Living Things & Ecology
Ecology Basics
1st Year · 2nd Year · 3rd Year (Junior Cert)
- ✓By the end of this lesson students will be able to define and give examples of key ecological terms such as habitat, population, community, and ecosystem.
- ✓By the end of this lesson students will be able to construct and interpret simple food chains and food webs, identifying producers, consumers, and decomposers.
- ✓By the end of this lesson students will be able to explain the flow of energy through an ecosystem.
- ✓By the end of this lesson students will be able to outline the importance of nutrient cycles within an ecosystem.
Key concepts
Ecology is the study of how living organisms interact with each other and with their non-living environment.
A habitat is the natural home or environment where an organism lives. It provides everything the organism needs to survive, such as food, water, shelter, and space.
A population is a group of organisms of the same species living in the same habitat at the same time.
A community consists of all the different populations of organisms (different species) living and interacting in the same habitat.
An ecosystem is a community of living organisms (biotic factors) interacting with their non-living physical environment (abiotic factors). Abiotic factors include things like sunlight, water, soil, temperature, and air.
A food chain shows the feeding relationships between different organisms and how energy is transferred from one living organism to another. The arrows in a food chain point in the direction of energy flow.
Producers are organisms, mainly green plants, that make their own food using energy from the sun through photosynthesis. They form the base of all food chains.
Consumers are organisms that obtain energy by feeding on other organisms. They are classified based on what they eat: - Primary Consumers (Herbivores): Eat producers (plants). - Secondary Consumers (Carnivores/Omnivores): Eat primary consumers. - Tertiary Consumers (Carnivores/Omnivores): Eat secondary consumers.
Decomposers are organisms, such as bacteria and fungi, that break down dead organic matter (dead plants and animals) and waste products. They recycle nutrients back into the ecosystem.
A food web consists of many interconnected food chains in an ecosystem. It shows a more realistic and complex representation of feeding relationships than a single food chain.
Nutrient cycles describe the continuous movement of essential chemical elements (nutrients) like carbon and nitrogen through the living and non-living components of an ecosystem. These cycles ensure that nutrients are reused.
The carbon cycle involves the movement of carbon through the atmosphere, oceans, soil, and living organisms. Key processes include photosynthesis (plants take in carbon dioxide), respiration (organisms release carbon dioxide), decomposition, and combustion (burning of fossil fuels).
The nitrogen cycle describes how nitrogen moves between the atmosphere, soil, and living organisms. Atmospheric nitrogen is converted into usable forms by bacteria (nitrogen fixation), taken up by plants, consumed by animals, and returned to the soil through waste and decomposition.
Key facts to remember
- 1Ecology is the study of interactions between organisms and their environment.
- 2A habitat is an organism's home, while an ecosystem includes all living and non-living things interacting in an area.
- 3Food chains show the flow of energy, with arrows pointing from the eaten to the eater.
- 4Producers (like plants) make their own food; consumers eat other organisms; decomposers break down dead matter.
- 5Food webs are interconnected food chains, showing more complex feeding relationships.
- 6Nutrient cycles (e.g., carbon, nitrogen) ensure essential elements are continuously reused in an ecosystem.
- 7Biotic factors are living components; abiotic factors are non-living components of an ecosystem.
Worked examples
Example 1
Construct a simple food chain using the following organisms: grass, fox, rabbit. Identify the producer, primary consumer, and secondary consumer.
Answer
Grass → Rabbit → Fox Producer: Grass Primary Consumer: Rabbit Secondary Consumer: Fox
Remember, the arrows show the flow of energy, from the organism being eaten to the organism that eats it.
Example 2
In a forest ecosystem, what would likely happen to the population of deer if the population of wolves (their main predator) significantly decreased? Explain your reasoning.
Answer
If the population of wolves significantly decreased, the population of deer would likely increase. This is because there would be fewer predators to hunt and kill the deer, allowing more deer to survive and reproduce. This could then lead to overgrazing of vegetation by the increased deer population.
Example 3
Match the following descriptions to the correct ecological term: (a) All the blackbirds living in a particular garden. (b) The natural environment where a badger lives. (c) All the plants, animals, fungi, soil, and climate in a pond.
Answer
(a) Population (b) Habitat (c) Ecosystem
Common mistakes
- ✗Confusing the direction of arrows in a food chain: arrows should point from the organism being eaten to the organism that eats it (showing energy flow).
- ✗Mixing up definitions of habitat, population, community, and ecosystem. Remember the hierarchy: Population → Community → Ecosystem.
- ✗Forgetting the crucial role of decomposers in recycling nutrients back into the ecosystem.
- ✗Not including producers at the start of every food chain, as they are the source of energy for almost all ecosystems.
- ✗Assuming all food chains are simple and linear; in reality, most organisms are part of complex food webs.
Exam tips
- ★Always define key terms clearly and accurately when asked. Use specific examples where appropriate.
- ★When drawing food chains or webs, ensure all arrows are correctly drawn to show the flow of energy.
- ★Be able to identify producers, primary consumers, secondary consumers, tertiary consumers, and decomposers in any given scenario.
- ★Understand the impact of changes in one population on other populations within a food web (e.g., what happens if a predator population decreases?).
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