troposphere

Most of the mass (about 75-80%) of the atmosphere is in the troposphere. Most types of clouds are found in the troposphere, and almost all weather occurs within this layer. Air is warmest at the bottom of the troposphere near ground level. Air gets colder as one rises through the troposphere.

The Earth is divided into three main layers. The dense, hot inner core (yellow), the molten outer core (orange), the mantle (red), and the thin crust (brown), which supports all life in the known universe. Earth’s interior is generally divided into three major layers: the crust, the mantle, and the core.

crust

A lot like the Sun, Jupiter is mostly composed of hydrogen and helium. Jupiter contains the largest ocean in the solar system, an ocean of liquid hydrogen.

Above the core is Earth’s mantle, which is made up of rock containing silicon, iron, magnesium, aluminum, oxygen and other minerals. The rocky surface layer of Earth, called the crust, is made up of mostly oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium.

The longest living mammal is the bowhead whale, which can live up to 200 years. Also known as the Arctic whale, this animal is big, and lives in cold waters so its metabolism is slow. The record age for a bowhead is 211 years.

While our ancestors have been around for about six million years, the modern form of humans only evolved about 200,000 years ago.

One of the youngest known is a species named Senecio eboracensis which seems to have occurred sometime in the past 40 to 50 years.

Humans are one type of several living species of great apes. Humans evolved alongside orangutans, chimpanzees, bonobos, and gorillas. All of these share a common ancestor before about 7 million years ago. Learn more about apes.

But humans are not descended from monkeys or any other primate living today. We do share a common ape ancestor with chimpanzees. It lived between 8 and 6 million years ago. All apes and monkeys share a more distant relative, which lived about 25 million years ago.

We evolved and descended from the common ancestor of apes, which lived and died in the distant past. This means that we are related to other apes and that we are apes ourselves. And alongside us, the other living ape species have also evolved from that same common ancestor, and exist today in the wild and zoos.

Evolution, in this context, is both a fact and a theory. It is an incontrovertible fact that organisms have changed, or evolved, during the history of life on Earth. And biologists have identified and investigated mechanisms that can explain the major patterns of change.”

Early humans first migrated out of Africa into Asia probably between 2 million and 1.8 million years ago. They entered Europe somewhat later, between 1.5 million and 1 million years. Species of modern humans populated many parts of the world much later.