Cambridge International AS and A Level Biology Coursebook with CD-ROM
Biology cie 9700 A level notes on topic 18( 7th topic from A level section)
summary made out of notes from both CIE textbook, classnotes and past papers. covers all the syllabus checklist for 2018.
Achieved 91% on my biology A level this june. Prepared for the exam using these notes and past pape...
The biodiversity of the Earth is threatened by human activities and climate change. Classification systems
attempt to put order on the chaos of all the organisms that exist on Earth. Field work is an important part
of a biological education to appreciate this diversity and find out how to analyse it.
Conserving biodiversity is a difficult task but is achieved by individuals, local groups,
national and international organisations. Candidates should appreciate the threats to biodiversity and
consider the steps taken in conservation, both locally and globally.
Species: a specie is a group of organisms with similar morphology and physiology, which can breed
together to produce fertile offspring and are reproductively isolated from other species.
Ecosystem: an ecosystem is a relatively self-contained, interacting community of organisms, and
the environment in which they live and with which they interact.
Niche: A niche is the role of an organism in an ecosystem.
Biodiversity can be defined as the degree of variation of life forms in an ecosystem. This is
usually taken to include diversity at three levels.
(variety of/different/total number of species.
Genetic diversity of species)
1. Variation in ecosystems or habitats.
2. The number of different species in the ecosystem and their relative abundance
Species diversity take species richness into account, bit also includes a measure of the
evenness of abundance of the different species. The more species there are and the more
evenly the number of organisms are distributed among the different species, the greater the
species diversity. Ecosystems with high species diversity tend to be more stable, able to resist
changes.
3. The genetic variation within each specie.
Genetic diversity is the diversity of alleles within the genes in the genome of a single species.
All the individuals in a specie have the same genes but they might have different alleles to
that gene. Genetic diversity within a specie can be assessed by finding out what proportion of
genes have different alleles and how many alleles there are per gene. This diversity is
important in providing populations with the ability to adapt to changes in biotic and abiotic
factors..
Countries such as the Caribbean , central America, Amazonia have high biodiversity’s. And have
endemic species: species only found in these specific areas
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