Presentation on theme: "Control & Regulation Regulation & Monitoring of Populations M r G D a v i d s o n."— Presentation transcript:
Control & Regulation Regulation & Monitoring of Populations M r G D a v i d s o n
Saturday, May 09, 2015G Davidson2 Populations A population is a group of individuals of the same species which makes up part of an ecosystem. The number of individuals of the same species in a unit area/volume of habitat is called the population density.
Saturday, May 09, 2015G Davidson3 Population Stability When an environment is colonised by a species, the population grows to the highest level supportable by the environment. The limit is known as the carrying capacity.
Saturday, May 09, 2015G Davidson4 Population Stability The population level is now relatively stable save short-term oscillations from generation to generation. It is said to be in a state of dynamic equilibrium.
Saturday, May 09, 2015G Davidson5 Factors influencing change Every species has a large reproductive potential, but population increase is restricted by environmental resistance, which consists of factors such as: –Food- Water –Space- Oxygen –Light- Shelter –Predation- Disease –Climate
Saturday, May 09, 2015G Davidson6 Factors influencing change A density independent factor is one which affects population growth regardless of density, e.g. weather extremes, forest fire, flood, etc. A density dependent factor is one which affects a population once it has grown to a certain size and density.
Saturday, May 09, 2015G Davidson7 Factors influencing change Once a population reaches this level, it is inevitably affected by one such factor, e.g. –competition starvation –build up of population’s toxic wastes –disease –predation
Saturday, May 09, 2015G Davidson8 Factors influencing change Predator and prey populations are linked and balanced. If conditions favour prey, their numbers will increase. As a result, there will be more food for predators, whose numbers will also rise. An increase in predator numbers will increase predation and therefore prey numbers will fall.
Saturday, May 09, 2015G Davidson9 Factors influencing change Increased competition following this reduction in food will cause predator numbers to drop as some die of starvation. This brings the population back to its original state. Since there tends to be less predators than prey, population graphs of predator and prey numbers are usually very similar:
Saturday, May 09, 2015G Davidson10 Factors influencing change Time Numbers of Population Prey Predator
Saturday, May 09, 2015G Davidson11 Monitoring Populations Many species of wild plants and animals are surveyed closely by scientists to monitor population numbers and affecting factors. This data is needed for: –management of species which provide food or raw materials –pest control –pollution assessment –protection and conservation of endangered species
Saturday, May 09, 2015G Davidson12 Food Species The maximum sustainable yield of a population is a measure of the maximum rate at which individuals can be removed without affecting the population’s future productivity. This keeps populations in check, e.g. –fish – prevent over-fishing by quotas. –keep down red deer populations with cullings.
Saturday, May 09, 2015G Davidson13 Pests Pests are species which threaten mankind’s health or economy. They can include insects, fungi and vermin which spread disease and ruin crops. Noted examples are: –green fly- pathogenic fungi –locusts- mosquitoes –brown rats
Saturday, May 09, 2015G Davidson14 Indicator Species Environmental health can be assessed by examining certain indicator species. Fresh water indicator species include mayfly and stonefly, which show that pollution is low. Birds of prey are affected by over-use of pesticide sprays as toxic chemicals move up the food chain and accumulate in the bird’s diet.
Saturday, May 09, 2015G Davidson15 Indicator Species If, however, water is polluted, it can be shown by the presence of rat-tailed maggots and sludgeworms. On land, air pollution levels can be shown by lichens. The presence of lichens indicates low air pollution.
Saturday, May 09, 2015G Davidson16 Indicator Species Phytoplankton, microscopic, oceanic plants acts as the first link in the marine food chains. They convert much CO 2 into O 2 during photosynthesis and could possibly make a big difference to the greenhouse effect.
Saturday, May 09, 2015G Davidson17 Endangered Species Rare species may have values ranging from medicinal to aesthetical. To prevent extinction, the areas in which some endangered species live in are converted into nature reserves. Over-hunting, poaching, picking and harvesting are controlled or restricted to maintain species numbers.