Figure 1.1 All the plants and animals in this forest are dependent upon each other. They work together as an ecosystem.

Look at the picture of a forest in Tobago. It is an ecosystem; it consists of an

environment and a community of interacting plants and animals. Eco comes

from the Greek word meaning house; system means a group of things that

interact with one another. The many different organisms in an ecosystem –

plants, birds, insects and mammals – are dependent upon one another

(directly or indirectly) for their survival. For example, moss grows on the bark

of a tree, the hummingbird draws nectar from the heliconia fl owers and

pollinates them in return, and the tiger cat preys on the lizard. The study of

the interactions between organisms and their environment is called

ecology, and so ecology is the study of ecosystems.

Ecologists divide an ecosystem into its biotic (living) parts, such as plants,

animals, insects and micro-organisms; and its abiotic (physical or non-living)

parts, such as light, temperature, water, gases, wind and the soil. An abiotic

component such as water can vary in different environments. Look at the

examples shown on page 7 (Figures 1.2a–d).

The abiotic parts of a particular place determine which plants can grow,

and which animals can live there. When species of plants and animals adapt

to the physical conditions of their environment, we call this process

evolution.

abiotic, aquarium, biotic, ecology, ecosystem, evolution, interaction, terrarium

Gaia theory was developed by the scientist James Lovelock to help understand global climate change. Lovelock says that we should think of both living and non-living parts of the planet Earth as part of one large organism.

Keywords

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Science Extra

Abiotic components also

include features of the

landscape such as altitude

and the steepness of

a slope.

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Figure 1.3 A terrarium.

Figure 1.2a

Very little water in a desert makes a good home for this cactus, which can survive in drought-like conditions.

Figure 1.2b

Plenty of water in this swamp makes a good home for a mangrove tree.

Figure 1.2c

The fresh water in this pond is the natural environment of this frog.

Figure 1.2d

The salt water of the sea (with 3.5% average salinity) is the natural environment of these barracudas.

An ecosystem is a sustainable self-contained unit. This means that it can

continue for a long time on its own without needing anything from outside

itself. A terrarium (a glass container in which plants are grown) is a model

of an ecosystem. An aquarium (a tank in which fish and water plants are

kept) is also a model of an ecosystem.

1 Write a short paragraph of your understanding of what an

ecosystem is.

2 It is quite dark underneath the canopy of a forest.

a Describe two ways in which plants can maximise the sunlight they

receive.

b List two other abiotic components and describe their particular

quality in a forest.

3 Look at the picture of the terrarium.

a Where do plants in a terrarium get their water from?

b What would happen if you kept the terrarium inside a dark

cupboard?

Do some research on mangrove trees such as those that grow in the Nariva

Swamp. What physical conditions do they need? Consider things like the

salinity of the water and the acidity of the soil.

OR

Do a project in which you design an aquarium as a model of an ecosystem.

Explain the role of each component of the aquarium.

Ecosystems

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Ecologists call the part of an ecosystem

where a particular organism lives, its

habitat.

Trinidad and Tobago has a rich and

varied environment with many different

habitats. Each habitat is characterised by the

different kinds of plants growing there, and

animals living there. For example, the

golden tree frog is found in the montane

forest habitat of the El Tucuche mountain

area of the Northern Range.

Here are two more examples of different

habitats.

community, habitat

The macaw lives in the Nariva Swamp and eats the fruit of only one type of palm tree.

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Figure 2.1 The golden tree frog.

Figure 2.2 The macaw.

Figure 2.3 This moist forest is characterised by tall evergreen trees, mora trees, vines, orchids, mosses and ferns. It is also home to numerous birds and butterfly species, venomous snakes, the howler monkey and the pig-like peccary.

Figure 2.4 The savannah area has sandy, acidic soil with a low nitrogen content. Plant species include grasses, the Moriche palm, and the insect-eating sundew plant.

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The diet and lifestyle of an organism are suited to its habitat. Within a

particular habitat, different animals live in different places, such as under a

stone, or in a nest, or in a cave.

The Northern Range of Trinidad is characterised by montane forest and

cliffs. The oilbirds or diablotin (French for little devil) are nocturnal and roost

in the caves during the day. At night, they feed on the fruit of the oil palm

and tropical laurels growing in this region.

The habitat for the oilbird is the dark caves in the Northern Range,

but they are not the only animals that live there. The caves are also

home to different species of bat and a species of blind catfi sh that

lives in the water at the bottom of the caves.

We call the different species that live together in one habitat, its

community.

In groups, research different habitats in

Trinidad and Tobago. Each group should give

a fi ve-minute presentation on what the physical

environment is like, and what plants and

animals live there.

The Buccoo Reef on Tobago provides a habitat for a whole variety

of organisms such as sea anemones and sea sponges. Research

and write a report or prepare a poster on this important habitat.

Science Extra

Sulphurous pools are

poisonous for most organisms, but

some bacteria and algae have adapted

to exist in them and nowhere else.

Micro-organisms that live in harsh

environments (at high pressure, high

salinity or high temperature) are

called extremophiles.

Figure 2.6 This bat is part of the oilbird’s community.

Figure 2.5 The habitat of these oilbirds is the dark Aripo Caves in the Northern Range of Trinidad.

Ecosystems

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