Populations are so interesting to study. Why don't predators completely eat all the prey and then move on? Why do the prey continue to live in the population if they keep getting eaten? In nature a balance tends to exist between the predators and prey within an environment. There is an old time cartoon that dealt with this phenomenon. Tom and Jerry. Every episode Tom, the cat, would chase the mouse, Jerry, and they would go round and round and round. The Tom and Jerry cycle is a never ending cycle. Tom gets Jerry, Jerry gets Tom, and on and on. In a population, when the prey species is numerous, the number of predators will increase because there is more food to feed them and a higher population can be supported with all the available food. As the number of predators begins to rise, the number of the prey population will get less in response to increased rates of predation. That results in a decrease in the number of predators decreasing as food availability becomes smaller, which in turn makes the rate of predation less, allowing the prey population to grow again! (Phew, that was a mouthful!) If we graphed this cycle, it would look like this: The predator and prey are always one step ahead of the other in the population and extinction of all the prey never seems to happen. Of course there are other factors that need to be considered in a population that might limit it, like disasters, disease and reduction of space. Invasive species is something that happens when someone, thing or event introduces this unnatural species into the population and they go and take over! Like the carp in Utah Lake...The invasive species disrupts the balance within an environment by eliminating both predators and prey within the system causing a disastrous effect. A trophic cascade can occur through all levels of the energy and nutrient cycle within the population. Not a good cascade...even the producers are affected by the invasive species and the whole population will change into a totally different ecosystem. Again, there are other factors like adaptations, camouflage, hiding, reproduction-DNA changes that seem to preserve many species. I know! Populations are really very fascinating how they hang on and change to keep their home stable and productive. You've heard that saying..."life finds a way". It's really true! How cheesey...oh well, I love that movie!
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Mrs. TaylorI love science! Everything about the world is interesting and never boring. I love to study plants, animals, insects, and people. My favorite subjects are my students who are the most unique organisms on the planet! Categories |