Ecosystems Flashcards
Define ecosystem
A natural system in which biotic and abiotic factors interact with each other (and the environment)
Define biotic factor
The living components of an ecosystem that affect distribution and abundance of species
Give an example of biotic factors
feeding, predation, parasitism, mutualism and competition
Define abiotic factor
The non-living components of an ecosystem that affect distribution and abundance of species
Give an example of abiotics factors
temp, light intensity, O2 conc, CO2 conc, water supply, pH, humidity, wind speed
Define producer
Organisms that transfer light energy into organic or inorganic compunds e.g. plants
Define primary consumer
The first consumer in a food chain; a herbivore
Define secondary consumer
The second consumer in a food chain; carnivore that eats herbivores
Define tertiary consumer
The third consumer in a food chain; a carnivore that feeds on a secondary consumer
Define trophic levels
The levels in the food chain in which an organism feeds
Define food web
Many interconnection food chains which show sequence of organisms and how energy is passed
Define decomposer
- An organism that breaks down organic remains of other organisms into the soil
- Death of plants and animals means organic N moves into soil
Define detritus feeders
Remains of plants and animals e.g. dead leaves which are used as a nutrient source for by decomposers and detritivores
Define detritivores
An organism that feeds on detritus (remains of plants and animals) for nutrient sources
Why is some energy lost by plants
- The plants convert less than 3% of sunlight into chemical energy
- The sunlight misses leaves entirely so little photosynthesis
- Sunlight reflected from surfaces of leaves
- Only certain wavelengths of light being absorbed by chlorophyll
Why is some energy lost by animals
- Movement
- Excretion
- Respiration
- Lost as heat energy from digestive system
Define efficiency of a food chain
The total energy put into the system divided by the useful energy obtained
Define productivity of a food chain
Rate at which energy passes through each trophic level
Define primary productivity
The conversion of the sunlight energy into biomass/chemical energy by plants per unit of area, per unit of time measured in kJ
Define gross primary productivity
The total quantity of energy transferred by plants from sunlight into plant tissues
Define net primary productivity
The chemical energy left after plants have supplied needs for respiration (GPP-R)
How do you measure the energy transfer between trophic levels
- Population size of each species is measured
- Mean dry mass of a single organism is calculated
- Energy content per gram of dry material calculated for each kind of organism by burning sample of known mass in a calorimeter and measuring heat produced
Define monoculture
When a single variety of crop is just grown in one area
Define photosynthetic efficiency
The amount of light energy onto a crop divided by the amount of light energy converted to carbohydrate
What is a pyramid of numbers
- Measures number of organisms on a trophic level
- Doesn’t show the mass so not as accurate
What is a pyramid of biomass
- The dry mass of each organism on a trophic level
- Usually a pyramid shape
What is a pyramid of energy
- How much energy in a particular area at a particular time of the year
- Changes throughout the year
Define succession
A directional change in a community of organisms over time
What is the role of pioneer plants in succession
- They alter the soil as when they shed leaves, they provide nutrients for decomposers so numbers increase
- Proper soil can form which helps hold water and mineral ions and so other species can live there
Define pioneer plant
A plant that is adapted to grow on newly exposed ground and therefore are often found in very early stages of primary succession
What is primary succession
Succession that occurs on a piece of ground that began with no soil
Define secondary succession
Succession that occurs following the clearance of land that already has soil
What is deflected succession
- When human intervention stabilses/halts the plant communities and therefore succession, preventing ecosystems from developing further
- Also known as a plagioclimax
What is a climax community
The final stage at the end of the process of succession
Define sere
A composition of a series of different plant communities that change with time. Communities are known as seral stages
What are seral stages
One of the communities that exist during a succession
What is a line transect
Taking samples along a line running across the area to be surveyed
What is a belt transect
Taking samples from quadrats placed along a line running across the area to be surveyed
What is a continuous transect
A line along which the organisms at every point on the line are recorded
What are interrupted transects
Taking samples at intervals along the length of a line
Describe the process of succession on sand dunes
- FOREDUNE- Very few plants can survive mobile sand and sea water spray. Sea holly can survive
- YELLOW DUNE- Dominated by a few grasses e.g. sea couch grass and marram grass
- GREY DUNE- sand is fixed by roots and has accumulated humus. Nutrient levels are higher and water supply is so diverse range of species can live there e.g. restharrow. Temporary pools of water can form
What is nitrogen fixation
- The process where nitrogen gas is converted to nitrogen containing compounds.
- Can be carried out industrially or naturally when lightning passes through the atmosphere.
- Also carried out by two types of micro-organism:
- Free living nitrogen fixing bacteria - Reduce gaseous nitrogen to ammonia, which they use to manufacture amino acids. Nitrogen rich compounds are released from them when they die.
- Mutalistic nitrogen fixing bacteria - Are attached to nodules of roots of plants, plants provide them with carbohydrates and they provide plants with amino acids.
What is nitrification
- The production of nitrate and nitrite ions by oxidation of ammonium ions
- Nitrosomonas bacteria; oxidation of ammonium ions intro nitrites in soil (NH4+ to NO2-)
- Nitrobacteria bacteria; oxidation of nitrites into nitrates in soil (NO2- to NO3-)
What is denitification
- The process by which denitrifying bacteria convert nitrogen ions in the soil to gaseous nitrogen.
- Takes place in waterlogged fields where there is not much oxygen.
- As there is not much oxygen, few aerobic bacteria like nitrifying bacteria remain, this means that there are more anaerobic denitrifying bacteria.
- So in order to keep nitrogen in the soil drainage and aerated fields are important.
Define ammonification
The production of ammonia from nitrogen-containing compounds e.g. urea
What is mutualism
A close relationship between 2 organisms in which both benefit
What is rhizobium
Nitrogen fixing bacteria
What are root nodules
Location for Rhizobium in legumes
What is nitrosomonas
Bacteria which convert ammonium compounds –> nitrites
What is nitrobacter
Bacteria which convert nitrites –> nitrates
Describe the lag phase (populations)
No increase, the population grows slowly as the organisms are acclimatising to the conditions and the rate of reproduction is low
Describe the exponential phase (populations)
If resources are plentiful the population will start to increase rapidly i.e birth rate > death rate
What is environmental resistance
Prevents the population from increasing indefinitely due to environmental resistance
What are limiting factors
The variable that limits a particular process- These can be both abiotic and biotic factors
Define carrying capacity
The maximum population density of an organism that can be supported permanently in a habitat and is determined by one or more density dependant limiting factors.
Why is a population not static
Population tends to fluctuate over time depending on the birth rate and death rate and migration.
Define predation
Animals eating other organisms
Describe the predator-prey relationship
As the prey population increases there is more food available for the predators so they are more likely to survive, successfully breed, their population will increase. As the predator population increases more prey are eaten, which brings about a decrease in the prey population. As the prey numbers fall there is less food for the predator so they do not survive and predator numbers also fall.
Define intra-specific competition
Competition for a limited resource between members of the same species
Define inter-specific competition
Competition between members of a different species.
What is competitive exclusion
Due to competition two species cannot occupy the same niche in a habitat
Describe sustainable forestry
Seeks to provide a regular supply of timber without adverse side effects to the environment and ensure that thee habitat is largely unaffected and the biodiversity maintained.
What is coppicing
The tree is cut leaving a live stump from which new shoos grow.
It can be done rotationally to ensure a constant supply of wood for several years. This maintains biodiversity and ensures a range of different trees.
What is pollarding
A pruning system in which the tree is cut back to promote a dense head of foliage
Describe selective felling
Largest most valuable trees, diseased trees or unwanted trees are cut down and removed.
Describe strip felling
Each year different small strips of forest are removed completely and replanted. This gives each area time to regrow, ensuring a range of ages of trees
Describe clear felling
Not sustainable - removing all the trees leaves bare soil which is susceptible to erosion and leaching out of minerals. heavy rainfall can wash the soil into rivers causing silting and increased risk of flooding.
Define conservation
The dynamic process of protecting, managing an retaining ecosystems with the purpose of maintaining increasing biodiversity between species, genetic diversity within species and the maintenance of a variety of habitats & ecosystems.
Define preservation
Protection of ecosystems so that they are kept with purpose of maintaining biodiversity between species and genetic diversity within the species. Nothing is removed or added.
Give 2 threats to species of the galapogos
- Increase human population and tourisim meaning greater demands for water, sanitation and energy
- Habitat disturbance for agriculture, infrastructure and buildings
- Over exploitation of resources- fishing, tortoises for food
- Deforestation - wood for building
- Introduction of non-native species e.g Goats (out compete tortoises for food) & Red quinine tree (threatens scalesia tree)
Describe conservation methods in the Galapagos
- Wildlife sanctuary in 1959, national park in 1986, marine reserve
- Quarantine system introduced to reduce the chance of exotic species arriving in the islands.
- Culling of goats and pigs on some islands to prevent soil erosion
- Fishing exclusion zone
- Restrictions on the areas that tourists can visit
