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I really did not like sandboxes as a kid.
It’s not that I have a problem with sand or sand on the beach for sand castles.
Just sand boxes.
See, as a little kid, I’d play with something, then I’d kind of forget about it--- and
then rediscover it and it’d be all new again.
This is what happened with my sandbox.
Except when I rediscovered my sandbox, the sand had all these tiny holes.
My dad was with me and exclaimed, “Why look at that, your sandbox is full of antlions!”
Perhaps my dad should not have assumed that I knew what antlions were.
I eventually figured out what they were, later on, and it makes sense now because my father
really loves insects.
Antlions are insects.
In their adult form they sort of look—in my personal opinion---like a less cool version
of a dragonfly- they are not a dragonfly.
But in their larvae stage- they look---well like not many things I can compare it to.
They have these mandibles and they make these sand pit traps.
And then they wait with their mandibles just showing above the surface.
When an ant or other small insect walks over their sand pit, they drag it in.
They pull the ant underground, biting it and injecting it with enzymes to digest it, in
order to consume the ant’s juices.
I also have learned, by watching them, that they toss sand at their ant victim too if
they need help subduing it before they drag them under.
Thankfully, antlions are small.
In fact, ‘doodlebug’ is evidently another name for these things---I’m not exactly
sure how you go from antlion to doodlebug---but okay.
It’s all relative; they’re bad news for an ant.
Because the antlion is a predator of the ant.
The ant is their prey.
That’s an ecological relationship right there.
And that’s what we’re going to talk about---ecological relationships.
Typically if we were to graph the predator and prey populations in our example---when
the population of ants in this confined area increase, it is likely that the antlions---which
are the predators---also will increase over time because they have more food to eat.
However, if the antlions increase too much, there won’t be enough ants---which are the
prey----to feed on.
So the antlions will decrease.
You can see that relationship in this predator and prey graph.
In most ecosystems, predator and prey graphs go up and down frequently---it cycles.
Also, just because this antlion is a predator doesn’t mean that this is the only role
it plays.
An antlion can get eaten by a bird.
Now the antlion has just become the bird’s prey.
Competition is also another relationship to consider.
Antlions are consumers which means that they have to eat other things- they can’t make
their own food.
They have to compete with other antlions for this food too, this food being their prey:
the ants.
This example shows competition for a limiting biotic factor.
And they’re not just competing with other antlions for this biotic factor--- they may
have to compete with completely different species in the area that are also predators
of ants too.
For example, jumping spiders like ants.
You know…it’s not just consumers that compete!
Producers, like this plant, make their own food---but that does not mean they don’t
have to deal with competition.
For example, this plant here is competing for this limiting abiotic factor: light.
Symbiotic relationships are specific types of relationships where different species live
Parasitism is an example of a symbiotic relationship where one organism benefits and the other
is harmed.
An example?
Well, you know, I love dogs- Petunia is the cat person.
When my family took in our rescue dog---she was 4 months old at the time--- we learned
from the vet that she would need to be treated for fleas and hookworms.
We were able to give her medicine to treat these parasites---a good thing---because these
parasites can hurt the dog by feeding on their blood.
A parasite is an organism that gets its nutrients from another organism and causes harm to its
They can live inside or on their host.
Mutualism is an example of a symbiotic relationship where both organisms involved benefit.
You really need to look up a video about acacia ants and acacia trees because this is a fascinating
See, some species of acacia trees form these hollow thorns which provide housing to acacia
Some species even provide a nectar for food for these ants.
So with a great home and potentially free food, what does the tree get in return?
I’d hate to be a type of consumer that eats acacia trees because if it has acacia ants,
the ants will come out of the thorns and attack the consumer.
They’ll even destroy plants that try to try to grow close to the acacia tree so the
ants can eliminate the tree’s competition.
Nice mutual relationship between the acacia tree and the ant.
The last symbiotic relationship we’ll mention is commensalism.
This one is interesting, because in this relationship, one organism benefits and the other is neither
helped nor harmed: it has a neutral effect.
Some species of barnacles and whales are a great example.
Many barnacle species can attach themselves to moving things, like a boat…or a whale.
On a free whale ride, the barnacles get a lot of access to food since they are filter
feeders, and the whale may travel to nutrient rich waters.
In this particular example, the barnacles benefit but neither help nor harm the whale
so this would be commensalism.
But I do like to remind my students that sometimes there is more to the story with a relationship
labeled as commensalism and sometimes what we thought was a completely neutral effect-
may not always be in every case.
So why do all these relationships matter anyway?
Well, ONE reason is that these interactions can make significant impacts on populations
of different species living together.
That means if the population of a certain species is threatened by human activity for
example, it can affect more than just that one species.
Scientists continue to learn about new ecological relationships all the time.
Well that’s it for the Amoeba Sisters and we remind you to stay curious.