Populations In Ecosystems Flashcards
Define biosphere
The regions of the earth where life exists
Define biotic
The living components of an ecosystem
Define abiotic
Non living components of the ecosystem
Define ecosystem
A community and its abiotic environment. An Ecosystem supports a certain size of population of a species called carrying capacity
Define population
A group of individuals of the same species found in the same area at the same time
Define community
All the populations of different species living and interacting in a particular place at the same time
Define habitat
The place an organism usually lives/ the address of a species
What is a niche
The role of a species in an ecosystem, including what it eats, it’s behaviour, where it lives, what eats it. (two species can’t occupy the same niche otherwise there is competition)
Abiotic factors and how they determine the size of the population
- Temperature: every species has optimum at which best able to survive as metabolic processes controlled by enzymes 2. Light: ultimate source of energy for ecosystems, affects the rate of photosynthesis and producers are food for consumers 3. pH: have optimum as affects enzyme action 4. Water and humidity: where water scarce, populations are small and are only those well adapted, humidity affects transpiration and evaporation. Of any factor is below optimum, fewer are able to survive
Define competition/ the factors species compete for
results when two or more individuals share any resource (eg. light, food, space/breeding territories etc) that is insufficient to satisfy all their requirements fully.
Define intraspecific competition
occurs when individuals of the same species compete for resources. The availability of that resource determines the size of that population. Those best adapted survive and reproduce and pass on their alleles to their offspring (natural selection)
Interspecific competition
occurs when individuals of different species compete for resources (one species will usually have a competitive advantage over the other causing it to increase in size and the other to diminish).
What is meant by predation
Predation occurs when one organism (the prey) is consumed by another organisms (the predator). Both the predator and prey are animals.
Prey are adapted to hide from the predator (camouflage)Predators are adapted to catch their prey though faster movement, camouflage, ways of detecting prey.
How predator prey relationship affects their relative population sizes
An example: 4 year cycles; predator / stoat peaks after prey / lemming; lemmings increase due to low numbers of stoats / available food; more food for stoats so numbers increase; increased predation reduces number of lemmings; number of stoats decreases due to lack of food / starvation; .
Factors to consider when using a quadrat
1.The size of quadrat to use - larger species require larger quadrats. If a species is unevenly distributed, a large number of small quadrats will give more representative data than fewer large quadrats. 2The number of sample quadrats to record - larger sample size will give more reliable results 3.The position of each quadrat within the study area - random sampling avoids bias
What is the abundance
The number of individuals in a given space/ area
How to calculate the abundance using a quadrat
Only used for counting sessile or slow moving organisms. 1.Place 2 tape measures at right angles to set up a coordinates grid.2.Obtain random numbers using a calculator/random number generator/a table to get coordinates. 3.Place the quadrat at the intersection of each pair of coordinates and count the number of x inside.4. Repeat for at least 10 samples and calculate the mean number per quadrat.5. Multiply the mean number per quadrats by the number of quadrats in the x area / find mean number per quadrat which is per 0.25m squared then x 4 to find per m squared then times by total area
How to find the percentage frequency using quadrats
Obtain random numbers and place along right angles tape measures at the coordinates. After positioning the quadrat, just record the presence or absence of the species that you are interested in.
If the species is present in 20 out of 40 quadrats then the percentage frequency is 50 %
How to find percentage cover using quadrat
After positioning the quadrat, estimate the area in the quadrat that is covered by the species. /Obtain random numbers using a calculator to get coordinates to place quadrats.
Measure % cover of x for at least 10 samples.
Add up the total percentage and divide by the number of quadrats
How a belt transect is used to obtain quantitative data about changes in communities along a line
Lay out a tape measure as a transect line along the area of interest (where gradient exists)
Place a quadrat next to the tape measure at 0 m.
Record abiotic data inside the quadrat (if appropriate).
Count the number of species inside the quadrat.
Move the quadrat further along the line and repeat at regular intervals.
Ecology definition
The study of inter relationships between organisms and their environment
Define succession
Ecosystems are dynamic systems, ecological succession is the process of change in the species structure of an ecological community over time
The difference between primary and secondary succession
Primary occurs when bare rock or barren land is present and is first colonised by a pioneer species. Secondary is land that previously sustained life is altered- it occurs more rapidly as soil already exists and spores/seeds may be alive and disperse
Outline the process of succession
- Begins with colonisation by a pioneer species, these change the abiotic environment, causing it to become less hostile 2. These changes means it’s more suitable for the next species to survive and less suitable for the current species 3. This leads to an increase in biodiversity and a greater number/ variety of habitats and niches, also more complex food chains. 4. There is an increase in biomass and the process continues until a stable climax community is reached
The features of a pioneer species
Asexual reproduction (rapidly reproduce to form a population), production of large quantities of wind dispersed seeds or pores (spread easily and reach isolated areas). Ability to photosynthesise as no food, ability to fix nitrogen from atmosphere (as no soil nutrients), tolerance to extreme conditions
The features of a climax community
Same numerous species present ver long periods of time (a stable community), abiotic factors more or less the same over a long period of time, population numbers stable over long periods of time (around maximum carrying capacity)
How to conserve habitats
Species that exist in the earlier stages of succession are no longer present in the climax community because their habitats have have disappeared as a result of succession (change in the community/abiotic environment) or competition or human activity
One way to conserve these habitats (and their species) is by managing succession (preventing it from changing to the next stage)
Reasons for conservation
Personal - to maintain our planet (which is our life support system).
Ethical - other species have occupied the Earth far longer than us and should be allowed to coexist with us. We should respect other living things.
Economic - living organisms have a huge pool of genes with the capability to make millions of substances which may be valuable to us in the future. Ecosystems also provide many other goods and services that benefit humans.
Cultural and aesthetic (appreciation for beauty) - habitats and organisms enrich our lives. Their variety adds interest to everyday life and inspires writers, poets, artists, composers and others who entertain and fulfill us
Describe the mark, release, recapture method
- An area is defined and marked off and a selection of x are captured, counted, marked and released. 2. The marking must not be easily removable, not harm or affect the survival chances of x 3. Allow time for x to randomly distribute/ reintegrate 4. Collect and count a second sample and count how many are marked. 5. The population size is sample 1 times sample 2 divided by the number marked in the second sample
What assumptions are needed for mark release recapture method
There are no changes in the population size during sampling due to em/immigration, births or deaths. Marking does not affect survival or rub off and the marked individuals have time to mix with the population
