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UNIT 3. ECOSYSTEMS AND THE ENVIRONMENT

Endangered animals. Nowadays many species are en-dangered, and some may also become extinct. All species are part of a food chain: they are dependent on each other. Consequently, if one species becomes extinct, others may also disappear.

WHAT IS AN ECOSYSTEM? An ecosystem consists of living things in an specific environment and the relationships between them and their habitat. For example a forest is an ecosystem. It is made of the:

panda bear iberian lynx grey whale

Physical environment

Soil, water, rocks, light, climate ...

+

Living things (Biological community)

Trees, grass, rabbits,

birds, foxes ...

=

ECOSYSTEM

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There are many different ecosystems on Earth. They can be:

Terrestrial: Forests, grasslands, de-

serts ...

Aquatic: rivers, lakes, coral reefs ...

Ecosystems can be different sizes, as small as a pond or as large as the Amazon rain-forest.

LIVING THINGS IN AN ECOSYSTEM We know that all living things interact with the others organisms that live around them. In an ecosystem all the individual organisms that belong to the same species are called the

population of that species. The group of all populations of living things in an ecosystem is

called a biological community. The biological community of a forest, for example, is made up of the population of trees, the population of rabbits, the population of foxes ...

BIOLOGICAL COMMNUNITY OF A FOREST

Our planet, the Earth, is the global sum of all ecosystems that we call biosphere.

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LIVING THINGS AND FOOD The most important relationships between the living things in an ecosystem are con-nected with what the different populations eat. Living things can be classified according to how they obtain food:

PRODUCERS make their own food. Plants and algae are the most common producers.

PRIMARY CONSUMERS are animals which feed on producers. All herbivorous animals

are primary consumers.

SECONDARY CONSUMERS are animals which feed on primary consumers. For example,

predators like lions or eagles belong to this group.

TERTIARY CONSUMERS are organisms that consume secondary consumers.

DECOMPOSERS are living things which feed on the remains of other living things. Most

decomposers are fungi and bacteria.

FOOD CHAINS — FOOD WEBS A food chain shows how food passes through different living things in an ecosystem. Food chains usually consist of a producer, a primary consumer and a secondary consumer. Most animals are part of more than one food chain and eat more than one kind of food. There are many food chains in an ecosystem, and most of them are linked, making up compli-cated food webs.

TERTIARY CONSUMER

Eagle

SECONDARY CONSUMER Ladder snake

PRIMARY CONSUMER Field mouse

PRODUCER Wheat

FOOD WEB

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WHAT IS THE ENVIRONMENT? The environment is all the circumstances, living things and habitats that interact with a living thing. Environment refers to:

Living things

Physical features

Soil

Water

Air

Climate

Human beings affect and are affected by the en-vironment. Agriculture, hunting, factories, construction and other activities can change the environment.

ENVIRONMENTAL PROBLEMS

Human impact on the environment has been great. As a result, many harmful changes have occurred. The main problems that humans cause on environment are: POLLUTION. The contamination of air, soil or water with harmful substances is called pollution. GLOBAL WARMING. The gradual increase in global temperatures is called global warming. Carbon dioxide in the atmosphere acts like a blanket and maintains heat on the Earth. However, the amount of carbon dioxide has increased in recent decades because more fossil fuels, such as coal and oil are used. Scientists believe that the Earth’s temperature is increasing because the atmosphere contains too many of these gases. DEFORESTATION. The destruction of for-ested areas has resulted in a degraded envi-ronment with reduced biodiversity. SPECIES EXTINCTION. Nowadays many spe-cies are endangered, and some may also be-come extinct. Pollution, global warming, defor-estation, illegal hunting and fishing may cause a species to become extinct. In fact, many plant and animal species have disappeared forever.

Wind is a non-polluting source of energy. Wind energy can produce electricity.

Rabbit environment. It consists in everything that affects the rabbit:

physical environment, living things, soil, water, climate, food ...

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ENVIRONMENTAL PROTECTION

National, regional and local authorities are responsible for protecting the envi-

ronment against pollution. They can do this in the following ways:

Build recycling and water treatment plants.

Reduce industrial activities.

Protect natural habitats where many animals or plants live. Some areas can be made

into natural or national parks, where the species are protected.

Encourage the use of non-polluting sources of energy, such as solar and wind

power.

The conservation of the environment is everyone’s responsibility, children and adults. We can help reduce pollution by having good habits. We can:

Separate rubbish into organic waste, paper,

plastic and glass. By separating waste, it be-comes easier to recycle things.

Turn off the lights and disconnect electrical

devices when they not being used. This saves electricity.

Respect the animals and plants.

Do not throw leftover oil down the sink, as

this will contaminate the water.

Using public transport more often.

Three R for environment protection:

Reuse, Recycle, Reduce.

Picos de Europa National Park. The first national park in Spain. It was cre-ated in 1918.