Vascular tissue composed of xylem<span> (red) and </span>phloem<span> tissue (green, between the</span>xylem<span> and </span>cortex<span>) surrounds the pith. Collenchyma cells are elongated cells with unevenly-thickened walls . They provide structural support, mainly to the stem and leaves.</span>
The geological history of Earth follows the major events in Earth's past based on the geological time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System.
Earth was initially molten due to extreme volcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon afterwards, possibly as a result of the impact of a planetoid with the Earth. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered from comets, produced the oceans.
As the surface continually reshaped itself over hundreds of millions of years, continents formed and broke apart. They migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago, the earliest-known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia, 600 to 540 million years ago, then finally Pangaea, which broke apart 200 million years ago.
The present pattern of ice ages began about 40 million years ago, then intensified at the end of the Pliocene. The polar regions have since undergone repeated cycles of glaciation and thaw, repeating every 40,000–100,000 years. The last glacial period of the current ice age ended about 10,000 years ago
Carbon dioxide and methane.
In order for cells to become whole organisms, they must divide and differentiate. Cells divide all the time. That means that just one cell, a fertilized egg, is able to become the trillions of cells that make up your body, just by dividing. Those trillions of cells are not all the same though.
Just a little while after you started out as a fertilized egg, your cells started performing specific tasks, even started to look different because of that. Differentiation means that one cell performs a different function than another cell, depending on where it is in your body.
Not sure if this will help.
Because in asexual reproduction, only one parent is needed; unlike sexual reproduction that takes a male and female mating to produce offspring.
Cloning comes from a single parent that has not mated; the offspring will have the exact same DNA as the parent.