Lecture 7 Ecosystems, Nutrient Cycling, and Biogeochemical Cycles

Bio-120

What is an ecosystem?

An ecosystem is a complex community of living organisms interacting with each other and their physical environment. The biotic components include plants, animals, and microorganisms, while the abiotic components include temperature, water, soil, and sunlight. Ecosystems operate through energy flow and matter cycling.

What are the two fundamental processes in ecosystems?

The two fundamental processes in ecosystems are energy flow (the one-way passage of energy through an ecosystem) and matter cycling (the movement of essential nutrients through the ecosystem, recycled by both biotic and abiotic components).

What are the components of an ecosystem?

An ecosystem consists of biotic components (living organisms like plants, animals, and microorganisms) and abiotic components (non-living factors such as temperature, water, soil, and sunlight).

What is the hierarchy of ecological organization?

The hierarchy of ecological organization includes: Biosphere, Biome, Ecosystem, Community, Population, and Species.

What was the Biosphere 2 experiment?

Biosphere 2 was an experimental project designed to simulate Earth's ecosystem in a sealed environment. The goals were to test if a closed ecosystem could sustain life and to learn more about Earth’s ecosystem functions. Despite its failure, it provided valuable insights into carbon cycling and climate change.

What is the role of energy and matter in ecosystems?

Earth is a closed system for matter but an open system for energy. Matter cannot leave or enter Earth, but energy flows into the ecosystem from sunlight and exits as heat. Energy flow involves photosynthesis and cellular respiration, while matter is cycled through ecosystems in various biogeochemical cycles.

What is photosynthesis?

Photosynthesis is the process by which producers like plants use sunlight to convert carbon dioxide (CO2) and water into sugars (glucose) and oxygen, which provides energy to the plant.

What is cellular respiration?

Cellular respiration is the process by which organisms break down sugars (glucose) to release energy in the form of ATP, with CO2 and water as byproducts.

What is matter cycling in ecosystems?

Matter cycling refers to the movement of essential nutrients (such as carbon, nitrogen, and phosphorus) through ecosystems, which are recycled and reused by both biotic and abiotic components.

What are the key steps in the carbon cycle?

In the carbon cycle, plants absorb CO2 from the atmosphere through photosynthesis and convert it into organic compounds. The carbon is then released back into the atmosphere via cellular respiration, fossil fuel combustion, and deforestation, which increase atmospheric CO2 levels.

What is human impact on the carbon cycle?

Human activities like burning fossil fuels and deforestation have increased atmospheric CO2, contributing to global warming and climate change.

What is the nitrogen cycle?

The nitrogen cycle involves the conversion of nitrogen in the atmosphere into usable forms for plants. Key processes include nitrogen fixation (conversion of atmospheric nitrogen into ammonia), nitrification (conversion of ammonia to nitrate), and denitrification (conversion of nitrate back to atmospheric nitrogen).

What is nitrogen fixation?

Nitrogen fixation is the process by which specialized bacteria convert atmospheric nitrogen (N2) into ammonia (NH3), which plants can absorb.

What is nitrification?

Nitrification is the process by which ammonia (NH3) is converted into nitrate (NO3-), a form that plants can use.

What is denitrification?

Denitrification is the process where bacteria convert nitrate (NO3-) back into nitrogen gas (N2), completing the nitrogen cycle.

How do human activities affect the nitrogen cycle?

The use of synthetic fertilizers and vehicle emissions has doubled nitrogen availability in ecosystems, leading to issues like eutrophication, hypoxia, and disturbances in biodiversity.

What is the phosphorus cycle?

The phosphorus cycle is a land-based process that involves the movement of phosphorus through soil, water, plants, and animals. Phosphorus is essential for producing ATP and nucleic acids and is released from rocks through weathering.

How is phosphorus released into ecosystems?

Phosphorus is released into ecosystems primarily through the weathering of rocks, after which it moves through soil, water, plants, and animals.

How do human activities impact the phosphorus cycle?

Human activities like mining and the use of phosphorus-based fertilizers have disrupted the phosphorus cycle, leading to eutrophication in water bodies.

What is the role of biotic and abiotic factors in nutrient cycling?

Biotic factors (plants, animals, microorganisms) interact with abiotic factors (rocks, water, air) to cycle essential nutrients like carbon, nitrogen, and phosphorus. Sinks are storage places for nutrients (e.g., soil, water, plants), and residence time refers to how long a nutrient stays in a sink before moving to another part of the cycle.

What are sinks in nutrient cycling?

Sinks are storage places where nutrients are held within an ecosystem, such as soil, water, or plants. These nutrients are later released or cycled to other parts of the ecosystem.

What is residence time in nutrient cycling?

Residence time refers to how long a nutrient stays in a sink (like soil, water, or plants) before it moves to another part of the cycle.

What is the core message about ecosystems from the Biosphere 2 experiment?

Ecosystems are complex assemblages of interacting living and nonliving components. Living organisms play irreplaceable roles in nature, supporting life and allowing ecosystems to function. It's essential to protect ecosystems and restore damaged areas for continued survival and thriving of species.

What were the goals of the Biosphere 2 experiment?

The two goals of Biosphere 2 were: 1. To prove that an entirely self-contained, humanmade ecosystem could sustain life. 2. To better understand Earth’s delicate balance and how to protect it.

What is the hierarchy of ecological organization from biosphere to individual?

The ecological hierarchy includes the following levels: - Species: A group of organisms that can interbreed and produce fertile offspring. - Population: All individuals of a species in a given area that interact and interbreed. - Community: All the populations (plants, animals, and other species) living and interacting in an area. - Ecosystem: All of the organisms in a given area, plus the physical environment in which they interact. - Biome: A large geographical area characterized by climate, vegetation, and organisms. - Biosphere: The sum of all Earth's ecosystems.

How does the biosphere differ from a biome?

The biosphere is the total area on Earth where living things are found, while a biome is a specific area characterized by climate and identified by predominant vegetation and organisms that have adapted to the environment.

What is the role of energy in ecosystems?

Energy enters ecosystems primarily as sunlight and exits as heat. This energy is utilized by producers through photosynthesis to form organic compounds, which are then consumed by other organisms.

What are the differences between biotic and abiotic components of an ecosystem?

Biotic components include all living organisms such as plants, animals, and microorganisms. Abiotic components are nonliving factors such as water, soil, temperature, and sunlight.

What is the role of the carbon cycle in ecosystems?

The carbon cycle describes the movement of carbon through biotic and abiotic parts of an ecosystem. It includes processes like photosynthesis, where carbon dioxide is absorbed and converted into glucose, and cellular respiration, which releases carbon back into the atmosphere.

What human activities disrupt the carbon cycle?

Burning fossil fuels, deforestation, and forest fires increase atmospheric carbon, disrupting the balance of the carbon cycle and contributing to global warming.

How does nitrogen cycle through ecosystems?

The nitrogen cycle involves nitrogen fixation (conversion of atmospheric nitrogen to ammonia), nitrification (conversion of ammonia to nitrate), and denitrification (conversion of nitrate back to atmospheric nitrogen).

What are the human impacts on the nitrogen cycle?

Human activities like the use of synthetic fertilizers and vehicle emissions have increased the availability of nitrogen, leading to disruptions in ecosystems, including eutrophication and loss of biodiversity.

What is the phosphorus cycle and how does it differ from other biogeochemical cycles?

The phosphorus cycle is unique in that it does not have a significant atmospheric phase. It moves through land-based processes, from rocks and soil to plants, animals, and back to soil, primarily through weathering.

What disruptions exist in the phosphorus cycle?

Human activities like mining and the use of phosphorus-based fertilizers have disrupted the phosphorus cycle, leading to eutrophication in water bodies.

What is the concept of "range of tolerance" in population ecology?

Range of tolerance refers to the range of a limiting factor (such as temperature or water availability) that allows a species to survive and reproduce. Factors outside of this range can limit the species' distribution.

How does energy flow through ecosystems?

Energy flows through ecosystems in a one-way path, starting from producers (through photosynthesis) and passing through consumers. Energy is ultimately lost as heat through processes like respiration.

How do biotic and abiotic factors contribute to nutrient cycling?

Biotic factors like plants, animals, and microorganisms interact with abiotic factors such as rocks, water, and air to cycle essential nutrients like carbon, nitrogen, and phosphorus.

What are sinks in nutrient cycling?

Sinks are storage places for nutrients, either abiotic (e.g., soil, water) or biotic (e.g., plants), where nutrients remain until they are cycled through the ecosystem.

What is the significance of residence time in nutrient cycling?

Residence time refers to the amount of time a nutrient stays in a sink before it moves to another part of the ecosystem. This impacts how quickly nutrients are cycled.