Topic 5.1: Communities and Ecosystems

5.1 Assessment Statements Define species, habitat, population, community, ecosystem and ecology Distinguish between autotroph and heterotroph Distinguish between consumers, detrivores and saprotrophs Describe what is meant by a food chain, giving 3 examples, each with at least 3 linkages (four organisms) Describe what is meant by a food web Define trophic level Deduce the trophic level of organisms in a food chain/web Construct a food web containing up to 10 organisms, using appropriate information State that light is the initial energy source for most communities Explain energy flow in a food chain State that energy transformations are never 100% efficient Explain reasons for the shape of the pyramids of energy Explain that energy enters and leaves ecosystems, but nutrients must be recycled State that saprotrophic bacteria and fungi (decomposers) recycle nutrients.

Ecology  The study of the relationships between living organisms and between organisms and their environment. The word ecology is derived from the word ‘oikos’ or home. The word ‘environment’ refers to everything which surrounds an organism. The environment includes: 1. The hydrosphere: Water 2. The Atmosphere: Gases 3. The Lithosphere: Rocks 4. The Biosphere: All Living Things

5.1.1 Define species, habitat, population, community, ecosystem, and ecology Define: Give a precise meaning of a word, phrase, or physical quantity. The study of ecology includes various levels of organization and complexity Species: a group of organisms that can normally interbreed and produce fertile offspring.  Habitat  The environment in which a species normally lives or the location of a living organism. Population: a group of organisms of the same species who live in the same area at the same time. Community: a group of populations living and interacting with each other in an area. Ecosystem: a community AND its abiotic (non-living) environment.

Mules are not considered a separate species. Why?

Key Abiotic Factors Terrestrial Ecosystems  Sunlight, Water, Wind, Disturbances, Soil, Temperature, Gases, Humidity, Nutrients, Minerals, Climate. Aquatic Ecosystems  Temperature, Water Quality/Salinity, Light Penetration, Dissolved Gases, Minerals, Nutrient Availability all determine where organisms can live in the water.

5.1.2 Distinguish between autotroph and heterotroph Distinguish: Give the differences between two or more different items. 1. Autotroph (self-feeding): An autotroph is an organism that synthesizes its organic molecules (food) from simple inorganic substances.  Photoautotrophs and Chemoautotrophs  Includes some cyanobacteria, some protists (algae) and plants (grasses, trees, etc.). 2. Heterotroph (other nutrition): An organism that obtains organic molecules from other organisms. All heterotrophs ultimately depend on autotrophs for survival.  Also known as ‘consumers’.  Examples include zooplankton, fish, sheep, insects, etc.

Types of Consumers Trophic Levels T5 Quaternary Consumer T4 Tertiary Consumer T3 Secondary Consumer T2 Primary Consumer T1 Producer

5.1.3 Distinguish between consumers, detrivores AND saprotrophs Distinguish: Give the differences between two or more items.  Saprotroph (heterotroph): an organism that lives on or in dead organic matter, secreting digestive enzymes into it and absorbing the products of digestion.  Are nature’s recyclers.  Detrivore (or decomposer/heterotrph): is an organism that ingests dead organic matter.

5.1.4 Describe what is meant by a food chain, giving 3 examples, each with at least 3 linkages (four organisms). Describe: Give a detailed account.  Food chains are feeding relationships in which a carnivore eats an herbivore which itself has eaten plant matter.  Light is the initial/primary source of energy in a food chain.  Arrows indicate the direction of energy flow.  Food chains can be temporary and are generally not isolated (they are part of complex food webs).  Food chains only indicate qualitative relationships (who eats whom – do not tell you how many organisms you might find at each level).

5.1.5 Describe what is meant by a food web Describe: Give a detailed account  Food webs consist of interconnected (and sometimes temporary) food chains linked together in complex relationships.  We can construct food webs for terrestrial or marine environments.  We can deduce the trophic level of organisms within a food chain or food web.

5.1.6 Define a trophic level Define: Give the precise meaning of a word, phrase, or physical quantity.

Trophic Levels  Trophic levels are ‘feeding levels’ in a food chain.  Trophic Levels include primary producers, primary consumers, secondary consumers, tertiary consumers and quaternary consumers.  Although there aren’t a fixed number of trophic levels in a food chain, most food chains are quite short (for very good reasons).

5.1.7 Deduce the trophic level of organisms in a food chain and a food web Deduce : Reach a conclusion from the information given

5.1.8 Construct a food web containing up to 10 organisms, using appropriate information. Construct: Represent in graphical form. See Page 117 in Your Textbook Use the common names of organisms (red fox, oak tree) instead of just ‘fox’ or ‘tree’. Make sure the arrows are pointing in the direction of energy flow. At least one of the 10 organisms must be a primary producer. Include primary consumers, secondary consumers, tertiary consumers and quaternary consumers.

5.1.9 State that light is the initial energy source for almost all communities State: Give a specific name, value or other brief answer without explanation or calculation.

Explain the energy flow in a food chain Explain: Give a detailed account of causes, reasons or mechanisms.  Between each trophic level, there is an energy transfer.  Energy is neither created nor destroyed... But it can be changed from one form (light) to another (chemical energy, heat, etc.)  Because energy transfer is never 100% efficient between trophic levels, living systems need a continuous supply of energy.  90% of the energy is lost between trophic levels (as undigested food, waste, heat energy, muscular movements, metabolic processes).  Any energy that remains is ultimately passed to detrivores and saprotrophs (decomposers).  Because there is less energy available at higher trophic levels, there tends to be fewer organisms at those trophic levels.

State that energy transformations are never 100% efficient State: Give a specific name, value or other brief answer without explanation or calculation.

 Pyramids of energy illustrate the fact that energy transformations are never 100% efficient.  The width of the bars is proportional to the amount of energy available at that level.  Use the 10% rule. Approximately 10% of the energy passed from one trophic level to the next is stored (while 90% is ‘lost’). Pyramids of energy are representations of food chains

5.1.2 Explain reasons for the shape of the Pyramids of Energy Explain: Give a detailed account of causes, reasons or mechanisms.

Crash Course (s)

Explain that energy enters and leaves ecosystems, but nutrients must be recycled Explain: Give a detailed account of causes, reasons or mechanisms.

Nutrient Cycling and the Biogeochemical Cycle  Nutrients are chemicals found in the environment that are essential to life and required by all living things.  While energy continuously flows in one direction through an ecosystem, water and nutrients (carbon, oxygen, nitrogen, phosphorus, etc.) cycle (or are recycled).  Biogeochemical cycling: cycling between the atmosphere, hydrosphere and lithosphere (rocks and soil)  Without nutrient cycling, essential life chemicals would be essentially ‘locked-up’ and unavailable to living things.

5.1.4 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients in an ecosystem State: Give a specific name, value, or other brief answer without explanation or calculation.  Ultimately, both plants and animals depend on the actions of saprotrophic bacteria and fungi to RELEASE matter (nutrients) from dead organisms for reuse.  Recycling is an essential part of life as there is a limited supply of nutrients (chemical elements) required for life.  When organisms die, a succession of organisms will participate in the breakdown and recycling process.  Saprotrophs will release important compounds containing carbon, phosphorous and nitrogen into the air, soil and water. These nutrients can then be used by other organisms.