Ecosystem Interactions
Ecosystems are composed of living (biotic) and non-living (abiotic) parts that interact and rely upon each other. The size of an ecosystem can depend on the scope of the person observing it, interactions occur at small scale levels, like the ecosystem in your gut, or large scale like the Great Lakes region.
It’s important to remember that ecosystems are not designed! They function well because natural selection favours creatures that can exploit their environment, for instance, using abundant available resources.
Energy is not created or destroyed. This is one of the basic principles of physics, but it applies to all sciences. Life requires energy (food/fuel) is a fundamental biology concept. In an ecosystem energy is transferred up and around by different types of interactions.
| Type of Interaction | Example, Description, (Positive or Negative) |
|---|---|
| Predation | Wolves and Dear. Wolves are the preditor and dear are the prey. Typically, these are lethal relationships. ( +, - ) |
| Parasitism | Humans and Leaches. Leaches benefit from our blood loss. Typically, these are not lethal relationships. (+, - ) |
| Mutualism |
Bees and Flowers. Bees get nectar and flowers spread their pollen. ( +, + ) |
| Competition |
Different bird species compete for limited ideal shelter, this isn’t good for either party. ( - , - ) |
| Commensalism | Lichens and Trees. The tree is unaffected while the lichens that grow on it get access to more sunlight. ( +, neutral) |
The Food Chain
Predator
- The creature that eats another or damages another for its own benefit
- Eg. Wolves
Prey
- The creature that is eaten or damaged for the predator's benefit
- Eg. Dear
Primary Producer
- A creature that harnesses the energy from a non living source, usually the sun
- Eg. Clovers
Image: National Geographic - Tim Gunther
Primary producers are energy gateways! Plants and other organisms that photosynthesize (capture the suns energy) bring energy into an ecosystem in a usable form for other species. From there those that eat the plants gain some of their energy.
When an animal eats another animal (or a plant) only about 10% of the prey’s energy is retained by the predator, the rest is left behind or was used up and released during the prey’s life. So, if a dear only gets 10% of a plant's energy they have to eat many more plants. This theory explains why predators are much fewer in number than primary producers. It also explains why populations don’t grow out of control, more wolves can’t survive long-term if their prey populations remain the same.
Human intervention into these natural balances creates issues. Areas of Southern Ontario have seen a growth in dear population as wolf numbers drop (human activity scares them and has destroyed their habitats). Having so many dear has made roads more dangerous and damaged more crops.
Energy flow doesn’t stop when we get to the top predator in an ecosystem! Even that animal will pass, and their energy will be returned to lower levels and they will feed the microorganisms in the soil and scavengers.
Ecosystem interactions are not just related to life and death though. The shade of trees cools the forest below, beaver dams shape aquatic environments, and snow can insulate the ground.
Try removing or doubling the population of your favourite species, can you predict a chain of 5 changes? Or even 10?
Past Ecosystems
Over the course of the 3.7 billion years life has existed on our planet it has continued to change! Humans have only been around for 200-300 thousand years and we have drastically changed the planet we live on. We have brought foreign creatures to distant lands (invasive species), created new species through breeding (woof woof), and dramatically increased the populations of our favourite animals like cats and dogs!
But what about before us? It is estimated that over 99% of all species that have ever existed have gone extinct, that’s around 5,000,000,000 species. You may be familiar with some of the more infamous ones like Dinosaurs and the Megalodon that you see in movies, but these creatures didn’t live alone. They had thriving complex ecosystems like ours!
If you’re familiar with plate tectonics you know that land masses or continents are changing and moving. Significant portions of Canada were much closer to the equator in the past and if you think about the tropics today, you know that they have very different plants and animals. What is above water today probably wasn’t always, shallow seas covered areas of Canada for millions of years and they evolved their own odd life forms. While we can’t see these ancient ecosystems in action, we do have access to the fossils some left behind, and we possess the tools to date them!
Image: Earth.com
You can have a lot of fun googling extinct creatures, try words like, largest, scariest, and strangest extinct animals and plants! Pictured here is an artist's rendering of a Sea Scorpion based on fossil evidence.
Image: Yale University - Patrick Lynch
Future Ecosystems
It is important to remember that ecosystems have always changed, and things go extinct naturally! Though you might have heard terms like Climate Change, Global Change and Global Warming, so what are they talking about? While ecosystems change, and extinction happens, both usually happen at very slow rates, sometimes called background extinction. The problem is scientists know that these things are happening much more quickly in the last 200 years. Through extensive research we know that human activity has changed the composition of our atmosphere to include more gasses that trap more heat, in particular carbon dioxide, CO2. We also know that our expanding presence has taken up more land, and we’ve pushed animals and plants out of large spaces further increasing the rate of extinction while decreasing biodiversity.
The Green House Effect describes how some incoming radiation escapes and other remains. Without this effect Earth would be freezing! The issue is we are increasing the amount of retained energy by changing the atmosphere's composition. Image: The Open University
Human created climate change has lots of implications, we simply can’t list them all and we likely don’t know of them all yet. Major ones include rising sea levels and more extreme weather like floods, droughts, and heat waves. These problems have implications outside of the obvious, many people will be displaced, and tropical diseases may extend their ranges. Human created climate change is already in motion and we have a limited amount of time to take drastic action. Countries have begun making changes to ensure we avoid the worst effects, but we need further action and cooperation to tackle this crisis and protect our ecosystems.
It’s not all doom and gloom though! Action like the Paris Agreement show international cooperation and recognition of climate change is increasing. 2020 saw thousands of people take to the streets to voice their desire for serious action to combat climate change.