3.5 Population Size And Ecosystems Flashcards
Ecology
The study of living things and their interactions with each other and their environment
Ecosystem
A characteristic community of interdependent species interacting with the abiotic components of their habitat
Population
All the members of one species in an area
Habitat
The place in an ecosystem where an organism lives
Niche
The role of an organism in an ecosystem, generally a feeding role
Biotic
All the living and organic component of an ecosystem
Abiotic
All the non-living parts of an ecosystem
Is an ecosystem static
No
Ut is dynamic
What is the source of energy for an ecosystem
The sun
How does the sun being the source of energy for an ecosystem mean an ecosystem is subject to change
The duration and intensity of sunlight changes which effects the energy flow
What does population size depend on
Reproduction rate
Death rate
Immigration rate
Emigration rate
Population size will increase when
Reproduction and immigration rates are higher than death and emigration rates
Population size will decrease when
Reproduction and immigration rates are less than death and emigration rates
lag phase of animal growth curve
Animals first arrives in an area
Population increases slowly
Time is needed for enough individuals to reach sexual maturity
Log phase of animal growth curve
Plenty of food
Population increases exponentially
Competition for food, territory and habitats are low
Stationary phase of animal growth curve
Carrying capacity is reached
Numbers will fluctuate around this in response to environmental changes such as predator-prey negative feedback.
If an overshoot occurs when growth exceeds carrying capacity there may be a degraded carrying capacity due to resource destruction
What are density dependent factors
Biotic factors such as competition, predation and disease
The effect of the factor is bigger when the population is higher
What are density independent factors
Abiotic factors eg light intensity, temperature, wildfires
Effects the population whether it is large, small or just the same
Why does sampling need to be random
Each individual has an equal chance of being included
It ensures the sample is representative of the whole population of each species
It reduces subjectivity and removes bias
Examples of ecosystems
Tropical rainforest
Tundra
Desert
What is the first energy transfer in an ecosystem
From sunlight to plants
Why is not all of the light hitting the leaf used in photosynthesis
• some is reflected by the waxy cuticle
• some is of the wrong wavelength to be absorbed
• some is transmitted through the leaf as it doesn’t hit a chloroplast
What are producers
Autotrophic organisms at the start of a food chain that convert light energy into chemical energy
Why is less than 10% of energy incorporated into biomass and is available to the next trophic level
Most energy is released in respiration and incorporated into other molecules or into electrochemical gradients
What are trophic levels
The feeding level within a food chain and shows the number of times that energy has been transferred to successive organisms along a food chain
What is biomass
The mass of biological material in living or recently living organisms
What are primary consumers
Herbivores
They feed on producers
What are secondary and tertiary consumers
Include carnivores
Feed on trophic levels below
Some feed at more than 1 trophic levels
What kind of organisms does decomposition involve
Detritivores and decomposera
Detritivores
Earth worms and woodlice
They feed on detritus
What is detritus
Remnants of dead organisms and leaves
Decomposers
Bacteria and fungi
Feed via external digestion
Complete process started by detrivores
What trophic level do decomposers feed on
All
How to calculate photosynthetic efficiency?
Quantify of light energy fixed by plants/Quantity of light energy falling on plant X 100
What is Gross primary production
Rate of production of chemical energy in organic molecules by photosynthesis in a given area, in a given time
Unit = kJm-2y-1
What is net primary production
Energy in the plant’s biomass which is available to primary consumers
Units= kJm-2y-1
How to calculate NPP
NPP= GPP-R
Why is the true value of biomass even lower than predicted
Some of the biomass is used to form inedible materials such as bark or its biomass in roots which is out of reach of primary consumers
What kind of NPP does a tropical rainforests have?
High
Plentiful rainfall, high light intensity and high temperatures
What kind of NPP does a tundra have and why?
Low
Cold, low light intensity
How to calculate % efficiency
Energy fixed as biomass/energy available to next trophic level X 100
Pyramid of numbers
Easy to construct
Shows the energy flow through a food chain
Doesn’t consider the size of the organisms
Pyramid of biomass
More accurate than pyramid of numbers
Is difficult to measure and calculate
May be inverted
Pyramid of energy
• most accurate way of representing feeding relationships
• shows the energy flow through an ecosystem
• Shows clearly the energy lost at each level
• is difficult to calculate
What can pyramids not show
Organisms operating at several trophic levels
What is succession
Change in structure and species composition of a community over time
What is a seral stage
Each stage in succession where different communities dominate
What is primary succession
Organisms invade spaces that did not previously support life
What is secondary succession
The reintroduction of organisms into a habitat previously occupied by plants/animals
Surface of primary and secondary succession
Primary - bare surface
Secondary - soil
What are the pioneer species of primary and secondary succession?
Primary - mosses and lichens
Secondary - small weedy plants
What is pioneer species?
The first species to colonise a new area in an ecological succession
What is a climax community
A stable community that undergoes no further change
What is a sere
Entire sequence of communities that changes successively in a given area
What changes as succession progresses
• soil depth increases
• nutrient content increases
• humus content increases
• water content increases
• diversity increases
• stability increases
What is it called when a climax community is not reached and what would cause this
Deflected or disclimax
Human intervention eg Monoculture and grazing
Interspecific competition
Different species
Intraspecific competition
Same species
Term for species that exist in a relationship that is beneficial to both
Mutualism
Term for when a species is able to obtain benefit from one species whilst other is unaffected
Commensalism
What does the carbon cycle involve
Photosynthesis
Respiration
Combustion of fossil fuels
Effect of photosynthesis on carbon cycle
Photo autotrophs remove CO2 from the atmosphere and fix it into organic molecules
Effect of respiration on carbon cycle
Done by all organisms
Returns CO2 to the atmosphere
Effect of combustion of fossil fuels on carbon cycle
• fossil fuels formed millions of years ago and derived from partially decayed remains of plants
• combustion releases CO2 into the atmosphere
Human activities that affect the carbon cycle
Deforestation and combustion
What is deforestation
Removal of trees and subsequent use of land for another purpose
Effect of deforestation on carbon cycle
Significantly reduces the volume of CO2 removed from the atmosphere through photosynthesis
How does increased atmospheric CO2 leads to global warming
CO2 is a greenhouse gas so it re-radiates infra-red back towards the Earth’s surface rather than allowing it to escape to space
Increase in CO2 emissions over recent decades are leading to an enhanced greenhouse effect
What is the effect of global warming on species?
• global temperatures rise so polar ice melts so sea levels rise and coastal flooding occurs
• increases incidence of forest fires leading to desertification
• changes to climate patterns, temperature, wind patterns, rainfall, extreme weather conditions
• acidification of oceans due to increasing dissolved CO2
Species may not be able to adapt or migrate and many will become extinct
What is desertification
The process by which fertile land becomes desert as it loses water, vegetation and wildlife
Effect of acidification of ocean on fish and crustaceans
Fish - gills produce mucus and so reduces gas exchange
Crustaceans - lose CaCO3 from exoskeletons as it is soluble in acid
Effect of global warming on farming
• decreased crop yields and failed harvests
How to fix farming practices to help global warming
Use drought-tolerant crops
Why is farming having a negative effect on global warming?
Although it removes CO2 through photosynthesis energy is needed for
• insecticides and fertilisers
• powering farming machinery
• transport of produce to market
What is carbon footprint
The total amount of CO2 attributable to the actions of an individual or a product or service over a period of one year
Effect of the 3Rs to reduce carbon footprint
Reduces energy consumption and so reduces carbon footprint
What is the nitrogen cycle
Flow of organic and inorganic nitrogen withon the abiotic and biotic components of an ecosystem where there is an interchange between certain nitrogenous compounds and atmospheric nitrogen
In what form do plants uptake nitrogen by plant roots
Ammonium and nitrate ions
What are the 4 main processes of nitrogen cycle
Nitrification
Deniftrification
Putrefaction
Nitrogen fixation
Others words for ammonification
Putrefaction
Decomposition
Mineralisation
What happens during ammonification
• Decomposers feed on dead and organic matter and feaces saprophytically by secreting enzymes onto their food and absorbing small soluble products
• proteases hydrolyse proteins to amino acids and deaminase reduce the amino group to ammonium ions
What happens during nitrification
• addition of nitrogen to the soil most commonly as nitrite and nitrate ions
• ammonium is oxidised into nitrite by nitrosomonas bacteria
• nitrite oxidised to nitrate by nitrobacter conditions
• aerobic conditions required
Simply what happens in nitrification
NH4+ —> NO2- —> NO3-
What bacteria is used when ammonium is oxidised to nitrite
Nitrosomonas
What bacteria is used when nitrite is oxidised to nitrate
Nitrobacter
What is nitrogen fixation
The reduction of nitrogen atoms in nitrogen molecules to ammonium ions by prokaryotic organisms
It is carried out by nitrogen fixing bacteria such as azotobacter and rhizobium
Azotobacter
Nitrogen fixing bacteria
Free living in soul
Accounts for most nitrogen fixation
Rhizobium
• mutualistic bacterium found in root nodules of leguminous plants
• invades the roots of the legumes and the plant responds by forming a nodule where the bacteria will live
• nitrogen gas diffuses into the nodule where nitrogenase enzyme produced by the bacteria redcluces N2 to ammonium ions in anaerobic conditions
• the ammonium ions are converted to organic acids and amino acids for the bacteria
• excess ammonium and amino acids are exported to the plant through the phloem for protein synthesis
• this requires ATP
How are anaerobic conditions maintained for Rhizobium
The plant provides this by producing the pigment leghemoglobin which takes up oxygen in the root nodule, removing it from the bacterial environment
How does Rhizobium get ATP
Gains sugars from the plants photosynthetic product
What is denitrification
Loss of nitrate from the soul by anaerobic bacteria, Pseudomonas, to atmospheric nitrogen
The denitrifying bacteria use the nitrate to provide oxygen for respiration and the remaining nitrogen atoms are converted into nitrogen gas
Simply, what happens during denitrification
Nitrate —> nitrogen gas
How does ploughing and draining soil increase soil aeration
• allows air to reach the roots of plants as nitrates and other minerals are uptaken by active transport which requires ATP from aerobic respiration
• favours the aerobic process of nitrogen fixation and nitrification
• inhibits denitrification which is anaerobic
Effect of using excess fertilisers
• eutrophication occurs where the excess fertilisers runs off into aquatic habitats which increases the ion content of the water and forms an algal bloom
• algal blooms block light to aquatic plants so plants and algae die and form detritus which is aerobically decompose which causes other aerobic organisms to die and further add to the detritus
• eventually all the oxygen is used up and only anaerobic bacteria can survive - these release ammonia, methane, hydrogen sulphide into the water which causes a toxic environment for most organisms
How can farmers reduce fertiliser run-off
• apply fertilisers when plants are actively grow
• not apply fertilisers within 10m of water courses
• dig drainage ditches to collect run off
Pros and cons of draining land
• the soil doesn’t get water logged so denitrification slows down and more oxygen means nitrification is sped up so more nitrate is added to the soil and more decomposition occurs
• it means the loss of habitat and biodiversity for some wet-land ecosystems
• plant rich habitats are more subject to wild-fires which release locked in carbon
