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Ecosystems
I. What is an ecosystem?
An ecosystem is a community of living and non-living things that work together.
Ecosystems have no particular size. An ecosystem can be as large as a desert
or as small as a tree. The major parts of an ecosystem are: water, water
temperature, plants, animals, air, light and soil. They all work together. If there
isn't enough light or water or if the soil doesn't have the right nutrients, the
plants will die. If the plants die, animals that depend on them will die. If the
animals that depend on the plants die, any animals that depend on those
animals will die. All the parts in ecosystem work together to achieve balance. A
healthy ecosystem has lots of species and is less likely to be damaged by
human interaction, natural disasters and climate changes. Every species has a
niche in its ecosystem that helps keep the system healthy.
I.1 Soil
Soil is a critical part of an ecosystem. It provides
important nutrients for the plants. It helps anchor the
plants to keep them in place. Soil absorbs and holds
water for plants and animals to use and provides a
home for lots of living organisms.
I.2 Air
The atmosphere provides oxygen and carbon dioxide
for the plants and animals in an ecosystem. The
atmosphere is also part of the water cycle. Without
the complex interactions and elements in the
atmosphere, there would be no life at all!
I.3 The sun
The heat and light from the sun are critical parts of
an ecosystem. The sun's heat helps water evaporate
and return to the atmosphere where it is cycled back
into water. The heat also keeps plants and animals
warm. The light from the sun is necessary for
photosynthesis, so that plants have the energy they
need to make food.
I.4 Water
Without water there would be no life. Water is a large
percentage of the cells that make up all living
organisms. Without water all life would die. Water is
also used by plants to carry and distribute the
nutrients they need to survive.
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II. Examples of ecosystems
Examples of ecosystems are: agroecosystem, aquatic ecosystem, coral reef,
desert, forest, human ecosystem, littoral zone, marine ecosystem, prairie,
rainforest, savanna, steppe, taiga, tundra, urban ecosystem and others.
Rainforests often show a lot of biodiversity with many plant and animal species.
The picture above shows a rainforest together with an aquatic ecosystem: The
Gambia River in a Senegal national park.
A desert ecosystem in Mexico consists of abiotic (soil, water, air) and biotic
parts (flora, fauna).
A typical savanna ecosystem in Tanzania (Ngorongoro National Park) also
combines abiotic and biotic elements.
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Forest as an ecosystem can appear in very different forms with various kinds of
vegetation. Three pictures of various examples of a forest were taken in
Madagascar, in California and on San Juan Island.
Coral reefs are special examples of a marine ecosystem.
III. Biomes
Biomes are globally similar areas, including ecosystems, as regards
combinations of plants, animals, soil organisms and climatic conditions. They
have certain common factors, e.g. plant structures (trees, shrubs, grasses), leaf
types (broadleaf, needles), plant spacing (forest, woodland, savanna) and
climate. The basic types of biomes are: land, freshwater and marine biomes.
Map of land biomes
Certain plants grow in certain climates and thus create the biomes – vegetation
types extending over a large geographic area. So climate affects the creation of
biomes strongly. The following chart shows the relationship between the biome
type and the climate.
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An illustration of a freshwater biome is the ecosystem in Gran Canaria:
IV. Habitats
Within each ecosystem there are habitats of various sizes. A habitat is a place
with a population (a group of living organisms of the same kind). All the
populations living in the same place at the same time interact, forming a
community. Such community also interacts with the non-living world around it,
thus forming an ecosystem. The habitat must provide the organisms with food,
water, temperature, oxygen and other goods they need. Among populations in
the same habitat different processes may occur, such as cooperation,
symbiosis, but also competition and predation. An aquarium or a terrarium are
good examples of a shared habitat.
V. Function of ecosystems
Considering the benefit from ecosystems for the human race, ecosystems may
be regarded as production units producing goods (forest ecosystems supply
wood, grass enables cattle growing, wild animals are used for food) and
services (enjoyment of nature, income and employment in tourism, water
retention, soil protection etc.).
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VI. Ecosystem dynamics
When new biotic or abiotic elements enter into an ecosystem, they cause an
interruption. This can also lead to death of certain species within the ecosystem.
But often ecosystems can protect themselves from intruders, depending on the
toxicity of the new element and the resiliency of the original ecosystem.
Organisms have survived despite continuous changes, natural selection and
intruders, but they had to adapt to new conditions. Changes are always gradual.
Some species even disappear and new ones move in. Usually the population
remains within limits of the food supply within an ecosystem. In general,
ecosystems are more resilient to sudden or great changes than each species
individually.
Arctic tundra in Russia is an example of an ecosystem which has remained
relatively unchanged for a long period of time.
VII. The energy cycle
All living things need energy. In an ecosystem, the sun is the source of energy.
Different species in an ecosystem have different functions: producers,
consumers or decomposers, all of them being important parts of an
ecosystem. Producers are green plants which make their own food.
Consumers are animals which get their energy from the producers or
organisms that eat producers. There are three types of consumers:
- herbivores: animals that eat plants;
- carnivores: animals that eat herbivores and sometimes other
carnivores;
- omnivores: animals that eat plants and other animals.
Decomposers are plants and animals that break down dead plants and animals
into organic materials which go back into the soil.
www.mansfield.ohio-state.edu/.../image004.gif
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Living beings also need water within their habitats. Their needs are met through
the water cycle.
foper.unu.edu/.../uploads/2007/02/figf01.gif
Energy and water are vital to the survival of an ecosystem, thus a system of
conservation is necessary. The exchange of carbon dioxide and oxygen is a
process of conservation. What one species discards, means food for another.
When food is limited, the conservation processes and the need for recycling
become more urgent. If it is not successful, species are endangered and may
even become extinct.
VIII. Material flow
Living organisms also need certain nutrients. Plants obtain elements such as
carbon, nitrogen or phosphorus from the atmosphere, water or soil. Animals can
also obtain them directly from the environment, but mostly from food (eating
other organisms). The nutrients are transformed within the bodies of organisms
and later on returned to an inorganic state. Often bacteria are involved in such
processes, e.g. decomposition. The elements in the environment are then again
used by new organisms.
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IX. Ecosystem ecology
Ecosystem ecology is an integrated study of biotic (plants and animals) and
abiotic (chemicals, bedrock, soil) components of ecosystems and their
interaction within an ecosystem. The aim of this science is to try to understand
how the system operates as a whole, focusing on the functional aspects of the
system, e.g. the amount of energy produced by photosynthesis, energy and
material flow within the food chain, the rate of decomposition of materials or the
rate of nutrients recycling within the system.
X. Ecosystem legal rights
The Rights of Nature or Ecosystem Rights were first enforced in Ecuador's
constitution in 2008. Later on some local governments in Pennsylvania followed.
These rights give individuals the right to file lawsuits on behalf of the ecosystem
due to pollution, destruction and the like. Other countries are likely to pass
similar laws in the future.
QUESTIONS
I. Answer the following questions:
1. What is an ecosystem?
2. What are the major parts of an ecosystem? How do they interact?
3. What does the soil provide for the plants?
4. What is the meaning of the air for the plants and the animals?
5. What role does the water play in the living organisms?
6. Ennumerate some kinds of ecosystems.
7. Define a biome.
8. What is a habitat?
9. What causes changes in ecosystems?
10. Describe the functions of certain species within an ecosystem
(producers, consumers, decomposers).
11. Explain the material flow within an ecosystem.
12. Define ecosystem ecology and explain its aims.
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Literature and sources:
www.mansfield.ohio-state.edu/.../image004.gif
foper.unu.edu/.../uploads/2007/02/figf01.gif
en.wikipedia.org/wiki/Ecosystem
www.fi.edu/tfi/units/life/habitat/habitat.html
www.biophage.com/.../2010/04/Ecosystems.gif
www.nhptv.org/natureworks/nwepecosystems.htm
geoscape.nrcan.gc.ca
www.globalchange.umich.edu/.../ecosystem/ecosystem.html -
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