7.4 Populations in an Ecosystem Flashcards
What is a population?
induviduals of the same species living in the same habitat at the same time
What is a habitat?
part of an ecosystem in which a particular organism lives
What is a community?
all the populations of different species in a particular area at a particular time
What is an ecosystem?
a community and the non-living components of an environment (biotic and abiotic factors)
they can range in size from very small to very large
What is a niche?
an organisms role within an ecosystem, including their position in the food web and habitat. Each species occupies their own niche governed by adaptation to both biotic and abiotic conditions
What is carrying capacity?
the maximum population size an ecosystem can support
What are abiotic factors?
non-living conditions of an ecosystem
What are biotic factors?
living conditions of an ecosystem
What are some examples of abiotic factors?
temp
oxygen
CO2 conc
light intensity
pH
soil conditions
How do animals and plants adapt to abiotic factors within their ecosystem?
the process of natural selection over many generations
How do abiotic factors affect population size?
less harsh abiotic factors = the larger the range of species and the larger the population size
What is interspecific competition?
members of different species are fighting for the same resource that is in limited supply
Which species wins interspecific competition?
induvidual better adapted to the environment is more likely to succeed in the competition
What is intraspecific competition?
when members of the same species are fighting for the same resources and mates
Which induvidual wins intraspecific competition?
induviduals that are fitter will have more energy to perfrom a more impressive courtship ritual or have fur or feathers in a better condition to attract a mate
Which type of competition has a greater effect on the population size and why?
intraspecific = there is competition within the entire niche
the fundamental niche is the same
What are the key features of a predator-prey graph?
the size of the predators and prey population both fluctuate
there will always be more prey than predators
the size of the population will always change in the prey then the predators = there is a lag time
Why is the prey population always higher than the predator population?
due to trophic levels and the energy transferres through these levels, the energy decreases working up the food chain, so the prey have more energy
Why is there a lag time for the predator population behind the prey population on the graph?
the predator population decreases the prey population
What happens to an organism in their ideal ecological niche?
orgnaimsis increase in number exponentially up to the carrying capacity of their habitat
What is a fundamental niche?
the role an organism could possibly play in their ecosysyem
What is a realised niche?
the acutal found role of the species within the ecosystem
What shape is a growth curve?
s-shaped
What does a growth curve show?
no two species can co-exist in the same ecological niche
when competing for the same food supply
What type of sampling is used in uniform areas?
random sampling avoids bias
What type of sampling is used to examine a change over distance?
line transects
What type of sampling is used for moving organsims?
mark-release-recapture method
What type of sampling is used for non-moving or slow moving organisms?
use of a quadrat
What sampling method is used for a non-uniform environment?
systematic sampling = a transect
What is the random sampling method?
- lie two tape measure at a right angle to create a gridded area
- use a randome no. generator to generate two coordinates
- place the quatrat at this coordinate and collecrt the data (density/% cover/ frequency)
- repeat at least 30 times to calculate a mean
What is the method of a belt transects?
the quadrat is placed at every position along the transect (tape measure)
What is the belt transect method?
the quadrat is placed at uniform intervals along the transect (tape measure)
What is the method of a line transect?
- place the tape measure at a right angle to the area being sampled eg. the shore line
- place the quadrat every 5 metres / every position along transect
- collect the data (density/ % cover/ local frequency)
- repeat another 30 transects along the beach at right angles to the shore line
What is local frequency?
the % of squares in the quadrat with the species present
What is the species density?
the number of one species in a given area
How do you calculate the species density for the entire area?
average no. in quadrat (Q) multiplied by the entire feild area divided by the area of a quadrat
Q x (E / a)
What is percentage cover?
the proportion of the ground occupied by the species
How do you calculate the % cover?
count how many squares of the quadrat are completely covered / no. of squares in quadrat
What is the advantage of local frequency?
quick method to sample large area
useful if the species is difficult to count induvidually
What is the disadvantage of local frequency?
poor accuracy as it doesnt cosider overlapping plants or the size of the plant
What are the advanatges of using species density?
more accurate if you can easily distinguish induviduals
can be used to measure species richness
How do you meausre species richness?
count the number of different species present
What is an issue with using species density?
more time consuming
What are the advantages of using % cover?
quick method
useful if it is too difficult to identify induviduals or too many to count
data is more comparable when plants vary in size
What are the disadvantages of using % cover?
subjectibe so limiting accuracy
doesnt consider overlapping plants or the size of the plant
What is the method of mark-release-recapture?
- an intial sample of the pop is captured
- these induviduals are marked and releases back into the wild, the number caught is recorded
- marked are left for a period of time to allow them to randomly disperse throught the habitat
- the second sample is captured
- the tot number captured in 2nd sample and the no, recaptured with marks are recorded
- the size of pop is estimated
When is mark-release-recapture used?
to estimate the size of populations of moving animals
What is the mark-release-recapture equation?
est. tot pop = (no. organisms marked in 1st x no. of organsims in 2nd sample) / number of marked in 2nd
What should be considered for ethics in the marking tech of mark-release-recapture?
non toxic
must not increase chances of predation
mucts not reduce chances of reproduction
no permanent harm is caused
What are the 4 assumptions of mark-release-recapture?
the pop size is constant - no births, deaths or migration
the animals always redistribute evenly - may huddle near food in reality
the proportion of marked to unmarked in 2nd sample is the same proportion in the whole pop
animals are part of the same population
What is sucession?
the change in an ecological community over time
what is each stage of succesion called?
seral stage
What is a seral stage?
when there is a noticeable difference in the community
What is the climax community?
the final seral stage - there is no other changes in the combination of species normally a forest
What does primary succession start with?
a pioneer species colonising bare rock or sand
What are pioneer species?
species first to colonise that are adapted to survive harsh abiotic factors to form a thin layer of soil by changing the abiotic factors through death and decomposition
What is an example of a pioneer species?
lichen
What is a symbiotic relationship example?
lichen is made up of 2 different species working symbiotically
What 2 species is lichen made of?
algae and fungus
What is the thin layer of soil produced by lichen decomposing called?
humus
How is each previously existing species in 1’ succession outcompeted by a new species colonising?
the new species may change the environment that it becomes less suitable for the previous species
What do changes that organisms produce in their abiotic environment result in for their environment?
a less hostile environment and increases biodiversity
What is secondary succession?
1’ succession is disrupted and plants are destroyed so succession starts again but the soil is already created and doesnt start from bare rock
What happens to species richness and biodiversity in succession?
they both increase
How do food webs become more complex with succession?
as larger plant species and animals start to colonise the area
What does destruction of habitats by humans cause?
a loss of food and space for organisms
can lead to extinction
How can you conserve a habitat?
succession is managed by maintaining earlier stages and preventing a climax community
What does preventing a climax community result in?
greater variety of habitats that are conserved
What is biotic potential?
the max rate of reproduction in ideal conditions
What is environmental resistance?
factors that limit pop growth - abiotic and biotic
What points must be said when describing stages in the prey-predator graph?
increase/reduced pop?
increase/decrease food? competition for food?
mortality rate increase or decrease?
increase or decreases in energy for reproduction?
What happens to the mortality rate with increased predation?
increases mortality
What happens to mortality rate with increased prey?
decrease mortality
What does distribution mean?
describes the area or volume in which species are found
What is the equation for the diversity index?
D = ( N(N-1) / sum n(n-1) )
D = diversity
N = tot no. of organims of all species
n = tot no. of organisms of a particular species
How can you tell one environment is less diverse than another without calculating species diversity?
there are fewer species present
there are fewer induviduals in most species
Why is a kite diagram useful for displaying % cover?
you can easily compare populations
What increases as succession occurs?
depth and quality of soil
hight abd biomass of plants
biodiversity
What is the level of significance?
P = 0.05
What is a T-test?
tests for significant difference between mean values
What is chi-squared?
tests for significant difference between observed and expected
What is spearman’s rank?
tests for significant correlation
What do you say about the results* if the probability is less than or equal to P = 0.05?
results are significant
you can reject the null hypothesis
the difference/ correlation is NOT due to chance - less than a 0.05 probability that the difference is due to chance
what do you say about the results if the P value is greater than 0.05?
the results are NOT significant
accept the null hypothesis
the diffrenece/ correlation is due to chance
What does the probablity of the test as a % represent?
the % that the results are due to chance
How do you calculate the mean no. of species per quadrat?
total no. of species / no. of quadrats placed
How do you calculate the mean of species in the whole sample area?
the mean of species in quadrats x the sample area
/ the area of the quadrat
Why would the species diversity decrease after removing a forest?
you decrease the variety of plant species
so there are fewer habitats
and less food supply
What is a species?
a group of similar oranisms that can reproduce and produce fertile offspring
Why would you take samples more frequently?
for more data plots for a graph to draw a line of best fit
Why would you increase the number of sample sites?
to increase the accuracy of mean data
How would you get more precise values of index of diversity?
take more samles to find a mean number of species
by using a randomised sampling method
Why do hedgerows /grassy strips increase biodiversity of animals?
increase plant diversity so there is more types of food
increase in habitats
Explain why it is more useful to calculate an index of diversity than to record species richness.
Index of diversity also measures number of each species
So useful because may be many of some species
Suggest how the scientist measured the rate of water flow in the river
Use of data logging device = digital flow meter
How would you standadise the sampling methods?
Same size area sampled
Same size net/quadrat
Same sampling time
Samples taken at the same time of day or on the same day
What data would you need to collect to calculate their index of diversity?
Number of species and number of individuals in each species in each habitat
How can you make the index of diversity more representative?
random samples
large no. of samples
What are the advantages of planting hedges?
Greater biodiversity so increase in predators of pests
Increase in predators of pests so more yield/income/less pesticides/less damage to crops
Increase in pollinators so more yield/income
What are the disadvanatges of planting hedges?
Reduced land area for crop growth/income
Greater (bio)diversity so increase pest population
Increase pest population so less yield/less income/(more) need for pesticides/(more) damage to crops
Increased (interspecific) competition so less yield/income
What is the method for determining species richness?
select sampling sites at random
use a quadrat
identify plant species
count no of different species
Why does the index of diversity (biodiversity) increase with hedges?
More plant species
More variety of food
More habitats
How would you select an appropriate time for sampling?
sort soil for various different times eg 10 mins 20mins 30mins 40mins 50mins 50mins.
choose the length of time beyond which you didn’t increase the count so:
10mins sorting you found 100 orgs
20mins sorting you found 150 orgs
30mins sorting you found 240 orgs
40mins sorting you found 300 orgs
50mins sorting you found 300 orgs
60mins sorting you found 300 orgs
40 mins is the appropriate time
Why do non-native species decrease populations?
Non-native species out-competes / kills / eats / is a disease of native plants
Some (populations of) native species become extinct
What is the difference between species richness and index of diversity?
Species richness measures only number of (different) species / does not measure number of individuals.
Why would loss of nutrients in a lake cause a decrease in fish populations?
Growth/increase of) algae/surface plants/algal bloom blocks light
Reduced/no photosynthesis so (submerged) plants die
Saprobiotic (microorganisms) aerobically respire
Less oxygen for fish to respire
How can using large sample areas for mark-release-recapture be misrepresentative?
Less chance of recapturing species
Unlikely species distribute randomly/evenly
Describe and explain how succession occurs.
Colonization by pioneer species
Pioneers/species/organisms change the environment/habitat/conditions/factors
Environment becomes less hostile for other/new species
OR
Environment becomes more suitable for other/new species
Change/increase in diversity/biodiversity
To climax community
How does introducing infertile male species in a population decrease population size?
Compete (with fertile males) to mate / for food / resources OR intraspecific competition;
They do not reproduce = reduces population
What are features of a climax community?
Same species present (over long time) / stable community (over long time)
Abiotic factors (more or less) constant (over time)
Populations stable (around carrying capacity)
Why are trees unable to survive waterlogged soils?
the roots need oxygen for aerobic resp
there is no active transport of mineral ions
what are ways pioneer species change the environment?
adding organic matter = death, improves soil quality
makes the environment more suitable for other species
provides resources like food and shelter
