BES Facebook groupAdaptations of aquatic species
Pond organisms are adapted to their habitats in a number of ways. Invertebrates need to be able to move around so that they can hunt or avoid being hunted. They must be able to gather enough oxygen for their needs and they must be able reproduce.
The key to identifying any adaptation is by observation of behaviours, movements and lifecycles
The following is meant a very brief introduction only.
Movement
Organisms living in water and in particular the predators are usually streamlined like the Great Diving Beetle, reducing water friction and the energy needed to swim fast.
Others, like the water hog louse use their streamlining to help them stay on the bottom of the pond amid the detritus.
Pond skaters can walk on the water surface because they have tiny hairs on their feet which trap air.
Removing organisms to a clear collection jar will allow students to observe the various adaptations organisms have developed for moving through water.
Reproduction
Many pond organisms have adult stages which are not aquatic, for example the damselfly, dragonfly, mayfly and caddis fly. The adults are free to travel further in search of mates and lay their eggs in different ponds.
It is a useful activity to follow any pond dipping activity with some tree beating in the adjacent bushes and shrubs to find adult stages, in particular of caddisflies and mayflies.
Oxygen
Oxygen levels in water are significantly lower than in the air we breathe. Ponds which warm up through the day or have variable temperatures will also have varying levels of oxygen dissolved in the water. This can be an added problem for aquatic organisms and affects their behaviours.
As in terrestrial habitats, the smallest organisms rely on diffusion across surface membranes for their oxygen supply, larger organisms must find alternative strategies to gather the oxygen they need.
Students should be able to observe gills of various designs such as in the mayfly and the freshwater shrimp, air sacs carried by the water boatman and the water spider and physical adaptations similar to breathing tubes for such as the mosquito larvae which allow invertebrates to respire underwater. Smaller organisms such as the freshwater worms might not show visually obvious adaptations to gathering oxygen but their red colour can act as a trigger for looking at oxygen carrying chemicals.
