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
