(6) Populations and Sustainability Flashcards
Population growth curve
Fluctuation in population growth - carrying capacity met (population is the maximum size that the environment can support). Not subject to anymore succession.
If all resources were in plentiful supply the population would grow exponentially.
Limiting factors affecting carrying capacity
Abiotic factors
Biotic factors - immigration (organisms moving in) and emigration (organisms moving out).
Interactions between populations
Interspecific competition - between 2 different species (light and food)
Intraspecific competition - between the same species (mates).
Predation (biotic) - predators evolved to catch prey, prey evolved to avoid capture. Graphs show fluctuating birth and death rates.
Conservation
Management of nature to protect species and habitats
Important for economic reasons - ecotourism, potential for future medicine.
Social reasons - aesthetic, prevent impact of deforestation.
Ethical reasons - preserve biodiversity and stop extinction.
Preservation
Leaving an environment alone, so ecosystem is untouched.
Management of an ecosystem to provide resources
Sustainability - preserve the environment, ensure resources are available for future generations, enable less economically develop3d countries to develop (exploiting natural resources).
Timber production : coppicing - thru j cut close to the ground and several new shoots will grow, process is repeated after a certain time, this protects from grazers. New stems grow more rapidly than saplings , life span extended, allows more light for smaller plants, provides habitats which maintains biodiversity and prevents soil erosion.
Selective felling - cutting down selected mature trees forest, allows other trees to grow leaves for animals.
Rotational felling - planting a site, then felling when trees have reached maturity.
Strip felling - cutting selected, mature tees in a strip allows other trees to grow and leaves habitats.
Replants after felling.
Fishing : quotas - limits number of species that can be caught.
Holes in nets - allows smaller fish to escape and reach maturity to breed.
Only fishing at certain times of the year - allowing populations to reach a sustainable level.
Effects of human activity on environmental resources - control in environmentally sensitive ecosystems
Galápagos Islands - endemic species (found nowhere else) - habitat destruction to build roads, deforestation for farming, more boats, more pollution in the sea, overfishing and collecting eggs, new disease.
Park rangers limit human access, stricter control on migration and introduction of animals
Antarctica - overfishing and whaling.
Bans on whaling and restrictions on fishing, waste must be taken away and boats cannot dump waste in the sea.
Snowdonia National Park and Lake District.
Visitors are encouraged to use paths to protect native species, litter to be taken and disposed of, speed limits on boats.
Conservation and preservation vs human needs
Masai Mara (Kenya) - poaching lowered animal population.
Introduced park rangers.
Elephants trample crops.
Fencing off land and legal hunting of overpopulation species allowed at certain times.
Terai Region (Nepal) - forests being cleared for products.
Increase of retail price of forestry products for a greater economic input, more sustainable wood fuel sources, promotion of fruits and vegetables from other areas, improve irrigation of crops, use more nitrogen fixing plants.
Peat Bogs - used for fertilisers, takes thousands of years to form, supports rare species of plant.
No large trees planting nearby because they take water, no grazing for sheep or cattle
