Let's learn a little bit about relationships in organisms! There are 2 main types of relationships between organisms - the predator/prey relationship and symbiotic relationships. Let's take a look at each:

Predator/Prey Relationship:

In this relationship, one organism is benefiting and the other is getting...well...killed. One organism plays the role of the predator, which depends on the other - the prey - for food. The prey is not usually happy about this! Food chains and food webs are based on this important relationship though - it is the way that organisms survive and the way that energy is passed from one organism to another.

We've talked about this in class so this shouldn't be new information! But just as a recap, go to http://www.vtaide.com/png/foodchains.htm , read through and scroll all the way to the bottom. See the link that says 'Food Chain Movie'? Go ahead and click it to get a refresher course on food chains and the predator prey relationship that they all depend on. Make sure you have your headphones on! When you're done with the movie, take the quiz for some extra practice!

Symbiotic Relationships:

A symbiotic relationship is a relationship that involves two organisms that share resources, sometimes in a good or a bad way. A symbiosis is a close relationship between species. There are three main types of symbiosis found in nature. Check them out!

Mutualism: In a mutualistic relationship, both organisms benefit from the relationship. For example, take a look at lichen. Lichen is actually two organisms living together - an algae or cyanobacteria (blue bacteria) living inside a fungus. The fungus provides a safe home for the bacteria or algae and because the bacteria or algae perform photosynthesis, they provide food for the fungus. See? Both organisms are getting something good out of the relationship they have with each other.

Commensalism: In commensalism, one organism is benefiting while the other is unharmed or benefited. For example, a woodpecker living inside of a tree. The woodpecker gets a safe home where it can raise its young while the tree isn't really harmed just because the woodpecker is living inside of it. The tree isn't hurt when a woodpecker lives inside of its trunk. That's commensalism.

Parasitism: When one organism is benefiting but the other is being harmed, that's parasitism. Take a tapeworm for example. If a tapeworm is living inside of an organism, such as an organism, the tapeworm is in heaven. It has a warm, wet home where food is constantly coming in and it can just grow and grow. Meanwhile, the organism that it is living inside of is getting sick - losing weight, vomiting, in pain and getting more and more sick as the tapeworm gets larger. That's parasitism.


So there are your two types of relationships.