Flow of energy and matter through ecosystems | High school biology | Khan Academy

Summary

This video explains how energy flows and matter is recycled in ecosystems. Energy from the Sun is captured by primary producers like plants through photosynthesis and stored in biological molecules. This energy flows through the food chain, passing from primary consumers to secondary consumers, with only about 10% of energy transferred at each trophic level. Matter, unlike energy, is recycled within the ecosystem, with carbon from the air being fixed into plants and passed through consumers, eventually decomposed and returned to the soil. The video highlights the inefficiencies in energy transfer and the continual recycling of matter in ecosystems.

Takeaways

• 😀 Energy for most ecosystems comes from the Sun, which is the primary source of energy for plants and other producers.
• 🌱 Primary producers, such as plants and photosynthesizing bacteria, convert solar energy into stored energy in biological molecules.
• 🔋 Energy is stored in the form of bonds between carbon atoms in plants, which are created through photosynthesis.
• ☀️ Photosynthesis fixes carbon from the air (carbon dioxide) into solid forms within plants, storing energy in the process.
• 🌾 Primary consumers, like rabbits and squirrels, eat primary producers to obtain energy from the bonds in plant molecules.
• ⚡ Only about 10% of the energy from one trophic level is transferred to the next, with the rest lost as heat or waste.
• 🦊 Secondary consumers, such as foxes, eat primary consumers and gain energy from their biomass.
• 🏞️ Tertiary consumers, like apex predators, eat secondary consumers for energy, continuing the energy flow in the ecosystem.
• 💀 Decomposers break down dead organisms and waste products, recycling matter and releasing nutrients back into the ecosystem.
• 🌍 Matter, such as carbon, is constantly recycled within ecosystems and does not disappear. The same atoms have existed since they were formed in stars billions of years ago.

Q & A

What is the primary source of energy for most ecosystems?

The primary source of energy for most ecosystems is the Sun, although other sources like moonlight and geothermal energy exist, they are much less significant.

What are primary producers, and what role do they play in an ecosystem?

Primary producers, such as plants and photosynthetic bacteria, are organisms that convert solar energy into chemical energy by photosynthesizing, storing energy in the form of biological molecules like carbohydrates.

How is energy stored in plants?

Energy is stored in plants through the creation of bonds between carbon atoms in biological molecules, which store the energy from sunlight. This process is called photosynthesis.

What happens to the energy from the Sun as it moves through an ecosystem?

As energy moves through an ecosystem, it is passed from one trophic level to another, starting with primary producers and moving to primary consumers, secondary consumers, and so on. At each level, a significant portion of the energy is lost as heat, making the process inefficient.

What is the 10% energy transfer rule in ecosystems?

In ecosystems, only about 10% of the energy from one trophic level is transferred to the next. This is because much of the energy is lost through digestion, excretion, and metabolic processes, leaving only a small amount available for growth and reproduction.

What are decomposers, and what is their role in an ecosystem?

Decomposers, such as bacteria and fungi, break down dead organisms and waste materials, releasing nutrients and energy back into the ecosystem, which can then be used by plants to start the cycle again.

How is matter recycled in an ecosystem?

Matter in an ecosystem is recycled through processes like photosynthesis and respiration. For example, carbon is absorbed by plants as carbon dioxide and released back into the atmosphere during respiration by consumers and decomposers.

Why is energy flow in ecosystems inefficient?

Energy flow in ecosystems is inefficient because much of the energy is lost as heat at each trophic level due to metabolic processes, digestion, and other life activities, making only a small fraction available to the next level.

What happens to the matter in organisms when they die?

When organisms die, their matter is broken down by decomposers into simple inorganic molecules, which are then recycled back into the ecosystem, where plants can use them to grow.

How does the flow of energy in an ecosystem relate to the concept of thermodynamics?

The flow of energy in an ecosystem follows the laws of thermodynamics, where energy is used to do work but is eventually released as heat. This is why energy flow is not completely efficient and why ecosystems lose energy as it moves through different trophic levels.