Topic 3: Ecosystems
An
ecosystem can encompass a vast area, such as a forest, or a microcosm, such as
the space under a fallen log or a small pool.
As with populations and communities, the boundaries of ecosystems are
sometime not discrete. Many ecologists view
the entire biosphere as a global ecosystem, a composite of all the local ecosystems
on Earth.
Regardless of its size, its dynamics involve two processes that cannot be fully described by population or community phenomena: · Energy Flow, and · Chemical Cycling There are some physical laws that govern the flow of energy and chemical cycling; conservation of mass and energy. Trophic levels as discussed in Topic 2 describes the energy and chemical mass as it flows through a food web from producers →primary consumers →secondary consumers →tertiary consumers (top predators) →decomposers →to be made available for the cycle to begin again at the producer level. This cycling requires autotrophs to produce the foundation for the trophic pyramid to support the needs for all the heterotrophs above them. |
Trophic efficiency is dependent upon the autotroph’s ability to convert the Sun’s light energy into chemical energy stored in the basic four food molecules, carbohydrates, lipids, nucleic acids, and proteins.
There are four basic molecular cycles that explain how an ecosystems chemical resources are recycled through a food web and decomposers. They are the carbon, water, nitrogen, and phosphorus cycles. See illustrations below.
With increased industrialization, human burning of fossil fuels has dramatically increased the CO2 load in the earth’s atmosphere. This dramatic increase over the last century has contributed, many scientists believe, to the greenhouse effect and global warming. This is considered to be a global ecosystem imbalance and therefore has global consequences. As biologists of all disciplines come to understand the impact of human fossil fuel use, many are looking to reduce human consumption of these fossil fuels and look for more sustainable biofuel alternatives.
There are four basic molecular cycles that explain how an ecosystems chemical resources are recycled through a food web and decomposers. They are the carbon, water, nitrogen, and phosphorus cycles. See illustrations below.
With increased industrialization, human burning of fossil fuels has dramatically increased the CO2 load in the earth’s atmosphere. This dramatic increase over the last century has contributed, many scientists believe, to the greenhouse effect and global warming. This is considered to be a global ecosystem imbalance and therefore has global consequences. As biologists of all disciplines come to understand the impact of human fossil fuel use, many are looking to reduce human consumption of these fossil fuels and look for more sustainable biofuel alternatives.