But these mutations are organized, in a way. For example, let's say that 10,000 years after the most recent common ancestor, one of the mtDNA branches experienced a mutation. From that point on, that line of mtDNA would include that alteration. Another branch might experience a mutation in a different location. This alteration would also be passed on.
The pelagic zone can be contrasted with the benthic and demersal zones at the bottom of the sea. The benthic zone is the ecological region at the very bottom of the sea. It includes the sediment surface and some subsurface layers.Marine organisms living in this zone, such as clams and crabs, are called benthos.epending on the depth, the water column, rather like the Earth's atmosphere, can be divided into different layers. The pelagic zone occupies 1,330 million km 3 (320 million mi 3) with a mean depth of 3.68 km (2.29 mi) and maximum depth of 11 km (6.8 mi).
In a cool climate (outside the ocean), the temperature can be below freezing, but in a really warm climate, this zone can have warm waters. The pelagic zone: -- This zone is generally a warm zone, however, because warm and cold currents are constantly mixing, it can be cold in some parts and cooler in others.The benthic zone: -- The temperature of this zone is colder than the pelagic zone and is pretty much always cold.The abyssal zone: -- This zone is the coldest of all of the zones.Because no sunlight reaches this zone the water is never heated.n a cool climate (outside the ocean), the temperature can be below freezing, but in a really warm climate, this zone can have warm waters. The pelagic zone: -- This zone is generally a warm zone, however, because warm and cold currents are constantly mixing, it can be cold in some parts and cooler in others.