Populations Flashcards
what does population mean?
-a group of organisms of the same species living in a particualr area
what are 3 factors that influence population growth?
-birth and death rate
-immigration
-emigration
what is the most common population that is studied?
-bacteria or yeast
what does closed conditions mean?
-when a population growth is monitored in closed conditions e.g. beaker or flask
what are the 4 phases of growth in a population which is shown on a graph?
-the lag phase
-the exponential phase
-the stationary phase
-the decline phase
what does the lag phase mean?
-very slow increase in numbers of the population
-nutrient assimilation occurs at this stage
what is nutrient assimilation?
-process by which organisms absorb and convert nutrients from food or the environment into usable forms for growth
what is the exponential phase?
-when the bacteria divide exponentially
-no restrictions to growth
-the bacteria can divide to produce new bacteria at a maximum rate
what is the stationary phase?
-food supplies may become limiting and so the number of new individuals falls
-waste products can also accumulate which can restrict growth
what is the decline phase?
-death rate exceeds the birth rate and the population declines
what does biotic potential mean?
-the reproductive potential of a population under optimum environmental conditions with unlimited resources
what does environmental resistance mean?
-the restriction by the environment on the population reaching its maximum growth rate and its biotic potential
what are some of the factors that contribute to environmental resistance?
-nutrient shortage
-accumulation of waste
-climate competition
-predation
-disease
what does abiotic factors mean? what are 3 example?
-non-living, chemical or environmental factors
-water, sunlight, oxygen
what does biotic factors mean? what are 2 examples?
-living factors
-food supply and predation
what does carrying capacity mean?
-the maximum number of a population that the ecosystem can support
what is the carrying capacity dependent on?
-the amount of resources available
what type of resources result in the decline phase in bacteria?
-non- renewable which means that nutrients that were used at the beginning of the investigation were not replaced
what is another shape of a graph that shows population growth and decline? what does it show specifically?
-J- shaped curve
-shows very rapid growth period until a peak
-after the peak a population crash occurs and rapid decline
what are 2 reasons for population growth in a J- shaped graph showing the growth of algae?
-few herbivores in water at this time
-both temp and light levels are increasing
what does competition between organisms mean?
-both organisms are competing for the same resource
what are the two types of competition and what do they mean?
-intraspecific meaning competition between members of the same species
-interspecific meaning competition between members of different species
what is the competitive exclusion principle?
-when two species are competing for the same ecological niche, one species will lose out as consequence of this principle
what is the process of the predator- prey interaction?
-large numbers of prey result in more food for predators
-numbers of predators increase causing number of prey to decrease
-low prey causes numbers of predators to decrease
-prey increase as low numbers of predators etc.
what are three common features of the predator- prey graph?
-the predator peaks and troughs lag behind the preys peaks and troughs- because the time lag depends on the rate offspring are produced
-length of predator cycle is similar to prey cycle
-the number of predators is usually lover than prey
