Zusammenfassung der Ressource
B3.5
- Factors in an ecosystem that affect all living organisms constantly change
- ecosystems are dynamic
- intensity of energy flowing through ecosystem varies
- biological cycles vary mineral availability
- nitrogen cycle
- habitats change overtime as succession occurs
- new species arrive
- some no longer present
- number of individuals in a population changes
- birth rate
- increases population
- death rate
- decreases population
- immigration
- increase population
- emigration
- decrease population
- different strategies for population growth are used by different species
- depends on their characteristics
- fugitive species
- poor at competition, rely on a large capacity for reproduction and disposal to increase their numbers
- invade a new environment rapidly
- algae colonising bare rock
- equilibrium species
- control their population by competition within a stable habitat
- usual pattern of growth is sigmoid curve
- one-step growth curve
- bacteria put into fresh nutrient solution
- 1. lag phase
- period of slow growth, adaptation/adjustment to environment, intense metabolic activity
- enzyme synthesis, sexual maturity
- 2. log/exponential phase
- no factors limiting growth, constant cell division, more individuals reproduce
- can't be maintained
- environmental resistance
- less food, conc of waste products becomes toxic, space
- overcrowding, competition
- abiotic factors
- temperature, light intensity
- biotic factors
- predation, parasitism, disease, competition
- 3. Stationary phase
- number of cells being produced = number of cells dying
- max carrying capacity
- population fluctuates
- no. of predators
- 4. death/decline phase
- factors that slow population growth becomes more significant
- population decreases
- abundance of prey limits the number of predators
- controls number of prey
- predator-prey relationship causes both populations to oscillate
- regulated by negative feedback
- lynx and snow-shoe hares
- large numbers of lynx predate hares
- population decreases
- not enough food for lynx
- population decreases
- less predation on hares
- population increases
- more prey for lynx
- population increases
- llustrates how population numbers at the carrying capacity can depend on the number in other species