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Biology

Biomes are large natural terrestrial ecosystem, identified by their dominant vegetation. They are terrestrial because plants form the bulk of the community in any ecosystem e.g. a forest biome has densely packed tall trees while grasses and few scattered shrubs are found in a savanna biome. Climatic factors determine the type of vegetation in a biome. These factors may include rainfall, relative humidity, temperature, wind and light.

 

EVALUATION

  1. What is a biome?
  2. Mention four factors that determine the vegetation of a biome.

 

LOCAL BIOMES

The local biomes particular to Nigeria include the following:

  • mangrove swamp
  • tropical rain forest
  • savanna (northern and southern Guinea savanna, Sudan savanna and sahel savanna)
  1. MANGROVE SWAMPS

These are found in the tropics along coastal region and river mouths. Mangrove swamps are forest of small, evergreen, broad-leaved trees growing in shallow, brackish water or wet soil. Many mangrove trees have pop roots and breathing roots called pneumatophores. The climate here is hot and wet, with total annual rain fall of above 250cm and temperature of about 260c. In Nigeria, mangrove swamps are found in the delta region of Lagos, Delta, Rivers, Bayelsa and Cross rivers states.

  1. TROPICAL RAIN FOREST:

This occurs in the region that is between the equator and latitude 50-100N and S. It has the following characteristics:

  • The forest are mainly lowland.
  • The climate is hot and wet.
  • It consists of broad leaved trees that are mostly ever green; the leaves are gradually shed throughout the year and replaced by new ones.
  • The trees form canopy strata with their interior having low light intensity, high humidity and damp floor.
  • The trees possess thin bark.
  • The forest is rich in epiphytes and wood climbers.
  • The annual rainfall and temperature are 200cm and 270c respectively.

In Nigeria, tropical rainfall is found in Edo, Delta, Ondo, Imo, Lagos, Rivers state e.t.c.

  1. SAVANNA

These are tropical grassland in Africa. They are usually flat for miles at a stretch and made up mainly of grasses. The savanna region has a hot and wet seasons (290c) which alternate with a cool and dry season (180c). The total annual rainfall around 50cm-150cm. During the dry season, the grasses are usually dry and brown and bush fire is common occurrences.

South Guinea savanna (the largest of all the biomes in Nigeria) has tall grasses with scattered, deciduous trees. It is found in Enugu, Kogi, Benue, Kwara, Oyo, Osun, Ekiti State etc.

Northern Guinea Savanna has scattered, deciduous trees, sometimes with thorns and tick barks. Grasses are short and numerous. it is found in plateau, Kaduna, Bauchi, Niger, Kano, Adamawa states etc.

 

Sudan savanna has the shorter grasses fewer trees   which are more scattered. It is found in Kano and parts of Borno, Sokoto, Niger, Bauchi states e.t.c

 

Sahel savanna has high temperature and low rainfall with short and scanty grasses as well as

short and tough shrubs or trees. The plants are drought-resistant. It is found in Borno, Kastina, Sokoto, Yobe, Kano, Jigawa states etc.

 

EVALUATION

  1. In a tabular form, distinguish between the three major biomes in Nigeria using the following
  2. Total annual rainfall
  3. Temperature
  4. Regions found
  5. List five characteristics of savanna.

 

WORLD BIOMES

Of all abiotic factors affecting ecological system, temperature and rainfall determine the world biomes. The biomes include: tropical rain forest, temperate forest, coniferous forest, temperate shrubland, savanna, temperate grassland, desert, and tundra and mountain vegetation.

  1. TEMPERATE FORESTS

These are forests with the following characteristics they are

  • Mainly of broad leaved deciduous trees which shed their leaves during winter.
  • Possession of moderately wet climate with a dry or cold season.
  1. CONIFEROUS FORESTS

These are characterized by

  • Needle-leaved evergreen conifers such as pines, firs.
  • Possessing few trees.
  • Possessing tall tree forming upper storey.
  • The forest floor being covered with a thick layer or conifer needles.
  • Possessing cool temperature climate with light rainfall and snow.
  1. TEMPERATE SHRUBLAND

This is forest with the following characteristics

  • It consists of drought-resistant shrub plants and dwarf trees, often fire-resistant e.g. marquis.
  • It has temperate climate with low rainfall.
  1. TEMPERATE GRASSLAND

This is characterized by:

  • perennial grasses grow on very fertile soil to support herds of grazing mammals
  • It has moderately dry climate with a cold winter and a hot summer
  1. SAVANNA

This is a tropical grassland with:

  • scattered trees and often infertile soil
  • moderately dry climate with a warm dry season and a hot rainy season
  1. DESERT

This has:

  • very sparse vegetation, with succulent perennials that have deep root systems.
  • tropical temperate and afro-alpine regions with less than 25 cm annual rainfall.
  1. TUNDRA

This is characterized by:

  • treeless marshy vegetation composed mainly of dwarf shrubs, grasses, lichen and moss with very few plant trees.
  • cold climate with long icy winter and very short summer with an average temperature of 100
  1. MOUNTANE VEGETATION

This has:

  • evergreen rainforest on slopes of mountain, these forest are less luxuriant than the tropical rainforest.
  • Afro alpine vegetation occurs at heights above 3000m on mountain, vegetation consists mainly of heath, grasses and sedges.

 

GENERAL EVALUATION/REVISIONAL QUESTIONS

  1. What do you understand by the term biome?
  2. State the local biomes found in Nigeria.
  3. State the four savannas present in Nigeria.
  4. What are the two factors that determine the world biomes?
  5. State four of the world biomes with two characteristics each.
  6. Using their characteristics, differentiate between savanna and desert.

 

READING ASSIGNMENT

College Biology, chapter 23, page 499 – 504

 

WEEKEND ASSIGNMENT

  1. How is savanna plants protected from bush fires? They have A. sunken stomata B. thorn bark C. thick barks D. soft leaves
  2. Which of the following limiting resources is competed for by organisms in the desert?
  3. Light B. oxygen C. temperature D. water
  4. Which of these is not a true characteristic of the tropical rain forest? A. Vegetation consists predominantly of tall tree with thick canopy B. forest is rich in epiphytes and climbers C. annual rainfall is less than 100 cm annual temperature is 270c
  5. Which of the following does not describe the coniferous forest? A. needle leaved evergreen conifers B. broad leaved evergreen conifers possessing few trees
  6. possessing cool temperate climate
  7. Montane vegetation is described by the following except A. treeless marshy vegetation B. evergreen rainforest on slopes of mountain C. forest are less luxuriant than tropical rain forest D. afro alpine vegetation at heights above 300m on mountain

 

THEORY                                                                

  1. Outline the properties of the savanna as a world biome.
  2. State four characteristic features of vegetation found in savanna  B. tropical rainforest C. desert.

 

 

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