PDCN/Web of Life Part 1: HINTS!!! (5/7/15)

Relationships:  What counts as an interaction and what doesn’t?

Hints for completing Part 1 of the PCDN/Web of Life


Ecosystems are made of living things, nonliving things and their interactions.  Interactions between the factors in an ecosystem might be simple: eating, mating, fertilizing, pollinating.  They may be more complex: competition, affecting shared habitat, providing shelter.  Some relationships are direct while others are multistep – organisms who never meet can still interact indirectly!  Below are some examples that might help give ideas for tonight’s homework.  Students should research their assigned factor to make sure they are providing a true possible interaction.   


Here are some examples of interactions between living things and living things in a sample ecosystem:

Feeding/Predator-Prey Interactions

A red-tailed hawk preys on and eats a robin.

A blue jay eats the eggs of the robin.


Habitat and shelter interactions

A robin uses the tree as a place to build its nest.

A robin sits in the branches of the red maple tree to sing its territorial song.


Service, parasitic, or competitive interactions

A mosquito pollinates a wild violet.

A mosquito draws blood from a squirrel.

A wild violet covers grass with its leaves and outcompetes it for sunlight.


Multistep/indirect interactions

A squirrel plants an acorn, and later a red-tailed hawk sits in the oak tree that grew from the acorn.

A mallard duck’s feces add nutrients to the soil.  The nutrients fertilize the wild violet which is pollinated by the mosquito.


Here are some examples of interactions between living things and nonliving things in a sample ecosystem:


Energy and matter exchange

The sun provides light so a wild violet can do photosynthesis.

A red maple tree does photosynthesis and gives off oxygen.

A red-tailed hawk does cellular respiration and breathes out carbon dioxide.

A mallard duck’s feces add nutrients to the soil.


Service and shelter interactions

The wind blows pollen from grass to other grass plants so it can be pollinated.

A roly-poly finds shelter under a rock.


Here are some examples of interactions between nonliving things and nonliving things in a sample ecosystem:


Energy and matter exchange.

The sun warms a rock.

Wind blows dry soil and causes erosion.

A rock breaks down into nutrients in the soil.

Sun causes water to evaporate.


More complex/Multistep/indirect interactions

The sun allows a plant to do photosynthesis and in turn give off oxygen which is breathed in by the blue jay.





A similarity is NOT the same as an interaction. 

“Squirrel and bird interact because they both breath air.”  – They are not competing for air (there is enough to go around) so this is not an interaction.  This is just something they have in common.

Being in the same place does not guarantee interaction.

“Grass and violet are in the same place.”  – Being in the same place does not guarantee interaction is happening.  If they are competing for soil or pollinators, they are interacting, but this statement as it is is not a good enough answer.


Other notes:

  • Answers should be written right next to the factor on the worksheet.  Complete sentences are not required, but I must be able to understand the meaning of your answer without asking.
  • You are relating everything to YOUR term, not to the other terms on the page.  This is a story about YOUR factor.
  • I don't expect you to start out as an expert about your factor - but I DO expect you to look them up and find out more!  If you have something living - What does it eat? Where does it live? What eats it?  If you have a nonliving factor - What chemical processes is it involved in?  How does it cycle through the ecosystem?  Knowing about your factor will help you make connections! 
  • You do not have to put the relationship into one of the above categories.  Just write a way they could interact.
  • Finally, YES some interactions will make you think!  That is a GOOD thing.  DON'T GIVE IN AND QUIT!  Show me all 35 relationships tomorrow!