Classwork Series and Exercises {Biology – SS2}: Forest Habitats

Biology, SS 2 Week 7

Topic: Forest Habitats

Introduction

A forest is an extensive community of plants dominated by tall trees. These trees are of different species and height. The distribution of forest is mainly determined by climate especially rainfall and temperature. The rain forest is the dominant forest in Nigeria.

Characteristics of the Rain Forest

1. Presence of broad leaves: Most trees in rain forest usually possess broad leaves which enable the plants to receive abundant light and enhance transpiration
2. Presence of buttress roots: Most trees because of their large sizes often have buttress roots to support their heavy weight and height
3. Presence of tall trees: The bulk of the trees in rain forest are tall. Some are even 40 metres and above in height
4. Existence of canopies: The trees in the rain forest are shaped in such a way as to form canopies
5. Trees exists in layers or storeys: The trees in rain forest are zoned or stratified in such a way that they are arranged in layers or canopies, i.e., upper layers, middle layers and lower layers
6. Presence of fallen leaves on ground: The forest is characterised by the flooring of the ground with lots of leaves as litters
7. Trees have thin bark: Most of the trees have thin bark to enhance gaseous exchange and transpiration
8. Presence of epiphytes: The rain forest is also characterised by the presence of climbers and epiphytes on the trees which possess aerial roots for moisture absorption and respiration

Strata in the Forest

The main forest vegetation have plants which are naturally arranged in layers, strata or storeys. There are about five storeys in the forest. These are:

1. The upper layer: The upper layer or storey is made up of the tallest trees of over 40 metres tall. These trees are called emergents. The crown of the emergents do not normally touch each other. Examples of plants in this category are Iroko, Obeche, Mahogamy, African walnut, Ebony, etc.
2. The middle layer: The second layer in the rain forest is made up of fall trees of about 16-40 metres tall. Their crown touches each other, thereby forming a continuous canopy just below the emergents
3. The lower layer: This is the third layer which is made up of small trees, less than 16m tall. They also form a continuous canopy below the middle storey
4. The shrub layer: This layer is made up of small trees, 1-5 metres in height. These are essentially small trees collectively referred to as shrubs
5. Ground layer or forest floor: This contains wet and shade loving plants which grow on the floor of the forest. These plants hardly receive sunlight due to canopies formed by bigger plants. Most plants are bryophytes and they include mosses, liverwort, lichens and thin leaved ferns

Distribution of Plants in a Forest Habitat

Varieties of plants exist in the forest. Popular examples of forest trees include African walnut, Mahogany (Khaya ivorensis), teak (Tectonia grandis), Opepe (Sarcocephalus), Obeche (Triplochiton), Iroko (Chlorophora), Oil palm (Elaeis guineensis), ferns, orchids, lianas, mosses, lichens, liverwort, fungi and mistletoe

Adaptive Features of Plants in a Forest Habitat

• Iroko and Mahogany: These plants have strong tap root system and buttress roots which aid anchorage and support for the weight of the plants
• African walnut: These plants have broad leaves which aid transpiration and photosynthesis
• Obeche: These plants have tap root system and large buttress roots for support as well as broad leaves to aid photosynthetic activities
• Orchid: These are epiphytes which have mechanism for storing water and absorbing moisture form air while growing on tree branches
• Mistletoe: These are complete plant parasites capable of developing root system that can penetrate the stem of a plant and feed directly from manufactured food by placing their roots on the phloem vessels of the host plants

Distribution of Animals in a Forest Habitat

Most animals in the forest live on trees (i.e. they are aboreal animals). The animals include bats, monkeys, snakes, squirrels, birds, lizards, tree frogs and chameleons. Some animals like earthworms and beetles live in the soil while some live among the litter on the ground, e.g. millipedes, ants and snails.

Adaptive Feature of Animals in a Forest Habitat

• Monkeys: Monkeys have prehensile tails and long limbs for climbing trees and jumping form one tree branch to another
• Bats: Bats have a way in which the forelimbs and the hind limbs are joined on each side of the body by a fold of skin to form wings used for flight
• Green snakes: These snakes have protective colouration on their skin which makes it difficult to be detected by their enemies. They also have slim elongated body with grasping scales for winding around tree branches
• Chameleon: It has prehensile tail and opposable digits for grasping. It also has protective colouration to camouflage or disguise itself form predators
• Apes: Apes move in groups or herds to protect themselves from predators. They also have high sense of sight to detect enemies
• Earthworms and snails: They have water permeable cuticle which reduces water loss and prevent drying up
• Birds: Birds have powerful wings used for flying

Factors Affecting the Forest

Climatic factors which affect the rain forest include rainfall, temperature, wind, relative humidity, sunlight, etc. rainfall and temperature are the dominant factors that affect the rain forest. High rainfall and temperature give rise to luxuriant rain forest vegetation