BEACH Natural Selection
Storyboard Text
- Founding Population
- Population increase Random Reproduction
- Variation Selective Pressures
- The snail species, Fentonius laudermithi, was shifted to a new beach by a storm. A diversity of snails with genes for a variety of colors colonize the new sandy beach. The snails have predators that spot them from above.
- Environmental Pressure Survival
- More juvenile snails are born and survive on the beach they have color variations. There is enough food or space for all of them to live despite being prey to the birds and being eaten.
- Differential Survival
- Not all of the snails are brown. Some snails are born with other colors. All of the snails on the beach are competing for resources and trying to stay hidden from the birds of prey.
- Adaptation of a Population over generations
- As the bird population reproduces and increases in number, the brightly colored snails are eaten more frequently since they really stand out against the sandy beach. The light brown snails match the color of their environment, making them hard to spot.
- The snail color is an adaptation to the beach environment, light brown snails are better at avoiding the birds. Light brown snails are eaten less often and survive longer. The bird population declines since they do not have enough food.
- Only surviving snails get a chance to reproduce. The fittest phenotype to the environmental pressure (birds) in this environment(sandy beach) is a light brown snail. Generations pass on their light brown color trait to their offspring. The future generations have a greater percentage of the gene pool coding for light brown snails.
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