6:3:1 Ecosystems Flashcards
Define species
A group of organisms that have a common ancestry, sharing the same genes, causing them to be able to breed together to produce fertile offspring
Define communities
Multiple populations of different species living and interacting in the same area
How are ecosystems formed
- Species don’t exist alone they interact with other to form communities
- Communities interact with each other and the environment they’re in to form ecosystems
What are features of ecosystems
- Flow of energy within the ecosystem, nutrients within it are recycled
- There are biotic and abiotic components
- Ecosystems vary in size (e.g. ponds vs ocean)
- Never fully self-contained as organisms from one ecosystem link to other organisms from other ecosystems
- Vary in complexity (e.g. desert vs rainforest)
Define an ecosystem
A relatively self-contained community of interacting organisms and the environment they live in and interact with
Define biotic factors
Anything that influences the populations within a community that is a result of another organisms activity
What are examples of biotic factors
- Predators
- Competition
- Cooperation between organisms
- Parasitism
- Disease
- Camouflage (disadvantages predators)
- Mimicry (deters predators)
- Mankind
Define an abiotic factor
- An abiotic factor is any physical or chemical factor that influences the populations within a community
- The environment conditions can majorly impact the spread of a species
What are examples of abiotic factors
- Availability of water
- Light
- Radiation
- Temperature
- Turbidity (cloudiness) of water
- Humidity
- Atmospheric composition
- pH
- Salinity
- Soil composition
What is biomass
- The mass of a living material of the organism or tissue
- The chemical energy that is stored within the organism or tissue
How can biomass be measured
- Dry mass of an organism or tissue
- The mass of carbon that an organism or tissue contains (generally 50% of the dry mass)
- The chemical energy content of the organism when burned in pure oxygen
What is the dry mass of an organism and how to use it in calculations
- The mass of the organism or tissue after all the water has been removed
- Can be used to calculate biomass of a total population of organisms or of particular areas
- e.g. Dry mass of 1 tree = 10kg therefore dry mass of 250 trees = 2500kg
- e.g. Dry mass from 1m^2 = 0.2kg therefore 200m^2 = 40kg
Why is biomass given with units of time
- Biomass can change over time
- e.g. Decreases for deciduous trees over autumn and winter due to leaf loss
- Units of time show the average biomass of an organism over a given period
How can the chemical energy of organisms be measured
- Calorimetry used to estimate
- By burning the sample, a fixed volume of water is heated and the change of temperature is a measurement of energy transferred
How do plants gain energy
- Primary producers convert light energy into chemical energy in biological molecules
- They store this energy as plant biomass
How is energy transferred within food chains
- Energy stored as plant biomass
- Next trophic level (primary consumers) are transferred a certain amount of this energy
- Only a small amount of energy is transferred due to not all biomass being consumed then digested
- The consumer converts the energy to movement and heat and only a small portion to biomass
- Efficiency of biomass transfer from one to the next is around 10%
What is the equation to calculate efficiency of energy transfer
Efficiency of transfer = (biomass passed to the higher trophic level/biomass of the lower trophic level that has been consumed) x 100
How to calculate the net productivity of producers
NPP = gross primary productivity - respiratory losses
How to calculate the net productivity of consumers
NPC = chemical energy store in ingested food - (chemical energy lost to the environment in faeces and urine + respiratory losses to the environment)
How do human activities manipulate the transfer of biomass through ecosystem to maximise agricultural productivity
- Providing artificial light in greenhouses on overcast days
- Use of fertilisers
- Fencing to exclude grazers
- Use of vaccinations for livestock
- Reduce competition for grazing
What is the importance of microorganisms in ecosystems (define decomposition)
To ensure that the nutrients stored within dead organisms and in the waste products of organisms are recycled and are made available to producers again
What are saprobionts
True decomposers that come from fungi and bacteria kingdoms, which secrete enzymes onto their food and digests it externally (saprobiotic nutrition)
What is extracellular digestion
- Secretion of enzymes onto food by saprobionts
- Enzymes digest the food externally
- Products of digestion are absorbed by saprobionts
Why are saprobionts essential components of ecosystems
- Not all nutrients get absorbed by them after digestion
- Nutrients remain in the soil to be absorbed by other organisms
- They release nutrients from dead waste matter so that producers can have access to them
- Some saprobionts excrete important nutrient mineral ions as their own waste products
What is mycorrhizae
- The symbiotic relationship between plant roots and fungi
- Fungi hyphae interact with plant roots, increasing the SA of the root system and the amount of minerals/water absorbed
- It also allows fungi to receive organic compounds from the roots
What is the nitrogen cycle
The cycle through which nitrogen is converted into many forms, moving through living and non living things p
Describe the nitrogen cycle
- Nitrogen in atmosphere (N2) is converted into ammonium ions (NH4^-) by nitrogen fixing bacteria (azobactar + rhizobium) in the soil (ammonification)
- Gaseous nitrogen is also converted into nitrate ions (NO3^-) by nitrogen fixing bacteria which is absorbed by plant roots (assimilation)
- Ammonium ions are nitrified by nitrifying bacteria (nitrobacter + nitrosomonas) into nitrite (NO2^-) and nitrate ions which are soluble and are absorbed by plant roots
- Deamination of organic waste by decomposers occurs to produce ammonium ions
- Denitrifying bacteria (thiobacillus denitrificans) use nitrates for respiration and return gaseous nitrogen to the atmosphere
Describe the carbon cycle
- Autotrophs use energy from light to fix carbon dioxide, removing carbon from the atmosphere (Calvin cycle)
- Terestrial plants use gaseous CO2 directly from air
- Aquatic organisms use CO2 dissolved in water
- Dead plants form sediment which locks carbon into the ground (store of fossil fuels e.g. coal)
- Aquatic organisms and shells also form sediment storing carbon
- Respiring organism releasing CO2 into the atmosphere, along with fermentation by yeast
- Carbon is passed from autotrophs to heterotrophs during feeding (also through trophic levels)
- Dead organisms are fed on and decayed, supplying carbon to consumers and the surroundings
What are the effects of burning fossil fuels
- Extraction and burning of fossil fuels releases CO2 into the atmosphere at high rates
- CO2 levels in the atmosphere have increased drastically causing dramatic climate change
- This has changed habitats and increased the water temperature so less CO2 can be fixed in seas
What is succession
The process of ecosystems and their abiotic/biotic factors changing from simple to complex over time
What is primary succession
When newly formed/exposed land is colonised by an increasing number of species
What are pioneer species
A species that can colonise newly formed/bare rock or ground (e.g. marram grass in sand dunes, often moss and lichens)
Describe the stages of primary succession
- Seeds/spores carried by wind land on rock and begin to grow (pioneer species)
- As pioneer species die and decompose, the matter forms a basic soil
- Seeds of small plants and grasses can be transported in other ways (bird faeces) and land on the basic soil and grow
- The roots form networks which hold the soil in place
- These plants die and decompose to form more nutrient rich soil
- Larger plants that need deep nutrient rich soil can now grow
- Allowing final species to colonise the land and become the dominant species of this complex ecosystem, forming the climax community
What is a climax community
The stable, final community that exists in a balanced equilibrium that makes up the final stage of succession
Why does the environment change during succession
- Species change the local environment to make is more suitable for other species
- Often the new species change the environment so it isn’t suitable for the previous species
- E.g. Trees outcompeting lichen on rock faces
What is deflected succession
When human activities prevent or interrupt the process of succession, stopping the climax community from developing
How can succession be managed
- Conservation through protection and management of ecosystems
- Preventing areas from reaching climax communities so they can hold more biodiversity
- This high diversity promotes high diversity of animal species
- This can protect threatened species that are important in the ecosystems functions
- E.g. Scottish moorlands provide habitats for species to avoid climax communities in some areas and promote it in others
How can succession be prevented
- Grazing animals introduced temporarily
- Managed burning, with controlled fires that burn away trees to reset succession
What is sampling
A method of investigating the abundance and distribution of species and populations
Define abundance
The number of different species/individuals of a particular species found within a given area
Define distribution
Where species are found within an ecosystem
Define population
Group of organisms of the same species who live in the same area at the same time
Define habitat
The environment in which a species normally lives or the location of a living organism
What is an apex carnivore
Top of food web/chain
What is a keystone species
An organism that helps keep the ecosystem together
What is shown by a pyramid of biomass
They show the mass of material at each trophic level (usually upright pyramid) but they don’t take into account the changes of biomass over time
What is shown by pyramids of numbers
The width of each block is proportional to the number of organisms at each trophic level, but it doesn’t take account if the biomass at each trophic level
What is shown by pyramids of energy
Productivity for each trophic level is plotted against the rate at which biomass is produced per unit area and expressed as units of energy in relation to time (most accurate)
What is random sampling
The positions of the sampling points are completely random which is beneficial to avoid sampling bias
What is systematic sampling
Positions of the sampling point are chosen, which can be unrepresentative of the whole area or provide sampling bias
What are the main sampling methods to estimate size of population (and when are they used)
- Quadrats (non-motile/slow-moving species)
- Transects (non-motile/slow-moving species)
- Mark-release-recapture (motile species)
Describe how to use frame quadrats
- Random number generator/random placing of quadrat in area
- Species frequency can be determined by calculating how many squares are occupied
- Usually 100 squares in quadrats so a percentage can be found
- If a square is half full, it is counted as a full square
Describe how to use belt transects
- Systematic sampling method where a transect line is placed using a measuring tape
- Quadrats are placed at regular intervals along the tape
- Species abundance is measured
Describe how mark-release-recapture works
- A first sample of a species is taken, including as many individuals as possible
- They are counted and marked then returned to their habitat
- After a sufficient amount of time another sample is collected
- The number of marked and unmarked individuals in the sample are counted
- This proportion is used to calculate an estimate of population size
What is the mark-release-recapture equation
N = (n1 x n2) / m2
- N = population estimate
- n1 = number of marked individuals released
- n2 = number of marked and unmarked individuals in second sample
- m2 = number of marked individuals in second sample
What are the assumptions of the mark-release-recapture method
- Marked individuals are given enough time to disperse into the main population
- Marking doesn’t affect survival rate of individuals
- Marking remains visible
- Population stays the same size during the study period
What is the AFCOR scale
- Scale used to estimate abundance of species that it is hard to estimate (e.g. aquatic species)
- Abundant
- Common
- Frequent
- Occasional
- Rare
