Sunday, March 14, 2010

6 Weeks Left to Earth Day! Week 11: Keystone Species!

Spending time in Florida has allowed me to gain new respect for one of its most famous residents, the alligator!  These prehistoric reptiles are quite remarkable, and when you see them up close (not too close!) they give us a glimpse into a past Earth, when dinosaurs ruled the land!

I learned that alligators are important because they are a keystone species; what is a keystone species?  I rather like this explanation, courtesy of: Bagheera
“A keystone is the stone at the top of an arch that supports the other stones and keeps the whole arch from falling.  A keystone species is a species on which the persistence of a large number of other species in the ecosystem depends.  If a keystone species is extirpated from a system, the species it supported also will disappear, as will the other dependent species.”  You can read the full description on their website.

Inhabiting the swamps, ponds, creeks, rivers and shallow lakes of Florida, Louisiana, Mississippi, Alabama and Georgia, alligators play an important role in shaping the landscape.  During the dry season, alligators swish their tails around in shallow pools to make “gator holes”; deep holes which retain water when there is little rainfall thus providing a vital drinking reservoir for many other species.

The favored food source for alligators is fish, crabs, birds, snakes and small mammals such as rabbits.  They are carnivores with extremely strong jaws that can easily crack a turtle shell.  Lurking just below the surface of the water, looking rather like a submerged log, alligators wait patiently for their prey.  When they do strike, it is with lightning speed and ferocious precision.  However, they do not have to eat all the time, and one good meal for a healthy alligator can last for a few days, weeks or even months.
Female alligators build their nests beside the water, using plants and leaves. When the time is right, they deposit up to 50 eggs into the nest and cover them with vegetation; they do not sit on their nests like birds.  It is fascinating to note that the sex of the babies is actually determined by the heat of the nest!  If the nest is extremely hot, the babies will be all male; if the nest is cooler, all female; and if the nest is temperate, there will be a mix of both sexes!

Lesson Plans
1.  Learn what a Keystone Species is; lessons obviously dependent upon the age group. With young children you could begin with the alligator. Explore which other species depend on the alligator keeping the ponds open during the dry season – turtles and wading birds are an example.  What would happen to those species if the alligator was not there and the ponds dried up?  This Video shows how alligator mother’s care for their young.
2.  For Grade 6-8 here is a selection of National Geographic Lesson Plans on Keystone Species and another Plan for Grades 3-5. 
3. Explore some other kinds of keystone species.  For example, Prairie Dogs dogs,  or wolves; learn how wolves play a Key Role in maintaing the health of ecosystems of Yellowstone National Park.
4.  Find out which is a keystone species in your area of the world.  Remember that Keystone species are not just important to wild animals or plants, they are also important to us!  For example, Salmon is a keystone species for fishermen in Alaska and the Pacific Northwest.  Make this into a geography lesson and explore species around the world and see how humans also are impacted by their health.  Everything is interconnected and it is important that students understand this.

The interactions between a keystone species and others in clearly evident in the example of the wolves and Yellowstone National Park.  Once you have discovered which species is key to your local ecology invite students to list all the species that are dependent on it.  A very easy one that is pretty much everywhere would be bees! Without bees we would lose a whole host of plants upon which we, and other species depend. Here is a short Video about bees.

Green Action of the Week
Once you have discovered which species in your neighborhood is key to all others, then create an action to help protect it.  For example, if you decided to help bees, find out which wildflowers are native to your region and plant some.  See if you could begin a petition to ban pesticides locally or nationally – bees and so many other important insects are negatively affected by many common pesticides used in landscaping.

I have uploaded the  Alligator Rock! for this post – you could also use the Coral Reef song since corals are a keystone oceanic species.

Have a great time discovering keystone species and please let me know which species is key in your area!  
In gratitude for life, and this Earth!

Elephants as a Keystone Species
Bullfrog Films has a Video about Keystone Species
Learning about Global Biodiversity
Alligator Photo By Matthew Field - Wikimedia
Alligator with babies By User Catholic 85 Wikimedia

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