2. Ecology is the study of how organisms interact with each other and with their environments. Every organism on Earth lives in an ecosystem—the living and nonliving things in one place. ecosystem Different organisms depend on different parts of an ecosystem to survive. What are ecosystems?

3. Abiotic factors are the nonliving parts of an ecosystem. Abiotic factors Important abiotic factors include water, light, temperature, atmosphere, and soil. The types and amounts of abiotic factors in an ecosystem help to determine which organisms can live there. Abiotic Factors

4. All organisms need water to live, but some need more water than others. The amount of light available and the temperature of an ecosystem can also determine which organisms can live there. Different ecosystems contain different amounts and types of nutrients, minerals, and rocks in the soil. Very few living things can survive in an ecosystem without oxygen in the atmosphere. Abiotic Factors (cont.)

5. Biotic factors are all of the living or once-living things in an ecosystem. Biotic factors A population is made up of all the members of one species that live in an area.population Organisms in a population interact and compete for food, shelter, and mates. A community is all the populations that live together in the same place.community Biotic Factors

6. A biome is a large region on Earth with a specific climate, physical features, plants, and other organisms.biome Biomes contain ecosystems, populations, and communities, as well as specific biotic and abiotic factors. All biomes are part of the biosphere—the part of Earth that supports life—and can be described as either terrestrial or aquatic. Biotic Factors (cont.)

7. Image by Reto Stockli, NASA/Goddard Space Flight Center. Enhancements by Robert Simmon

8. Terrestrial means related to land, and aquatic means related to water. Terrestrial biomes include forests, deserts, tundra, and grasslands. Aquatic biomes include saltwater areas and freshwater areas. Biomes, like communities, can affect each other. Biotic Factors (cont.)

9. Changes in the environment are caused by both natural processes and human actions. Changes in an environment can occur slowly or rapidly and can have positive or negative effects. What happens when environments change?

10. The area in which a population lives can be very large, such as the population of all the fish in the ocean, or very small, like fish in a lake. If either biotic or abiotic factors that affect an organism change, that organism’s population can also change. Populations

11. A volcanic eruption can cause sudden change in an ecosystem. Succession is the gradual change from one community to another community in an area. Succession What happens when environments change? (cont.)

12. The area a population lives in can be large or small.

13. Sometimes the size of a population changes because the ecosystem changes. Population density describes the number of organisms in the population relative to the amount of space available. If a population is very dense, organisms might have a hard time finding enough resources to survive. Populations (cont.)

14. The size of a population can change in different ways.

15. Limiting factorsLimiting factors are factors that can limit the growth of a population.

16. Biotic potential is the potential growth of a population if it could grow in perfect conditions with no limiting factors. Biotic potential Carrying capacity is the largest number of individuals that can survive in an area over a long time. Carrying capacity The limiting factors of an area determine the area’s carrying capacity. Populations (cont.)

17. Overpopulation is when a population’s size grows beyond the ability of the area to support it. This often results in overcrowding, a lack of resources, and an unhealthy environment. Populations (cont.)

18. Communities (cont.) Competition: Some populations might compete with each other for resources and space. Predation: Other populations may rely on each other for food (rabbits and grass, coyotes and rabbits).

19. Communities All the populations in the same area interact as a community.

20. Each population has different ways to stay alive and reproduce. All of the populations in a community share a habitat, the physical place where a population or organism lives. habitat A niche is the unique ways an organism survives, obtains food and shelter, and avoids danger in its habitat.niche Symbiotic Relationships

21. A symbiotic relationship is one in which two different species live together and interact closely over a long period of time.symbiotic relationship These relationships can be beneficial to both organisms, beneficial to one and harmful to the other, or beneficial to one and neutral to the other. Symbiotic Relationships (cont.)

22. Mutualism—two species in a community benefit from the relationship. Parasitism—one species (the parasite) benefits while another (the host) is harmed. Commensalism—one species benefits and the other is neither helped nor harmed. Types of Symbiotic Relationships

23. Organisms get energy from food that they make using light or chemical energy or by eating other organisms. When one organism eats another, the energy in the organism that is eaten is transferred to the organism that eats it. Energy Flow

24. Energy travels through organisms, populations, communities, and ecosystems in a flow. When energy moves in a flow it does not return to its source, as it does in cycles. Energy Flow (cont.)

25. Scientists classify organisms by the way they get the energy they need to survive. Some organisms, such as plants, are able to capture the Sun’s energy directly and convert it into energy-rich sugars that they use for food. Organisms and Energy

26. Light energy is changed to food energy by a process called photosynthesis.

27. A few organisms are able to capture energy from chemicals in the environment and make food by a process called chemosynthesis. Other organisms cannot capture energy from sunlight or chemicals and must obtain their energy by eating food. Organisms that cannot make their own food using the Sun must depend on organisms that can. Organisms and Energy (cont.)

28. ProducersProducers change the energy available in their environment into food energy that they use to live and reproduce.

29. Consumers use the energy and nutrients stored in other organisms for living and reproducing. Consumers Consumers are classified as herbivores, omnivores, carnivores, or detritivores, based on their diet. Herbivores are animals that eat only producers, such as plants. Organisms and Energy (cont.)

30. Omnivores, such as human beings, are animals that eat both producers and other consumers. Carnivores, such as lions, eat only other consumers. Decomposers, including some insects, fungi, worms, bacteria, and protists, eat dead plant or animal material. Organisms and Energy (cont.)

31. A food chain models how food energy moves from the environment to several organisms.food chain Modeling Energy Flow

32. Each stage of a food chain has less available food energy than the last one, because some food energy is converted to thermal energy and moves to the environment. Modeling Energy Flow (cont.)

33. Food Web A food web is a model that shows several connected food chains.food web

34. Food chains and food webs are models used to help understand how energy travels through a community. Terrestrial and aquatic organisms can interact within a food chain or food web. Food webs show that food energy can move through several different pathways. Modeling Energy Flow (cont.)

35. An energy pyramid shows the amount of food energy available at each level of a community.energy pyramid More food energy is available at the “base” of an energy pyramid, where producers are. Modeling Energy Pyramids

36. Food energy from producers moves into consumers at the next level. At each level of the pyramid, the amount of usable food energy decreases. The top level of a food pyramid usually shows the carnivores in an ecosystem. Modeling Energy Pyramids (cont.)

37. This energy pyramid shows how energy flows from producers to consumers.