ENVS200-wk2.2-ecology-foodchains

Overview

  • This document covers essential topics for the ENVS 200 course, exploring Earth's systems and environments.

Student Learning Outcomes

  • By the end of the week, students will be able to:

    • Calculate the residence time of a reservoir and determine its inputs/outputs.

    • Differentiate between positive and negative feedback loops.

    • Define an ecosystem and identify its main components.

    • Explain the photosynthesis equation's significance for ecosystems.

    • Assign a trophic level to an organism in a food chain/web.

    • Understand how energy flows through ecosystems.

Energy Concepts

  • Energy Definition: The ability to do work or transfer heat.

    • Work is done when energy is displaced from one form to another (Work = Force × Distance).

    • Example: Moving an object, such as a book or touching a hot stove.

Major Reservoirs on Earth

  • Atmosphere: Mixture of gases surrounding Earth.

  • Hydrosphere: All of Earth's water.

  • Biosphere: All living organisms and undecomposed organic matter.

  • Geosphere: Solid Earth including rocks and soils.

Studying Complex Systems

  1. Identify system components and their interactions.

  2. Determine residence time of elements, assessing interaction speed and change propagation through the system.

  3. Identify feedback loops:

    • Interactions that amplify (positive feedback) or dampen (negative feedback) changes in the system.

  4. For complex systems with many interactions, construct computer models to predict response to disturbances (e.g., climate change from increased CO2).

System Components

  • Reservoir: Amount of material of interest in a given form.

  • Flux: Amount of material added (source) or removed (sink) from a reservoir over time.

  • Steady State: Condition where sources equal sinks, leading to no net change.

  • Residence Time: Duration it takes to empty or fill a reservoir.

Example of Residence Time Calculation

  • If a college has 12,000 students, with 6,000 new students enrolling and 6,000 graduating each year, what is the residence time?

    • Options:

      • a) 2 years

      • b) 4 years

      • c) 5 years

      • d) 6 years

Feedback Loops

  • Feedback systems can be classified as follows:

    1. Positive Feedback: Amplifying; increasing leads to more increase, and decreasing leads to more decrease.

    2. Negative Feedback: Stabilizing; increasing leads to decrease and decreasing leads to increase.

Practical Applications of Feedback Loops

  • Example in an apartment: Temperature and air conditioning usage.

    • Positive coupling: Increase in temperature leads to more air conditioning, further increasing cooling.

    • Negative coupling: Increased temperature results in more air conditioning, which lowers temperature.

Global Systems Example - Albedo

  • Albedo: Measure of surface reflectivity.

    • High albedo = More reflective; Low albedo = Less reflective.

  • Feedback loops involving sunlight, temperature, and ice.

    • Dark surfaces absorb more sunlight; light surfaces reflect sunlight.

Earth Cycles Overview

  • Movement of matter forms cycles, often stabilized by negative feedbacks, resulting in equilibrium (steady state).

  • Human activities are altering many of these natural cycles.

Carbon and Nitrogen Cycles

  • Overview of various components in Earth's cycles, including the Carbon Cycle and Nitrogen Cycle, illustrating movement and storage of materials.

Ecology Basics

  • Ecology Definition: Study of relationships between living organisms and their environment (including humans).

    • Components:

      • Biotic: Living components.

      • Abiotic: Non-living components.

Levels of Organization in Nature

  • Focus on five ecological levels:

    • Biosphere

    • Ecosystems

    • Communities

    • Population

    • Organisms

Ecosystem Components

  • Definition: A biological community of interacting organisms with their environment.

    • Major components:

      • Producers: Organisms that produce their own nutrition.

      • Consumers: Organisms satisfying needs by consuming others.

      • Decomposers: Organisms recycling nutrients by decomposing waste and remains.

Energy Flow in Ecosystems

  • Energy enters ecosystems via photosynthesis by autotrophs.

    • Autotroph: Organisms that create their own nutrition.

    • Heterotroph: Organisms that consume other organisms for nutrition.

Primary and Net Primary Productivity

  • Primary Production: Creation of new organic matter via photosynthesis.

    • Net Primary Productivity (NPP): Remaining energy available after accounting for energy used in respiration.

    • NPP varies between terrestrial and aquatic ecosystems.

    • Despite low individual NPP, oceans produce the majority of the world's biomass due to vast life.

    • Tropical rainforests have high NPP, but much is lost through degradation.

Trophic Level and Feeding Relationships

  • Organisms assigned a feeding level known as the Trophic Level:

    • Producers: Base of the food web (autotrophs).

    • Primary Consumers: Herbivores.

    • Secondary Consumers: Carnivores or omnivores.

    • Tertiary Consumers: Top of the food chain.

  • Energy Transfer: Energy flows from one trophic level to another, with a significant loss of energy (approximately 90%) at each transfer.

Food Chains and Food Webs

  • Food Chain: Linear sequence of organisms, each serving as a nutritional source for the next.

  • Food Web: Complex network of interconnected food chains.