Ecosystem Dynamics: Energy, Balance, and Human Impact

Energy Use in Trophic Levels

At each level, a portion of the energy is used for growth, some for metabolic processes, and some is lost through respiration as heat and is not reused.

Energy Transfer to Higher Levels

The energy that accumulates in organic matter can pass to the next trophic level. Therefore, the amount of energy that passes from one trophic level to the next diminishes.

Ecosystem Balance: An Ideal State?

For an ecosystem to be balanced:

• Environmental factors must be stable.
• The number of individuals must be relatively constant.
• External factors should not drastically change the ecosystem.

The balance in an ecosystem is an ideal state!

Early vs. Mature Ecosystems

Early Stage:

• Low species diversity and structural complexity.
• Low biomass.
• Low energy use.
• Low ecosystem stability.

Mature Stage:

• High diversity and structural complexity.
• High biomass.
• High energy use.
• High ecosystem stability.

Primary and Secondary Succession

Primary Succession:

Occurs in a place that has not previously been colonized and where a soil base has formed.

Example: A new volcanic island.

Secondary Succession:

Occurs in an area where a previous community has been removed by a disturbance.

Example: After a drought.

Resource Limitation and Unlimitedness

Unlimited Resources:

In a population where resources are unlimited, the population grows exponentially. This growth is represented as a J-shaped curve.

Limited Resources:

The population begins to grow exponentially to a point where environmental resistance hinders growth. This growth is represented as an S-shaped curve.

Chemical Control: Benefits and Drawbacks

Benefits:

• Improved crop yields.
• Allows control of certain epidemics.

Disadvantages:

• Development of resistance in pests.
• Environmental pollution.
• High persistence in the environment.
• Non-selective and bioaccumulative effects.

Natural Resources

Natural resources are all the materials and attributes (actual and potential) provided by nature that can be used by humans.

Reasons for increased use: World population growth and changing lifestyles.

Renewable and Nonrenewable Resources

Renewable Resources:

These resources can regenerate over time, or their depletion rate is less than the rate of human consumption. Example: Biological resources.

Nonrenewable Resources:

These resources do not regenerate, at least not on a human timescale, and their reserves diminish with use. Example: Coal or oil.

Biodiversity Threats

Overexploitation:

Harvesting plants or animals at a rate greater than their natural regeneration rate.

Habitat Destruction:

In many cases, this leads to the extinction of species.

Introduction of Invasive Species:

Species that have been artificially introduced into an ecosystem.

Human Activities with Negative Environmental Impact

Burning Fossil Fuels:

Produces increased emissions of CO₂.

Industrial Processes:

Emissions of pollutants.

Changes in Land Use:

Actions needed for human habitation and agriculture.