Populations In Ecosystems Flashcards
What is ecology
The study of inter relationships between organisms and their environment
Name the abiotic factors of an ecosystem
Light
Temp
Soil PH
water availability
How does light affect an ecosystem
Affects rate of Photosynthesis and so plant growth and so food availability as biomass is affected
More energy available for spore and seed formation with more light
How does temperature affect an ecosystem
Affects rate of Respiration and Photosynthesis due to enzymes.
Affects water availability
Affects body temp so energy used to regulate temp not growth and reproduction
Cold blooded= enzymes denature
Warm blooded= less energy for reproduction so mature slower
What biotic factors are there in an ecosystem
Food availability
Predation
Disease
Competition
How do predators affect an ecosystem
Kill organisms so reduce population
How does food availability affect an ecosystem
Competition
Starvation
How does competition affect an ecosystem
Some will starve and die reducing population
Not enough supply to support all
How does disease affect an ecosystem
Makes more succeptible to predation so may fall prey
May die from disease
Define population
All individuals of same species in same place at the same time
Define ecosystem
Habitat and the community of organisms within it
Define community
All populations of different species living at the same place at the same time
Define habitat
Place where an organism normally lives
Define ecological niche
Where an organisms lives and what it does
the biotic and abiotic factors its adapted to
Define the competitive exclusion principle
No two species can occupy the same ecological niche because they will outcompete one another
Define carrying capacity
The maximum size of the population able to be supported by an ecosystem
Describe the growth curve
Slowth then rapid and then fluctuations
Why is a logarithmic scale used
To clearly show the rate of growth
How does PH affect a population
Alter enzyme activity
Decreased Respiration and Photosynthesis so reduced carrying capacity
How does water and humidity affect a population
More humid = lower WP gradient= reduced transpiration and water loss
Less water = only adapted organisms survive
What are the two types of competition
Intra and inter
What does intraspecific competition occur for
Light water mates
What does interspecific competition occur for
Habitat light water food
How are predators adapted
Camouflage
Faster movement
Better sense to detect prey
How are prey adapted
Camouflage
Concealment behaviour
Spines (protective features)
Why might lab results be different in terms of predator prey relationships
Prey will go extinct as no other source of food or refuges
What is a selection pressure
A factor that drives selection
Define succession
Gradual changes in community over time
Describe the process of succession
New species arrives changing the conditions making them less hostile, making them less suitable for the previous species and more suitable for other species which outcompete it.
What happens to biodiversity during succession
Increases and then decreases at climax community
Define pioneer species
First species to colonise
How are pioneer species adapted
Asexual reproduction (single organism can establish whole pop)
Produce many wind dispersed seeds
Rapidly germinating seeds
Able to Photosynthesise (no other animals available)
Fix nitrogen from air
Tolerate extreme conditions
Define climax community
Stable community where no further succession occurs
What are the features of succession
Abiotic factors become less hostile Greater no and variety of habitats Greater biodiversity More complex food webs Greater biomass
Describe primary succession
Bare rock is colonated by lichens
Weathering of rock and decomposition of dead lichen =soil and nutrients
Nutritious soil can support a variety of life
Biodiversity increases so environment is less hostile
Thicker soil builds
Flowers and ferns establish
Climax community reached so species in equilibrium and biodiversity decreases
What is the difference between primary and secondary succession
Secondary begins with a devastated ecosystem where soil is available and succession is more rapid
How does DOM change with succession
Increases as more organisms are present which then die
How does humidity change with succession
Increases as more plants means more transpiration and less air flow
How does PH change with succession
Decreases as DOM is broken down into fatty acids and carboxylic acids
How does transpiration/evaporation change with succession
Decreases as more plants are present and so humidity decreases, decreasing the WP gradient
How does NaCl conc change with succession
Decreases as less sea spray hits the soil
How does soil temp change with succession
Increases as more plants means more Respiration so more energy released
More decomposition so more DOM so less drainage and more water
How does wind speed change with succession
Decreases as more plants act as wind break
Define conservation
Management of earth’s natural resources to. Maximise use in the future
Reasons for conservation
Personal (life support system)
Ethical (species should be able to coexist)
Economic (many genes able to produce many valuable substances)
Cultural and aesthetics (inspiration for books and songs)
Why might we want to manage succession
So that rare species don’t go extinct due to being outcompeted
How might succession be managed
Grazing of sheep
Burning
What organisms are quadrats used for
Non-motile organisms
Describe the types of quadrat
Frame
Count organisms in squares
Point
Count organisms touching poles
What factors need to be taken into account when using quadrats
Size (large quadrats for large organisms)
No of samples (large is more reliable but more time consuming)
Position (random sampling to avoid bias)
What is a running mean and why is it used
Mean calculate everytime a new sample is taken
When mean is constant the number of samples is representative
Describe random sampling using quadrats
Set out grid Randomly choose coordinates Place quadrat at coordinates Count organisms in quadrat Repeat 10 times and calculate Mean
Define systematic sampling and an example
Collecting data at regular intervals
Belt transect
What’s the difference between a line and belt transect
With a line transect quadrats are placed at regular intervals
With belt transects the quadrats are placed every length of the quadrat
What are the advantages of belt transect over line transects
More accurate
Less bias
What are the disadvantages of belt compared to line transects
More damaging
More time consuming
Define abundance
Number of individuals of a species in an area
What are the ways to measure abundance
Percentage cover
Frequency
Population density
Describe how frequency is calculated
Expressed as a percentage or as a X out of y.
How is population density calculated
Number of individuals per area
What are the advantages and disadvantages of using percentage cover
Ad:
Good when organisms are difficult to count
Less time consuming
Dis:
Organisms may overlap making % over 100
What are the advantages and disadvantages of Using frequency
Ad:
Quick and easy
Dis:
No information on density or distribution
When is Mark release recapture used
On motile organisms
What assumptions are made in MRR
Markings don’t rub off
Sample is proportional to population
Organisms have enough time to mix
Marking is non toxic and doesn’t make them more likely to be prey
No births or deaths
No immigration or emigration
Outline method of MRR
Capture organisms Mark all Release and leave for 24 hrs Capture and ratio of marked to total captures Use ratio to calculate whole population
