798 ANIMALS AND THEIR ENVIRONMENT 



tion of Streams by sewage or industrial wastes may kill the fauna either 

 by direct toxic ellect of one of the chemicals or indirectly by encouraging 

 the growth of decomposer organisms which reduce the oxygen tension 

 in the water. 



The adaptations made by animals for survival in streams are con- 

 cerned primarily with ways of maintaining their position in the current. 

 Some have developed permanent connections with the substrate by 

 evolving hooks, suckers or glands for the secretion of threads or sticky 

 masses with which to attach to the substrate. Others have evolved stream- 

 lined, flattened bodies and behavior patterns by which they normally 

 orient themselves so as to head upstream and swim against the current. 



In studying any animal it is important to consider whether it is a 

 generalized or specialized representative of its group, what adaptations 

 it has made for survival in its habitat, and what its ecologic role is in 

 the population, community, biome or ecosystem of which it is a member. 



Questions 



1. Define and give an example of adaptive radiation. 



2. Define the term con\ergent evolution. Discuss convergent evolution of flying animals 

 and of burrowing animals. 



3. Differentiate between protective coloration and mimicry. Give examples of each. 



4. What experiments could you devise to determine whether color adaptations have a 

 selective advantage? 



5. Discuss the subdivisions of the marine habitat and give examples of animals found 

 typically in each. 



6. What is a biome? How does it differ from a biotic community? 



7. What adaptations are needed for survival in the intertidal zone? 



8. Differentiate between plankton and nekton. Give examples of each. 



9. Why are similar biomes found at high latitudes and high altitudes? Would you expect 

 to find exactly the same species of plants and animals in the tundra region of Alaska 

 and in the tundra region of the Andes? Why? 



10. Describe briefly the characteristics of the temperate deciduous forest biome; of the 

 desert biome. 



Supplementary Reading 



A wonderfully illustrated account of animal camouflage is to be found in H. B. Cott's 

 Adaptive Coloration in Animals. 



