Terrestrial Habitat – SS2 Biology Lesson Note (Third Term)

A terrestrial habitat is a land environment where plants and animals live on the ground and under the ground. It is divided into four main parts: marsh, forest, grassland or savanna, and arid land or desert. This note covers the marsh and the forest, including their characteristics, organisms, adaptations and food chains.

Behavioural objectives

By the end of the lesson, students should be able to:

1. define a terrestrial habitat and name its four main parts;
2. describe how a marsh is formed and state its characteristics;
3. name organisms of the marsh and state how they are adapted;
4. state the characteristics of a forest;
5. describe how forest plants and animals are adapted to life in the forest;
6. write food chains for the marsh and the forest.

What are the main parts of the terrestrial habitat?

Organisms of the land are called terrestrial organisms. They include plants and animals that are found living on the ground and under the ground.

The terrestrial habitat is subdivided into four main parts, namely:

1. Marsh
2. Forest
3. Grassland/savanna
4. Arid land/desert

What is a marsh?

A marsh is a low land, flooded in the rainy season and usually waterlogged because of poor drainage. The vegetation is predominantly grasses and shrubs. When trees grow in a marsh, it is called a swamp. A marsh is a transition between the aquatic habitat and the terrestrial habitat.

How is a marsh formed?

Marshes develop as a result of water overflowing its banks to accumulate on the adjoining coastal or lowland areas such as floodplains or rivers. This can be enhanced by extensive rainfall. Marshes can also form when ponds and lakes are filled up with soil and organic debris of plants.

The formation of a marsh is therefore a gradual process. Marshes can be either freshwater or saltwater marshes.

Characteristics of a marsh

1. A marsh is a lowland.
2. It is always flooded, wet and waterlogged.
3. It sometimes has a pool of standing water.
4. It has a high relative humidity.
5. Its water sometimes contains many decaying organisms.
6. The water has a foul smell.

Organisms of the marsh

There are various plants and animals in this habitat. The plants include algae, grasses, water lettuce, water lilies, white and red mangroves, raphia palms etc.

Animals found in the marsh include mangrove crabs, lagoon crabs, hermit crabs, mud-skippers, fishes, frogs, snakes, crocodiles, mammals etc.

Adaptive features of marsh organisms

1. They must be able to tolerate the salinity of the soil or water.
2. They have to tolerate low oxygen concentrations in the soil or water.

Plants of a freshwater marsh have other adaptive features similar to those of freshwater habitats. Likewise, plants of a saltwater marsh have features similar to those of saltwater habitats.

Saprophytic organisms (e.g. bacteria), which live on dead organic matter in marshes, have to adapt to anaerobic conditions.

Food chains in marshes

• Flowering plants → insects → frogs → crocodiles
• Humus → earthworms → frogs → snakes

What is a forest?

A forest is a community of plants in which tree species are dominant. There are different kinds of forests. Their distribution is determined mainly by climatic factors such as temperature and rainfall, and at times by soil elevation. It is also affected by human activities such as farming, lumbering, bush burning, construction of roads and building.

The major type of forest in Nigeria is the rainforest.

Characteristics of a forest

1. The forest is rich in epiphytes and climbers.
2. The interior of the forest has high humidity, low light intensity and a damp floor.
3. Tall trees with canopies are present and exist in layers (stratified).
4. Trees are mesophytes with broad leaves.
5. The trees have buttress roots to support their heavy weight and height.
6. The trees have thin barks for gaseous exchange and transpiration.

Distribution and adaptation of forest plants

Forest plants include African walnut, mahogany, teak, obeche, iroko, oil palm, ferns (pteridophytes), bryophytes (mosses and liverworts), epiphytes (orchid), fungi and mistletoe etc. These plants adapt to life in the forest in the following ways:

1. Possession of strong tap root systems and buttress roots.
2. Possession of tall unbranched trunks.
3. Possession of broad leaves.
4. Epiphytes have mechanisms (the aerial roots) for storing water and absorbing moisture from the air while growing on tree branches.
5. Mistletoe (a plant parasite) develops a root system that can penetrate the stem of a plant, withdrawing manufactured food directly from the phloem vessels of the host plant.

Distribution and adaptation of forest animals

Most forest animals are arboreal (living on trees). These include bats, monkeys, snakes, squirrels, birds, tree frogs and chameleons. Some live in the soil, e.g. earthworms and beetles, while others live among the litter on the ground, e.g. millipedes, ants and snails.

These animals adapt to the forest in the following ways:

1. Monkeys have prehensile tails and long limbs for climbing and jumping.
2. Bats modify their limbs into wings for flight.
3. Green snakes have protective colouration to camouflage.
4. Chameleons have a prehensile tail and opposable digits for grasping, as well as protective colouration to camouflage.
5. Apes move in groups for protection, with a high sense of sight.
6. Earthworms and snails have water-permeable cuticles to reduce water loss and prevent desiccation.
7. Birds have powerful wings for flight.

Food chains in a forest

• Green plants → grasshoppers → toads → hawks
• Green plants → monkeys → lions

Evaluation

1. What is a terrestrial habitat? Name its four main parts.
2. Describe how a marsh is formed.
3. State four characteristics of a forest.
4. Explain how monkeys and earthworms are adapted to life in the forest.
5. Write one food chain found in a marsh.

Assignment

1. List four characteristics of a marsh.
2. Explain how epiphytes and mistletoe are adapted to life in the forest.
3. Write one food chain found in a forest.