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Science  10:  Energy  Flow  

 

Science  10:  Biology!     Energy Flow & Trophic Levels (Ch 2.1, 2.2, 2.4)    

        :  a  thin  layer  of  atmosphere,  land  and  water  in  which  all  life  is  found  on  Earth.      Biotic  factors  (components)  are           .    

Example:    

Abiotic  factors  (components)  are         .       Example:  

 Large  regions  that  contain  many  ecosystems  with  similar  abiotic  and  biotic  components  are  called       .      A. Practice Questions: Textbook (2.1) p.24 #1-3                    Organisms  interact  with  ecosystem  in  two  ways:  

1.               FROM  ecosystems    

2.              TO  ecosystems    The  transfer  of  energy  from  ecosystems  to  organisms  and  between  organisms  is  called  energy       .   Producers  (aka         )  produce  energy.    Plants  are  producers  because  they  produce  carbohydrates  during           .    Consumers  (aka         )  consume  energy.    Consumers  can  also  be  an  energy  source  for  another  consumer.  

•          eat  plants  (e.g.  grasshopper)  •          eat  consumers  (e.g.  wolf)  •          eat  consumers  and  producers  

(e.g.  black  bear)    But where does this energy flow really start…?      Food Chains and Food Webs  Food  chain:  model  showing  the  energy  flow  from                and                 .      This  energy  flow  can  also  be  represented  by  food        or  food         .    Trophic  level:            in  the  food  chain.  

60 MHR • Unit 1 Sustaining Earth’s Ecosystems

Food chains and food websFood chains are models that show the flow of energy from plant to animaland from animal to animal (Figure 2.6). Each step in a food chain is called atrophic level. Trophic levels in a food chain show the feeding and nicherelationships among organisms. Since plants and phytoplankton such asalgae are the producers, they are at the first trophic level and are referred toas primary producers.

Figure 2.6 A terrestrial foodchain and an aquatic foodchain show the flow ofenergy up the trophic levels.

In Figure 2.6, you can see that primary consumerssuch as grasshoppers and zooplankton (microscopicaquatic animals) are in the second trophic level. Theyobtain their energy by eating primary producers.Secondary consumers such as frogs and crabs are inthe third trophic level and obtain their energy by eatingprimary consumers. In the fourth trophic level aretertiary consumers such as hawks and sea otters thatfeed on secondary consumers to obtain energy.

When ecologists discuss the diet or behaviour oforganisms in a food chain, they often use the termsdetrivores, herbivores, and carnivores. In terrestrialecosystems, detrivores include small insects,earthworms, bacteria, and fungi (Figure 2.7). Figure 2.7 Detrivores in this forest ecosystem include

carpenter ants, pill bugs, snails, and mites. Unseen aredecomposer bacteria that vastly outnumber these detrivores.

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Science  10:  Energy  Flow  

 Trophic  Level   Example   Name  of  Type  of  Organism   Energy  Source  

4th   Top  carnivores:  hawks,  sea  otter   _________________  Consumers  (TC)   Obtain  energy  from  ___________  

3rd   Carnivores:  frogs,  crabs   _________________  Consumers  (SC)   Obtain  energy  from  ___________  

2nd   Herbivores:  grasshopper,  krill   _________________  Consumers  (PC)   Obtain  energy  from  ___________  

1st   Plants:  grass,  algae   __________________  Producer  (PP)   Obtain  energy  from  ___________  

 At the end of the chain (the tertiary consumer), where does the energy go…?                                              digest  detritus  (dead  animals  and  plants  and  waste)  (e.g.  earthworm  &  fungus)    Decomposers:  break  down          and               ,  changing  them  into  usable  nutrients.    This  is  called             .    What  are  examples  of  decomposers?    What  happened  to  this  leaf?    Where  did  the  rest  of  the  leaf  go?  

    B. Practice Questions: Textbook (2.2) p.29 #2-4, 7, 11  C. Practice Questions: Textbook (2.4) p.37 #1, 2, 4, 5, 7-9, 12

Chapter 2 Energy flow and nutrient cycles support life in ecosystems. • MHR 61

Figure 2.9 Bighorn sheep (A) and western tiger swallowtail butterflies (B) are herbivores.

A B

Detrivores are consumers that obtain their energy and nutrients byeating the bodies of small dead animals, dead plant matter, and animalwastes. Detrivores feed at every trophic level (Figure 2.8) and make uptheir own important food chains. In fact, food chains based on deadplant and animal matter actually outnumber food chains based on livingplants and animals. Detrivores such as earthworms and beetles are also animportant energy source for consumers such as birds.

Herbivores, such as grasshoppers, are primary consumers that eatplants. Carnivores, such as spotted frogs, are secondary consumers thateat primary consumers. Carnivores also eat other secondary consumersand are often at the tertiary level of a food chain. Carnivores at this levelare often referred to as top carnivores, top consumers, or top predators.Figure 2.9 and Figure 2.10 on the next page show more examples ofherbivores and carnivores.

first trophic level

primary producers(plants)

secondtrophic level

primary consumers(herbivores)

third trophic level

secondary consumers(carnivores)

fourthtrophic level

tertiary consumers (top carnivores)

Figure 2.8 Detrivores feedat every trophic level.

detrivores and decomposers

energy fromthe Sun

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Science  10:  Energy  Flow  

 Science  10:  Biology!      Ecological Pyramids (Ch 2.5)  

 There  are  three  types  of  ecological  pyramids  (or  food  pyramids).    1.  Pyramid  of  Energy:  a  model  that  shows  the        of  energy  from  one  trophic  level  to  the  next.      *This  is  the  most  commonly  used  ecological  pyramid.  Since          %  of  the  energy  is  lost  between  each  trophic  level,  ecosystems  support       -­‐many              

  -­‐less              

  -­‐far  less            

  -­‐very  few              

 2.  Pyramid  of  Numbers:  a  model  that  shows  the  total  number  of  organisms  in  each  trophic  level.    

                     

3.  Pyramid  of  Biomass  Biomass:  the  total  mass  of          and            organisms  (plants,  animals,  fungi  and  microorganisms)  in  a  certain  area.  *The  biomass  of  plants  on  Earth  is  >100  x  greater  than  the  biomass  of  animals.    

     D. Practice Questions: Textbook (2.5) p.41 #1-7, 9, 13

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Science  10:  Energy  Flow