Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332



Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332
Textbook Problem

Think back to Section 44.6. When researchers moved guppies from populations preyed on by cichlids to a habitat with killifish, the life histories of the transplanted guppies evolved. They came to resemble those of guppy populations preyed on by killifish. Males became gaudier; some scales formed larger, more colorful spots. How might a decrease in predation pressure on sexually mature fish allow this change?

Summary Introduction

To examine: The reason for the decrease in the predation pressure on a sexually mature fish that allows the changes in guppies.

Concept introduction: Density- dependent factor are the factors that are increasingly limit the population growth as the population density increases. Predation is a kind of density- dependent factor. Predation is killing of one organism for the food that affects the life history of target species. This plays a significant role in the food chain that determines the structure of biological communities. Predation pressure is the effect of predation on the population of prey organisms.


Researchers reared the collected guppies from cichlid and killifish streams in separate aquariums under identical predator- free environment. They found the differences in the natural populations of guppies preyed on different predators must have a genetic basis. Then they introduced the guppies from the site where there were cichlids but no killifish. Thus the guppies previously preyed upon only by cichlids were then exposed only to killifish. Thus, the life history traits in guppies evolve rapidly in response to the selective pressure exerted by predation...

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