Biodiversity and evolution SPEC

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Biodiversity is a measure of the number of species on the planet. A species is a group of organisms that can interbreed under natural conditions and produce fertile offspring. 

The number of species per square kilometre increases as one move from the poles to the tropics. Tropical rain forests and coral reefs are the most diverse habitats on the planet 


The fossil record shows that most species are now extinctEvolutionary history shows that biodiversity has gone through several bottlenecks called mass extinctions followed by radiations of new species. 

Natural selection drives the evolution of new species. Darwin’s finches are an example of adaptive radiation. They found a niche to specialise in (seeds or insects).

The classification of organisms is based on their evolutionary relationshipsOne classification concept is that of a simple phylogenetic tree. All organisms can be placed into a hierarchical system of classification that includes – kingdom, phylum, class, order, family, genus, and species. Organisms are more closely related with progression from kingdom to species.


Taxonomy is dynamic and there are differences of opinion about whether morphology or genetics are more central for a basis of classification. 

The animal kingdom is split into major phyla and several smaller ones. Each phylum includes animals based on a shared basic blueprintA genus is a group of closely related species; the binomial system includes both a genus and species name. 

The basic features of some important phyla to include: 

 a. annelids (8000 named species) examples - earthworm, leech, and lugworm.


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