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We love Disney movies and we have to say---Lion King is one of our favorites. And like a lot
of Disney movies, it has a happy ending. We’re not going to give spoilers just in case you
are one of the few people left in the world that hasn’t seen the Lion King--- go see
it ---but at the end of Lion King, you start to see all this life growing back. The sun
comes out and all these plants start growing. Happy music plays. The animals that had disappeared
start to come back! I never really understood where they went but…they come back!
And being a biology teacher, everything is destined to have a biology reference. So here’s
what it reminds me of: ecological succession. Although, the movie is kind of like ultra
fast impossible ecological succession. It’s not that fast in real life.
Most dictionaries define succession as the following of one person or thing after another
in an order or sequence. Well ecological succession is that but in terms of ecology. Ecological
succession is a process---over time--- of organisms in an ecological community. What’s
a community?
Well in ecology, we have different levels of organization. We have a living organism
as our first level. A hippo for example. Then we have a population, which is when you have
the same species of an organism in a given area. For example, a population of hippos.
Same species so that’s one population. Then we have a community. A community includes
many populations living together in a particular area. So now we have hippos, lions, giraffes,
and don’t forget plants because those are populations too. Trees and…shrubs. All of
this together is a community. That’s where we are going to focus for succession. There
are more levels beyond the community level, but this is our focus right now.
There are two types of succession that we will talk about. One is called primary succession.
In primary succession, the area this is happening in is brand new---well in the sense that you’re
usually talking about an area that doesn’t have any soil. So this usually has to be a
special circumstance. An example could be a volcano lava flow that now has left this
new area with no soil present. Usually you have a pioneer species, which is a name for
the species that colonize first. It sounds exciting…pioneer species in primary succession
can be organisms like lichen. Who doesn’t like lichen? Ha…if you are unsure about
what lichen is…google it! It’s very likely you’ve seen lichen before. Moss is another
potential pioneer. After pioneer species colonize the area, they slowly break down rock into
smaller, more plant friendly substrate---and over time, contributing more organic matter
in newly formed soil which will support plants. Small vascular plants like grasses and plants
that you might consider “weeds” can come in. Shrubs can follow. Then trees. Animals
can move into the area. How long this takes can vary…but it’s often hundreds of years
before you get a climax community going. And if you’re wondering---why this sequence?
Why doesn’t it just stop with grass? Well, keep in mind that as other plants come in…bigger
plants…you are going to see more competition for space and resources. Think about how it
would be by the time trees come in! Trees are going to block some of the light that
small plants underneath them may be dependent on. As new larger plant species come in, this
competition brings about a new order. And if you are wondering---where did these plants
even come from? Well there are so many ways that seeds can be dispersed---wind, water,
animals. Check out our plant reproduction video for more information about how these
plants could have actually come into the area.
Now for secondary succession. Similar to primary succession, it follows a typical ecological
sequence. With secondary succession---I like to think second---because it’s like a “coming
back again a second time.” What I mean by that is usually you’re talking about an
area that once had plants and animals and a full ecological community going on. But
then we had a disturbance…an ecological disturbance…like a forest fire, a flood,
a tornado. Actually it doesn’t have to be a natural disaster---human activity can be
involved with secondary succession. Regardless of the type of event, in secondary succession,
the soil is still there and that’s kind of the big key point here, because your pioneer
species will actually have soil to grow in. That means your pioneer species in secondary
succession will often be small plants as there is already soil present. Secondary succession
will then follow a similar sequence to primary succession after that point. Since secondary
succession involves soil already being available, it is more likely to be a faster process than
primary succession.
An important thing to remember about ecological succession is that it really shows the diversity
of organisms---the sequence we had talked about--- in an ecological community over a
period of time. Usually a long period of time. Ecological succession, over time, can support
an ecological community that continues to increase in biodiversity. And, biodiversity
is a beautiful thing. That’s it for the amoeba sisters and we remind you to stay curious!