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Biodiversity and Interdependence (b) Impacts on Biodiversity Learning Intention • To be able to explain the effect of increasing human population on natural resources. More People More Food More Energy More Land More _______ More ______ ________ being burnt More buildings and __________ sites More __________ and ____________ being used on crops More _______ _________ and _________ ________ in the atmosphere Fewer ________ for plants and animals More ________ and __________ pollution More _____ pollution More ____________ Words For Fill the Blanks • • • • • • • • • Pollution More Sulphur Dioxide Building Fossil Fuels Carbon Dioxide Space Food Land Learning Intention • To be able to describe the effects of human activities on pollution and biodiversity. Pollution • Sulphur Dioxide (SO2) is a pollutant that is released from car exhausts and coal power stations. • Lichen is a plant found on trees and is very sensitive to SO2, they can be used as an indicator species for SO2 pollution in the atmosphere. • SO2 and can combine with water to form acid rain. Sewage • When sewage pollutes a river, it acts as a food source for the bacteria that are already present in low numbers. The number of bacteria will increase. • Bacteria use up the oxygen present in the water, so as the number of bacteria increase, the oxygen concentration in the water decreases. • This means that the number of other species present in the water will decrease, as there isn't enough oxygen in the water for them to survive. Sewage Pollution Point where sewage is added High concentration Concentration of bacteria Concentration of oxygen Low concentration Increasing distance downstream Effect of oxygen shortage • A clean water ecosystem normally contains a large number of plant and animal species. • The balance between living organisms in the ecosystem is upset by a high level of pollution since it completely eliminates all of the clean water species. • This leads to a decrease in species diversity, since only a few pollution tolerant species (eg. Sludgeworms) survive. River study Clean Water Sewage polluting river Very badly polluted water Badly polluted water Partly polluted water Deforestation • This term is used to refer to the complete clearing away of vast tracts of natural forest and the failure to plant new forest in their place. • Deforestation happens when land is cleared for farming, or timber is needed for building materials. • Intensive deforestation can lead to a number of disastrous consequences. Desertification • In some parts of the world, the area of land covered by desert is increasing. When this process is the result of human activities, it is called desertification. • Desertification can be caused by overgrazing of animals, or when population increases put pressure on the land. Biodiversity in Crisis • Human activities are causing the current wave of extinction to run at about 400 times its natural rate. Since the year 1600, hundreds of birds and mammals have been wiped out by over-hunting and habitat destruction. • Many species are now endangered. Learning Intention • To be able to describe the effect of grazing on biodiversity. Effects of Grazing • Natural grassland normally contains a rich variety of plant species. Some are sturdy and show vigorous growth while others are more delicate. • Rabbits are relatively unselective grazers. By eating almost all types of plant growing on grassland, they maintain a high diversity of plant species since the vigorous species are kept in check. Effects of Grazing • If the disease myxomatosis or human activities remove rabbits from a piece of grassland then the aggressive dominant grasses are no longer kept in check. • They drive the other less vigorous species out, which reduces the variety present in that ecosystem. Effects of Grazing • But, if there is a high intensity of grazing, this can reduce the species diversity if the less vigorous species become overgrazed. Learning Intention • To be able to describe the effect of competition between species on diversity. Competition • Competition occurs when 2 or more living things need the same resource. • Competition between members of the same species is more intense as they need exactly the same resources. Competition In Plants • Plants compete for resources like: – light – water – soil nutrients. Competition in Animals • Animals compete for resources like: – food – water – shelter Investigating competition • To investigate competition, we could set up the experiment below 100 radish seeds + 100 cress seeds 100 radish seeds 100 cress seeds growth (Radish) % Seeds showing growth (Cress) A 96 67 B 94 Absent C absent 89 Carton % Seeds showing What does this tell us? • Although the conditions in dish A are crowded, the Radish seeds are still found to grow as successfully as those in control A. • The Cress seeds in dish A are not found to grow as successfully as those in dish C – Cress seeds seem to be affected in some way by competition. • In this experiment the seeds are competing for light. Which has been most successful?
