U1T4 - Keywords (1) Flashcards
Populations + Communities
Population
Group of organisms of same species living in particular habitat.
Lag Phase
Pop nums remain relatively constant or decline/slow increase in nums. Nutrient assimilation + reproduction.
Exponential/Log Phase
Pop nums increase by same factor each time unit. Each new member reproduces so rapid growth as low competition as sufficient resources + little waste. Increase by intrinsic rate of natural increase (r) as pop exhibits biotic potential.
Stationary Phase
Increased pop numbers result in environmental resistance due to waste accumulation, lack resources + increased comp. Reduced birth rate + increased death rate so pop stays constant. Reaches carrying capacity (k). Most pops stay at this stage.
Decline Phase
Lack resources + increase in toxic waste means birth rate 0 + high death rate. Steep decline/crash in pop nums.
Biotic Potential
Max growth/repro rate of pop under optimum conditions.
Carrying Capacity
Max pop size that can be supported by available resources. Max num organisms ecosystem can support.
Intrinsic Rate of Natural Increase
The rate at which a population increases in size if there are no density-dependent forces regulating the population. Births - deaths per generation time.
Environmental Resistance
Sum of environmental factors which restrict biotic potential of population + limit increase.
Renewable Resource
Resource which can be used repeatedly + replaced naturally.
Non-renewable Resource
Resource that doesn’t renew itself at sufficient rate for sustainable economic extraction in human time-frames.
Detritivores
An animal which feeds on dead organic material.
Survivorship Curve
Shows % of individuals surviving over a year/number of years.
R + K Selection Theory
Relates to selection of traits which promote success in certain environments + originates from work on island biogeography by MacArthur + Wilson. Selective pressures are hypothesised to drive evolution in r or k directions.
R Selected Species
Grow v. quickly as individual, pop size increases rapidly under ideal conditions, numbers decline rapidly in less favourable conditions, emphasis on reproduction + colonisation, less parental involvement, small, short life, high dispersal, not competitive, not specialised so adaptable, unstable habitats + high fecundity.
K Selected Species
Stable pops, large, long life, more specialised so less resistant to environment change, stable habitats, pop close to carrying capacity, emphasis on survival + dominance, not colonisation, successful competition, more parental involvement, low fecundity, less able to migrate so more likely to become extinct.
High/Low Fecundity
Many/Few Offspring at once.
Intraspecific Competition
Competition between members of the same species. Becomes more severe as pop increases + resources become limited.