19: Ecosystems Flashcards
Define ecology
The study of inter-relationships between organisms and their environment
Define abiotic and biotic factors
Abiotic = non-living factors Biotic = living factors
Give some examples of abiotic factors
Temperature
Rainfall
Give some examples of biotic factors
Competition
Predation
Define a community
All the populations of different species living and interacting in particular place at the same time
Define an ecosystem
Dynamic systems made up of a community and all the abiotic factors
What are the two processes in an ecosystem which should be considered?
Flow of energy
Cycling of elements
Define population
Group of individuals of one species, in the same habitat at the same time that could interbreed
Define carrying capacity
Size of a population that an ecosystem can support
How does the size of a population vary?
Effect of abiotic factors
Interactions between organisms (biotic)
Define a habitat
Place where an organism lives and is characterised by the physical conditions and other organisms present
Define a microhabitat
Smaller units within habitats called microhabitats with their own microclimate
Define an ecological niche
Where an organism lives and what it does there
What is the competitive exclusion principle?
No two species occupy exactly the same niche
Define population size
Number of individuals in a population
What should be done to the population size if it increases at a ever-increasing rate? e.g bacteria growth is exponential
Plot the log number of bacteria
This shows all data points
How is temperature a limiting factor for plants cold-blooded animals? (e.g reptiles)
Too cold: Reactions slow down (enzymes slow down) and metabolic rate is reduced
Carrying capacity of a population decreases
Too hot: enzymes will denature
Carry capacity decreases
How is temperature a limiting factor for warm-blooded animals?
Any change: although animals maintain body temp
Significant change causes a large amount of energy spent to maintain it
Less energy for growth and maturation, reproductive rate decreases
Carrying capacity of the population is reduced
How is light a limiting factor?
Ultimate source of energy in ecosystems
More light, more photosynthesis, plants grow faster
Carrying capacity increases
Carrying capacity of consumers etc. could increase
How is pH a limiting factor?
Affects action of enzymes (denaturation)
Population of organisms in optimum pH is larger than that where pH is not optimum
How is water a limiting factor?
Populations are small where there is a lack of water unless well adapted
Water is essential
How is humidity a limiting factor?
Effects transpiration rates
Dry air causes a large amount, meaning non-adapted organisms will die quickly
Define intraspecific competition
Competition between members of the same species
Define interspecific competition
Competition between members of different species
Give some examples of things organisms compete for
Water
Food
Breeding sites/partners
How does availability of resources effect population size in intraspecific competition?
Increase in availability causes increase in population
How does availability of resources effect population size in interspecific competition?
One population will normally have an advantage
That population will increase gradually and the other decreases
Can two species occupy the same niche if there are limiting resources?
No, cannot happen as one will have an advantage
What does an increase in food supply cause?
More individuals are likely to survive
Increased probability of reproduction and population will increase
Takes a long time to take effect
Define predator
An organism that feeds on another organism (prey)
Define prey
An organism that is eaten by another (predator)
How are predators adapted?
Better adapted for capturing prey
E.g - faster, better camo
How have prey become better at avoiding predators?
Better camo
Protective features (spines)
Concealment behaviour
Define predation
When one organism is consumed by the other
What occurs when a predator and prey are introduced in a lab?
Predator exterminates prey
What are the limitations of predator-prey interactions in labs?
The situation is completely different from real world
More area that a prey can be found
More diverse environment, places to hide
What happens to prey numbers when they get low?
Rarely goes extinct due to increased difficulty in finding and catching prey
What is the relationship of population size in predator and prey?
Predators eat prey, reduces population of prey
Greater competition in predators due to less prey
Predator population decreases due to lack of prey
Fewer predators mean more prey survive and reproduce
Prey population increases
Repeats
Define selection pressure
Individuals that survive (disease, predation, etc.) are more likely to survive and reproduce
Causes evolution with advantageous traits
What is the abundance?
Number of individuals of a species in a given space
Why is it unreasonable to count every organism in a population?
Time-consuming
Causes damage to the environment
When can a conclusion be drawn about a habitat or population?
If the samples are representative of the habitat as a whole
What are the sampling techniques used in the study of habitats?
Random sampling using frame or point quadrats
Systematic sampling along a belt transect
What is a point quadrat?
Horizontal bar on two legs, ten evenly spaced holes on the bar
Long pin dropped through each hole
Any species the pin touches is recorded
What is a frame quadrat?
Square frame divided by string/wire into equally sized subdivisions
Placed in different locations in study area
Abundance of each species within the quadrat recorded
What should you consider when using quadrats?
Size of the quadrat
Number of samples to take in the study area
Position of each quadrat in the study area
Why should you consider the size of the quadrat?
Depends of size of plants/animals being counted
Larger species require larger quadrat
Uneven distribution requires a large number of small quadrats (more representative)
Why should you consider the number of quadrat samples you take in an area?
More samples, more representative
Balance between time-consuming and representative
Greater number of species in the area, greater number of quadrats required
Why should you consider the position of each quadrat in the study area?
For statistically significant results random sampling must be used
Why is random sampling used?
Avoids bias in collecting data
Ensures reliable data
What is the method for sampling at random?
Lay out two tape measures at right angles along two sides of the study area
Generate a series of random coordinates using a computer
Place quadrat at intersection at each pair of coordinates and record species within it
When should systematic sampling along belt transects be used?
When there is a gradual change in the communities of plants and animals
What is the method for systematic sampling?
Belt transect made by stretching a string/tape along the ground in a straight line
Frame quadrat is laid down alongside the line and abundance is recorded
Moved a set length along the line and process repeated
Gives a record of species in a continuous belt
What types of abundance are measured?
Frequency - likelihood of a species occurring in a quadrat, does not provide information on density and detailed distribution of a species
Percentage cover - estimate of area in a quadrat that a species covers
What are the advantages and disadvantages of measuring % cover?
Adv: Rapid collecting of data
Individual organisms don’t need to be counted
Dis: Not useful when there are layers of overlapping layers
What is mark-release-recapture?
Known number of animals are caught and marked
Released back into the community
New individuals captured randomly and the number of marked ones are recorded
What is the equation for estimated population size in mark-release-capture?
estimated population size = (total individuals in first sample x second sample)/ number of marked individuals recaptured
What are the assumptions made in mark-release-capture?
Proportion of marked:unmarked in 2nd sample is same as in the whole population
Marked individuals distribute evenly among others
Few births/deaths in population
Marking is does not cause death
Mark is not lost/rubbed off during the investigation
Define succession
Changes, over time, in species that occupy a particular area
What happens in a stage of succession?
A new species colonises the area
This could change the area
What is primary succession?
Succession which starts from bare rock/barren land
What is the first stage of succession?
Colonoisation of an inhospitable environment by organisms called a pioneer species
Define pioneer species
Species which are able to colonise inhospitable environments
What are some common features of pioneer species?
Adapted to tough environment (e.g xerophyte)
Ability to photosynthesize
Rapid germination of seeds (wind-dispersed)
Nitrogen-fixing from atmosphere
Asexual reproduction
How does a pioneer species allow others to grow there?
Pioneers die and decay
Release nutrients and over time make soil
Mosses and ferns erode rock and increase the soil
What are the normal stages of plant succession and examples ?
Colonisers -> Pioneers -> Weeds -> Shrubs -> Climax community
lichens -> grasses -> weeds -> bushes -> trees
What is a climax community?
Organisms that make up the final stage of ecological succession
Applies for animals, relies on plants and each other
What is the usual climax community in the UK?
Deciduous woodland
What are some common features that emerge during succession?
Abiotic environment becomes less hostile - more soil meaning more water and nutrient retention
Increased number and variety of habitats
Greater biodiversity - increases until climax then slightly decreases
More complex food webs - increased biomass
Define secondary succession
Land which has sustained life is altered (e.g forest fire) and undergoes succession
How is secondary succession different?
Area goes through stages faster due to more soil there
Doesn’t begin with a pioneer species
Define conservation
Management of the Earth’s natural resources by humans
Active intervention to maintain ecosystems and biodiversity
What are the reasons for conversations?
Personal - maintain planet for our lives
Ethical - respect other living things
Economic - productivity is greater if ecosystems are maintained
Cultural/aesthetic - people find it inspirational
How are habitats maintained by managing succession?
Species that lived before the climax community no longer present in climax community
Humans stop succession (e.g burning) to maintain these species
How are moorlands managed?
Areas are burned to kill saplings etc. to prevent the climax community from forming
