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Global biomes

Global biomes

A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that particular environment. The climate and geography of a region determines what type of biome can exist in that region. Major biomes include deserts, forests, grasslands, tundra, and several types of aquatic environments. Each biome consists of many ecosystems whose communities have adapted to the small differences in climate and the environment inside the biome.


An ecosystem is a living community of plants and animals sharing an environment with non-living elements such as climate and soil. Ecosystems exist on a variety of scales. An example of a small scale ecosystem (micro) is a pond. A medium scale ecosystem (messo) could be a forest. The tropical rainforest is an example of a very large ecosystem (biome).

Global biomes


The Earth has many different environments, varying in temperature, moisture, light, and many other factors. Each of these habitats has distinct life forms living in it, forming complex communities of interdependent organisms. A complex community of plants and animals in a region and a climate is called a biome.

In this unit we shall study two of the major biomes, namely – tropical rainforest and deserts.

Tropical rainforest


A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator (in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn). This ecosystem experiences high average temperatures and a significant amount of rainfall.

PowerPoint Tropical rainforests



The structure of the tropical rainforest


Emergents are the tallest trees and are usually over 50 metres tall. The Kapok tree is an example of an emergent.

The sea of leaves blocking out the sun from the lower layers is called the canopy. The canopy contains over 50% of the rainforest wildlife. This includes birds, snakes and monkeys. Lianas (vines) climb to the canopy to reach this sun light.

The under canopy mainly contains bare tree trunks and lianas.

The shrub layer has the densest plant growth. It contains shrubs and ferns and other plants needing less light. Saplings of emergents and canopy trees can also be found here.

The forest floor is usually dark and damp. It contains a layer of rotting leaves and dead animals called litter. This decomposes rapidly (within 6 weeks) to form a thin humus, rich in nutrients.

How has vegetation adapted to the climate?


In the tropical rainforest most trees in the rainforest have wide buttress roots. This is to support them as they grow incredibly tall (over 200ft in some cases) as there is great competition for sunlight. Lianas (vines) grow around trees as they bid to reach sunlight.


The leaves of many trees are waxy and have drip tips to allow water to run off them (so that water does not gather on leaves and cause them to rot, it also allows water to reach the roots on the forest floor). Leaf stems are also flexible to allow leaves to move with the sun to maximise photosynthesis.



Deforestation (cutting down trees) is a major problem caused by humans in the tropical rainforest. Deforestation, clearance or clearing is the removal of a forest or stand of trees where the land is thereafter converted to a non-forest use.

The main reasons for deforestation are:

Slash and burn : Vegetation is cut down and then burned. The ash acts like a fertiliser adding nutrients to the soil. When the soil begins to turn infertile (usually after 3-5 years) the people move on. This is called shifting cultivation.


Road Building: allows increased access to the Amazon Rainforest.

Logging : commercial logging is the major cause of primary rainforest destruction

Cattle Ranching : two-thirds of lowland tropical forests have been turned into pasture since 1950.

Hydroelectric Power : unlimited water supplies have led to the development of hydro electric power stations.

Farming : chopping down trees to plant crops and the over-use of the soil,has made the soils in these regions infertile.

Mining : it has also devastated large areas of rainforest e.g. The Amazon.


Problems caused by deforestation:

Flooding: Flash floods become more common after deforestation because there is less interception and less root uptake and transpiration.

Landslides: By removing trees and vegetation, you are making the soil less stable.

Biodiversity loss: because the ecosystem is being destroyed (cut down) the animals and insects are loosing their habitat (homes).

Silting of rivers: With increased flooding and surface run-off soils are being washed into the rivers, this can not only change local ecosystems (water temperature and clarity) but can also reduce the depth of rivers making navigation harder.

Loss of indigenous (locals) homes: By clearing rain forests you are obviously destroying the homes of indigenous groups.
Reduced rainfall: Deforestation can lead to reduction in local rainfall because less water is going into the atmosphere therefore reducing the formation of clouds and rainfall.


What is the future for the tropical rainforest? – Sustainable Development


If development in the rainforest is to be sustainable (e.g. although the resources are used to aid development, it/they will still exist for future generations to use) a number of measures must be taken. These include:

Sustainable forestry: Forestry that does not cause permanent damage to any ecosystem and that can be maintained indefinitely (not damaging for future generations).

Afforestation – Trees should be replanted in areas of deforestation.

Creation of National Parks: More National Parks can be created to stop deforestation and loss of biodiversity. National Parks are areas of land protected by government law.

Shifting Cultivation – Farmers should move on after 2-3 years to allow the rainforest to recover.

Ecotourism: The promotion of ecotourism gives tropical rainforests and biodiversity an economic value. If the value of tourism is greater than the value of selling trees and wild animals then locals will have the incentive to protect them.

Education: Improved global education on the importance of biodiversity and tropical rainforests.

Click on the link below for the classwork.

Word Document Year 9 Tropical rainforest



Deserts are found across our planet along two fringes parallel to the equator at 25–35° latitude in both the northern and southern hemispheres. Deserts are arid or dry regions and receive less than 10 inches of rain per year. Biologically, they contain plants and animals adapted for survival in arid environments. Physically they are large areas with a lot of bare soil and low vegetation cover.


Reason for the location of deserts

The Hadley cell one of the main reasons for desert locations.
Temperatures at the equator are highest. Warm air rises containing evaporated moisture.
The air cools, condenses and forms clouds.
Heavy equatorial rainfall occurs (in the rainforest!)
The cool, dry air then begins descending. The air warms up. Any moisture in the air is held as water vapour (invisible).
Cloudless sky.

Formation of deserts


Deserts are extremely dry (arid) places. True deserts normally have less than 250mm a year, although some deserts like the Atacama can go for years without any rainfall.

Due to the fact that there is no moisture in the air, there are very few clouds in deserts which means desert areas are exposed to high levels of incoming radiation from the sun. This means that daytime temperatures in the desert are very high. However, the lack of cloud cover also means that a lot of outgoing radiation is able to escape, making desert temperatures very cold at night.

Flora and fauna


Because of the very arid conditions found in deserts, both plants and animals have had to adapt to survive. Adaptations include:

Succulents e.g. cacti: Succulents tend to be fairly fat fleshy plants that are able to store water in their leaves, trunks and roots.

Long and wide roots: Plants in deserts have very long roots so that they are able to absorb the maximum amount of rainfall during periods of rainfall. It also makes them more stable in very lose soil.

Spiky and waxy surface: Many plants like cacti protect themselves with spikes and wax so that they are not eaten or damaged by animals.

Deserts don’t have the same variety of animals as tropical rainforests, but many insects, reptiles and mammals have adapted to survive.

Nocturnal: Many animals will hide in burrows or behind rocks and vegetation during the hot daylight hours and only emerge at night.

Camels: Camels store fatty tissue in their humps which when metabolised actually releases water as well fat enabling them to survive in deserts.


Click on the link below for the classwork.

Word document Year 9 deserts


Africa – geographic understanding – location and climate of the Sahara, Sahel, Sevanna and the Tropical Rainforests. 


The Sahara 

  • The Sahara region of Africa is mostly made up of Algeria, Libya, Egypt, Mauritania, Niger, and parts of Morocco, Tunisia, Sudan, Chad, Eritrea, Western Sahara, and Mali.
  • It’s climate is desert HOT!!!! It is labeled as a dry, arid climate.

The Sahel

  • The Sahel region transitions South of the Sahara Desert. It spans from the Atlantic Ocean to the Red Sea.
  • From West to East the Sahel stretches across Senegal, Mauritania, Mali, Niger, Chad, Sudan, Eritrea, and the southern tip of Algeria. 
    • The Sahel region transitions South of the Sahara Desert. It spans from the Atlantic Ocean to the Red Sea.
    • From West to East the Sahel stretches across Senegal, Mauritania, Mali, Niger, Chad, Sudan, Eritrea, and the southern tip of Algeria. 
    • The Sahel climate is relatively similar to that of the Sahara. It’s climate is a mix of semiarid and arid dry land.

    The Sahel climate is relatively similar to that of the Sahara. It’s climate is a mix of semiarid and arid dry land.

The Savanna

  • The Savanna is spread throughout Africa with the exception of Northern Africa.
  • The majority of the Savanna consists of tropical climate. Meaning that the daily temperature has a drastic change from morning to night and a more strongly seasonal distribution of rainfall is recorded in this area.
  • This area is where the majority of Africa’s safari-wildlife is located.

The Tropical Rainforest 

  • The rain forest region in Africa is the smallest out of the four areas of Africa that we will discuss.
  • The African rain forest is mainly contained in Cameroon, Equatorial Guinea, Gabon, Congo, Democratic Republic of Congo, and Central African Republic.
  • Congo has the world’s 2nd largest rain forest.
One Comment
  1. Ian Browne permalink

    This will realy help me with my test 🙂

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