Populations in ecosystems Flashcards
what is ecology?
the study of the inter-relationships between organisms and their environment
what are the two major processes of an ecosystem?
– the flow of energy through the system
– the cycling of elements within the system
what is a population?
a group of individuals of same species, in same habitat, at same time
what causes the size of a population to vary?
– the effect of abiotic factors
– interactions between organisms
what is a community?
all the populations of different species living and interacting in a particular place at the same time
what is a habitat?
the place where an organism normally lives and is characterised by physical conditions and other types of organism present
what is an ecological niche?
how an organisms fits into the environment
what is an abiotic factor?
a non-living factor
what are some example of abiotic factors
– temperature
– light
– pH
– Water and humidity
what is intraspecific competition?
competition between members of the same species
what is interspecific competition?
competition between members of different species
what is predation?
when one organism is consumed by another
what are the relationships between predators and prey and how can it affect population size?
– predators eat their prey, reducing population of prey
– fewer prey available the predators are in greater competition with each other
– the predator population is reduced as some individuals are unable to obtain prey
– with fewer predators left, fewer prey are eaten so more survive so can reproduce
– the prey population increases
– more prey available as food predator population increases
what is a point quadrat?
a horizontal bar supported by two legs. Ten holes along the horizontal bar which a pin can be dopped through. each species touching the pin is counted
what is a frame quadrat?
a quare frame divided by string it equally sized divisions.
what are the three factors to consider when using quadrats?
– the size of quadrat to use
– the number of sample quadrats to record within the study area
– the position of each quadrat within the study area
Describe a good method of random sampling.
– lay out two long tape measures at right angles, along 2 sides of the study area
– obtain a series of coordinates by using random numbers taken from a table
– place a quadrat at the intersection of each pair of coordinates and record the species within it
how do you measure frequency of a species?
percentage of the quadrats that gave the species in it.
how do you measure percentage cover of a species?
only count the square if the species covers over half the square
what is the equation for estimating size of population.
estimated population size
(total number of individuals in the 1st sample x total number of individuals in the 2nd sample)
/
number of marked individuals recaptured
what are assumptions are made in order to be able to rely on the mark-release-recapture techniques.
– the population of marked to unmarked individuals in the second sample is the same as the proportion of marked to unmarked individuals in the population as a whole.
– the marked individuals released from the first sample distribute themselves evenly amongst the remainder of the population
– the population has a definite boundary
– few deaths
– marking method not toxic
– mark is not rubbed off
what is a pioneer species?
the first species in succession
what features do pioneer species usually have?
– asexual reproduction so a single organism can rapidly multiply
– production of vast quantities of wind-dispersed seeds or spores
– rapid germination of seeds on arrival as they do no require dormancy
– the ability to photosynthesise
– ability to fix nitrogen
– tolerance to extreme conditions
what are common features of succession?
– the non-living environment becomes less hostile
– a greater number and variety of habitats and niches
– increased biodiversity
– more complex food webs
– increased biomass
what are the main reasons for conservation?
– personal
– ethical
– economic
– cultural and aesthetic
