Food Chains and Food Webs PDF

1.3 Food Chains and Food Webs  Learning Goals Build food webs and food chains Identify what trophic level an organism belongs to Determine the impact on the food web of removing or adding an organism  What do these organisms have in common? They’re all...

1.3 Food Chains and Food Webs  Learning Goals Build food webs and food chains Identify what trophic level an organism belongs to Determine the impact on the food web of removing or adding an organism  What do these organisms have in common? They’re all CONSUMERS! Spiny Softshell Turtle White Tailed Deer Green Heron  What do these organisms have in common? They’re all PRODUCERS! Moss Sugar Maple Tree Ostrich Fern  What do these organisms have in common? They’re all DECOMPOSERS! Chicken of the Woods Fungi Lichen  Producers Most producers make their own food from the sun through photosynthesis CO2 + H2O → C6H12O6 + O2 The energy is stored in the bonds of the glucose molecule  Consumers Need to consume (eat) other organisms to get the energy they need to survive Consumers/Heterotrophs An organism that gets its energy from other organisms. Herbivore: an organism that ONLY eats plants or other producers. a. Example: panda, giraffe, rabbit Carnivore: an organism that ONLY eats animals. a. Example: lion, lynx Omnivore: animal that eats BOTH plants and animals a. Example: humans, dogs Scavenger: animal that eats on remains of other organisms a. Example: vultures Decomposers/Detritivores Decomposers or Detritivores are organisms that feed on organic matter Organic matter is the remains of dead organisms or animal waste Food Chains The most common interactions between species are through feeding relationships. The easiest way to display these relationships is with food chains. Food chains illustrate who eats whom in an ecosystem.  Food Chains and Food Webs There may be multiple consumers that feed on each other Their ‘rank’ (primary, secondary, etc.) tell us where they are in the food chain → Arrows in Food Chains & Webs ← Arrows point TOWARDS the one doing the eating The arrows represent energy flow What’s the Mistake? What’s the Mistake?  Trophic Levels Organisms in the ecosystem are often classified according to which level that they feed at compared to the producers in the ecosystem An organism’s feeding level may change depending on food sources available and predators Ecologists refer to the trophic level, or feeding level, to describe the position of an organism along a food chain.  TROPH Trophic Levels Meaning: to nourish Tertiary consumers: store 10% of the energy from the secondary consumers Secondary consumers: store 10% of the energy from the primary consumers Primary consumer: store only 10% of the energy of the primary producers Primary Producers: store the most energy  The 10% Rule Each trophic level in an ecosystem only transfers 10% of its energy to the level above it. This limits the number of trophic levels an ecosystem can support This explains why there are more organisms at the bottom of a trophic pyramid than at the top.  Role of Decomposers ♻ the energy and matter from dead organisms Typically left out of food webs & food chains because eventually ALL arrows would point to them  Food Webs Food chains do not exist in nature. They are only used to show simple feeding relationships. Food chains are part of more complex set of relationships that exist among species. A more accurate, but still incomplete, way to illustrate interactions is with a food web. A food web shows a series of interconnecting food chains.  What is a food web? All the food chains in an ecosystem put together Shows all the relationships between the living organisms in an ecosystem What’s the Mistake?  Food Webs Food webs are useful tools to figure out what may happen when a species is removed from or added to an ecosystem.  What would happen if all the wolves were removed?  What would happen if the population of sugar maple decreased?  Invasive Species in Food Webs For example, the invasive rusty crayfish (labelled in red) competes with native crayfish for many of the same foods. It also feeds on the eggs of bass and pickerel. Large fish feed on native crayfish but usually avoid eating the rusty crayfish.