Population Size And Ecosystems Flashcards
Define the term habitat
The place in which the organism lives
Define the term ecology
The study of the interrelationships between organisms and their abiotic and biotic environment
Define the term abiotic environment
Non-living conditions affecting a community or an organism like temperature and soil ph
Define the term biotic environment
The living conditions affecting a community or an organism like competition predation and disease
Define the term population
An interbreeding group of organisms of the same species occupying a particular habitat
Define the term ecosystem
A characteristic community of interdependent species interacting with the abiotic components of the habitat
Define the term community
Interacting populations of two or more species in the same habitat at one times
Define the term niche
The role and position a species has in its environment including all interactions with the biotic and abiotic factors of its environment
What are the levels of organisation (from most broad to least)
Biosphere, ecosystem, community, population, organism
Explain how ecosystems are dynamic
- the energy flowing through it changes
- biological cycles vary
- habitats change over time as succession occurs
- new species arrive and some die out
What determines the size of a population?
Birth rate
Death rate
Immigration
Emigration
Define birth rate
The reproductive capacity of a population the number of new individuals derived from reproduction per unit of time
Define immigration
The movement of individuals into a population of the same species
Define emigration
Individuals or species leaving a habitat to enter and live in a new one.
What is the equation for population number?
(Birth rate-death rate)+(immigration-emigration)
Why should we talk about death rate when it comes to bacteria and fungi?
They are not born. They are reproduced by binary fission
What is environmental resistance?
Any factor which may slow down the growth of a population
List some biotic factors
Predation Parasitism Competition Overcrowding Disease
List some abiotic factors
Weather Light intensity Temperature Ph Accumulation of toxic waste
What sort of factors can increase population growth?
- good food and water supply
- plenty of space
- resist disease and parasitism
- small number of predators
- high reproduction rate
- favourable light
- stable abiotic conditions
Factors which cause environmental resistance
Competition for food Not enough space so toxic waste accumulates Can not resist disease Low reproduction rate Unfavourable light
What is the carrying capacity?
The maximum population number a given environment can support or maintain around which a population fluctuates dependant if the availability of resources
What are the four stages of the population growth curve in order?
Lag phase
Exponential phase
Stationary phase
Death phase
Describe the lag phase in the population growth curve
- initially population won’t increase
- then there is a period of adaptation, preparation for growth and enzyme synthesis
- intense metabolic activity
Describe the exponential phase of the population growth curve
- no factors limiting reproduction
- eventually environmental resistance sets
- cells divide at a constant rate with the population doubling per unit time
Describe the stationary phase of the population growth curve
Birth rate = death rate
- due to certain factor limiting the population growth
- the population has reached its carrying capacity for that particular environment
Describe the death phase of the population growth curve
Death rate is bigger than birth rate
-due to all nutrients being used up or toxic substances like waste building up.
Define intraspecific competition
Competition between individuals of the same species
Define inter specific competition
Competition between individuals of different species
Define saprobiont
A microorganism that obtains it’s food from the dead or decaying remains of other organisms
Define set point
The numbers of most species that lie near an equilibrium point
Define what the sigmoid growth curve is
An a-shaped graph to show the population growth pattern when the animal occupies a new habitat
Define the term density independant factor
The effect of an abiotic factor in the environment that does not depend on the density of a population
Define the term density dependent factor
Biotic factors which will affect a greater proportion of the population if the population is denser
What is a limiting factor?
And abiotic or biotic factor which restricts the number or reproduction of organisms in an ecosystem is a limiting factor
Give an example of a density dependant factor
Depletion if food supply
Disease
Parasitism
Predators
Give examples of density independent factors
Flood
Fire
Define the term abundance
The measure of how many organisms are in a habitat.
What methods can be used to measure the abundance of animals?
Capture mark recapture
Kick sampling
What methods can be used to measure the abundance in plants?
- quadrat to find density
- estimating % cover
- estimating % frequency
- transects (line and belt)
What does a kite diagram enable you to do?
Represent percentage cover of plants along a transects
What is the equation to estimate population size using capture recapture?
(Total no organisms(sample 1) X total no organisms (sample 2) ) / no marked organisms (sample 2)
*round to nearest whole number
Describe how you would carry out a capture recapture
Capture a group of organisms and mark them and count the number of them
Release back into habitat and allow time to mix
Capture a second sample and count the total and count the number of them marked.
What does kick sampling explore?
Investigates the biodiversity of streams
Define the term ecosystems
A natural unit of living components in a given area as well as the non living factors with which they interact
Define the term ecological energetics
The study of the flow of energy through the ecosystem
Define the term trophies level
Feeding level
Define the term primary consumer
Also known as herbivores. Animals which feed on plants
Define the term carnivores
Animals that feed on other animals
Define the term detritivores
Organisms such as earthworms that feed on small fragments of organic debris, called detritus, made up of non living organic material like fallen leaves or the remains of dead organisms
Define the term decomposes
Microbes such as bacteria and fungi that obtain their nutrients from dead organisms and faeces. They complete the process of decomposition started by detritivores
What is the source of energy in an ecosystem?
Sunlight energy trapped by photosynthesis (except for chemosynthesis)
What happens to sunlight energy once absorbed by chloroplasts?
Used in photosynthesis to drive the conversion of co2+water into glucose
What are organic substances?
Those molecules that contain carbon
What happens to glucose in plants?
Used in respiration
What is the name for plants because they manufacture organic substances from light water and carbon dioxide?
Producers
Are plants the only producers?
No. Some protoctista and bacteria also photosynthesise (photoautotrophs) and some bacteria are chemoautotrophs
What are the possible energy sources on earth?
Geothermal
Electrical
Chemical
What are producers in a food chain?
Green plants, Cyanobacteria, protoctista
Incorporate the suns energy into carbohydrates and therefore an energy for the next organism in the food chain
Trap solar energy and synthesise sugar from inorganic compounds by photosynthesis
Only a small amount of the total energy that reaches the plant al light is incorporated into the plants tissue
How is energy passed along trophies levels?
Material of the previous organism is consumed from the next trophic level
Energy is converted into the molecules of the consumer
Some energy is lost at each level
Therefore energy flowing through the ecosystem reduces the further up you go, ultimately leaving the system as heat
What is a food web?
It shows you how the organisms in a community interact with each other through food consumption
What is a food chain?
A linear sequence of organisms in a food web
Why can’t a food chain be very long?
Because after about 4 or 5 trophic levels there is not enough energy left to support another level
What does the length of a food chain depend on?
- energy entering the chain in the first place (more energy fixed by photosynthesis linger chain)
- energy transfer efficiency
- predator prey population fluctuate and relative Abundace affects length
- larger ecosystems support longer chains
- 3D environments longer chains
Name ways in which sunlight energy is lost so that it isn’t all absorbed into the leaf
- wrong wavelength for photosynthesis
- reflected by the leaf
- passes through the leaf
- some is lost as heat before being absorbed by chloroplasts
What is the equation used to find the photosynthetic efficiency to find the % of light energy that is converted into glucose?
(Quantity of light incorporated into product) / (quantity of energy falling on the plant) X 100 = ……%
What is primary productivity?
The rate at which energy is converted by producers into biomass
What is secondary productivity
The rate at which the consumers convert the chemical energy of their food into biomass in their cells or tissue
Where does secondary productivity occur?
Heterotrophs (animals & fungi)
Some bacteria
Some protoctista
Why is there a loss of energy at each trophies level?
- energy in molecules which are egested, which is transferred to decomposers (carnivores diet is protein rich so more efficiently digested than herbivores)
- lost as heat fuelled by energy generated from respiration
- energy remains in molecules in parts of the animals which cannot be eaten like horns fur and bone.
How can you calculate the efficiency of energy transfer?
Energy incorporated into biomass after transfer / energy available in biomass before transfer X 100 = …… %
What does GPP stand for?
Gross primary productivity
What is GPP?
The rate of production of chemical energy (KJ m-2 y-1) in organic molecules by photosynthesis in a given area in a given time.
What does NPP stand for?
Net primary productivity
What is NPP?
Energy in the plants biomass which is available to the primary consumer
What is respiration?
Process in living organisms involving production of energy - glucose and other substances are broken down to produce ATP
What is the relationship between GPP NPP AND R
GPP= NPP+respiration
Why is plant material difficult to digest?
It contains indigestible cellulose and lignin
Why are carnivores more efficient at converting their food into body tissue?
The diet is rich in protein which is more readily and efficiently digested
What determines the number of trophic levels?
- the total producer biomass
- efficiency of energy transfer
What are ecological pyramids?
A diagram that shows a particular feature of each trophic level in an ecosystem
What is always at the bottom of an ecological pyramid?
Producers
What are the three types of ecological pyramid?
Pyramid of number
Pyramid of energy
Pyramid of biomass
What is a disadvantage of ecological pyramids?
Don’t take into account that some organisms operate at more than one trophic level at the same time
What is an advantage of a pyramid of numbers
Easy to construct
What are some disadvantages of pyramid of numbers
Doesn’t take size of organism into account
Doesn’t recognise difference in adult and juvenile forms
Hard to draw to scale when there is a large number range
Can become inverted
What are some advantages of pyramids of energy?
- most accurate way to represent feeding relationships
- never inverted as energy can only be lost at each stage
- easy to compare efficiency of energy transfer between trophic levels and different communities.
Disadvantages of pyramid of biomass
Hard to measure accurately
They don’t indicate productivity or amount of energy flowing through the ecosystem
Can be inverted
Not all of one trophic level will transfer to the next
Species with similar biomass may have different life spans
Why do we try to use dry biomass and why is it hard?
Hard to do and time consuming.
Wet biomass is affected by water uptake and loss so will change where as dry will remain constant.
Define the term biomass
The mass of living material present at a given time
Define the term succession
The change in structure and composition of a species of a community over time
Define the term climax community
A community that has reached equilibrium with its environment and no further changes occur
Define the term sere
A stage in succession. the sequence of communities with different species and structures.
Define the term pioneer
The first organism ms to colonise bars rock such as lichens and algae
Define the term primary succession
The introduction of plants and animals into areas that have not previously supported a community
Define the term secondary succession
Reintroduction of organisms into a bare habitat previously occupied by plants and animals
Define the term xerosere
A sere in a very dry environment
What sort of human activities interfere with or prevent succession?
Sheep grazing
Farming
Deforestation
Soil erosion
What are seral stages?
Different stages in the sere where there are changes in the environment which makes it suitable for other species.
What helps succession to progress?
Immigration of a new species.
In a climax community what is the equilibrium between?
GPP and total respiration
Energy used from sunlight and released by decomposition
Uptake of nutrients from soil and return by decayed remains
What would a stable community look like?
Good species diversity
Complex food web
Dominated by long lived plants
As a xerosere progresses what increases?
Soil thickness Biomass Biodiversity Resistance to invasion from new species Stability to disruption by new environmental challenges like abnormal weather
What adaptations would a pioneer species have?
Vast quantities of wind dispersed seeds or spores Rapid seed germination Ability to photosynthesise Ability to fix nitrogen from atmosphere Tolerance to extreme conditions
Define secondary succession
The changes in a community following the disturbance or damage to a colonised habitat
What is disclimax in a habitat?
Human interference can affect a succession and may prevent the development of the climax community
What factors affect succession?
Immigration (spores and seeds help provide primitive soil with more minerals)
Competition to establish new seral stages
How are nutrients cycled through a habitat?
Detritivores and decomposers break down remains and waste products of producers and consumers
Minerals return to the soil and plants take them up again
What does it mean when we say the energy transfer has a linear fashion?
Minerals cycle between biotic and abiotic components of the environment
How do microorganisms return nutrients to the soil?
Fungi and bacteria secrete enzymes to extracellularly digest the organic matter, the products of which are then absorbed to be used in respiration and waste products are released
Give examples of organic molecules
Carbohydrates
Lipids
Proteins
What are the two main human activities which increase the carbon dioxide levels in the atmosphere?
Deforestation
Burning of fossil fuel
What are the main processes in the carbon cycle?
Respiration
Photosynthesis
Decomposition
Define respiration
Carbon dioxide is added to the air by respiration of animals plants and microorganisms
Define photosynthesis
It reuses almost as much carbon dioxide as is released into the atmosphere my respiration
Define decomposition
Dead remains of animals and plants are acted upon by detritivores and saprobionts in soil releasing carbon dioxide into the atmosphere
Define combustion
Burning fossil fuels releases carbon dioxide that was previously locked up in them into the atmosphere
Define deforestation
The removal of trees in large numbers as well as large amounts of photosynthesising biomass so that less carbon dioxide is removed from the atmosphere
Define the term fossilisation
Geological process of converting biological remains into coal oil and natural gas or peat is decay of biological remains is prevented by anaerobic conditions or acidic conditions
How does carbon become a part of chalk stone and marble?
There is bicarbonate in shells and exoskeletons of anthropods which sink to the bottom of the ocean when they die.
What is meant by the term carbon footprint?
A way of measuring the contribution to the greenhouse gases in the atmosphere by an individual, product or service
Is the greenhouse effect a natural process?
Yes
How does deforestation affect the carbon cycle?
- reduces the rate at which co2 it’s taken out of the atmosphere by photosynthesis by cutting down large amounts of photosynthesising biomass
- once cut down, trees are burned or left to decay which releases co2 into the atmosphere
How does climate change affect the carbon cycle?
Carbon dioxide is a greenhouse gas meaning it absorbs radiation from earth and if excess is accumulated leads to global warming
What are the greenhouse gases
Co2 Methane Nitrous oxides CFC Ozone Water vapour
How do greenhouse gases cause the earths atmosphere to warm up?
Short wavelength radiation from sun passes through to the earths surface
Much is absorbed by the earth so it warms up
Earth retaliated lower energy longer wavelength infra red radiation
It’s absorbed and trapped by greenhouse gases in the atmosphere
This retaliates the energy is many directions
What would happen if the greenhouse effect didn’t occur naturally?
The earth would be too cold to sustain life.
What are the consequences of global warming?
- melting of polar ice leading to flooding in coastal areas
- increased frequency of extreme weather like droughts and hurricanes
- increase forest fire frequency
- desertification in tropical areas
- world food production decreases
- ocean acidification as co2 diffuses into the water
What is global warming?
The increase in average global temperature in excess of the greenhouse effect caused by the atmospheres historical concentration of carbon dioxide
How can you reduce your carbon foot print?
Reduce reuse and recycle Drive less Less air con or heating Eat less meat Avoid food waste-compost Plant trees in deforested regions
What types of biological molecules contain nitrogen?
Amino acids
Nucleotides
ATP
chlorophyll
What is the nitrogen cycle?
The flow of nitrogen atoms between organic and inorganic nitrogen compounds and atmospheric nitrogen gas in an ecosystem
How do plants take in nitrogen?
Root hair cells actively transport it into the plant by carrier molecules from the soil
How do animals take in nitrogen?
By eating and digesting plants
What are the stages in the nitrogen cycle?
Nitrogen fixation Assimilation (putrefaction) Ammonification Nitrification Denitrification
What does the bacteria nitrosominas do?
NH 4+ => NO 2-
Ammonium ions to nitrites
What does the bacteria nitrobacter do?
NO2- => NO3-
Nitrites to nitrates
What does the bacteria pseudomonas do?
NO3- => N2
Nitrates to nitrogen gas
What does the bacteria rhizobium do?
N2 => NH4+
Nitrogen gas to ammonium ions
Root nodules
Using the enzyme nitrogenase
Anaerobic conditions
What does the bacteria azotobacter do?
N2 => NH4 +
Nitrogen gas to ammonium ions
Free living in the soil
Anaerobic conditions
Enzyme nitrogenase
What is nitrogen fixation?
The process by which atmospheric nitrogen is converted fixed into nitrogen containing compounds
What are the ways in which nitrogen can be fixed?
Lightning
Industrial processes (Haber process)
Nitrogen fixation by microorganisms (rhizobium and azotobacter)
Describe the first stage of nitrogen cycle (nitrogen fixation)
- fixed by microorganisms like rhizobium (in root nodules) and azotobacter (free living in soil)
- plant and bacteria have a mutualistic relationship
- this happens when the plant dies to decompose plant and rhizobium and release them into the soil.
Where can you find rhizobium?
In the root nodules of leguminous plants like beans
Describe the second stage of the nitrogen cycle (assimilation)
Bacteria convert nitrogen gas from soil into ammonium compounds in the legume root
Plant absorbs ammonium compounds and convert them into amino acids
Describe the third stage of the nitrogen cycle (ammonification (putrefaction))
The process by which decomposers break down dead plants/animals/faeces into ammonium.
Decomposers (fungi and bacteria) secrete enzymes to exracellularly digest matter
Describe the 4th stage in the nitrogen cycle (nitrification)
The process by which bacteria convert ammonium compounds into nitrites and nitrates in the soil
Step 1: oxidation of ammonium ions into nitrite by nitrosomonas (NH4+=>NO2-)
Step 2: oxidisation of nitrites into nitrates by nitrobacter (NO2-=>NO3-)
AEROBIC conditions
Ploughing
Describe the 5th stage of nitrogen cycle (denitrification)
The process by which bacteria convert nitrates in soil into nitrogen gas in the atmosphere ANAEROBIC conditions (reduction) Pseudomonas converts NO3- => N2
Why is denitrification a problem for waterlogged soils?
It’s favoured by anaerobic conditions so happens easily.
What is a consumer?
Animals that feed on another food source like plants or other animals
What is a decomposer?
Organisms, fungi, and bacteria that break down dead organic matter to obtain nutrients.
What is an excretory product?
The waste products that have been produced as a result of metabolic processes in an organism
What is a legume?
A dicotyledonous plant that forms a mutualistic relationship with nitrogen fixing bacteria found in root nodules. These plants improve soil fertility and are used in crop rotations
Eg prawns beans and clover
What does mutualistic mean?
A relationship between two species which result in benefit to both
What is a producer?
An autotrophic organism that converts light energy into chemical energy by photosynthesis
What is a root module?
A small swelling on the root of a leguminous plant which results from infection with nitrogen fixing bacteria like rhizobium.
What does saprobiontic mean?
An organism that obtains its nutrients from dead or decaying organic matter. They secrete digestive enzymes onto the surface of their food. The breakdown of complex organic molecules into simple inorganic products which are then absorbed by the bacteria or fungi or recycled as nutrients
What is translocation?
The transport of amino acids form one part of the plant to the other.
What is eutrophication?
The artificial enrichment of aquatic habitats by excess nutrients often caused by run off fertilisers
What human activities can improve the circulation of nitrogen in fields?
Ploughing Draining land Treated sewage sludge Planting legume fields Artificial nitrogen fixation Slurry Animal waste as brown manure
How does ploughing fields improve circulation of nitrogen in soils?
Improves aeration which favours:
- aerobic organisms like free living nitrogen fixers
- nitrifying bacteria
- plant roots respire aerobically and generate ATP
How does draining land improve circulation of nitrogen in soils?
Allows air to enter the soils which reduces anaerobic conditions, favouring denitrifying bacteria so loss of nitrates reduces
How does treated sewage improve circulation of nitrogen in soils?
Sustainable alternative to inorganic fertiliser
How does planting legume fields improve circulation of nitrogen in soils?
Like alfalfa or clover to enhance nitrogen fixation and when the crops die it’s ploughed back into soil as green manure supplying Hugh nitrogen content to soil
How does artificial nitrogen fixation improve circulation of nitrogen in soils?
Like the haber process converts oxygen into fertilisers to produce high volumes of good quality food
What problems are caused by excess nitrate in soil?
More fertiliser used on agricultural land and decreased diversity in grassland
Fertilisers increase growth of grasses and plants like nettles which reduce light intensity for smaller plants
What problem is caused by nitrates in rivers?
- salt concentrations increase
- eutrophication
Outline the process of eutrophication
- nitrates from fertilisers leached from soil into lake and rainfall
- algal bloom turns surface water green in response to the fertiliser
- reduces light intensity for aquatic plants. So reduces photosynthesis leading to plants dying
- aerobic decomposing bacteria decompose dead plants using the o2 in water to respire leading to reduced oxygen levels
- water becomes deoxygenated so all oxygen requiring species die
