19 Populations In Ecosystems Flashcards
What is a population
A group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed
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
Place where an organism normally lives and is characterised by physical conditions and the other types of organisms present Within each habits there are smaller units each with their own microclimate, these are called microhabitats
What is an ecological niche
Describe how an organism fits into an environment, refers to where an organism lives and what it does there, Includes all biotic and abiotic conditions to which an organism is adapted in order to survive reproduce and maintain a viable population
Why can no population continue to grow in definitely
Certain factors limit growth for example the availability of food light water oxygen and shelter and the accumulation of toxic waste, disease, and predators Each population has a certain size, the carrying capacity, that can be sustained over a relatively long period and this is determined by these limiting factors
What happens To warm blooded animals in extreme temperatures
More energy to maintain body temperature Leaves less energy for growth and so they mature more slowly and reproductive rate slows, carrying capacity of population is therefore reduced
What is the competitive Exclusion principle
No two species can occupy the same niche indefinitely when resources are limiting When populations of two species are in competition one will have a competitive advantage over the other normally One population will increase in size while the other will diminish If conditions remain the same this will lead to the complete removal of one species
Type of into specific relationship
Predator prey relationships A predator is an organism that feeds on another organism known as their prey
How have predators and prey evolved
Predators, Faster movement more affective camouflage better means of detecting prey Prey, Better camouflage more protective features such as spines concealments behaviour
Relationship between predators and the prey and its affect on population size
Predators eat their prey reducing population of prey With fewer prey available predators are in greater competition with each other for prey that are left Predator population is reduced as some individuals unable to obtain enough prey for survival or to reproduce With fewer predators left fewer prey are eaten and so more survive and are able to reproduce Prey population therefore increases With more prey now available as food, predator population increases
In natural ecosystems fluctuations of predator and prey population sizes are less severe why is this the case
Organisms eat a range of foods and therefore the fluctuations are less severe
What other than predator prey relationships causes fluctuations in populations
Disease and climactic factors also play a part , these periodic population crashes are important in evolution as there is a selection pressure which means that those individuals who are able to escape predators are more likely to survive and reproduce
What is abundance
Number of individuals of the species in a given space
Which sampling techniques used in study of habitats
Random sampling using Frame quadrat or point quadratic Systematic sampling along a belt transect
What is a point quadrat
Horizontal bar supported by two legs, at set intervals along horizontal bar 10 holes through which a pin may be dropped, each species that touches the pin is then recorded SEE TXTBOOK PG 481
What is a frame quadrat
Square frame divided by string or wire into equally size subdivisions, abundance of each species within quadrat is recorded SEE TXTBOOK PG 481
Three factors to consider when using quadrat
Size of quadrat, depends on size of plants or animals being counted and how they are distributed within the area, Where a population of species not evenly distributed large number of small quadrats will give more representative results Number of sample quadrants to record within the study area Position of each quadrat within the study area, random sampling must be used to avoid bias
Method of random sampling when using quadrat
Lay out 2 long tape measures at right angles along two sides of study area Obtain a series of coordinates by using random numbers taken from a table or generated by computer Place a quadrat at the intersection of each pair of coordinates and record the species within it
What is a belt transect and what is its importance
Made by stretching a string or tape across the ground in a straight line, a frame quadrat is laid down alongside the line in the species within it is recorded, process is repeated Important with some form of gradual change (transition) in communities of plants and animals take place, for example distribution of organisms along a line of succession
For species that don’t move around abundance can be measured by taking into account either
Frequency, likelihood of particular species occurring in a quadrat Percentage cover, an estimate of the area within a quadrat that a particular plant species covers
To obtain reliable results When using quadrat it is necessary to ensure that
Sample size is large, so many quadrats used and mean of all samples is obtained
Mark release recapture technique
Known number of animals are caught, marked in some way and then released back into community Sometime later a given number of individuals are collected randomly a number of marked individuals are recorded Estimated population size = total number Of individuals in the first sample x total number of individuals in the second sample/ number of marks individuals recaptured
Assumptions of Mark release recapture technique
Proportion of marked to unmarked individuals in second sample is same as population as a whole Marked individuals released from the sample distribute themselves evenly amongst remainder of population and have sufficient time to do so Population has a definite Boundry so no immigration into emigration out of population There are a few if any deaths and births within the population Method of marking is not toxic to individual nor does it make individual more conspicuous and therefore more liable to predation Mark or label is not lost or rubbed off during investigation
What is succession
Term used to describe changes of ecosystem as populations fluctuate over time in the species that occupy a particular area
