Ecosystems 101
What do we call a place on Earth where living things interact with other living things and non-living things?
An Ecosystem
What process do plants use to make their own food using sunlight, water, and carbon dioxide?
Photosynthesis
What do we call organisms, like plants, that make their own food and form the base of an ecological pyramid?
Producers
What is the natural process in which one group of species is gradually replaced by another over time?
Ecological Succession
What do we call organisms, such as fungi and bacteria, that break down dead plants and animals and recycle nutrients?
Decomposers
Name two types of components found in every ecosystem.
Biotic (living)
Abiotic (non-living)
Which process releases energy for cells by breaking down sugar using oxygen?
Cellular respiration
They eat producers and are found directly above producers in an ecological pyramid?
Primary consumers
What is one negative human activity that can disrupt ecological succession?
Preventing natural forest fires
Introducing non-indigenous (invasive) species
Draining wetlands for farming or housing
What is the role of micro-organisms in an ecosystem?
They break down dead plants and animals and help recycle nutrients back into the ecosystem.
A tapeworm lives in the intestines of a dog, taking nutrients from the dog without giving anything in return. Explain what type of symbiotic relationship this is and why.
Parasitism – the tapeworm benefits by getting nutrients, while the dog is harmed.
How are photosynthesis and cellular respiration connected in an ecosystem?
Photosynthesis makes sugar and oxygen, which are used in cellular respiration to release energy. Cellular respiration produces carbon dioxide and water, which are used again in photosynthesis.
Why is there less available energy at the top of an ecological pyramid than at the bottom?
Energy is lost at each level as heat and through life processes, so less energy is passed on to higher-level consumers.
Give one example of a positive human action that helps ecosystems and explain how it helps.
Examples include protecting habitats, reintroducing species, or restoring wetlands, which help maintain biodiversity and ecosystem balance.
What would likely happen to an ecosystem if decomposers such as bacteria and fungi did not exist?
Dead plants and animals would build up, nutrients would not be recycled, and plants would not get the nutrients they need to grow.
A pond contains fish, frogs, algae, sunlight, rocks, and water. Explain how this pond is an ecosystem and name biotic and abiotic factors from the example.
It is an ecosystem because living things interact with each other and with non-living factors.
Biotic: fish, frogs, or algae
Abiotic: water, sunlight, or rocks
If plants in a forest receive less sunlight for several months, predict how this could affect photosynthesis and cellular respiration in the ecosystem.
Less sunlight would reduce photosynthesis, meaning less sugar and oxygen are produced. This would reduce the energy available for cellular respiration in plants and animals.
In an ecosystem, the number of producers suddenly decreases. Predict how this change would affect primary and secondary consumers.
Primary consumers would have less food and their population would decrease. Secondary consumers would also decrease because there would be fewer primary consumers to eat.
A wildfire naturally clears part of a forest. Explain how this event can lead to ecological succession and name one sign that succession is occurring.
The fire removes existing plants, allowing new species to grow. Succession occurs as grasses, shrubs, and later trees begin to grow. A sign is the appearance of new plant species.
After many leaves fall to the forest floor in autumn, they slowly disappear over time. Explain what causes this and why it is important for the ecosystem.
Decomposers like bacteria and fungi break down the leaves. This is important because nutrients are returned to the soil and reused by plants.
Explain how a microscopic ecosystem (such as bacteria living in soil) and the biosphere are similar, even though they are very different in size.
Both are ecosystems because living organisms interact with each other and with non-living factors like water, air, and nutrients. They both depend on energy flow and the cycling of matter to survive.
Carbon dioxide released by animals during cellular respiration is later used by plants. Explain how this shows that matter is recycled while energy is transferred in an ecosystem.
Matter, such as carbon dioxide, is recycled because it is reused by plants during photosynthesis. Energy is transferred because light energy is changed into chemical energy in plants and then passed to animals, but some energy is lost as heat at each step.
A harmful chemical enters a lake ecosystem and is absorbed by producers. Explain how this chemical can affect organisms at the top of the ecological pyramid.
The chemical builds up in organisms at each level of the food web. Top consumers receive the highest concentration due to bioaccumulation, which can harm or kill them.
A wetland is drained to build houses. Explain one environmental, one social, and one economic factor that should be considered before making this decision.
Environmental: loss of habitat and biodiversity
Social: loss of recreational or cultural spaces
Economic: short-term construction jobs vs. long-term loss of ecosystem services
A forest ecosystem has producers, consumers, and decomposers. Explain how decomposers support producers indirectly, even though they do not provide energy directly.
Decomposers break down dead organisms and waste, returning nutrients to the soil. Producers absorb these nutrients to grow and carry out photosynthesis, allowing energy to continue moving through the ecosystem.