terms of their actual operation in a natural community. As an 

 introduction to ecology this film is especially valuable since these 

 phenomena are more readily observable in the Arctic where popu- 

 lations of certain species fluctuate greatly over a regular period 

 of years. 



The lemmings and their relationships to their predators and the 

 plants forming their food supply are the major topic of the Arctic 

 portion of the film. In the Antarctic section the principal emphasis 

 is upon the penguin, its life history, and the role of the nearby 

 colonies of other seabirds. 



AUDIENCE: High school; college; adult 



POPULATION ECOLOGY 



Color Sound Encyclopaedia Britannica Films 



21 minutes Rental Sale 



The principles of population dynamics are introduced through 

 controlled experiments with mice and fruit flies. These demonstrate 

 that an animal population will reach a certain size and remain there 

 unless there is a sudden change in conditions. Births and deaths 

 are in approximate balance. 



Human populations once behaved in the same way when man 

 was a hunter and a food-gatherer. As civilization developed, man's 

 numbers would increase only to level off again. Today there is no 

 sign of a leveling off. Our current "population explosion", the result 

 of man's ability to change his environment, is chillingly documented 

 in a sequence showing the human misery which has resulted in 

 many places from overpopulation. 



AUDIENCE: High school; college; adult 



SUCCESSION FROM SAND DUNE TO FOREST 



Color Sound Encyclopaedia Britannica Films, Inc. 



16 minutes Rental Sale 



This film documents the best-studied example of ecological suc- 

 cession the dunes area along the southern end of Lake Michigan 

 where various stages of this process are continually visible. Each 

 phase is examined and explained. These are named for the domi- 

 nant plants which in this area are grasses, cottonwoods, pines, oaks, 

 and maple-beech climax. The basic underlying soil is still sand 



36 



