Let’s talk about Ecology for a second. I know that I said that the next post would be on evolution, but ecology is basically the stage for evolution. Every good story has a setting ;), and every good narrator sets the scene.
1. On Ecology
Ecology is the study of the relationships between organisms and their environment. We’ve been desperately studying this field basically forever. The success of our species has relied heavily on our ability to notice changes in our environment and try with some degree of success to predict how organisms will respond to said changes.
We gotta eat. Our ancestors had to be familiar with the movements of prey and know how to find fruits and vegetables for food. Being a hunter gatherer is tough, and knowing where your next meal is coming from is the name of the game.
Imagine having to be able to predict the seasonal movements of herds of bison or knowing when and when not to plant crops? Too early or too late and BOOM…congratulations Farmer Dan, your village just starved to death.
2. Big Science Little Science
Ecology covers a huge range of levels of biological organization.
We know from what we learned about the scientific method that science is all about asking questions, and within the field of ecology, there are virtually zero limits to how many questions you can ask or to what scale you ask them.
Current research in ecology addresses levels of organization that range from individual organisms to the entire biosphere (that’s the whole world). Questions range from “How do resurrection ferns survive periods of drought and revive so spectacularly after a nice rain shower?” to “What role does the concentration of atmospheric CO2 play in the regulation of global temperature?” and everything in between.
3. Carrying Capacity and Competition; This Section is Long, but it’s How the Game Works
The earth’s natural resources are finite. At any given time, there is a quantifiable amount of energy circulating through the ecosystems of the world, and it all comes from the sun. It makes sense that so many ancient cultures worshiped the sun. It is the single source of all of the available energy on our planet. Except for maybe geothermal vents but I have zero clue how all of that works.
Energy is transferred from the sun and moves through different levels of trophic structure (trophic means relating to food or nutrition) starting with producers. These are organisms that make their own food from sunlight through a process called photosynthesis.
It’s all the green stuff: algae, photosynthetic bacteria, grass, trees, flowers etc, and the green stuff gets eaten by, you guessed it, consumers.
That, my friends, is how energy gets from the sun to an animal. You gotta eat it. Consumers are heterotrophs (they acquire their food by eating other organisms), and they’re divided into the familiar categories: herbivores, carnivores, omnivores, and detritivores/ decomposers.
You know the words to this song. Herbivores eat plant matter, carnivores eat other organisms in the animal kingdom, omnivores eat both plants and other animals, and detritivores/ decomposers eat the dead stuff.
Now, it gets a little tricky here because there are multiple levels of consumers. There are primary consumers, secondary consumers, and tertiary consumers.
Calm down, it’s not as scary as it sounds, and trophic structure is a fairly simple concept to follow. First, we need to collect some critters for an example. We’ll use a grasshopper, a bird, and a feral cat. Our grasshopper would be the primary consumer because it eats a producer like grass. The bird would be a secondary consumer because it eats the grasshopper which is a primary consumer. Finally, the current ecological crisis in the form of the feral cat eats the bird making it a tertiary consumer.
Voila. A complete trophic structure.
You can probably remember way back when you first encountered the concept of a food chain. There’s a reason that balanced trophic structures are displayed as a pyramid. As you climb the pyramid from producers to tertiary consumers, the amount of food required to obtain the same amount of energy reduces. Primary consumers have to eat a LOT of greens to get the same amount of energy that a hawk gets from eating a mouse. Think about calories. 100 calories of lettuce is a much larger volume than 100 calories of mouse.
Energy becomes more concentrated as trophic levels increase.
Remember how I said that the amount of resources in the biosphere is finite, meaning that it has a limit? This limit has some major implications, the foremost being carrying capacity. Carrying capacity is the maximum number of individuals of a species that the local environment can support at a particular time.
A direct application of that concept is that each level of trophic structure is dependent on the level below it. The amount of birds in an ecosystem is limited by the availability of food in the form of seeds or insects. By extension, the number of tertiary consumers like wolves in an ecosystem is limited by the availability of the trees and shrubs eaten by prey.
Even producers have to compete for resources. One tree can outgrow its surrounding trees and prevent sunlight from reaching them and hindering their growth. Cool Princeton article.
4. Keystone Species and Interdependent Relationships
Trophic structure is a solid example of interdependence of species, but some species play a larger role in their ecosystems than just eating or being eating.
Take the ecological celebrity (the state reptile of Georgia) for example, the gopher tortoise (Gopherus polyphemus).
This important fella digs burrows that provide shelter for at least 360 other animal species including the eastern indigo snake, and burrowing owls, that are threatened by predation and destructive natural events. Gopher tortoise holes even protect from fires which are a natural and necessary event in its habitat, the longleaf pine forest.
Because this species is so vital to the success and stability of its ecosystem, the gopher tortoise what we call a keystone species. Keystone species have a disproportionately large effect on their ecosystems relative to their abundance.
In review, ecology is how organisms interact with their environments, you can study ecology in scales ranging from organisms to the biosphere, organisms compete for the limited amount of energy in the ecosystem, and some organisms play a larger role in their ecosystems than others. That’s all for now! Next post will probably be completely dedicated to longleaf pine forests which contribute to so much of the historical ecology of the Southeastern United States!