Marine Diversity | Environment for UPSC 2026 (Pre & Mains) PDF Download

 Page 1


 
 
MARINE 
ORGANISMS 
Page 2


 
 
MARINE 
ORGANISMS 
Marine organisms range in size from 
tiny bacteria to the largest known animal, the 
blue whale.  
All are adapted for life in salt water. 
  
Page 3


 
 
MARINE 
ORGANISMS 
Marine organisms range in size from 
tiny bacteria to the largest known animal, the 
blue whale.  
All are adapted for life in salt water. 
  
PLANKTON 
Plankton are living things that float in the water.  
Most plankton are too small to see with the unaided eye  
Plankton are unable to move on their own.  
Ocean currents carry them along. 
 
There are two main types of plankton 
Phytoplankton are “plant-like” plankton.  
Since they make food by photosynthesis, they live in the 
photic zone.  
E.g. Algae 
 
Zooplankton are “animal-like” plankton that include 
tiny animals and fish larvae. 
 They feed on phytoplankton. 
 
Page 4


 
 
MARINE 
ORGANISMS 
Marine organisms range in size from 
tiny bacteria to the largest known animal, the 
blue whale.  
All are adapted for life in salt water. 
  
PLANKTON 
Plankton are living things that float in the water.  
Most plankton are too small to see with the unaided eye  
Plankton are unable to move on their own.  
Ocean currents carry them along. 
 
There are two main types of plankton 
Phytoplankton are “plant-like” plankton.  
Since they make food by photosynthesis, they live in the 
photic zone.  
E.g. Algae 
 
Zooplankton are “animal-like” plankton that include 
tiny animals and fish larvae. 
 They feed on phytoplankton. 
 
 
The zooplankton is divided into two groups.  
 
Temporary plankton/ Meroplankton consists of 
planktonic eggs and larvae of members of the 
benthos and nekton. 
 
Permanent plankton/Holoplankton includes all 
animals that live their complete life cycles in 
a floating state.  
Page 5


 
 
MARINE 
ORGANISMS 
Marine organisms range in size from 
tiny bacteria to the largest known animal, the 
blue whale.  
All are adapted for life in salt water. 
  
PLANKTON 
Plankton are living things that float in the water.  
Most plankton are too small to see with the unaided eye  
Plankton are unable to move on their own.  
Ocean currents carry them along. 
 
There are two main types of plankton 
Phytoplankton are “plant-like” plankton.  
Since they make food by photosynthesis, they live in the 
photic zone.  
E.g. Algae 
 
Zooplankton are “animal-like” plankton that include 
tiny animals and fish larvae. 
 They feed on phytoplankton. 
 
 
The zooplankton is divided into two groups.  
 
Temporary plankton/ Meroplankton consists of 
planktonic eggs and larvae of members of the 
benthos and nekton. 
 
Permanent plankton/Holoplankton includes all 
animals that live their complete life cycles in 
a floating state.  
Climate and the Carbon Cycle 
Phytoplankton are responsible for most of the transfer of 
carbon dioxide from the atmosphere to the ocean.  
 
Carbon dioxide is consumed during photosynthesis, and the 
carbon is incorporated in the phytoplankton, just as 
carbon is stored in the wood and leaves of a tree.  
 
Through photosynthesis, phytoplankton consume carbon 
dioxide on a scale equivalent to forests and other land 
plants. 
 
Some of this carbon is carried to the deep ocean when 
phytoplankton die, and some is transferred to different 
layers of the ocean as phytoplankton are eaten by other 
creatures, which themselves reproduce, generate waste, 
and die.