National 5 Biodiversity and the Distribution of Life

Biomes

 There are many different ecological areas across the world, each with it’s own distinct characteristics.

 These regions are called Biomes.

 Each biome has it’s own communities of animals (fauna) and plants (flora) which have adapted to live in these regions.

Saturday, 02 May 2020 Mr G Davidson Slide 2

Biomes

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Biomes

 Biomes are different from each other based on a number of abiotic factors such as rainfall and temperature.

 Abiotic factors are non-living and other examples include pH, light intensity, oxygen concentration, etc..

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Biomes

 There are also other factors which can affect the distribution of organisms, and these are called biotic factors.  Biotic factors are a direct result of living things and include amount of food, number of predators, competition with other organisms, disease, etc..

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Ecosystems

 An ecosystem is a natural biological unit composed of both living and non-living parts.

 An ecosystem is made up of a number of habitats, which are the places where organisms live.

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Ecosystems

 All the living organisms in an ecosystem make up the community.

 Each organism has a specific role to play within an ecosystem and this is called the niche, and includes the interaction with other organisms as well as the use of resources from within the ecosystem.

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Biodiversity

 Biodiversity is the degree of variation that exists amongst all living organisms on Earth.

 It can be increased or decreased within ecosystems depending on which factors are influencing the populations, and by how much.

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Grazing

 Grazing is a biotic factor responsible for affecting biodiversity.

 If a particular area is under-grazed, the biodiversity is decreased.

 This is because the dominant plants eventually smother the less dominant plants, stopping them growing, and this results in fewer plant species growing.

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Grazing

 If a particular area is over-grazed, the biodiversity is also reduced.

 This is because all the plants are being grazed and this can result in some of the species of plants being wiped out, so reducing the biodiversity.

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Grazing

 If, however, an area is moderately grazed, this can increase the biodiversity.

 The dominant plants are kept in check by the grazers, allowing the more delicate plants to flourish because they get more resources.

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Predation

 Predation is a biotic factor which can also affect the biodiversity.

 Predators can be responsible for keeping populations of prey in check, and thus allow an increase in biodiversity.  If predators are reduced or removed, the prey then increase in numbers and so this can lead to over-grazing and a reduction in the number of plant species.

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Predation

Prey Predator

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Time

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Temperature

 Gases such as carbon dioxide and nitrous oxide are released when fuels are burned.

 They are responsible for trapping the Earth’s heat causing global warming.

 The knock on effect of this is the melting of the polar ice caps and flooding.

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Temperature

 Temperature is also responsible for affecting the biodiversity of fish.

 A temperature increase in water reduces the amount of oxygen present in the water and therefore reduces the biodiversity of fish species.

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pH

 When fossil fuels are burned they release sulphur dioxide and nitrogen dioxide.

 These gases dissolve in water in the clouds and this lowers the pH making the rain acidic.

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pH

 This acid rain damages plant leaves which reduces photosynthesis and therefore the amount of plant material available for animals to eat.

 Acid rain also dissolves nutrients in the soil meaning less are available for plants.

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pH

 Acid rain is also responsible for reducing the pH of freshwater.

 This reduces the numbers of certain species of fish therefore reducing the biodiversity.

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The Impact of Humans

 Humans have a huge impact on biodiversity in a number of ways, as well as those already covered.

 With the increase of the human population and the improvements in technology, this has led to human over exploitation.

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The Impact of Humans

 Some species of animal are in danger of extinction due to over-hunting, mainly for food, but also for skins or simply trophies.

 Over-fishing has reduced the numbers of the populations of certain species of fish.  Fishing quotas have been put in place to try to prevent this worsening.

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The Impact of Humans

 Over-grazing of land is another major problem in some countries.

 This has resulted in soil erosion which means the soil can no longer be used to grow plants which return nutrients to the ground.

 The result is that no crops can be grown.

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Habitat Destruction

 Tropical rainforests are being cut down to create farmland to replace the land which has been over-grazed.

 This deforestation leads to the extinction of many species and the reduction of other population numbers.

 Habitats are being removed and the organisms left are subject to even greater competition.

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Habitat Destruction

 Over-farming of land, in order to meet the food demand, leads to the removal of nutrients from the soil.

 This results in reduced vegetation which in turns leads to soil erosion when the rain comes.

 This process is called desertification.

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Endangered Species

 Endangered organisms are on the verge of extinction.

 Some organisms are endangered due to human activity such as introducing new species to a certain habitat.

 This new species then ousts the native species and so reduces biodiversity, e.g. Japanese knotweed.

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Pollution

 Pollution is the addition of something to the environment which causes harm.

 Water can be polluted in a number of ways:  Litter – this can kill animals which live in the water as they may eat the litter.

 Organic waste – this provides food for bacteria and so their numbers increase leading to a reduction of oxygen in the water, and so reducing the biodiversity.

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Pollution

 Air can also become polluted due to the effects of humans, like the production of sulphur dioxide.

 Some plant species such as lichens are very sensitive to air pollution.

 We call these species indicator species because they give us information about the state of an ecosystem, i.e. if the lichen is present the air is unpolluted and vice versa.

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