People have wondered for years and scientists still don't know for sure.
The seahorse dads carry the babies in a pouch.
The short answer is no. An individual of one species cannot, during its lifetime, turn into another species. But your question helps us think about life, evolution and what it means to be human.
Sweat comes from special parts in our skin called glands. You might be able to see them if you have a very strong magnifying glass.
Wind is just air moving from one place where there is high pressure to another place where there is low pressure.
To stay up, the bird must overcome gravity with a force called 'lift'.
Flies need good grip because they often sleep upside down.
Some spiders produce silk than can actually be stronger than steel and 50 times as light.
Hiccups serve no clear purpose. Tadpoles have a hiccup reflex which helps keep their lungs safe while they transition. So our hiccup reflex might be from our amphibian ancestors.
Human eyes don't have x-ray vision. But we can use radiography machines to allow our eyes to see inside things the human eye cannot.
Birds can usually sense when they are not feeling well and like many other creatures, seem to seek out-of-the-way places to be alone.
Magnets, air blowers, centrifuges, crushers: your recyclables go through a lot before they get turned into something else.
In short, pain medicine is able to block the processes that cause the feeling of pain. To understand why, you need to know a bit about how pain works.
The short answer is that while lava is hot, it's not hot enough to melt the rocks that make up the side of the volcano.
To answer this question from Fiona, age 6, we need to know some things about clouds and light.
Pond snails use things like rocks or the side of their aquarium as their bed, attaching themselves while they sleep. This might not seem very relaxing but their shells do hang away from their body.
When and where you see the Moon in the daytime depends on what phase it is in.
Bones protect our insides, help us to move and even help make our blood.
The world is made of tiny building blocks called 'elements'. Scientists have worked out how fast some elements change into other elements. That gives us a very big clue about how old the Earth is.
Many people, from children to the elderly, wear glasses. Andy, age 5, wants to know how they work.