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).
Epipelagic, or Sunlit Zone-this is the topmost layer of the pelagic zone, from the surface to a depth of about 200 meters (660 ft). It receives enough sunlight to support photosynthetic organisms such as seaweed and phytoplankton, and also has a high level of dissolved oxygen due to the action of the waves.he organisms that make their home in the pelagic zone can be divide into three types, phytoplankton, zooplankton and nekton. Phytoplankton-these primary producers are the basis of the ocean's food chain.