Life Sciences - Term 1 - Week 5

An ecosystem is a community of living organisms interacting with their physical environment. It includes biotic factors, such as plants, animals, and microorganisms, and abiotic factors, such as water, soil, and climate. Ecosystems can vary in size and complexity, from a small pond to a vast forest. Understanding ecosystems is crucial for studying biodiversity and the interdependence of life forms.

Energy flow in ecosystems begins with sunlight, which is captured by producers through photosynthesis. Producers, such as plants and algae, convert solar energy into chemical energy stored in glucose. This energy is then transferred to consumers when they eat the producers. The energy diminishes at each trophic level due to metabolic processes and heat loss, leading to fewer organisms at higher levels. Decomposers play a vital role in recycling nutrients back into the ecosystem.

Consider a simple food chain: grass (producer) → rabbit (primary consumer) → fox (secondary consumer). In this chain, the grass captures solar energy and stores it as chemical energy. When the rabbit eats the grass, it obtains energy, but only about 10% of the energy from the grass is transferred to the rabbit. When the fox eats the rabbit, it again receives only a fraction of the energy. This illustrates the concept of energy transfer and the 10% rule in ecology.

In groups, students will create a chart listing various ecosystems (e.g., desert, rainforest, ocean) and identify the producers, primary consumers, secondary consumers, and decomposers in each. Discuss how energy flows through these ecosystems and the impact of removing one component, such as a top predator or a key producer.

Students will create their own energy flow diagram for a chosen ecosystem. They should include at least three trophic levels, label each organism as a producer, consumer, or decomposer, and indicate the direction of energy flow with arrows. Students will then write a short paragraph explaining the significance of each component in maintaining the ecosystem's balance.

• The soil
• The sun
• Water
• Wind

Answer: The sun

The sun provides the energy that drives photosynthesis in producers, forming the base of the energy pyramid in ecosystems.

• Grass
• Rabbit
• Fox
• Decomposer

Answer: Rabbit

Primary consumers are herbivores that eat producers, such as rabbits that consume grass.

Answer: Decomposers break down dead organic matter, recycling nutrients back into the soil and making them available for producers.

Decomposers are essential for nutrient cycling, ensuring that ecosystems remain productive.

• 1%
• 10%
• 50%
• 100%

Answer: 10%

The 10% rule states that only about 10% of the energy from one trophic level is passed on to the next, due to energy loss through metabolic processes.

Answer: Biotic factors: plants, animals; Abiotic factors: water, soil.

Biotic factors are living components, while abiotic factors are non-living elements that affect the ecosystem.

• Deer
• Tree
• Wolf
• Grass

Answer: Wolf

Wolves are apex predators in forest ecosystems, meaning they have no natural predators and sit at the top of the food chain.

• Respiration
• Photosynthesis
• Decomposition