Ostriches and gazelles eat together.  They both watch for predators and danger.  Since they see things differently, they each can identify threats the other animal may not see.  Both species are benefited.  

• mutualism
• commensalism
• predation
• parasitism

Yucca flowers are pollinated by yucca moths.  The moths lay their eggs in the flowers and the eggs hatch. The larvae eat some of the seeds, and  spread them around.  Both species are benefited.

• mutualism
• commensalism
• parasitism
• competition

Mistletoe takes water and nutrients from the oak tree. This is good for the mistletoe but bad for the tree.

• mutualism
• commensalism
• parasitism
• competition

A bison walks through the grass, insects fly up and are seen and eaten by egrets.  This neither harms nor helps the bison, but it is easier for the egrets to get food.

• mutualism
• parasitsm
• commensalism
• competition

A flea feeds on a mouse’s blood.  This is good for the flea but bad for the mouse.

• mutualism
• commensalism
• parasitism
• competition

Hermit crabs live in shells that snails don't use anymore. The hermit crab gets a nice free home.  This neither harms nor helps the snails.

• mutualism
• commensalism
• parasitsm
• predation

Birds build nests out of dead twigs and leaves.  They build their nests in living trees.  This doesn't hurt the tree.

• mutualism
• commensalism
• parasitism
• predation

In this food web, the grasshopper and the mouse have this relationship:

• mutualism
• commensalism
• competition
• predation

in this food web, the lizard and the hawk have this relationship

• mutualism
• commensalism
• predation
• parasitsm

In this food web, the snake and the mouse have this relationship

• mutualism
• commensalism
• predation
• parasitsm