Populations In Ecosystems Flashcards
The larger the sample ………
The more reliable the data
Why should the student not stop collecting data half way up the graph
Because the line has not reached the plateau so all the data is not being represented
Why should the student stop collecting data after the line plateaus
Because it would not improve the outcome of the data and would be a waste of time
How would you decide the number of samples to take to collect representative data
Calculate the running mean after 10 samples and continue until it stops increasing
What does a point quadrat do
Measures the frequency of how often a species is found
What does a frame quadrat do
Measures percentage cover of a species in an area
3 things to consider when using quadrats
Size of the quadrat depending on the size of species measured and how they are distributed in an area
Number of samples being taken in the area - the more samples the more reliable
Position of each quadrat to produce unbiased results - random sampling must be used
Why use random sampling in a uniform area
Avoid bias
Representative data
Allows for the use of statistical tests
Random sampling method
Set out a grid using tape measures at right angles
Divide into coordinates
Use a random number generator to pick coordinates
Count organisms in the quadrat on each coordinate
Record data
Repeat
How to measure data in an irregular size area
Divide into spaces and number them
Use random number generator to pick space
Place quadrat
Count
Repeat
When to use a belt transect
When the area varries and the abundance/ distribution of organisms changes
Measures percentage cover
Method using a belt transect
Lay out a tape measure and place quadrat frame at right angles at regular intervals
Use a pin quadrat to count species touching the pins
Flip quadrat frame over to the other side of the transect and repeat
Advantages of belt transect
Gives more info on abundance
Disadvantages of belt transect
Takes longer than a line transect
Might damage environment from standing on it
Frequency of species equation
Number of quadrat contains species / total number of quadrats X 100
Method of mark release recapture
Capture a number of animals
Mark them
Release them and allow for reintegration
Collect second sample
Count and record
Use MRR equation to estimate population size
MMR equation
Organisms in sample 1 X organisms in sample 2 / number of marked organisms recaptured
MRR assumptions
Proportion of marked to unmarked in sample 1 and 2 is the same as the whole population
Marked sample distributed themselves evenly
Population have definite boundaries
Few births and deaths
Marking method is not toxic and more liable to predation
Mark has not rubbed off
What is succession
Change in community over time due to changes in abiotic and biotic factors
How does succession change over time
Starts with pioneer species in harsh abiotic conditions and low diversity
Biodiversity increases over time and then becomes a climax community with more stable abiotic conditions
Biodiversity is lower because more dominant species outcompete others
How do the first species colonise an area
Wind dispensable seeds to reach isolated areas
Rapid seed germination
The ability to to photosynthesis
Ability to fix nitrogen because soil has no nutrients
Tolerant to extreme conditions
How is soil made by pioneering species
Weathering of rock and decomposition of dead organisms add nutrients to the soil which means more small plants colonise like Moses and ferns and the area become hostile
Process repeats and a thicker layer of developed
Why do pioneer species become replaced by other species over time
Competition prevents pioneer species from photosynthesising or absorbing water
What is a climax community
A stable community where no further succession occurs
How do successional changes effect animals
Depending what plants are present depends what animas are present because of food source availability
Flowering plants bring pollinators
Features of succession
Abiotic factors become less hostile
Greater variety of habitats and food sources
More complex food webs lead to more competition
Increase in biomass
What is secondary succession
The same a primary succession accept it starts from wildfires , tsunamis, hurricanes , deforestation clearing and area of land
But it happens quicker because seeds are already in the soil and from animal poop
How does dead organic matter change during succession
Increases because animals poop adding to soil and plants grow, die and decompose
How does humidity change during succession
Increases because rate of transpiration locally increases and air movement decreases due to plant protection
How does PH change during succession
Decreases because rain leaches basic ions from sea spray out of sandy soil and more plants die and decompose
How does rate of evaporation change during succession
Decreases because humidity increases so water potential decreases
How does sodium chloride conc change during succession
Rain leches basic ions out of Sand soil
Less sea spray reaches ground
How does soil temp change during succession
Increases because soil composition increases in dead organic matter so drainage decreases which increases water content
How does wind speed change during succession
Decreases because plants provide a wind break so air movement decreases
How is marram grass adapted
Hairs , stomata and rolled leaf shape reduces conc gradient of water by diffusion
Thick waxy cuticle avoids evaporation of water
What is ecology
The study of relationships between organisms and their environment
How does competition effect a population
More competition means less chance of getting food so organisms die
How does predation effect a population
More predation means prey population decreases
How does disease effect a population
More disease causes a population decrease
How does food availability effect a population
More food available means more population growth
How does temp effect population
Lower temp means less vegetation growth so more animals die of starvation
How does pH effect population
Incorrect pH means that vegetables can’t grow so more animals die of starvation or other food sources decrease
How does water availability effect population
Less water causes dehydration for animas and plants can’t grow
How does light effect population
Low light means plants can’t photosynthesis so can’t grow
How does natural disasters effect a population
Kills animals prevents them from reaching food , kills the food source
What is a micro habitat
A small pocket within a habitat
E.g pythons live on trees but wood lice live in the bark cracks
What is intraspesific competition
Competition of individuals within the same species
What is interspesific competition
Competition between individuals of different species
Why is it difficult to obtain valid data on predator - prey relationships
The labs results are not accurate because the environment is limited so their are no external factors
Whilst in the wild it is impossible to count every individual
what is carrying capasity
maximum population that can be supported by an environment long term
why is their a lag time in the first phase of a population growth curve
because organisums are acclimatising to the environment so no reproduction
why is their exponential growth in the second phase of a population growth curve
reproduction rates high - birth rates higher than death rates
why is there fluctuation in the final phase of population growth curve
lots of intraspesific competition because population is over carrying capasity and then a limiting factor will bring down the population
how will the population growth curve change for bacteria
it is quicker because bacteria reproduces quicker
less ossilation in stage 3
then a decline phase because food in a petri dish runs out
how does temperature effect cold blooded organisums populations
if temp is lower enzymes work more slowly so metabolic rate is lower so carrying capasity is lower
if temp is higher enzymes denature reducing carrying capasity
how does temperature effect warm blooded animal populations
they can maintain constant body temperatures but the further from optimum temp the more energy used to maintain temp so less available for reproduction so reduced carrying capasity
how does light effect population size
more light alllows more photosynthesis so more plant growth and food availabilty carrying capasity increases
how does pH effect population size
as you move away from the optimum more enzymes denature so less enzyme substrate complexes so carrying capasity decreases
how does water and humidity effect population size
more water means plants can grow more because it allows for more photosynthesis so acrrying capasity increases
what is polarding and when is it done
chop canopy off the tree and it will grow again
done because grazing animals are around and they would eat the sprouts if they are low enough
what is coppicing and when is it done
cut the tree down really low to a stump over time the stump grows new sprouts
done because it was over dominating other plants
why is controlled heath burning done
kills dominanting species
heat activated seeds germination of other species
