Topic 5: Ecology and evolution 5.1 Communities and ecosystems IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko ASSESSMENT STATEMENTS 5.1.1 Define species, habitat, population, community, ecosystem and ecology. 5.1.2 Distinguish between autotroph and heterotroph. 5.1.3 Distinguish between consumers, detritivores and saprotrophs. 5.1.4 Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms). 5.1.5 Describe what is meant by a food web. 5.1.6 Define trophic level. 5.1.7 Deduce the trophic level of organisms in a food chain and a food web. 5.1.8 Construct a food web containing up to 10 organisms, using appropriate information. 5.1.9 State that light is the initial energy source for almost all communities. 5.1.10 Explain the energy flow in a food chain. 5.1.11 State that energy transformations are never 100% efficient. 5.1.12 Explain reasons for the shape of pyramids of energy. 5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled. 5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.1 Define species, habitat, population, community, ecosystem and ecology. Species: a group of organisms that can 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 environment. Ecology: the study of relationships between living organisms and between organisms and their environment. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.2 Distinguish between autotroph and heterotroph. Autotroph: an organism that synthesizes its organic molecules from simple inorganic substances. Heterotroph: an organism that obtains organic molecules from other organisms. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.3 Distinguish between consumers, detritivores and saprotrophs. Consumer: an organism that ingests other organic matter that is living or recently killed. Detritivore: an organism that ingests non-living organic matter. Saprotroph: an organism that lives on or in nonliving organic matter, secreting digestive enzymes into it and absorbing the products of digestion. LINK LINK IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.4 Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms). Very few animals feed on only one kind of organism and very few have only one predator. So a food chain often shows only a section of the feed relationships that exist. A food web will include more of these relationships and will show a more accurate representation of the very complex interactions between species. In reality, even food webs rarely show all relationships since this would make the web too complicated. LINK IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.4 Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms). A→ B indicates that A is being “eaten” by B (that is, the arrow indicates the direction of energy flow) Terrestrial food chain Marine food chain Woodland food chain IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.6 Define trophic level. The trophic level is the position of the organism in a food chain. Producers are on the first trophic level, primary consumers on the second. 4th 3rd 2nd 1st IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.7 Deduce the trophic level of organisms in a food chain and a food web. It is rather simple to deduce trophic levels from a food chain. The autotrophs are always the producers, the herbivores the primary consumers, the ones who eat the herbivores the secondary consumers and the ones who feed on the last the tertiary consumers. To deduce the level from a food web is more complex as you can notice from the image below. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.8 Construct a food web containing up to 10 organisms, using appropriate information. Use PowerPoint to construct a food web, making sure the detritivores and at least one of all trophic levels is included. Producers are usually shown at the bottom, full names of organisms should be used and the arrows show the movement of matter. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.9 State that light is the initial energy source for almost all communities. The first trophic level of any community consists of the producers or autotrophs. They use the energy from light to fix carbon dioxide, i.e. use light energy to produce (large) organic molecules from simple inorganic molecules such as carbon dioxide. Then it is used, directly or indirectly, by other organisms in the community as a source of energy. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.10 Explain the energy flow in a food chain. In order to obtain food, chew and digest it, energy is required. Animals also use energy to breathe, move and keep warm. So a lot of the energy that is taken into the organism, will be used by this organism and will not be available to the next trophic level. As a very rough average, we can expect around 10% of the ingested energy to be available for the next trophic level; the other 90% is used by the organism itself. As the food chain becomes longer, more energy is needed at the first trophic level (producers) to sustain the top consumer(s). IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.11 State that energy transformations are never 100% efficient. When energy is changed from one form into another, the transformation is never 100% efficient. This means that some energy will be changed into a form other than the intended form and will usually not be very useful. The energy lost to the environment as heat needs to come from the food that the organism eats. This helps to explain why birds and mammals, which have a constant body temperature, need to eat much more per kg body mass than, for example, reptiles which do not. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.12 Explain reasons for the shape of pyramids of energy. A pyramid of energy is a graphical representation of the amount of energy of each trophic level in a food chain. The units are kJ/m2/yr. The pyramid will never be inverted since it is based on the amount of energy per unit area that flows through the trophic level of the food chain in a given amount of time. In order to produce a pyramid of energy, it is necessary to find out how much energy an organism contains and how many organisms there are in a trophic level. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko What would this look like if we were all vegetarians? IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled. Energy enters the system as sunlight. Some of it is absorbed and stored in products of photosynthesis by autotrophs. Then it is gradually used as these products make their way through the trophic levels. Finally all energy captured in chemical bonds will have been changed to other forms of energy which cannot be passed on. So energy is NOT recycled through the ecosystem. The earth constantly receives energy from the sun and also constantly radiates out energy in the form of light and heat. The earth, however, does not receive nor send out matter on a regular basis. This means that nutrients must be recycled through the ecosystems. The process of recycling nutrients requires energy. IB Biology SFP - Mark Polko

IB Biology SFP - Mark Polko 5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients. All living things produce organic waste during their life. Somehow, the organic nutrients need to be returned to the soil as inorganic minerals to allow the cycling of elements to start again. Various names are used relating to the group of organisms involved in this cyclical process. Decomposers are organisms that obtain their energy from dead organisms. Two main groups are detritivores (e.g. earthworms and dung beetles) and saprotrophs (e.g. fungi and bacteria). Saprotrophs absorb soluble organic compounds while detritivores ingest (parts of) dead plants or animals. These processes are essential for the cycling of nutrients. LINK IB Biology SFP - Mark Polko

Topic 5: Ecology and evolution 5.1 Communities and ecosystems IB Biology SFP - Mark Polko