Ecosystems A study of balance and cycles

Key Terms Ecosystem Consists of a biotic community and the abiotic factors that affect it Consists of a biotic community and the abiotic factors that affect it Ex – a rain forest, including the animals, plants, soil, rain, sunlight, and temperature Biotic factors Living or once-living organisms in the environment Ex – gorilla, red-eyed tree frog, moss, bacteria Abiotic factors All the non-living, physical features of the environment Ex. sunlight, soil, water, and temperature

Levels of organization Organism A single individual in a population Ex – the oak tree growing in my yard Population All of the individuals of one species that live in the same area at the same time Ex. – All oak trees in my neighborhood Community Populations of different species that interact in some way Ex. – Oak trees, squirrels, rabbits, mice, grass, robins, humans

Levels of Organization, cont. Ecosystem Communities and abiotic factors that affect them Ex. Community + soil, light, temperature, etc. Biosphere All the ecosystems on Earth

Populations Population density The number of organisms in a given area Formula - # of organisms / area The more organisms in a given space, the denser the population Limiting factor Any biotic or abiotic factor that restricts (limits) the number of individuals in a population Ex. Food supply, # of predators, disease, available shelter

Limiting Factors 1. Choose an organism. 2. Write five limiting factors for that organism. Be as specific as possible. Ex. Cow 1. Disease - Mad cow disease 2. Humans – Humans slaughter cows for food 3. Living space – Farms have limited space to house the cows.

Relationships Symbiosis Any close relationship between two or more species Parasitism, mutualism, and commensalism are all types of symbiosis Parasitism Relationship that benefits one (the parasite) and does definite harm to the other (host) Ex – Tapeworms benefit by getting nutrients from a dog, but the dog is harmed by the tapeworms

Relationships, cont. Mutualism A relationship in which both organisms benefit Ex Yucca moth and desert yucca plant – moth gets a food source and place for eggs; plant gets its flowers pollinated Commensalism A relationship in which one organism benefits, but the other is neither harmed nor helped. Ex. Sea anemone and anemone fish – The fish are protected by the sea anemone, but the sea anemone are not affected by the fish

Cycles Many abiotic factors change form as they travel through a cycle Matter is not destroyed, but it changes form ExamplesWaterCarbonNitrogen

Water Cycle Evaporation – Liquid water found in lakes, oceans, ponds, rivers, etc. evaporates when heat is added. The water takes the gaseous form of water vapor Condensation – Gaseous water vapor condenses when it is cooled and has a solid on which it can condense. The water becomes liquid form. Freezing – Some clouds are high enough in the atmosphere that the water freezes, forming snow or hail Precipitation –Liquid or solid water collects in clouds, and as more water collects, it becomes heavy enough to fall as rain, snow, or hail

Water Cycle, cont. Run-off – Precipitation hits the ground, is not absorbed, but flows from high elevation to low elevation. Ground water – Precipitation hits the ground and is absorbed into the ground Hydration of living organisms – Organisms take in water by drinking, eating, taking water in through roots, and osmosis Excretion – Animals release water in their liquid wastes Transpiration – Plants release water from stomata

Carbon Cycle Photosynthesis – Plants remove carbon dioxide from atmosphere to make carbohydrates Respiration – Other organisms eat the plants. In respiration, they use the energy from the carbohydrates. Carbon dioxide is released as a waste product Decay – Organisms die. The carbon in their decaying remains is returned to the ground Combustion – Carbon is released into the atmosphere when fossil fuels (ex coal and oil) are burned

Nitrogen Cycle Nitrogen is a gas in our atmosphere. It is also found in organisms in proteins and nucleic acids. Nitrogen gas – In the atmosphere, nitrogen will combine with oxygen in the presence of high temperatures and pressures (lightning) to form nitrogen dioxide Nitrogen dioxide combines with rain to form an acid, which falls to the ground with the rain. In the ground, bacteria “fix” nitrogen so that it can be used by plants

Nitrogen Cycle, cont. Plants use nitrogen as a fertilizer. The nitrogen is used to build proteins, which are necessary for growth Animals eat plants, taking in the proteins containing nitrogen. Animals release wastes, which contain nitrogen. These wastes may be used as fertilizer. Some bacteria convert nitrogen in the soil back into nitrogen gas, which is released into the atmosphere

Energy in Ecosystems Energy travels through an ecosystem, changing form Common forms of energy include light, chemical, mechanical, and heat energy Organisms gain energy by: Using light or chemical energy to produce their own food (producers) Eating other organisms (consumers)

Producers vs. Consumers Producers Plants and some bacteria Photosynthesis – use light energy to create carbohydrates Chemosynthesis – use chemical energy to create carbohydrates Found in organisms deep in ocean ridges Consumers Eat other organisms for energy Ordered by primary (eat consumers), secondary (eat primary consumers), and tertiary (eat secondary consumers)

Food Chains and Food Webs Food chains show relationships among a select group of producers and consumers. The chain shows the flow of energy as one organism eats another. Chains are RARELY more than five organisms long Consumers get only a fraction of the energy contained in the organism they eat. Some energy is used by the original organism Much energy is lost as heat energy

Example of a Food Chain

Food Chains and Food Webs, Cont. Food webs Show the complexity of consumer/producer relationships in an ecosystem Used to show that more than one organism may eat a producer or prey AND that an organism may have more than one food source Typically, producers are near the bottom of the web and secondary/tertiary consumers are near the top Arrows indicate the direction of energy flow

Example of a Food Web

Energy Pyramid Diagram used to show producer and consumer relationships Emphasizes the relationship of number of prey per organism and the amount of energy that gets transferred from one level (ex. producer) to another level (ex. primary consumer) Only about 10% of the energy from one level is passed on to the next level Not all parts of an organism are eaten Not all organisms at one level are eaten Some energy is “lost” as heat energy Therefore, in an ecosystem, we have MANY producers and primary consumers. As we move up the energy pyramid, the ecosystem can sustain fewer and fewer organisms because there is less and less energy available