Chapter 19 - Populations in Ecosystems Flashcards
What is a community?
Several different populations of species living together in one area
What is the difference between an ecosystem and a community?
A community is just the different species and their populations, whereas an ecosystem is the community as well as their environment and assosciated abiotic factors
What are abiotic factors?
The non-biological factors within an ecosystem, such as soil pH, precipitation levels, temperature, sunlight etc
What are biotic factors?
The living, or biological factors within an ecosystem, such as predation and competition
What are niches?
Within each habitat, a species occupies a niche governed by both its adaptation to the abiotic and biotic conditions. If two species occupy two very similar or identical niches, selection pressure is applied to the species which is less adapted to compete against the other species (as seen with invasive species)
What is the carrying capacity of an ecosystem? Give 2 factors
The maximum population each ecosystem can support, based upon the abiotic factors present (mineral ion concentration in the soil for primary production for example). And also the interactions between organisms within the community, interspecific and intraspecific competition as well as predation
What is the difference between interspecific and intraspecific competiton?
Interspecific is competition between different species, for example if they have similar prey and there is less prey then one species competes with another for that prey
Intraspecific is competition between organisms within a species, an functionally isn’t often massively different to interspecific competition, however because the species is the same they have more in common, such as hibernation spots in some species or breeding sites and therefore sexual competition
How can the size of a slow moving or non-motile organisms populations be determined?
By using quadrats at randomly selected squares in a certain area, or also using a belt transect and going incremental distances away from landmarks (e.g trees)
How do you measure the size of a population for motile organsims?
Using a mark-release-recapture method, this is where a known number of the measured organisms are captured and marked, and then a certain amount of time later you go back into the same area and recapture the same number of organisms and see how many are marked. The frequency of the captured organisms and how many of them are marked can be used to calculate the total population.
What assumptions do mark-release-recapture work off of?
They assume the size of the population hasn’t changed in the amount of time between the original marking and the recapturing
The proportion of marked to unmarked organisms reflects the real proportions of the population as a whole
The mark or label both: does not decrease the chance of survival of the organism(more obvious to predation/toxic) and is not rubbed off or removed
The population has definite boundaries and no immigration or emmigration occurs
What is succession?
Succession is the natural evolution of ecosystems, beginning with pioneer species colonising inhospitable areas in primary succession (e.g. volcanic rock), and slowly becoming more and more diverse as the area changes more and more
How does succession take place?
Succession begins with pioneer species, usually organisms such as mosses which have short life cycles and take root easily, making microscopic tears in the rock surface. These tears make it easier for the next species to take root, which may be larger and support some animals or other plants and is able to feed off of the hummus formed from the decomposing pioneer. This process continues as the area slowly becomes more hospitable, however certain species may make the new area less hospitable for previous species. This process continues until the area reaches a climax community. Stages of succession are marked by increased biomass, more complex foodwebs emerging and less hostile abiotic factors, as well as increased biodiversity and niches
How can environments become less hostile?
Typically through organisms being able to change abiotic factors in the environment, making the area more or less hostile for other organisms, changing biodiversity in that area
What is conservation?
Conservation is the active process of humans trying to prevent or reverse succession. This is often to either restore areas destroyed by humans or maintain areas currently considered beautiful, where later stages of succession may be less friendly to humans. However it can also be used to protect certain species which may be endangered, and later stages of succession make the ecosystem inhospitable
