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B2, Topic 6.4
Extension
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A Madagascan mystery
Aims
Speciation is the formation of a new species. New species can arise as a result of
isolation. Isolation is when two populations of a species become separated, for example,
geographically.
Natural selection occurs in each population. This means the alleles that control the
characteristics that help the organism to survive are selected. Eventually the populations
become so different that successful interbreeding is no longer possible. This is the
formation of a new species.
This happened for over 150,000 different species on the island of Madagascar. In this
activity you will think about how this happened. You will look in particular at the example
of lemurs.
Your task
Madagascar – an isolated island off the coast of Africa – has some of the highest
biodiversity on the planet. Madagascar is home to more than 250,000 species, 70% of
which are endemic – meaning they exist nowhere else on Earth.
Unique to the island are more than 50 species of lemur, nearly all of its frog species, and
36 species of bird. Madagascar is home to 100% of the world's lemurs, half of all
chameleon species and 6% of all frogs. Some species found in Madagascar have their
closest relatives not in Africa but in the South Pacific and South America.
Madagascar is an island nation in the Indian Ocean that has been completely isolated
from other land masses for the last 80 million years. Isolation has led to a high number
of unique species such as lemurs. Madagascar has been labelled a biodiversity ‘hotspot’
by conservation groups.
New species can form when a group of organisms becomes geographically isolated.
Over millions of years natural selection occurs and eventually the two populations are so
different they can no longer interbreed. Then a new species has arisen. This happened
many times on Madagascar.
Your task is to design a flow chart to explain the sequence of events that led to the
evolution of lemurs on Madagascar. You can use the information given above and any
other additional resources that are available. Your flow chart can utilise words, pictures,
diagrams and charts.
New AQA GCSE Science © Nelson Thornes Ltd 2011
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