13 1 Ecologists Study Relationships KEY CONCEPT Ecology

13. 1 Ecologists Study Relationships KEY CONCEPT Ecology is the study of the relationships among organisms and their environment.

13. 1 Ecologists Study Relationships Ecologists study environments at different levels of organization. • Ecology is the study of the interactions among living things, and between living things and their surroundings.

13. 1 Ecologists Study Relationships • An organism is an individual living thing, such as an alligator. Organism

13. 1 Ecologists Study Relationships • A population is a group of the same species that lives in one area. Population Organism

13. 1 Ecologists Study Relationships • A community is a group of different species that live together in one area. Community Population Organism

13. 1 Ecologists Study Relationships • An ecosystem includes all of the organisms as well as the climate, soil, water, rocks and other nonliving things in a given area. Ecosystem Community Population Organism

13. 1 Ecologists Study Relationships • A biome is a major regional or global community of organisms characterized by the climate conditions and plant communities that thrive there. Biome Ecosystem Community Population Organism

13. 1 Ecologists Study Relationships Ecological research methods include observation, experimentation, and modeling. • Observation is the act of carefully watching something over time. • Observations of populations can be done by visual surveys. – Direct surveys for easy to spot species employ binoculars or scopes. – Indirect surveys are used for species that are difficult to track and include looking for other signs of their presence.

13. 2 Biotic and Abiotic Factors KEY CONCEPT Every ecosystem includes both living and nonliving factors.

13. 2 Biotic and Abiotic Factors An ecosystem includes both biotic and abiotic factors. • Biotic factors are living things. – plants – animals – fungi – bacteria plants

13. 2 Biotic and Abiotic Factors • Abiotic factors are nonliving things. – moisture – temperature – wind – sunlight – soil sunlight moisture

13. 2 Biotic and Abiotic Factors Changing one factor in an ecosystem can affect many other factors. • Biodiversity is the assortment, or variety, of living things in an ecosystem. • Example: Rain forests have more biodiversity than other locations in the world, but are threatened by human activities.

13. 2 Biotic and Abiotic Factors • A keystone species is a species that has an unusually large effect on its ecosystem. keystone

13. 2 Biotic and Abiotic Factors • Keystone species form and maintain a complex web of life. – Example: Beaver creation of wetland ecosystem increased waterfowl Population increased fish population keystone species nesting sites for birds

13. 3 Energy in Ecosystems KEY CONCEPT Life in an ecosystem requires a source of energy.

13. 3 Energy in Ecosystems Producers provide energy for other organisms in an ecosystem. • Producers get their energy from non-living resources. • Producers are also called autotrophs because they make their own food.

13. 3 Energy in Ecosystems Producers provide energy for other organisms in an ecosystem. • Consumers are organisms that get their energy by eating other living or once-living resources. • Consumers are also called heterotrophs because they feed off of different things.

13. 3 Energy in Ecosystems Almost all producers obtain energy from sunlight • Photosynthesis in most producers uses sunlight as an energy source. • Chemosynthesis in prokaryote producers uses chemicals as an energy source. carbon dioxide + water + hydrogen sulfide + oxygen sugar + sulfuric acid

13. 4 Food Chains And Food Webs KEY CONCEPT Food chains and food webs model the flow of energy in an ecosystem.

13. 4 Food Chains And Food Webs A food chain is a model that shows a linear sequence of feeding relationships. • A food chain links species by their feeding relationships. • A food chain follows the connection between one producer and a single chain of consumers within an ecosystem. GRAMA GRASS DESERT COTTONTAIL HARRIS’S HAWK

13. 4 Food Chains And Food Webs • Consumers are not all alike. – Herbivores eat only plants. – Carnivores eat only animals. – Omnivores eat both plants and animals. – Detritivores eat dead organic matter. – Decomposers are detritivores that break down organic matter into simpler compounds. carnivore decomposer

13. 4 Food Chains And Food Webs

13. 4 Food Chains And Food Webs • Specialists are consumers that primarily eat one specific organism or a very small number of organisms. • Generalists are consumers that have a varying diet.

13. 4 Food Chains And Food Webs • Trophic levels are the nourishment levels in a food chain. – Primary consumers are herbivores that eat producers. – Secondary consumers are carnivores that eat herbivores. – Tertiary consumers are carnivores that eat secondary consumers. – Omnivores, such as humans that eat both plants and animals, may be listed at different trophic levels in different food chains depending on the situation

13. 4 Food Chains And Food Webs A food web shows a complex network of feeding relationships. • An organism may have multiple feeding relationships in an ecosystem. • A food web emphasizes complicated feeding relationships and energy flow in an ecosystem.

13. 4 Food Chains And Food Webs

13. 5 Cycling of Matter KEY CONCEPT Matter cycles in and out of an ecosystem.

13. 5 Cycling of Matter Water cycles through the environment. • The hydrologic, or water, cycle is the circular pathway of water on Earth. • Organisms all have bodies made mostly of water. precipitation condensation transpiration lake surface runoff evaporation water storage in ocean groundwater see pag e

13. 5 Cycling of Matter Elements essential for life also cycle through ecosystems. • A biogeochemical cycle is the movement of a particular chemical through the biological and geological parts of an ecosystem. • The main processes involved in the oxygen cycle are photosynthesis and respiration.

13. 5 Cycling of Matter • Oxygen cycles indirectly through an ecosystem by the cycling of other nutrients. oxygen photosynthesis respiration carbon dioxide

13. 5 Cycling of Matter • Carbon is the building block of life. – The carbon cycle moves carbon from the atmosphere, through the food web, and returns to the atmosphere. – Carbon is emitted by the burning of fossil fuels. – Some carbon is stored for long periods of time in areas called carbon sinks. carbon dioxide in air combustion respiration photosynthesis respiration decomposition of organisms fossil fuels photosynthesis carbon dioxide dissolved in water

13. 5 Cycling of Matter • The nitrogen cycle mostly takes place underground. – Some bacteria convert gaseous nitrogen into ammonia through a process called nitrogen fixation. – Some nitrogen-fixing bacteria live in nodules on the nitrogen in atmosphere roots of plants; animals others live freely in the soil. plant nitrogen-fixing bacteria in decomposers roots ammonification nitrogen-fixing ammonium bacteria in soil nitrifying bacteria nitrates nitrifying bacteria nitrites denitrifying bacteria

13. 5 Cycling of Matter – Ammonia released into the soil is transformed into ammonium. – Nitrifying bacteria change the ammonium into nitrate. – Nitrogen moves through the food web and returns nitrogen in atmosphere to the soil during animals decomposition. plant nitrogen-fixing bacteria in decomposers roots ammonification nitrogen-fixing ammonium bacteria in soil nitrifying bacteria nitrates nitrifying bacteria nitrites denitrifying bacteria

13. 5 Cycling of Matter • The phosphorus cycle takes place at and below ground level. – Phosphate is released by the weathering of rocks. – Phosphorus moves through the food web and returns to the soil during decomposition. rain geologic uplifting – Phosphorus leaches into groundwater weathering of phosphate from rocks from the soil and runoff plants is locked in sediments. animalsphosphate in solution in soil – Both mining and leaching agriculture add sedimentation phosphorus into decomposers forms new rocks the environment.

13. 6 Pyramid Models KEY CONCEPT Pyramids model the distribution of energy and matter in an ecosystem.

13. 6 Pyramid Models An energy pyramid shows the distribution of energy among trophic levels. • Energy pyramids compare energy used by producers and other organisms on trophic levels. • Between each tier of an energy pyramid, up to 90 percent of the energy is lost into the atmosphere as heat. • Only 10 percent of the energy at each tier is transferred from one trophic level to the next. Called the “ 10% Rule” energy lost energy transferred

13. 6 Pyramid Models Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms. • Biomass is a measure of the total dry mass of organisms in a given area. tertiary consumers 75 g/m 2 150 g/m 2 secondary consumers primary consumers producers 675 g/m 2 2000 g/m 2

13. 6 Pyramid Models • A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem. tertiary consumers 5 secondary consumers 5000 primary consumers 500, 000 producers 5, 000 • A vast number of producers are required to support even a few top level consumers.