1. Interactions among Living Things

2. Populations  There is a limit to the number of organisms (population) that an ecosystem can support based on different factors:  Climate  Availability of resources (water, food)  Relationships with other organisms

3. Competition  occurs when more than one organism tries to obtain the same basic resources in the same habitat  It affects the population by limiting number of organisms that can survive on resources in an area

4. Predation  Predator: an organism that hunts other living things for food  Prey: an animal that is hunted by a predator  Population of predators is affected by population of prey and vice versa

5. If predator population increases, prey population decreases because more predators eating prey

6. If prey population gets too low, there isn’t enough for predators to eat; predators decrease

7. If predator population increases, prey population decreases because more predators eating prey If prey population gets too low, there isn’t enough for predators to eat; predators decrease As predator population decreases, prey population increases because there are fewer predators hunting them

8. If predator population increases, prey population decreases because more predators eating prey If prey population gets too low, there isn’t enough for predators to eat; predators decrease As predator population decreases, prey population increases because there are fewer predators hunting them Results in an up-and-down predator and prey pattern

9. Predator-prey cycle affects plant populations Most prey eat plants; when prey population large, prey eat all available plants Plant populations get smaller, not enough for prey to eat—get weaker and easier for predators to catch Reduces the number of prey Plants can begin to recover

10. In competition and predation, one organism usually “wins” while another “loses” Mutualism is an interaction between individuals of different species that benefits both individuals Both organisms “win”

11. Think About What you Learned.. 1. Give three examples of competition 2. Give three examples of predator-prey relationships 3. Give three examples of mutualism