In this lesson we are going to look at what an ecosystem is, how it operates and the interactions and connections between all life and Earth. In understanding the balance needed for an ecosystem to remain healthy, we will be able to better navigate the world around us, allowing us to protect and cherish all life, putting a stop to the Anthropocene defaunation, the sixth mass extinction we currently find ourselves in.
To begin, there is some terminology we need to be familiar with when discussing how an ecosystem works.
Living things such as; sharks, whales, phytoplankton
Non living things; water, light, radiation, temperature, pH
Can you think of another example of a biotic and abiotic factor?
A living animal that hunts and kills in order to survive
Living animals that are hunted and killed by other animals
Can you think of another example of a predator - prey relationship?
The plants of a particular region, habitat, or geological period.
The animals of a particular region, habitat or geological period
A certain type of habitat that is occupied by a particular type of flora and fauna.
e.g. estuaries, coral reefs.
Trophic levels are categories that scientists use to separate different species depending on where they get their energy (food) from. They go: Decomposers (species that get their energy from dead organisms) —> Primary producers (species that get their energy from the sun) —> Primary consumers —> Secondary consumers —> Tertiary consumers .
Ok awesome! Now we are familiar with the terminology let’s dive on into ecosystems!
What is an ecosystem?
An ecosystem is any environment that has interactions between biotic and abiotic factors. We could start by saying that the Earth is an ecosystem, then, the ocean is an ecosystem, the Great Barrier Reef is an ecosystem and so on. Each time we get smaller and smaller, so too do our interactions, so describing ecosystems is not as broad as you may think. To really understand the differences between ecosystems we must study the interactions!
An interaction between two or more things in an ecosystem could be almost anything! It usually refers to the ‘transfer of energy’ but an interaction could also be seen between seaweed and a rock - although the rock isn’t alive, the seaweed needs the rock to grow, this is still an interaction and why we choose to describe ecosystems as the interactions between biotic and abiotic factors. Different ecosystems have different interactions.
Depending on the type of interaction you’re talking about, they can either be really simple like this illustration which describes predator-prey interactions:
they can be really complex like this illustration which describes how the sun’s energy interacts with an ecosystem:
When scientists study certain ecosystems and their interactions, one way that they explain what they see is through food chains and food webs.
Food chains are simple, linear maps that describe energy flow across different trophic levels. The arrow describes the flow of energy. In this case, the phytoplankton (primary producer) gives its energy to the squid (primary consumer) which then gives its energy to the seal (secondary consumer) and finally the seal gives its energy to the shark which is our tertiary consumer, or otherwise known as the apex predator - an animal with no natural predators in its ecosystem.
Use the below activity sheet can you correctly order the food chains provided?
Food webs are a good way to understand a complex process often referred to as energy flow. It gives us an idea of how a lot of individuals are dependent on each other. If we take the picture above we see a bunch of living organisms, the arrows between them are how energy is GIVEN to that organism, just like in food chains. For example, the squid has an arrow pointing to the penguin. This is because the squid is giving energy to the penguin when the penguin eats the squid.
So now that we understand certain interactions between these animals it’s time to look at what makes an ecosystem healthy.
For an ecosystem to be healthy, every animal needs to interact with biotic and abiotic factors equally. If for some reason one of those organisms is taken out of the equation, we can see by the above food web how that would affect other living organisms in that ecosystem. In an ideal ecosystem, each trophic level is allowed to prey on each other equally, however in reality, due to human activity that is not always the case.
Humans are constantly taking organisms out of ecosystems. Deforestation and fishing are just two examples where we do it directly.
The role of Phytoplankton
We have already learnt that Phytoplankton are microscopic, plant-like organisms that grow abundantly in the seas and oceans. Much like land-based plants, phytoplankton require sunlight, water and nutrients for growth. They get their green colour from chlorophyll which also allows them to perform photosynthesis, creating their own food from sunlight and carbon dioxide. They provide us with 70% of the Oxygen we breathe and make up the base of most marine ecosystems.
Discuss how introducing a new species into an ecosystem could impact on food webs?
Can you think of other examples from history?
Once students have had time to think - ask two groups to present their findings.
CASE STUDY - WOLVES OF YELLOWSTONE
In 1914 the culling of wolves, prairie dogs, and other animals injurious to agri-culture and humans began. By 1926 the last two wolves were killed.
Do livings things rely on their environment? Can you explain your answer?
All living things require
Air to breathe
Water to stay hydrated
Food to provide energy
Sunlight for energy
Suitable and safe environment to grow and reproduce.
Now we understand the interactions and interdependence of living things. Remember that 70% of the Earth’s surface is water and the ocean produces 70% off the oxygen we need to breathe.
What does all this have in common?
Unity - everything is connected.
Our individual health and the health of all species will always correlate to the health of the planet. Perhaps, in this connectivity we can find compassion, empathy - finding the wisdom to live in harmony with one another.
ACTIVITY - Jenga
Give each table a Jenga game. Ask them to split into two teams. While they are playing go around and ask each table how they think this game relates to ecosystems and what we’ve just been learning