Managing interactions between species Flashcards
Why are populations of organisms managed?
Populations used for food or raw material, for finding sustainable yields.
Species of conservation concern, to prevent decline and extinction.
Pest species, to prevent their densities reaching environmentally damaging levels.
What does the management of species involve?
The manipulation of density of species.
Define population density
The number of individuals of a species per unit space
What factors affect population?
Birth, death, immigration and emigration rates.
Define and list density-dependent factors.
Factors whose effect increases as the population density increases.
Disease, competition, predation.
Define biotic influence.
Impacts caused by living components of the ecosystem.
What is the effect of biotic influences?
Ecological homeostasis (regulatory and controlling effect).
Density-dependent effects change birth and death rates. How can a rate be calculate?
Dividing the number of births or deaths by the size of the population.
How can plant competition be managed and what is the effect of this method?
Herbicides. They tend to reduce species diversity and ecosystem stability.
Give an example of herbicide.
Auxins, destroy broad leafed plants.
How can disease be managed?
Pathogens can be controlled using pesticides such as fungicides, antibiotics or antiparasitic drugs.
Molluscicides and insecticides can reduce the transmission of parasites through destruction of secondary vectors.
What are antibiotics used for? What has evolved due to this?
prevent and control disease in farm animals. Selection of resistant strains of bacteria.
Why are ecosystems less resilient?
there is less diversity due to the removal of many species from the ecosystem.
How are species that are harmful to crops reduced?
Use of pesticide (such as insecticides) or agents of biological control (eg predators -beetle).
What is the problem in using pesticides?
Can lead to the selection of resistant populations of insects and can be toxic or polluting.
