Animation 19.2: Assessing the Costs of Adaptation

INTRODUCTION

Populations change when individuals within the population acquire new characteristics that improve their reproductive success, or when changing environmental conditions favor one existing trait over another. Characteristics that are the most adaptive are more likely to be passed on to offspring. Gradually, members of the population with the advantageous trait become the majority. However, adaptations typically impose costs and well as benefits, and the evolution of such changes typically depends on the trade-off between those costs and benefits.

Researchers wishing to evaluate these trade-offs must develop techniques for studying just one characteristic of an organism at a time, a task made difficult by the fact that individuals in the wild can vary greatly.

Video titled: Animation 19.2: Assessing the Costs of Adaptation

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CONCLUSION

Evolution takes place because individuals in a population that have a survival advantage typically produce more offspring and pass on that advantage to their offspring. Generally, however, these advantages impose a cost. Snakes that are able to eat poisonous newts and survive also move more slowly and are more susceptible to being eaten themselves. Flowers that can resist herbicide also produce fewer seeds than normal. Males in sexually dimorphic species carry a higher parasite load and have a higher mortality rate than males in monomorphic species, in which males and females look basically the same.

Scientists can study the costs of certain adaptations by creating a genetically identical population in the laboratory. Within this population, they can introduce one specific trait and compare individuals who carry the trait with individuals who don't. Another way to study the costs of adaptations is to compare entire populations in nature. By collecting data from a large number of individuals, scientists can draw conclusions about the effects of a particular adaptation.

Textbook Reference: Key Concept 19.6 Evolution Is Constrained by History and Trade-offs

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