Main Idea The size of any population can vary over time. It responds to change in climate and resources.
In This Lesson: We’ll learn how a decrease in food supply, changes in climate, and relocated species can upset the balance of an ecosystem.
Vocabulary: It’s journal time folks!!! Extinction Population Predator Prey
Extinction: When all members of a species die out
Population: All the organisms of a given species that live together in the same area
Predator: Animal that hunts and eats other animals
Prey: Animal that is hunted and eaten by predators
Hey, did you catch that? Predator and Prey are… Antonyms!!!(opposites)
Let’s Talk Population… Remember, a population is all the organisms of a given species that live together in the same area.
Let’s Talk Population… Population size responds to changes in climate and resources. How do you think the birds on the previous slide would respond to the 3 climate examples listed below?
Let’s Talk Population… In a healthy ecosystem, the population of predators and prey are balanced.
Changes in Population… Every ecosystem supports many populations. That means many different species live in the same ecosystem. A population is all the organisms of a given species that live together in the same area. Any change in one part of an ecosystem can upset the balance.
For Example: Suppose a fungus kills many of the plants that rabbits eat. Such an event could lower the rabbit population. This would affect the hawks, owls, and other animals that eat the rabbits. How would this affect the hawks, owls, and other animals that eat the rabbits?
Answer… The hawks, owls, and other animals would not have the rabbits to eat; therefore, they might go hungry. Or, they would have to find another food source which might cause another species to go hungry. Can you see how a change in population could upset the balance of an ecosystem?
Question… What would happen if a population of rabbits became too large?
Answer: They would crowd out the other species in that area!! Why would that be a bad thing?
Answer Ecosystems have limited resources, and can only support a limited number of living things. Hey…that makes sense!!!
Did you know… In an ecosystem, populations are ALWAYS changing. ALWAYS changing. Old animals die, and new ones are born. When a tree falls, plants that thrive in sunlight can begin to grow. These are good changes!!!
Consider the relationship between predators and their prey Predators are animals that hunt and eat other animals. Prey are animals hunted and eaten by predators. (I’d rather be a predator!)
In a healthy ecosystem… The population densities of predators and prey are balanced. But remember, we said certain factors can upset this balance. For example: Predators and prey are two factors that affect the balance of an ecosystem.
Let’s Read About It: May I have a volunteer to begin reading on P. 95, please?
How might a decrease in predators affect prey?
Answer: The prey population could grow. could grow.
Did you know… Once an ecosystem is changed it may take hundreds of years to recover! In some cases, it is changed FOREVER!!
Let’s Review: What factors affect ecosystems?
Review: What factors can cause the size of a population of living things to change?