Ecological Relationships

Captions are on! Click CC at bottom right to turn off. Hear updates by following us on Twitter (@AmoebaSisters) or Facebook! 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 together. 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 host. 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 example. See, some species of acacia trees form these
hollow thorns which provide housing to acacia ants. 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? Protection. 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.

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