Negative and Positive Feedback Loops in Ecology

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Questions and Answers

What is an example of negative feedback in population growth?

Increased food supply resulting in larger populations

Increased birth rates due to resource abundance

Population growth leading to more predators

Resource depletion leading to reduced birth or increased death rates (correct)

How does positive feedback contribute to climate change?

Melting ice reduces albedo, increasing heat absorption and further melting (correct)

Melting ice increases the Earth's albedo, reducing heat absorption

Increased CO₂ levels enhance plant growth, which lowers CO₂

The cooling effect of trees reduces atmospheric CO₂ levels

What does the First Law of Thermodynamics state about energy?

Energy efficiency increases with each trophic level

Energy flows are constant and not affected by heat loss

Energy is created and destroyed in ecosystems

Energy can be transformed but not created or destroyed (correct)

Which statement accurately reflects the Second Law of Thermodynamics?

Energy loss as heat during transfer reduces overall efficiency (B) Signup and view all the answers

What defines the boundaries of an ecosystem?

Criteria such as geographic, biological, or functional aspects (A) Signup and view all the answers

What characterizes a food chain?

It illustrates the flow of energy and nutrients through different organisms (C) Signup and view all the answers

Which of the following is NOT a typical role of decomposers in an ecosystem?

Increasing energy levels within the food web (A) Signup and view all the answers

How does increased atmospheric CO₂ positively affect plant growth?

By providing more resources for photosynthesis (B) Signup and view all the answers

What is the primary consequence of the second law of thermodynamics on energy transfer in food chains?

Energy decreases with each step in the food chain. (A) Signup and view all the answers

Which of the following is a significant way humans influence the nitrogen cycle?

Application of agricultural fertilizers. (B) Signup and view all the answers

How does the phosphorus cycle primarily differ from the nitrogen cycle?

The phosphorus cycle does not involve a gaseous phase. (D) Signup and view all the answers

Which of the following interactions is an example of mutualism?

Bees pollinating flowers. (D) Signup and view all the answers

What is the fundamental niche of a species?

The range of conditions without competition. (C) Signup and view all the answers

Which process describes how competition can lead to speciation?

Physical adaptation to reduce resource overlap. (A) Signup and view all the answers

What does species evenness measure in terms of species diversity?

How evenly individuals are distributed across species. (C) Signup and view all the answers

Which of the following methods is NOT typically used to measure species diversity?

Population genetic sequencing. (A) Signup and view all the answers

What can cause resource partitioning in species that compete for similar resources?

Using resources at different times. (B) Signup and view all the answers

Which of the following best defines the realized niche of a species?

The actual environmental conditions a species occupies. (D) Signup and view all the answers

Study Notes

Negative and Positive Feedback Loops

Negative Feedback: A stabilizing mechanism. A change triggers responses to counteract the initial change, maintaining balance.
- Example: Population growth leading to resource depletion, slowing population growth.
- Example: Increased atmospheric CO₂ boosts plant growth, absorbing CO₂, thus reducing CO₂ levels.
Positive Feedback: A reinforcing mechanism. A change amplifies further changes, often unstable.
- Example: Melting ice reducing Earth's albedo, increasing heat absorption, causing more ice to melt (Ice-albedo feedback).
- Example: Increased CO₂ causing warming, melting permafrost, releasing methane, further increasing warming (Methane-carbon cycle feedback loop).

Food Chains

A food chain represents the flow of energy and nutrients in an ecosystem.
Producers: Plants and algae. Convert solar energy to chemical energy via photosynthesis.
Primary Consumers: Herbivores that eat producers.
Secondary Consumers: Carnivores that eat primary consumers.
Tertiary Consumers: Eat secondary consumers.
Decomposers: Fungi and bacteria break down dead organisms, recycling nutrients.

Laws Governing Energy Flow in Ecosystems

First Law of Thermodynamics: Energy is neither created nor destroyed; it's transformed.
- Energy flows through trophic levels.
Second Law of Thermodynamics: Energy transfer results in some energy loss as heat, reducing efficiency.
- Energy pyramids show less energy at each higher trophic level (typically 10%).

Ecosystems

An ecosystem is a community of living organisms interacting with their physical environment.
Boundaries: Defined by geographic factors, biological factors, or functional aspects like nutrient cycles or predator-prey relationships.

Second Law of Thermodynamics and Pyramids

Diminishes energy and biomass at each step in the food chain.
Energy pyramids and biomass pyramids have a wide base (producers) and a narrow top (top consumers).
Fewer organisms exist at higher levels due to reduced energy.

Human Impact on the Nitrogen Cycle

Humans significantly alter the nitrogen cycle through:
- Agricultural Fertilizers (nitrogen compounds).
- Fossil Fuel Combustion (nitrogen oxides).
- Industrial Processes (fixing atmospheric nitrogen).
- Wastewater and Sewage (nitrogen runoff causing eutrophication).

Phosphorus Cycle vs. Nitrogen Cycle

Difference: The phosphorus cycle lacks a gaseous phase; it cycles through rocks, soil, and water. The nitrogen cycle involves atmospheric nitrogen fixation.
Similarity to Carbon Cycle: Both phosphorus and carbon cycles involve living organisms, water, and sediments.

Species Interactions

Mutualism: Beneficial to both species (e.g., bees pollinating flowers).
Commensalism: Beneficial to one species, no harm to the other (e.g., barnacles on whales).
Parasitism/Predation: Beneficial to one species, harmful to the other (e.g., ticks on mammals, lions hunting zebra).

Ecological Niches & Speciation

Fundamental Niche: Full range of environmental conditions a species can use without competition.
Realized Niche: Actual niche used by a species due to competition.
Response to Competition:
- Resource partitioning (using different parts of a resource).
- Temporal partitioning (using resources at different times).
- Morphological adaptations (specific physical traits).
Niche Differentiation and Speciation:
- Subpopulation isolation leading to directional selection (traits for specific niches).
- Reproductive isolation (genetic and behavioral changes).

Measuring Species Diversity

Species Richness: The total number of species.
Species Evenness: Distribution of individuals across species.
Diversity Indices:
- Shannon-Wiener Index (considering richness and evenness).
- Simpson's Index (probability of selecting two individuals from the same species).
Sampling Methods: Quadrat sampling, transect surveys, and mark-recapture techniques.

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Description

This quiz explores the concepts of negative and positive feedback loops within ecological systems, illustrating their impact on balance and change. Additionally, it covers the fundamentals of food chains, highlighting the roles of producers and consumers in energy flow. Test your understanding of these essential ecological principles!