The organisms which appeared on earth first was bacteria.
<u>Explanation:</u>
- The first-ever living organism on Earth was a bacteria known as cyanobacteria. It is believed by scientists that it first formed around 3 billion years ago.
- When the Earth was first formed, it was inhospitable for a long time until 3.8 billion years ago approximately, the core cooled down and the level of oxygen had risen. This, along with photosynthesis resulted in the formation of Cyanobacteria.
- These organisms were capable of carrying out the process of photosynthesis by which they prepared their food. These were known as common ancestors. All the living organisms thereafter are known to be their descendants.
The neritic zone is permanently covered with generally well-oxygenated water, receives plenty of sunlight and has low water pressure; moreover, it has relatively stable temperature, pressure, light and salinity levels, making it suitable for photosynthetic life.
Leukopenia means a low count of white blood cells in the body. When there is a low white blood cell count in the body, and in particular a low level of neutrophils (a kind of white blood cell that fights infection), there is quite a significant risk of developing an infection, and once an infection is developed and the white blood cell count is low, the body will not be able to protect itself and fight off the infection. In severe cases , infection may lead to death.
