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Ecosystems
1. Studying our living Planet
The biosphere consist of all life on Earth and all parts of the Earth in which life exists, including
land, water, and the atmosphere.
Ecology is the scientific study of interactions among and between organisms and their physical
environment.
Interactions within the biosphere produce a web of interdependence between organisms and the
environments in which they live
Levels of organization:
Organism a form of life form considered as an entity, plant, animals, fungus…
Population a group of individuals that belong to the same species and live in the same area
Community an assemblage of different populations that live together in a defined area
Ecosystem all the organisms that live in a place, together with their physical environment
Biome a group of ecosystems that share similar climates and typical organisms
Biosphere our entire planet, with all its organisms and physical environments
2. Ecosystem
Ecosystem: An ecosystem consists of a biotope (aquatic or terrestrial) which forms the physical
environment, a biocenosis which is made up of living things, and the relationships or interactions
between this physical environment and the organisms which live in it.
Biocenosis: Different populations which live in the same geographical territory and develop
relationships with each other and with the environment
Biotope: is an area which is occupied by a biocenosis and has its own physical and climatic
characteristics.
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Ecosystems
2.1 Components of an ecosystem
We can classify the components of an ecosystem into two groups:
Abiotic factors, which are the variables of a biotope or physical environment, for example, light,
temperature, humidity, etc., and how these affect each other and affect living things.
Biotic factors, which are the living things that inhabit an ecosystem, the relationships that they
develop with each other, and how these affect the environment.
Abiotic factor:
An ecosystem's abiotic factors determine the types of living things which develop in it.
Abiotic factors have a tremendous impact because they influence the ecosystem in many ways, for
example, climate, growth and food supply
The most important abiotic factors are:
• Temperature, which has an enormous influence on the development of life. Changes in
temperature are more rapid and extreme on land than in water
•Light, which autotrophic organisms need to carry out photosynthesis. Light affects animals' sleep
patterns and other biological activities.
•Humidity, which can vary a Iot in a terrestrial environment. It determines the characteristics of
living things and also where they live in a particular environment
•Chemical composition of the soil, which is a fundamental abiotic factor,
•Water salinity, which is very important in aquatic environments
•Pressure, which doesn't vary very much with altitude in a terrestrial environment, but increases
considerably with depth in an aquatic environment
Living things have to develop adaptations to adjust to the abiotic factors.
Adaptation
behavior to its environment.
Light
Photosynthetic organism
Capture the maximum possible
Sunlight
Animals
Many animals regulate their
activity according to changes
in sunlight (owls)
Temperature
Plants
Animals
reduce their activity in winter
Some of them hibernate or migrate
Water
Plants
Waterproof leaves to avoid the
loss of water
Develop waterproof la
(exoesqueleton or scales)
Animals
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Ecosystems
Biotic factors:
Biotic components are the living things that shape an ecosystem Living thing in an ecosystem
interact with other members of their species and with members of different species. This produces
a variety of intraspecific and interspecific relationships or interactions.
INTRASPECIFIC RELATIONSHIPS take place between members of the same species and they can be
competitive or cooperative relationships.
• Competitive relationships. The individual members of a group live in the same habitat and live
off its resources. The members will compete over resources if they become scarce.
• Cooperative relationships can be classified as:
- Family associations. These occur between members of the same family.
Their objective is to reproduce and look after their young.
- Gregarious associations. In these relationships members come together in a group to defend
each other, look for food etc.
- Colonial societies. The members establish a hierarchical society and distribute the work.
- Colonial forms. The members are all identical copies and they stay together for life.
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INTERSPECIFIC RELATIONSHIPS
Interspecific relationships occur between individuals of different species. The most important
interspecific relationships are:
• Interspecific competition (- - ) is a harmful relationship far both species. When two species have
the same resource, they will compete for it if it becomes scarce.
• Predation ( + - ) is a relationship in which a living thing, the predator ( +) catches and kills
another, the prey ( - ) so it can feed.
• Parasitism ( + - ) is a relationship in which one species, the parasite ( + ), lives thanks to another
species, the host (-). It feeds on the host without causing its death, or at least not immediately.
• Commensalism ( + O) is a relationship in which one species benefits and the other is unaffected,
or indifferent.
• Mutualism( + +) is an association between two organisms of different species where both
benefit. If both organisms are highly dependent on each other it is called symbiosis.
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3. TROPHIC LEVELS IN AN ECOSYSTEM
A trophic level refers to all living things in an ecosystem that obtain matter and energy in a similar
way and so occupy the same position in the food chain. An ecosystem has three levels: producers,
consumers and decomposers.
- Producers
These are autotrophic organisms: plants, algae and some bacteria. They take in solar energy during
photosynthesis and use it to transform inorganic matter from their surroundings into organic
matter. Autotrophic organisms don't need other living things to feed on.
- Consumers
These are heterotrophic organisms: animals, fungi and some bacteria.
They obtain matter and energy by feeding off other living things or their remains or dead living
things or organic matter. They are divided into:
•P
c
(herbivores), which feed directly on the producers
•S c
c
(carnivores), which feed on the organisms in the trophic level below them:
the primary consumers
•T
consumers (also carnivores), which feed on secondary consumers.
- Decomposers
Decomposers are bacteria and fungi which decompose the organic and inorganic remains
(carcasses, excrement, etc.) of other living things and transform them into useful matter for
producers.
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4. Food Chain
A food chain pr trophic chain shows all the trophic levels and their feeding relationships by arrows.
The tip of the arrow indicates the organisms that “eat” and the end of the arrow the one that “is
eaten”.
5. FOOD WEBS
Food webs represent all the food chain in an ecosystem and how they are interconnected.
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