populations and sustainability Flashcards
what is a limiting factor?
an environmental resource or constrain that limits population growth
a population growth curve can be operated into three different phases. Explain these phases?
- first phase of slow growth. Small numbers of individuals initially present reproduce increasing total population. As birth rate is higher than death rate, the population increases in size.
- second phase of rapid growth. The number of breeding individuals increases and the total population multiplies exponentially. No constraints act to limit population explosion.
- third phase of stable state (carrying capacity). Further population growth is prevented by external constraints (limiting factors). Population size fluctuates but overall size remains relatively stable.
what is an abiotic factor?
non-living factor e.g temp, humidity, water
what is a biotic factor?
living factor e.g disease, predator, prey
what is carrying capacity?
the maximum population size an enviroment can support
how does a population size remain stable?
when number of births and deaths are approximately equal.
types of limiting factors?
- abiotic
- biotic
- migration
2 types of migration?
immigration and emigration
what is immigration?
the movement of individual organisms into a particular area increases population size.
what is emigration?
the movement of individual organisms away from a particular area decreases population size
what are density independent factors?
factors that have an effect on the whole population regardless of its size e.g each quakes, fires, storms. These factors could remove whole populations of species in an area.
Unlike other species why does the population size of humans grow exponentially?
there is an imbalance between birth rate and death rate due to advances in medicine and agriculture and the industrial revolution.
how do you calculate population percentage growth?
(population change during the period/ population at ther start of the period) times 100
what are the two types of competition? (biotic factors)
interspecific competition and intraspecific competition
what is interspecific competition?
competition between different species e.g predation
what is intraspecific competition?
competition between the same species
Describe interspecific competition?
this interaction causes reduction of resource available for organisms of each species. However if one species is better adapted, the less adapted species will be outcompeted. If conditions remain, the species population will decline- competitive exclusion principle e.g squirrels
what is competitive exclusion principle?
two species competing for limited resources. The one that uses resources more effectively will ultimately eliminate the other.
why did the grey squirrels dominate the red squirrels?
grey squirrel can eat a wider range of food and can store more fat increasing change of survival and ability to reproduce
Describe intraspecific competition
availability of the resource determines the population size. Greater availability, larger population. This leads to fluctuations.
The intraspecific graphs can be separated into three stages. Explain these stages.
stage 1- when resource is plentiful, enough resource to survive and reproduce causing increase in population
stage 2- increased population causes limited resources which is not enough for survival and reproduction causing population to decrease
stage 3- less completion as the population. More resources for survival and reproduction causing population growth.
The predator prey relationship graph can be separated into 4 stages. Describe these stages.
stage 1- increase in prey population provides more food for predators, allowing them to survive and reproduce causing increase in predator population.
stage 2- increase predator population causes more prey eaten, causing decline in prey population. Death rate of prey is higher than birth rate.
stage 3-reduced prey population cannot support predator population. Intraspecific competition for food increases causing decrease in predator population
stage 4- reduced predators, less killed prey killed. More prey survive and reproduce, increasing population.
Why is the predator- prey relationship not simple?
other factors influence populations size e.g presence of other predators and prey food availability (plants)
what is conservation?
the maintenance of biodiversity through human action or management. Conversation approaches also includes reclamation- process of restoring damaged ecosystems.
