Terrestial Habitat – SS1 Biology Lesson Note (Third Term)

Terrestrial organisms are the plants and animals of the land. They live on the ground and under the ground. Their home is called a terrestrial habitat. The habitat is divided into four main parts, and this note describes two of them: the marsh and the forest, with their characteristics, organisms, adaptations and food chains.

Behavioural objectives

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

• define terrestrial organisms and list the four types of terrestrial habitat;
• explain how a marsh is formed and state its characteristics;
• name plants and animals of the marsh and the forest;
• describe how organisms are adapted to life in the marsh and the forest;
• describe the characteristics of a forest;
• write food chains for the marsh and the forest.

What are the types of terrestrial habitat?

Terrestrial habitat is divided into four main parts:

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 mainly 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 when water overflows its banks and accumulates on the adjoining coastal or lowland areas, such as flood plains or river sides. Extensive rainfall can add to this.

Marshes can also form when ponds and lakes are filled up with soil and organic debris of plants. The formation of marshes is therefore a gradual process. Marshes can be freshwater or saltwater marshes.

Characteristics of a marsh

1. A marsh is 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 and mammals.

Adaptive features of marsh organisms

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

Plants of freshwater marshes have other adaptive features similar to those of freshwater habitats. Plants of saltwater marshes likewise 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

1. Flowering plants → insects → frogs → crocodiles
2. 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 and 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 they 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.

Plant distribution and adaptation

Forest plants (trees) include African walnut, mahogany, teak, obeche, iroko, oil palm, ferns (pteridophytes), bryophytes (mosses and liverworts), epiphytes (orchids), fungi, 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 aerial roots, which store water and absorb moisture from the air while the plants grow on tree branches.
5. Mistletoe (a plant parasite) develops a root system that can penetrate the stem of a plant and withdraw manufactured food directly from the phloem vessels of the host plant.

Animal distribution and adaptation

Most forest animals are arboreal (living on trees). They 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. The chameleon has a prehensile tail and opposable digits for grasping, as well as protective colouration to camouflage.
5. Apes move in groups for protection and have 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

1. Green plants → grasshoppers → toads → hawks
2. Green plants → monkeys → lions

Evaluation

1. What is a swamp?
2. Name two adaptive features that all marsh organisms must have.
3. State three ways in which forest plants are adapted to life in the forest.
4. How does mistletoe obtain food from its host?
5. Give two examples of animals that are arboreal and state one adaptation of each.

Assignment

1. What are terrestrial organisms?
2. List four types of terrestrial habitats.
3. How is a marsh formed?
4. State four characteristics of a marsh.
5. List four plants and four animals found in the marsh.
6. Describe a forest habitat using its characteristics.
7. Give two examples of food chains in a forest.