7.4: Populations in ecosystems (ecology) Flashcards
Define population
all of the individuals of the same species in a habitat at the same time
Define community
all of the individuals of all species in a habitat at the same time
Define ecosystem
the relationship between the community and the abiotic environment
What is meant by the term ‘biotic factor’ and describe two examples
The living component - interactions between individuals within the community e.g. predation, competition, mutualism
What is meant by the term ‘abiotic factor’ and state two examples found in each of aquatic and terrestrial environments
non-living component
aquatic: pH and temperature of water
terrestrial: light intensity, water availability
Name the 2 types of competition and describe the difference between them
Intraspecific - between individuals of the same species
Interspecific - between individuals of different species
Using examples, explain the difference between primary and secondary succession
Primary = colonisation of bare rock e.g. on a lava flow
Secondary = recolonisation of an area e.g. following a forest fire
Compare and contrast the pioneer and climax communities
pioneer - harsh abiotic factors, few plant species (highly specialised), less stable (will change)
climax - less harsh abiotic factors, more plant species (less specialised), more stable (doesn’t change)
Explain why animal biodiversity is greater in a climax community
there are more plant species providing a greater variety of food sources and so there are more niches available and so there are more animal species
How can you link the Nitrogen cycle to a wet habitat
waterlogged soils, less O2, anaerobic conditions, decrease in nitrates, increase in nitrifying bacteria, increase in N2 gas
Fully describe how you could estimate the size of a population of sundews in a small marsh
1- Create a grid using two tape measures
2- Use a random number generator to produce coordinates
3- Place a quadrat at the coordinate and count the number of sundews it contains
4- Repeat at 10 different coordinates on the grid
5- Repeat steps 1-4 in a different area of the marsh
6- Add up the total number of sundews and divide by the number of quadrats used to calculate the mean number of sundews per quadrat
7- Multiply the mean number of sundews per quadrat by the total area of the marsh
Suggest two precautions needed when marking organisms when using the mark-release-recapture method to make sure the estimate of the number of organisms is valid
1- Mark isn’t visible to predators, so they are not more likely to be eaten
2- Mark isn’t toxic, so it doesn’t kill them
What is a parasitic relationship
Where one member gains, and the other is harmed
What is a mutualistic relationship
Where both members gain
What is a commensalistic relationship
Where one member gains, and the other neither gains nor is harmed
What is a niche
The role an organism plays in its environment
What is the difference between the realised niche and the fundamental niche
realised = no species is better than them in this area
fundamental = competition with other species
Define succession
The change in structure of a community and an ecosystem over time
What is the difference in time between secondary and primary succession and explain why
Secondary is quicker than primary as there are phosphates, nitrates, DOM, seeds, soil etc
How does the standard deviation suggest if the mean of something is significantly greater than the mean of something else
if the standard deviations of the mean masses do not overlap
The standard deviations of the mean masses of two samples do not overlap. What does this mean?
That the mean mass of one sample is significantly greater than the mean mass of the other sample
HYPOTHESIS TESTING
p =< 0.05 therefore…..
the result is significant as the result is not due to chance therefore the null hypothesis is rejected
In terms of ecology stats tests,
if measurements are taken and you are looking for a correlation between 2 different measurements, what test would you use?
Spearman’s Rank test
In terms of ecology stats tests,
if measurements are taken and you are not looking for a correlation between 2 different measurements, but are comparing means from 2 sets of data, what test would you use?
Student’s T-test
In terms of ecology stats tests,
if measurements are not taken but you collected frequencies, what test would you use?
Chi-squared test
What do the values for the correlation coefficient: -1,0,+1 mean in a Spearman’s Rank test
-1 = Perfect negative correlation between x and y
0 = no correlation between x and y
+1 = Perfect positive correlation between x and y
p =< 0.05 in a spearman’s rank test therefore…
There is a significant correlation between and y as the correlation is not due to chance and so the null hypothesis can be rejected
p =< 0.05 in a Student’s T-test therefore…
there is a significant difference between the means of samples x and y as the difference in means is not due to chance and so the null hypothesis can be rejected
p =< 0.05 in a Chi Square test therefore…
There is a significant different between observed and expected data as the difference is not due to chance and so the null hypothesis can be rejected
What would the null hypothesis of a Spearman’s Rank test be
There is no significant correlation between x and y
What would the null hypothesis of a Students T- test be
There is no significant difference between the mean of sample x and sample y
What would the null hypothesis of a Chi Square test be
There is no significant difference between the observed and the expected data
What does the carrying capacity of a population mean
The maximum size that a population can remain sustainable in an ecosystem
What does the biotic potential of a population mean and give an example
The maximum rate of reproduction in ideal conditions e.g. bacteria growing in a lab
What does competitive exclusion mean
when a population is wiped out due to another population’s fundamental niche completely overlapping that population’s fundamental niche
Is a population more or less likely to survive intra than interspecific competition and why
less likely because in intra, they all have the same niches and so their niches completely overlap, and so there is full competition
What are the 2 ways of working out population density
% cover or % frequency
What is the equation for mark-release-recapture and what do the letters mean
P = N1 x N2
———–
R
Where P = estimated population size
N1 = total number of individuals in the first sample
N2 = total number of individuals in the second sample
R = number of marked individuals recaptured
List the assumptions made by the mark-release-recapture method
There are few births/deaths in the population, there is no migration of individuals
Proportion of marked:unmarked in 2nd sample is the same proportion in the whole population
Marked individuals distribute themselves evenly amongst rest of population so that all individuals have equal chance of being captured and recaptured
Method of marking isn’t: lost, rubbed off, toxic, going to make them more conspicuous to predators
How many quadrats should be used for reliable results
20 or more
What is a transect
When you put down quadrats down along a transect (straight line) at regular intervals, measuring abundance
What is the difference between a line and a belt transect
Belt = Measure abundance in quadrat
Line = measure abundance of everything that touches the line
What type of sampling method would you use when measuring population distribution in a non-uniform area
Systematic sampling - either line or belt transects
What type of sampling method would you use when measuring population distribution in a uniform area
Random - quadrats
What type of sampling method would you use when measuring population abundance of plants
Quadrats
What type of sampling method would you use when measuring population abundance of animals
Kick sampling or capture, mark, release, recapture
What is the symbol for standard deviation in BIOLOGY
sx NOT 𝜎x
what is the equation for calculating diversity index and what do the letters represent
D = N(N-1)
———-
∑n(n-1)
N = total number of organisms of all species
n = total number of organisms of a particular species
What does biodiversity (diversity index) measure
The species richness - number of different species present
and the number of individuals in each species
What is species richness
the number of different species present
What is the pioneer community
the first species to colonise an area
Explain the events of succession
Gradually exposed rocks are weathered away, releasing minerals, gradually forming soil
Pioneer species such as lichens/algae/mosses colonise speeding up breakdown of rocks
Plants with roots colonise these improved soils, their roots grow and further break up the rock
Soil begins to develop as organisms from previous stages die, DOM, increases soil nutrients. Animal communities develop providing extra DOM. Diversity increases, competition increases, and so larger plants outcompete ground plants
Animal population increases, greater seed dispersal
Shrubs grow, trees grow -> climax community
What can affect the carrying capacity of a population
Food, shelter, water
