Pond Water Selection Experiments.
Ponds contain complex ecoystems. Before conducting any experiments, it is important to get a feel for the population dynamics and ecology of the pond in question. Plants, insects and animals exist in the pond, but when a sample is removed from the pond, only a subset of the system will be transferred, and so one expects an alteration in the steady state concentration of entities over time in the sample withdrawn and kept in a testtube for example.
Below are some examples of interresting organisms to be found in a pond.
Protozoans
Single-celled organisms of the Kingdom Protista. See here for more details.
Rotifers
Algae
Gastrotrichs
Platyhelminths
Annelids
Arachnids
Dipterans
Crustaceans