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Big on Biology A different kind of World Wide Web 9-12 Science Std: Bio 6f.

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Presentation on theme: "Big on Biology A different kind of World Wide Web 9-12 Science Std: Bio 6f."— Presentation transcript:

1 Big on Biology A different kind of World Wide Web 9-12 Science Std: Bio 6f

2 Food Chains and Webs  Food chain: step-by-step sequence that links together organisms that feed on each other o Ex: bat ate a mosquito that had bitten a coyote that had eaten a grasshopper that had chewed a leaf

3 Different Food Chains Terrestrial (Land-Based) Marine (Water-Based)

4 o Food chain supposes that organisms eat only that one particular organism  We know that organisms can eat more than one type of organism  Makes links to different organisms to create more realistic picture of a food web  Food web: complex relationship formed by interconnecting food chains or feeding relationships signified by arrows



7 Organisms in the Food Web  Two types of organisms based on where they get their energy (food): o 1. Autotrophs o 2. Heterotrophs

8 o1. Autotrophs: organisms capable of obtaining their energy from environment  Most get energy from photosynthesis when sunlight on plants makes sugar  Are called producers since they produce (make) their energy  Ex: all plants, phytoplankton, some bacteria

9 Aquatic Producers

10 o2. Heterotrophs: organisms that obtain energy from autotrophs or other heterotrophs  Are called consumers since they consume (eat) their energy  3 different kinds of consumers depending on where they feed in food web:  1. Primary consumers  2. Secondary consumers  3. Decomposers

11  1. Primary (first-order) consumers: feed directly on autotrophs  Eat plants only so are considered herbivores (herb/plant eaters) Ex: mice, rabbits, deer, cows Cows are primary consumers because they eat only plants (producer autotrophs)

12 o2. Secondary (second-order) consumers: feed on primary consumers  Eat animals only so are considered carnivores (meat eaters) Ex: owls, lions, tigers

13  Some secondary consumers can also be primary consumers since they are both herbivores and carnivores so are called omnivores Ex: humans, bears

14  3. Decomposers: feed on remains or bodies of all organisms to make energy  Ex: bacteria, fungi (mushrooms), some insects

15 Food Chains All Have Decomposers that Can Feed on Any Member of a Food Chain


17 Alternative Pathways Maintain Stability in Food Webs  Having alternatives to eat can help stability of food web o Ex: if rabbits in some areas decrease in population, owls won’t starve, they can focus on mice  Less rabbits – more grass - more mice since more places for mice to hide in  If owls focus on mice, rabbit numbers have a chance to increase  Food web stays stable since numbers of all organisms will always go back to original

18 Maintaining Stability EAT Owl can eat rabbit or mouse

19  Worldwide problem has arisen: land to grow producers is being taken over by urban cities o As human population grows, need more food to feed them, and according to food webs, all human food starts at producers

20  No land means producers can’t grow  No primary consumers will survive  No secondary consumers will survive  No decomposers will survive

21 Deforestation

22 Questions?

23  The removal of one part from an ecosystem, like the removal of a moving part from a car’s engine, can cause the collapse of an entire food chain.  In a food chain, there are predators and there are prey.  Prey – the organism that could be eaten by another organism  Predator – the organisms eating other organisms

24  Ex.: Cat = Predator Mice = Prey

25  A food chain is a series of predators and prey  Ex: Coyote  Dog  Cat  Mice  bread crumbs (wheat)

26  Predators keep the prey population in check.  The prey keep the predators alive by providing food. predator prey

27  Ex. Pacific Sea otters mainly eat sea urchins and sea urchins eat kelp (form of seaweed) and little fish hide in the kelp


29  Hunters used to kill sea otters for their fur. As a result, the number of sea urchins rapidly increased. As the number of sea urchins grew, the amount of kelp went down.  The fish that relied on the kelp for shelter and food also decreased in number.  So killing the sea otters for their fur (nearly becoming extinct), affected sea urchins, which affected the kelp, which affected the fish. (DOMINO EFFECT!!)


31 Restoring the Balance Is a Difficult Task  Can the “Domino Effect” be stopped? o Yes! The sea otter was reintroduced (more brought back in) which caused the sea urchin population to get smaller because they are being eaten. o The kelp bed have increased and so the number of fish are increasing too. o This has “restored the natural balance” of the food chain  This is not always easy to do.

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