Organism: Description - An individual living thing. Example - A single bacterium, a mushroom, or a human.

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Population: Description - A group of individuals of the same species living in the same area. Example - A herd of deer in a forest, a school of fish in a lake.

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Community: Description - All the different populations that live together in an area. Example - All the plants, animals, fungi, and bacteria in a forest.

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Ecosystem: Description - Includes all the living (biotic) and nonliving (abiotic) things in an area—example - A pond, a desert, or a grassland.

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Biome: Description - A large geographic area characterized by specific climate conditions, animal and plant populations. Example - A tropical rainforest, a tundra, or a desert.

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All ecosystems are made up of biotic and abiotic components.

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Biotic factors are living things, such as animals or plants.

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Abiotic factors are nonliving things like wind, sunlight, or water.

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Producers are organisms that get their energy from abiotic resources, meaning they make their own food.

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Consumers are organisms that get their energy by consuming other organisms.

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Herbivore: Definition - An organism that eats only plants. Example - A deer, a rabbit, or a grasshopper.

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Carnivore: Definition - An organism that eats only meat. Example - A lion, a wolf, or a snake.

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Omnivore: Definition - An organism that eats both plants and animals. Example - A human, a bear, or a pig.

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Trophic levels: Definition - The different feeding positions in a food chain or food web. Example - Producers, primary consumers, secondary consumers, tertiary consumers.

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Primary consumer: Definition - An organism that eats producers (plants). Example - A grasshopper, a cow, or a deer.

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Secondary consumer: Definition - An organism that eats primary consumers. Example - A snake that eats a grasshopper, a fox that eats a rabbit.

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Tertiary consumer: Definition - An organism that eats secondary consumers. Example - An eagle that eats a snake, a lion that eats a fox.

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Decomposer: Definition - An organism that breaks down dead plants and animals. Example - Bacteria, fungi, or earthworms.

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Producers are important because they are the base of the food chain. They convert sunlight into energy that other organisms can use.

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A food chain is a linear sequence of organisms through which nutrients and energy pass. A food web is a network of interconnected food chains. The arrows represent the flow of energy and nutrients, pointing from the organism being eaten to the organism that eats it.

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The four tiers of the energy pyramid are: Producers (100%), Primary Consumers (10%), Secondary Consumers (1%), Tertiary Consumers (0.1%).

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If all the producers died, the entire food web would collapse because there would be no energy source for the consumers. Primary consumers would die first, followed by secondary and tertiary consumers.

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Eliminating the producer trophic level would have the most drastic effect because they are the base of the food web. Without producers, there would be no energy entering the ecosystem, and all other trophic levels would eventually collapse.

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All the energy that organisms use originally comes from the sun.

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Biomagnification is the increasing concentration of a substance in the tissues of organisms at successively higher levels in a food chain. It is related to food webs because the higher an organism is in the food web, the more concentrated the toxic substance becomes.

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Symbiosis is any type of close and long-term biological interaction between two different biological organisms.

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Commensalism: Definition - A relationship in which one organism benefits and the other is neither harmed nor helped. Example - Barnacles attaching to a whale.

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Mutualism: Definition - A relationship in which both organisms benefit. Example - Bees pollinating flowers.

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Predation: Definition - A relationship in which one organism (the predator) kills and eats another organism (the prey). Example - A lion hunting a zebra.

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Parasitism: Definition - A relationship in which one organism (the parasite) benefits and the other organism (the host) is harmed. Example - A tick feeding on a dog.

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A habitat is the place where an organism lives. A niche is the role an organism plays in its environment. Example: A habitat for a fish is a lake. The niche of a fish might be a predator of insects and a food source for birds.

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Exponential growth (J-curve): Population increases rapidly without any limitations. Logistic growth (S-curve): Population growth slows down as it reaches carrying capacity.

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A density-dependent factor is a factor that limits population growth more strongly as population density increases. Example: Disease, competition for resources, predation.

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A density-independent factor is a factor that limits population growth regardless of population density. Example: Natural disasters (e.g., floods, fires), weather conditions.

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Carrying capacity is the maximum number of individuals of a species that an environment can support. It is determined by the availability of resources such as food, water, shelter, and other essential factors.