Ch.7 Lesson 3 How do organisms compete for resources? Competition: struggle among organisms to survive in a habitat with limited resources (species searching for the same kinds of food) Competition happens when organisms in an ecosystem have similar needs. Organisms with different needs can live and survive together in a habitat with little competition. Competition increases when the amount of available resources is low. Members of the same species compete for available resources. All organisms compete for resources (not just animals). Plants compete for sunlight, water, etc.

Predator: an animal that feeds on other animals Prey: animals that a predator eats The number of predators that can survive in an ecosystem depends on the amount of available prey. Predators have adaptations that help them hunt prey. Prey have adaptations that help them avoid predators.

Symbiosis: a close long term relationship where at least one of the organisms benefits. Parasitism: parasite is the organism that benefits and host is the organism that is harmed. Mutualism: both organisms benefit from each other Commensalism: one organism benefits and the other is neither helped nor harmed

Ch.7 Lesson 4 How do materials cycle through ecosystems? If important materials in nature didn’t cycle, we would soon run out! Nitrogen Cycle: 78% of the air is Nitrogen but not usable by most organisms because it is free Nitrogen (not combined with other elements) Fixed Nitrogen: is combined with other elements (bacteria fix Nitrogen in the soil, lightning fixes Nitrogen in the air, also decomposers fix Nitrogen) Animals get Nitrogen from eating plants or getting from the prey they eat.

CARBON CYCLE The most common element in all living things is CARBON. (18% of your body) Carbon is found in living things, Earth’s atmosphere, rocks, soil, etc. Carbon is cycled during photosynthesis and cellular respiration. Organisms that do not decompose get buried and over a long time form fossil fuels like coal, oil, or natural gas.

THE WATER CYCLE It helps make water available to all parts of an ecosystem. Water evaporates as liquid water becomes a gas, water vapor. Water vapor rises in the atmosphere, cools and condenses back to a liquid. That liquid falls back to the Earth as precipitation.

Lesson 5 How Do Ecosystems Change? Ecosystems can be changed by natural events. Some change ecosystems quickly like earthquakes, volcanoes, fires, and floods. Some changes occur slowly, like climate changes. Succession-a series of predictable changes that happen over time. Ex) After a forest fire, pioneer species are the first organisms to live there. Then organisms slowly start moving back into the area. Humans change ecosystems also. Ex.) cutting down trees, pollution Humans introducing a new species to an area changes the ecosystem because that species will not have any natural predators. Humans can save ecosystems by understanding the impact they have. (use resources wisely, conserve resources)