Sunday 30 September 2007

End of topic assessment - Ecosystems


I'm really impressed! Most of you managed to complete the whole question in the time available, including the case study section. You used a variety of case studies - the most successful answers were based on the Savanna Grasslands.
I noticed three main things about your answers:
(a) lots of people hadn't learnt their definitions - so they threw away easy marks!
(b) quite a few of you didn't read the questions carefully - you ended up describing where you should have been explaining and I couldn't give you any marks!
(c) most people didn't use the data from the graph appropriately - you must quote figures from the graph if you are asked to describe what it shows!
These things are easy to put right - I'm already looking forward to results day 2009 as I'm confident that you'll all do really well if you keep at it. Well done.
To revise your graph interpretations skills, you could use the BBC Bitesize summary. Why not take the test bite to see how much you can remember once you have worked through the online unit?

Saturday 22 September 2007

Desertification in The Sahel

Lesson objectives:


  • To know where the Sahel is located.

  • To know that the Sahel has undergone desertification in recent decades.

  • To understand the causes and consequences of desertification in the Sahel.

  • To recognise that people can manage land in a sustainable manner to reduce the impacts of further desertification.


Where is the Sahel?

The Sahel region lies just to the south of the Sahara Desert in Africa.



The Sahel has been heavily affected by the process of desertification - this means that the land is turning to desert. Desertification happens because of both physical and human factors. The term 'land degradation' tends to be linked to the human factors, with 'desertification' being linked to climate change.

This clip from BBC Bitesize provides a useful summary of the topic. It is a video file - you will need to turn your speakers on or plug your headphones in before you watch it! Alternatively (or additionally if you're feeling keen!) you could watch the green.tv clip - I can't work out how to embed this in the blog, so please click on the link and then watch the movie in a new window.







Here is the PowerPoint we used during the lesson:





The extension task was to add arrows to the flow chart showing how a range of factors interact to cause desertification. The chart without the arrows is here.




An example of a completed flow chart is shown below.








Thursday 13 September 2007

The Savanna Grasslands

The objectives of the lesson were:

• To be able to describe the location of the savanna grasslands biome.
• To be able to describe the climate, soils and vegetation of the biome.
• To draw a labelled diagram to show how a given plant from the savanna adapts to the wet and dry seasons.



This clip is from 'The Lion King', which is set in the African savanna grasslands. You can see a wide variety of animals in the clip. There are some isolated trees, such as the baobab and acacia.

As you watch the clip, think about what 'The Circle of Life' means in the context of your study of ecosystems.



The map below shows the location of the savanna grasslands. This biome is located mainly between 5 and 15 degrees north and south of the equator. It lies between the tropical rainforest and hot desert biomes.



There are clear seasons of wet and dry weather in the savanna. As a result, plants and animals have to adapt to extremes of moisture availability. The rain falls in short bursts (convectional rainfall). The main adaptation is to drought in the dry season. Most plants have xerophytic (drought-resistant) characteristics. The wet season allows the vegetation to grow and at this point of the year the vegetation can include lush green grasses and wooded areas. As you move further away from the equator and its heavy rainfall, the grassland becomes drier and drier - particularly in the dry season. Savannah vegetation includes scrub, grasses, and occasional trees which grow near water holes, seasonal rivers or aquifers. Animals migrate long distances to get to water.

Grasses
The grass grows very quickly, reaching up to two metres high in the short wet season. As many of the animals in this biome feed on grass, they have adapted in different ways in order to co-exist. For example,

• zebras eat the tall grass
• wildebeest eat the short grass
• gazelles eat the new growth left behind

Baobab Trees
Baobob trees (sometimes known as 'upside-down trees') can grow up to 25 metres tall and 10 metres wide. They store water in their trunks (up to 120,000 litres!) and they have a thick bark which protects against fire. This also reduces moisture loss. They have very few leaves, and the leaves are only on the tree for about 3 months each year. The trees lose their leaves through the dry season to conserve moisture and have long roots so they can get water from deep underground.



In 'The Lion King', Rafiki has made his home in a Baobab Tree.