Chapter 6.6-Population and sustainability Flashcards
What are the three stages in population growth of a species?
- lag phase:there many only be a few individuals, which are still acclimatising to their habitat. Rate of reproduction is low and the growth in population size is slow.
- log phase: resources are plentiful, and conditions are good. Reproduction can happen quickly, with the rate of reproduction exceeding mortality. Population size increases rapidly
- stationary phase: population size has reach its carrying capacity of the habitat. Rate of reproduction and mortality are equal. Population size remains relatively stable
What is meant by the carrying capacity(k)?
the maximum population size that can be maintained over a period in a particular habitat
What is meant by limiting factors?
the factor whose magnitude slows down the rate of a natural process
What are density independent limiting factors and name two examples?
- factors act just as strongly, irrespective of the size of the population
- low temperatures and light levels
What are density dependent factors and name two examples?
- factor influences population size more severely as the population size increases
- availability of resources like food and predation
Name two other biotic limiting factors
- disease
- competition for resources
Name two other abiotic limiting factors?
- pH
- humidity
What are k-strategists?
- species whose population size is determined by the carrying capacity (limiting factors)
- as the species population size increases, the effect of the limiting factors have a greater effect
- population size eventually levels out (stationary phase)
What are the main characteristics of k-strategists?
- low reproductive rate
- slow development
- later reproductive age
- long lifespan
- large body mass
What type of organisms are usually k-strategists and name some examples?
- larger mammals
- birds, humans, elephants and larger plants etc
What are r-strategists?
- species which try to outmanoeuvre the limiting factors
- population size increases quickly and it exceeds the theoretical carrying capacity and then the limiting factors start to have an effect
- one the carrying capacity has been exceeded, there are no longer enough resources for survival and there is a build up of waste products
- organism being to die entering a death phase
What are the main characteristics of r-strategists?
- high reproductive rate
- quick development
- young reproductive age
- short life span
- small body mass
What type of organisms are usually r-strategists and and name some example?
- smaller organisms
- mice
- insects
- spiders
What type of strategists colonise a disturbed habitat first, r or k-strategists?
- r-strategists
- r-strategists population can grow rapidly as they have short generation times, such as bacteria and pioneer species
Describe predator-prey relationship?
Cyclic fluctuations
- When predator population gets bigger, more prey are eaten
- The prey population gets smaller, leaving less food for the predators
- With less food, fewer predators can survive and their population size reduces
- With fewer predators, fewer prey are eaten, and their population size increases
- With more prey, the predator population gets bigger, and the cycle starts again
