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Transcript
Biodiversity Objectives • Define the terms species, habitat, and biodiversity • Identify the Levels of biodiversity – habitat, species, and genetic • Know how to measure biodiversity by sampling; taking of random samples Biodiversity - definitions Biodiversity All the different species of organisms worldwide, the genes they contain and the ecosystems they are a part of. Species Individuals that are very similar in appearance, anatomy, physiology, biochemistry and genetics so that they can interbreed and produce fertile viable offspring Ecosystem All the living (biotic) and non living (abiotic) components in a specific area and their interaction Habitat a place where an organism or population lives, including the climate, topography and abiotic factors there as well as the plants and animals (biotic factors) Different aspects of diversity Habitat Diversity • the range of habitats in which different species live Species Diversity the number of different species and the abundance of each species in an ecosystem. • Structural - tree and an ant • Functional – bacteria that cause decay and those that digest food Genetic Diversity • the variation of alleles within a species (or a population of species). • Genetic variation between individuals belonging to the same species • Note: A number of genes are the same in different species – similar fundamental biochemistry and cell structures – e.g. respiration – requires same enzymes The importance of genetic diversity • allows species to evolve. • allows organisms to adapt to changes in the environment such as: climate change, increased pollution, new disease, new pests Human effects on biodiversity • Clearing of natural vegetation reduces habitat size and Population size of the species in that habitat • Hunting • Introduction of predators and competitors • Monoculture and selective breeding reduces variation and genetic diversity and could lead to extinction of some varieties within a species (genetic erosion) reducing overall gene pool for the species. Decreased genetic variation reduces the ability of the species to adapt and evolve Measuring biodiversity • Need to find out what species are present in a habitat and what population size there is • Sampling can be random or systematic • Most plant sampling techniques use quadrats Quadrats Use square framed quadrats to measure plant abundancy Place the quadrat, identify the species and then assess their abundancy or percentage cover Point quadrats Have 10 metal pins in a row. Place in quadrat and count the number of plants each pin touches Random sampling • Random uses chance to determine the sampling points and eliminates bias • Mark the area to be sampled as a grid • use random numbers to generate coordinates to place quadrat • Identify and count plants Systematic sampling • To measure how vegetation changes e.g. from the shore away from the sea • Use systematic sampling with a transect • Place a quadrat at regular intervals along the transect • Identify and count the plants Line Transect A line (rope or tape) is laid across a habitat Record all the plants of the sampled species touching the line at set intervals along it Belt Transect Place a series of frame (or point) quadrats along a line at regular intervals (interrupted belt) or move them along the length (continuous belt) Count and identify the organisms in each quadrat A belt transect gives both distribution and abundance. Sampling Plants • Large plants can be counted • Smaller plants usually assessed by percentage cover • ACFOR is used as an abundancy scale A Abundant C Common F Frequent O Obvious R Rare ACFOR Sampling Animals Sampling animals offers the challenge of counting mobile organisms Sampling of large animals can be considered unethical so tracing tracks, droppings and food is used. Sampling of invertebrates has more variety of methods and not considered to be unethical. Light trapping (really good for moths) Trap, identify and count Tullgren funnel Sweep netting Consider size of net, sweeping action, no of sweeps, suitability to organisms and habitat Pooter To make a fair comparison between habitats • Sample randomly • use the same sampling technique and same procedure – e.g. number of quadrats, number of sweeps with net, method of sweep, number of sweeps Current Estimates of Global Biodiversity • Between 1.5 and 1.75 million species have been estimated to be present globally by scientists. • The figures are not exact • there is no central database of all species • different opinions exist between scientists about the classification of certain species • A large proportion of species on earth have not been named • Many species are undiscovered or known but not yet named Current estimates of global biodiversity are too low Different techniques being used to make estimates Lack of information for some species – e.g. bacteria and insects Variations in biodiversity in different parts of the world due to geographical factors. The greatest diversity is near the equator and it decreases towards the poles. Large areas of tropical rainforests, the poles, and deserts not yet explored Climate change affecting biodiversity Continuing evolution and speciation Many species becoming endangered or are becoming extinct Estimates change as scientists find out new information Do not take into account numbers of individual species or variation between or within species 27