-Module 6.3.1 Ecosystems Flashcards
What is the definition of a habitiat?
The place where an organism lives.
What is the definition of population?
Members of the same species living in the same place and at the same time, that can interbreed.
What is the definition of a community?
Populations of different species living in the same area at the same time, they can interact with each other.
What is the difference between a habitat vs an environment?
The environment is the conditions of the area due to biotic or abiotic factors.
Habitat is a defined place or area of the environment according to the life requirements of a particular life form.
-A habitat has life in it whereas an environment doesn’t ALWAYS.
-A habitat is always a preference of ONE species but an environment can be for multiple.
-Usually the environment governs the properties of the habitat and not vice versa.
What is an ecosystem?
A community of animals, plants and bacteria interrelated with the physical and chemical envrionment.
How big are ecosystems?
They can range in size from a tiny bacterial colony to the whole biosphere of the earth.
The size is determined by the person or team carrying out the study.
Ecosystems don’t have a clear edges.
What is an ecological niche?
A species’ niche is his ecological role, it is defined by the set of conditions, resources and interactions that it needs (or can make use of)
A description of it’s niche could include what it feeds on, what it excretes and how it reproduces.
What are the two groups of factors that affect an ecosystem?
Biotic and abotic factors.
What are examples of biotic factors?
Living organisms that can affect each other, it can involve competition.
What are examples of abiotic factors?
Light
Temp
Water availability
O2 availability
Edaphic (soil) factors
pH
Relative humidity
Concentration of pollutants
What are the 3 main soil types?
Clay, loam (retains water wothout getting water logged, fine particles) and sandy.
What is meant by ‘ecosystems are dynamic’? Why are they dynamic?
It means that ecosystems change.
Non-living elements change, living elements grow and die, populations of species rise and fall (mostly very small/not noticable)
Living things can interact with each other and with their physical environment and any small changes in one thing can affect another.
What are the 3 types of changes that affect population size?
Cyclic - repeat in a rhythm,
eg predator-prey cycles.
Directional - long lasting in one direction, eg erosion of coastline
Unpredictable/erratic - no rhythm/no constant direction, eg hurricane or effects of lightning.
What is a food web?
An interlinked system of food chains.
How is a food chain represented on a diagram?
Each level of the food chain is a trophic level.
Arrows show the flow of energy.
The first trophic level is always a producer - an organism that converts light energy into chemical energy by photosynthesis.
Subsequent trophic levels are all consumers - organisms that obtain energy by feeding on other organisms.
What are pyramids of numbers?
They represent food chains, each level represents the number of organisms at each trophic level.
Producers are always at the bottom.
It can look like a regular or irregular pyramid.
What is biomass?
The mass of living material present in a particular place or in a particular organism.
It can be equated to energy content and represented in a pyramid of biomass.
What are the units for energy available at each trophic level?
As biomass is transferred between trophic levels the energy contained is transferred.
Energy available at each trophic level is measured in kilojoules per metre squared per year (kJm-2 yr-1) to allow for changes in photosynthetic production and consumer feeding throughout the year.
What is the easiest way to measure biomass?
The easiest way is to measure the mass of fresh material present.
Why is it best to measure the dry mass of an organism?
Variable amounts of water in different organisms makes it unreliable unless very large samples are used.
How is dry mass created?
Organisms have to be killed, they are placed in an oven at 80 degrees until all water is evaporated.
They are periodically checked and measured until the mass stops reducing.
Why is biomass lost?
Only a small proportion of food ingested is actually converted into new tissue. Only this part of biomass available for the next trophic level to eat.
What is ecological efficiency?
Efficiency with which biomass or energy is transferred from one trophic level to the next.
What is primary production? How much sunlight is actually converted into chemical energy?
Generation of biomass in a producer.
Only 1-3% of sunlight is converted into chemical energy and hence biomass, 90% reflected, some transmitted through the leaf and some unusable wavelength.
Other factors limit photosynthesis, such as water availability.
What is gross production?
Total solar energy that plants convert to organic matter.
What is the equation for net production?
Net production = gross production - respiratory losses
How much biomass is converted into an organisms new organic tissue?
10% at most.
Why can trophic levels only convert small amounts of biomass into new tissue?
Not all biomass can be digested.
Living organisms have to carry out life processes.
Some material is lost from excretory materials like urine.
What are the units for net biomass?
Grams/Kg per square meter (g-1m-2) for areas of land.
Grams/kg per cubic meter (g-1m-3) for areas of water.
What is secondary production?
The generation of biomass in a consumer.
What are the 3 word equations for ecological efficiency?
Ecological efficiency = (biomass at the higher trophic level / biomass at the lower trophic level) x 100
Ecological efficiency = (biomass available after the transfer / biomass available before the transfer) x 100
Ecological efficiency = (biomass of the primary consumer / biomass of the producer) x 100
What are the 7 ways of increasing primary productivity?
1- Light levels
2- Water availability
3- Temperature
4- Nutrient availability
5- Pest control
6- Fungal disease
7- Competition from weeds for light, water and nutrients
How can light levels be used to increase primary productivity?
Light levels limit the rate of photosynthesis and hence production of biomass, some plants are planted early to provide a longer growing season to harvest more light.
How can water availability be used to increase primary productivity?
Water is a reactant in photosynthesis and irrigation systems ensure that plants/ crops have enough water.
How can temperature be used to increase primary productivity?
It affects rate of photosynthesis and therefore growth.
An optimum temperature is required for maximum production of biomass.
How can nutrient availability be used to increase primary productivity?
A lack of nutrients is a limiting factor of photosynthesis.
Crop rotation can be used, including nitrogen fixing crops like peas or beans which replenish nitrogen levels.
Many crops have been bred to respond to high levels of fertiliser which provide ammonium, nitrate, potassium and phosphorus.
How can pest control be used to increase primary productivity?
Pests remove biomass and create a lower yield by eating crop plants.
Pesticides, pest resistant plants can be used.
How can control of fungal disease be used to increase primary productivity?
Fungal disease causes a loss in biomass.
It can cause root rot (reduces water absorption), damage xylem, damage foliage through wilt/blight/spotting, damage phloem, damage flowers and fruit.
Fungicides can be used and crops can be bred to be resistant to fungal infections, potatoes have been GM to resist potato blight.
How can controlling competition from weeds for light, nutrients and water be used to increase primary productivity?
Herbicides are used to kill weeds.
Herbicide usually binds to an enzyme, stopping it from working, and frequently leading to a toxic build up of the enzyme’s substrate.
What are the 4 ways to increase secondary productivity?
1- Harvesting animals just before adulthood
2- Selective breeding
3- Prophylactic antibiotics
3- Intensive indoor farming
How can harvesting animals just before adulthood improve secondary productivity?
It minimises energy losses from the food chain.
A young animal invests a larger proportion of it’s energy into growth than an adult.
How can selective breeding improve secondary productivity?
It is used to produce improved animal breeds with faster growth rates, increased egg production and increased milk production for example.
How can prophylactic antibiotics improve secondary productivity?
They are given as a preventative for animals in intensive farming environments where there is a high risk of disease transmission.
Controversial due to antibiotic resistance.
EU has banned prophylactic use of antibiotics from 2022 except for in exceptional circumstances.
How can intensive indoor farming improve secondary productivity?
Lots of energy is wasted finding food and maintaining body temps.
Keeping them inside maximises energy for muscle (meat).
Why is intensive indoor farming controversial?
Concerns over animal welfare.
There are disputes over the line between animal welfare and efficient food production.
What does the distribution of organisms refer to?
It refers to where individual organisms are found within an ecosystem. The distribution is usually uneven throughout an ecosystem.
What is systemic sampling?
Not random sampling. Using a belt or a line transect provides more information.
What are the advantages of systemic sampling?
Scientists can study how differing abiotic factors in different areas of the habitat affect the distribution of the species.
What type of change is systemic sampling used to study ?
To study the successional changes that take place along a series of sand dune.
What does the abundance of organisms refer to?
The number of individuals of a species present in an area at any given time. It may fluctuate daily.
What two factors affect increase and decrease abundance of organisms?
Immigration and births will increase the number of individuals.
Emigration and death will decrease the number of individuals.
Why is random sampling used to measure abundance of organisms?
To reduce sampling bias.
How is more accuracy gained from sampling?
Take as large of a sample as possible.
The greater the number of individuals studied the less the chances are the it’s chance.
How is plant abundance measured?
Random sampling using quadrats.
Individual plants in the quadrats are counted (density) or count the number of smaller squares withing the quadrat that a particular species is present (frequency) or percentage cover is recorded.
Why can quadrats not be used when sampling animals?
Animals move.
What technique is used for measuring animal abundance?
Capture-mark-release-recapture.
How does energy flow through an ecosystem?
It has a linear flow, it enters the ecosystem from the sun and is ultimately transferred to the ecosystem through heat.
How does nutrients flow through an ecosystem?
Nutrients have to be constantly recycled throughout ecosystems in order for plants and animals to grow. This is because they are used up by living organisms and have no large external source constantly replenishing nutrients.
What is decomposition?
It is a chemical process in which a compound is broken down into smaller molecules, or it’s constituent elements.
Why do essential elements like nitrogen and carbon need processing?
They often cannot be used by an organism directly in the same organic form that it is found in dead/waste material.
How is dead/waste material broken down?
Can be broken down by decomposers (organisms that feed on and break down dead plant or animal matter, thus turning organic compounds into inorganic ones (nutrients) available to photosynthetic organisms in the ecosystem) which are microorganisms like bacteria and fungi.
What are decomposers?
Organisms that feed on and break down dead plant or animal matter, thus turning organic compounds into inorganic ones (nutrients) available to photosynthetic organisms in the ecosystem. They are saprotrophs.
What is a saprotroph?
They secrete enzymes onto dead and waste material.
The enzymes catalyse the digestion of material into smaller molecules which are then absorbed into the saprotroph’s body.
Having been absorbed, the molecules are stored or respired to release energy.
What are detritivores?
Another class of organism involved in decomposition. They help to speed up the decay process by feeding on detritus - dead and decaying material.
They break it down into smaller pieces of organic material, which increases the surface area for decomposers to work on.
Detritivores perform internal digestion.
Why is nitrogen so important?
All life requires nitrogen-compounds, eg used to make amino acids (and consequently proteins) and nucleic acids.
Why can’t organisms use nitrogen from the air?
Nitrogen (N2) in the air is inert.
Air is 79% nitrogen gas.
To be used by living organisms nitrogen needs to be combined with other elements such as oxygen and hydrogen.
What form do plants have to secure their nitrogen?
In a ‘fixed’ form, ie, incorporated in compounds such as:
Nitrate ions (NO3-)
Ammonia (NH3) / Ammonium (NH4+)
How do animals secure their nitrogen?
Animals secure their nitrogen (and all other) compounds from their food - plants or other animals.
What are the 4 biological processes that participate in the nitrogen cycle through the biosphere.
Nitrogen fixation.
Decomposition.
Nitrification.
Denitrification.
What is FNAD is relation to nitrogen cycle?
Fixation
Nitrification
Ammonification
Denitrification
Draw the nitrogen cycle diagram.
…
What are the features of biological nitrogen fixation?
Bacteria such as Azobacter live in the soil and fix nitrogen gas.
Symbiotic nitrogen fixing bact. such as Rhizobium live in the root nodules of legumes.
Rhizobium contains nitrogenase (enzyme), it combines atmospheric nitrogen and hydrogen to form ammonia. Nitrogenase can’t function in prescence of oxygen so fixation is anaerobic, any O2 present is quickly metabolised by the bact to stop it affecting the enzyme.
What is ammonia used for in plants?
It can be abosrbed and used to make amino acids -> proteins in the legume in return for supplying the bacteria with carbohydrates for respiration.
What are the features of nitrification?
Conversion of ammonia from decay to nitrates.
Ammonia from decay is converted to nitrates in two ways;
1) Free living soil bacteria from the genus Nitrosomanas oxidise NH3 to nitrites (NO2-)
2) Bact of the genus Nitrobacter oxidise the nitrites to nitrates (NO3-)
These bacteria are chemoautotrophic rather than other plant and bacteria which are photoautotrohic, means they obtain energy from oxidation rather than the sun.
Why are Nitrate ions good in uptake in plants?
They are highly soluble and so are the main form nitrogen enters a plant.
What are the features of uptake and assimilation by plants and transfer of nitrogen in the food
chain?
Nitrates are absorbed by the roots of the plant and are used to make amino acids etc.
Animals gain nitrogen containing compounds when eating the plant or other animals.
What are the features of ammonification?
It is the process by which decomposers convert nitrogen-containing molecules in dead organism, faeces and urine into ammonium compounds. (links to decay)
What are the features of denitrification?
Nitrogen fixation, Nitrification and ammonification all remove nitrogen from the atmosphere and pass it through ecosystems.
Denitrification reduces nitrates to nitrogen gas and replenishes the atmosphere, thus closing the cycle.
What is the purpose of bacteria in DENITRIFICATION?
Bact such as Pseudomonas are the agents and live in deep soil and aquatic settlements (water logged soil) where there are anaerobic conditions.
They use nitrates as a source of oxygen for respiration and produce nitrogen gas and nitrous oxide.
What are the processes that the carbon cycle is driven by? What is the main vehicle?
Respiration and photosynthesis, carbon is the main vehicle for cycling between biotic and abiotic components.
What are microorganisms important for in the carbon cycle.?
The decomposition of dead organisms and waste.
How is carbon exchanged between the air and water?
Carbon dioxide dissolves in water and then reacts to for carbonic acid. Carbon also enters rivers and lakes from weathering of limestone and chalk in the form of hydrogen carbonate.
Why do carbon dioxide levels fluctuate throughout the day?
Photosynthesis takes place during the light and so removes carbon dioxide from the atmosphere in the day.
Respiration takes place all the time which releases carbon dioxide at a relatively constant rate.
Atmospheric carbon dioxide levels are higher in the day.
Why do CO2 levels change seasonally?
Differences in photosynthesis rates (lower CO2 in summer)
Why do CO2 levels change seasonally?
Differences in photosynthesis rates (lower CO2 in summer)
How is the amount of CO2 dissolved in the sea and ocean affected by temperature?
The higher the temperature, the less gas dissolved, therefore rising temperatures is a positive feedback loop.
What is succession?
Changes to the environment cause the animal or plant species present to change. The gradual directional changes happen in a community over time. The process of the directional change is succession.
What is primary succession?
Rocky landscape has no life and is converted through different levels of species to a climax community where there is lots of life.
What is a seral stage?
Succession takes place in a number of steps each step is a seral stage.
What are the main seral stages in primary succession?
Pioneer species (colonise the bare rock and release minerals so that other organisms can survive)
Intermediate community (as plants grow and die they decompose and soil grows deeper and larger plants can survive diversity increases).
Climax community (dominant species take over eg oak trees)
How do pioneer species arrive?
Through spores or seeds which are carried by winds or by droppings of birds.
What is biomass like at pioneer stage?
Low
What are two examples of pioneer species?
Moss and lichen.
What are the adaptations that pioneer species have that enable them to colonise bare environments?
Ability to produce large quantities of spores or seeds.
Seeds that germinate rapidly.
Ability to photosynthesise.
Tolerance to extreme environments.
Ability to fix nitrogen from the atmosphere which adds nitrogen content to the soil.
How is an intermediate community formed?
Weathering of rock over time produces particles forming the basis of soil.
After lichens decompose small organic products are added to the soil, plants can grow in the new soil (humus).
The soil now contains minerals like nitrates and can retain water so is able to support the growth of new plant species.
Over time more humus formed, soil thickens and grasses and wild flowers take over.
What is a climax community?
The final seral stage.
The community is in a stable state and shows very little change.
Where is biodiversity usually the highest?
In the intermediate community.
What is secondary succession?
It takes place where there is already soil but no plants or animal species.
Eg after a wildfire.
It begins with an intermediate species.
How does animal succession work?
Similair to plant succession.
Primary consumers (worms and insects) colonise.
Animals move in from neighbouring areas.
Secondary consumers and eventually large animals move in when biotic conditions are favourable.
Why are sand dunes of interest in succession?
They display all stages of succession.
How is succession seen in sand dunes?
Fore dunes have the pioneer species.
Second dunes are the intermediate species as they have more shelter and nutrients.
Hind dunes are the climax community.
What is deflected succession?
When succession is stopped or interfered with?
The final stage is known as the plagioclimax.
It is an important conservation technique as it preserves the habitats in their current form.
What are the causes of deflected succession?
Grazing/trampling.
Cropland.
Herbicide/fertiliser.
Burning to clear forests.
Cutting grass (golf courses)
