4.1 Biodiversity in ecosystems
4.1.2 Outline the mechanism of natural selection as a possible driving force for speciation.

Speciation occurs as a result of the isolation (geographical or reproductive) of populations. The concept of fitness should be understood. The history of the development of the modern theory of evolution is not expected, nor is a detailed knowledge of genetics (including allele frequency).

4.1.3 State that isolation can lead to different species being produced that are unable to interbreed to yield fertile offspring.

Isolation of populations, behavioural differences that preclude reproduction and the inability to produce fertile offspring (leading to speciation) should all be examined, with examples.


The amount of biological or living diversity per unit area. It includes the concepts of species diversity, habitat diversity and genetic diversity.

The process through which new species form.

The cumulative, gradual change in the genetic characteristics of successive generations of a species or race of an organism, ultimately giving rise to species or races different from the common ancestor. Evolution reflects changes in the genetic composition of a population over time.

The process by which two populations become separated by geographical, behavioural, genetic or reproductive factors. If gene flow between the two subpopulations is prevented, new species may evolve.

Plate tectonics
The movement of the eight major and several minor internally rigid plates of the Earth’s lithosphere in relation to each other and to the partially mobile asthenosphere below.


Introdution to Topic 4: Conservation and biodiversity

This topic raises some engaging issues of debate concerning the moral justification for exploiting species and the moral imperative for conserving them. Do other organisms have a right to moral consideration? How is this justified? Do panda bears have a greater right than lichens? What about the rights of “pest” or pathogenic organisms? To what extent are these arguments based upon emotion and to what extent upon reason? And how does this affect their validity?

4.1.1 Define the terms biodiversity, genetic diversity, species diversity and habitat diversity.


From Mr G's Environmental Systems site
© Copyright 2007 www.sciencebitz.com

4.1.5 Explain the relationships among ecosystem stability, diversity, succession and habitat.

Consider how:

• diversity changes through succession

• greater habitat diversity leads to greater species and genetic diversity

• a complex ecosystem, with its variety of nutrient and energy pathways, provides stability

• human activities modify succession, for example, logging, grazing, burning

• human activities often simplify ecosystems, rendering them unstable, for example, North America wheat farming versus tall grass prairie

• an ecosystem’s capacity to survive change may depend on diversity, resilience and inertia.



4.1.4 Explain how plate activity has influenced evolution and biodiversity.

The consequences of plate tectonics on speciation should be understood (that is, the separation of gene pools, formation of physical barriers and land bridges) together with the implications these consequences have for evolution. The role of plate activity in generating new and diverse habitats, thus promoting biodiversity, should also be considered. Detailed understanding of the mechanism of plate tectonics is not required.


From Mr G's Environmental Systems site
© Copyright 2007 www.sciencebitz.com