Human Population Change Flashcards
animal population lag phase
- shortage of reproducing individuals - they haven’t reached maturity or a gestation period
- therefore the growth rate is very slow
- lag phase may last for a few months or years - period of adaptation to the new environment
animal log / exponential phase
- fastest population growth
- plentiful resources -> population grows at it’s maximum rate
- no limiting factors (lack of environmental resistance)
- reproductive rate > death rate
animal stationary phase
- carrying capacity - population is roughly constant
- growth rate slows -> intraspecific competition
- carrying capacity has been reached
- birth rate = death rate
carrying capacity
maximum population size that can be sustained over a period of time in a particular habitat
animal death phase (not often seen)
- death rate > reproductive rate
- may occur when deadly disease or when food source is wiped out leading to a population crash
bacterial / yeast lag phase
- bacteria / yeast are synthesising new enzymes and proteins
- slow rate of cell division
bacterial / yeast log / exponential phase
- plentiful mineral ions + glucose
- no limiting factors
- cells divide at maximum rate
- doubling for every unit time
- reproductive rate > death rate
bacterial / yeast stationary phase
- reproductive rate = death rate growth medium is running out
- toxins are starting to build up
bacterial / yeast death phase
- death rate > reproductive rate
- build up of toxins ie ethanol
environmental resistance
environmental factors that slow down population growth
what factors contribute to environmental resistance for bacterial culture?
- available growth medium
- overcrowding
- competition
what factors contribute to environmental resistance in an animal / plant population
- predation
- parasitism / disease
- competition
- light intensity
- water supply
- water mineral content
- temperature
- soil pH
- space available
if environmental resistance is increased, how would this affect the carrying capacity?
decrease as population decreases forcing carrying capacity to fluctuate around a lower point (harder for organisms to survive in a new environment)
what are density-dependant factors (biotic)
- disease (could lead to a population crash)
- competition
- predation
- parasitism
- food availability (could lead to a population crash)
- accumulation of toxic waste
- territory / shelter availability
what are density-dependent factors? (definition)
affect a higher proportion of the population if it is denser
what are density independent factors? (definition)
the effect of these factors does NOT depend on population size all members of the species are equally affected
what are density independent factors
- soil pH
- light intensity
- mineral ion availability
- temperature
- weather
what are the key patterns of predator of predator-prey cycle
- number of predators increase as there is more prey available
- the number of prey then decreases as there are now more predators
- the number of predators decreases as there is now less prey available
- the number of prey increases as there are now fewer predators
- cycle repeats
