conclusion there are one of the most extreme environments on the world and only some animals can live there
Extreme environments 

7. People or animals
The parrot is one of the most common animals of the amazone
The leopardo is not so commmon but it is an exelent animal.