C1: Populations size and ecosystems Flashcards
Define population
An interbreeding group of organisms of the same species occupying a particular habitat
Define birth rate
the reproductive capacity of a population; the number of new individuals derived from reproduction per unit time
Define immigration
the movement of individuals into a population of the same species
define emigration
the movement of individuals out of a population of the same species
define death rate
the rate at which organisms of the same species die per unit time
Describe the difference between biotic and abiotic
provide examples for each
abiotic a part of the enviroment that is non-living eg: light intensity, temperature and pH
biotic a part of the enviroment that is living eg: pathogens and predetors
Why are ecosystems described as dynamic
5 points
because Factors change constantly:
Energy flowing through ecosystem
Biological cycles (N cycle)
Habitat chage over time as succession occurs
Population sizes
Climate change alters habitats
What is the size of the population dependant on
4 points
immigration
emigration
birth rate
death rate
when does the population size increase
when immigration and birth rate > emigration and death rate
Define an equilibrium species
Species that control their population by competition rather than by reproduction and dispersal
When referring to bacteria or yeast what terminolgy should you use instead of birth rate
cell reproduction
What is the one step growth curve
A sigmoid (s- shaped) graph of the population size of an equilibrium species when it is introduced to a new environment.
Name the stages of the one step growth curve
Lag
Log (exponential)
Stationary
Death/decline
Describe the stages of the one step growth curve
Lag phase - Population does not increase because:
In bacteria, enzymes are being synthesised and DNA is being replicated for cellular reproduction
and in sexual reproductive organisms they need to reach sexual maturity
Log (exponential) - more individuals become available for cellular and sexual reproduction so population doubles per unit time
Stationary - Birth rate = Death rate population reached carrying capacity and fluctuates in response to environmental changes
Death/ decline - birth rate < death rate as the envirmonet can no longer support population so the population declines
Why might a log scale be used
To accommodate the large range of numbers involved and make them more easily comparable
Define carrying capacity
The maximium number around which a population fluctuates in a given environment
Define environmental resistance
Environmental factors that slow down population growth
Provide four examples of enviromental resistance in bacteria in a flask
food/nutrients/minerals
competition
space/overcrowding
accumulation of toxic waste
provide six exmaples of enviromental resistance for rabbits on an island
state the additional factors compared to bacteria in a flask
Food
competition
habitat space/shelter
accumulation of toxic waste
Additional:
predetors
pathogens/parasitism and disease
Once carrying capacity is reached how does the graph show this
it fluctuates above and below the carrying capacity due to the changes in environmental changed eg: the number of pedetors
Define Density Independant factor
provide an example
A factor in which the size of the population dictates the effect of the factor on the population eg: parasitism
Define density dependant factor
Factors that have the same effect upon a population regardless of the size of the population. eg: flood or fire
Define abundance
The number of individuals in a species in a given area or volume
Define distribution
The area/ volume in which individuals of the same species occupy and can be found
How can the abundance of a plant species be measured
percentage cover - count each grid that the plant is in at least 50% of
percentage frequency - count how many squares have the plant in it
Density - mean number per area(m) sqaured
Name and Describe the method to assess abundance and distribution on a uniform habitat ( an open field)
3 points
Random sampling :
Place two tape measures perpendicular to each other (axis)
randomly generate 2 numbers to use as co-ordinates for quadrat
take 10 readings of random co-ordinates and calculate a mean for each species
Describe the method to assess abundance and distribution on a habitat that is not uniform ( there is an environmental gradient )
Belt transect
Place a tape measure across environmental gradient
Place a square gridded quadrat at even intervals along the tape measure
Estimate the density or percentage frequency or percentage area cover.
As there is an environmental gradient, it is useful to measure the factor that varies, so in each quadrat, you could measure, for example, the light intensity,pH,or temperature.
Define ecosystem
A characteristic community of interdependant species interacting with the abiotic components of their habitat
Define ecology
The study of the relationships among organisms and their environment
Define enviroment
all the factors in a habitat which affect an organism; these may be either living (biotic) or non living (abiotic).
Characteristics of ecosystems
Can range from very large to small
Can be short or long living
What is the most signifiacnt source of energy for ecosystems
What is the exception?
Light energy
(other than those based on chemosynthesis, e.g. hydrothermal vents)
Define habitat
a place in which an organism lives
Define community
interacting populations of two or more species in the same habitat at the same time.
Name the order of a 5 trophic level food chain
Producers
primary consumers
secondary consumers
tertiary consumers
quarternary consumers
Decribe the food chain
Photosynthetic organisms are producers as they convert light energy to chemical energy (carbohydrates). Carbohydrates are food And therefore the source of energy for successive organisms.
A small amount of the total energy that reaches the plant is converted to biomass.
Herbivores are primary consumers (eat producers)
Carnivore are secondary consumers (eat primary consumers)
Each of these groups operates at a tropic level with energy passing from lower to higher trophic level as material is eaten
Energy in food molecules consumed are incorporated into the molecules of the consumer
As energy is passed along the food chain there is a loss of energy from each trophic level
The energy flowing through the ecosystem reduces and ultimately the energy leaves the system as heat
Define biomass
The mass of biological material in living or recently living organisms
Define trophic level
The number of times energy has been transferred between the sun and successive organisms along a food chain
What happens when producers and consumers die
Their energy remains in organic compounds and these are consumed by detritivores and they are broken down into smaller compounds by decomposers to be recycled and used again by producers.
define saprobiont
An Organism that derives energy and raw materials for growth from extracellular digestion of dead or decaying material.
describe the detritus food chain
detritioures
decomposers
Why is the number of trophic levels limited
Because energy is lost from each trophic level and eventually there is not enough energy to support another trophic level
Describe what GPP is
The rate of production of a chemical energy in organic molecules by photosynthesis in a given area,in a given time.
Value should be between 0.2-2.0%
Describe what NPP is
include an equation
Energy in the plants biomass which is available to primary consumers
in a given area, in a given time.
GPP - R
Value should be between 0.1 - 1.0%
How to calculate efficiency of energy transfer ?
Energy incorportated into biomass after transfer x 100 / energy available in biomass before transfer
remember to encorporate detritivores into energy incorporated into biomass
Define succession
The change in structure and species of a community over time
Define climax community
A stable, self perpetuating community that has reached equilibrium with its enviroment, and no further change occurs
Define pioneer species
The first species to colonise a new area in an ecological succession
what is the sequence of stages in a ecological succession called
and what are the each individual stages called
sere sequence - from the pionier species to the climax community
seral stages - refer to a single stage or community within a sere
What is a xerosere
provide an example of this sequence
a sere in a very dry enviroment
Herbs and grasses -> shrubs and small trees -> large trees (forest climax community)
Define primary succession
A change in structure and species composition of a community over time (succession) in an area that has not previously been colonised
Define secondary succession
a change in structure and species composition of a community over time (succession) in a area that has been colonised before following the disturbance or damage to that previously colonised habitat
Factors affecting succession
4 points
Immigration
competition
facilitation
human interference
Describe the two types of competition
intra-specific - competition (for food, mates,shelter) between individuals of the same species this is density dependant. those organisms with a selective advantage in alleles reproduce more successfully
inter-specific - Competitionn(for food,oxygen,light availability) between individuals of different species
Define Niche
The role and position a species has in its environment including all interactions with biotic and abiotic factors of its environment
Describe how niche and competition are linked
In the long term two species cannot occupy the same niche in a specific habitat.
what is the role of immigration in succession
It is vital for the progression of succession. as immigratinf non-native species spread themselves widely, altering the community and the soil.
Define mutualism
An interaction between two organisms of different species that benefits both organisms
Define commensalism
An interaction between two organisms of different species that only benefits one organism but the other organism is not affected
How does succession effect species diversity and stability of the community.
increases both
What role do detritivores and decomposers have in recycling minerals
They break down the remains and waste products of organisms so the minerals return to the soil and plants take them up again completing the cycle
What organisms are decomposers
Bacteria and fungi
What three main biological processes does the carbon cycle include
Photosynthesis
respiration
decomposition
Describe the Carbon cycle in terrestrial organisms
CO2 in atmosphere
Is used up by produces via photosynthesis but is also released by producers in respiration
Assimilation occurs and carbon is transferred to the carbon of the consumers
The consumers also respire so carbon is returned to the atmosphere
Both consumers and producers die
After death there is decayy decomposers which convert dead organic matter to co2 In the atmosphere
If decay is prevented then carbon is converted into fossil fuels
If these fossil fuels are burnt co2 is released into the atmosphere
How many ways does CO2 get returned to the athmosphere in the C cycle
four
repiration of producers
repiration of consumers
repiration of decomposers
combustion of fossil fuels
Two human activitys that have been the main cause of the rising CO2 conc.
burning fossil fuels
deforestation
State 2 ways in which deforestation contributes to the rising CO2 conc
Photosynthesis is reduced so the rate at which CO2 is removed from the atmosphere is also reduced
When trees are cut down they may be burnt or left to decay both
define gloabal warming
The increase of average global temperature, in excess of the greenhouse effect caused by the atmosphere’s hostorical concentration of CO2
State why increased atmospheric carbon dioxide leads to
an enhanced global warming
CO2 is a green house gas. these are gasses that heat up the earths surface by the absorption and reflection of radiation energy
How does climate change lead to the the possible extinction of species/whole ecosystems
Evolutionary adaptation is slow so, as climate changes, animals move to a more suitable environment. Plants can only move as fast if they are dispersed, and if this is not fast enough they may be driven to extinction. Animals dependent on the plants will then become extinct and entire ecosystems may collapse
Define Carbon footprint
The equivalant amount of CO2 generated by an individual, a product or a service in a year.
State the the significance of nitrates in biosynthesis
N is found in:
All amino acids for proteins
Nitrogenous bases for nucleic acids
chlorophyll
Therefore nitrates are needed as a source of N to synthesise these products
How is nitrogen taken up into plants
By the facilitated diffusion and active transport of NO3- and NH4+ ions
What are the four main biological processes in the nitrogen cycle?
Ammonification (Decomposition)
Nitrification
Dentrification
nitrogen fixing
Describe the nitrogen cycle
1 Ammonification (Decomposition) - occurs when saprophytic bacteria and fungi metabolise the nitrogen-containing organic matter in dead organisms, faeces and urine and release ammonium ions.
2 Nitrification — under aerobic conditions nitrifying bacteria convert: – ammonia to nitrites ( Nitrosomonas ) – nitrites to nitrates ( Nitrobacter ) Nitrates are then taken up from the soil by producers.
3 Denitrification — denitrifying bacteria ( Pseudomonas ) convert nitrates into atmospheric nitrogen. This occurs in anaerobic conditions , for example in waterlogged soils. Denitrification removes nitrogen from ecosystems.
4 Nitrogen fixation — nitrogen-fixing bacteria (Rhizobium and Azotobacter) convert atmospheric nitrogen into ammonium ions.
– Rhizobium is mutualistic bacteria found in the root nodules of leguminous plants. The plant rapidly converts ammonium ions into nitrogen-containing organic compounds. The bacterium benefits by gaining energy and nutrients, for example carbohydrates, from the plant.
– Azotobacter is found living free in the soil and accounts to most of the biological nitrogen fixation.
What are the conditions and names of bacteria invloved in the N cycle
Types nitrifying = 2 nitrogen fixing = 2 denitrifying = 1
Nitrifying - require aerobic conditions:
Nitrosomonas – convert ammonium to nitrite (NH4+ –> NO2-)
Nitrobacter – convert nitrite to nitrate (NO2- –>NO3-)
Nitrogen-fixing - convert nitrogen gas to ammonium (N2 –> NH4+)
Azotobacter – free living in soil (does the majority of nitrogen fixing) (aerobic conditions)
Rhizobium – in root nodules of legumes, symbiotic/mutalistic bacteria (anaerobic conditions)
Denitrifying – require anaerobic conditions - convert nitrate to nitrogen gas ( NO3- –> N2)
Pseudomonas – thrive in water-logged soils
Describe the importance of human activities such as ploughing and drainage.
Ploughing introduces air to the soil, encouraging nitrification. Drainage ditches reduce waterlogging and reduce denitrification. Water-logged soils lack O2; this favours denitrification and slows nitrification. This leads to nitrate poor soil. Insectivorous plants live in water-logged areas. They digest insect protein to gain amino acids so don’t rely on soil.
What is the value of fertilisers and cultivation of legumes on agriculture
name an organic and inorganic fertiliser
Increases nitrogen content in the soil which is essential for the efficient production of food
organic Manure
inorganic ammonium nitrate
Define eutrophication
The artificial enrichment of aquatic habitats by excess nutrients, often casued by run off of fertilisers
Describe the difference of eutrophic and dystrophic
Eutrophic when water is enriched with minerals and this leads to the growth of organisms
when the mineral conc in the water is so high it leads to the death of organisms
Problems caused to terrestrial plants by excess nitrate in soils
increase use of fertilisers has reduced species diversity on grassland. Fertilisers increase the growth of grasses and plants which shade out smaller plants
Problems caused by excess nitrated leaching into rivers compared to normal
The leaching of nitrates and phosphates from the surrounding land is slow, natural process during which mineral ions normally accumulate until equilibrium is reached, and their addition is counterbalanced by the rate at which they are removed. However sewage and fertilisers are an additional source of these minerals and their leaching from the land into water may result in eutrophication of lakes and rivers
How does increased rainfall affect the concentration of nitrates in a body of water
Nitrate is highly soluble and is readily leached from soil and washed into rivers from surrounding land. It drains through the soil under gravity, as ground water but the rate increases in heavy rainfall and increases the concentration of nitrate in bodies of water.
Describe the process of eutrophication by leaching of N fertiliser with reference to agal blooms
6 points
Nitrate is a fertiliser and Microscopic algae undergo a population boom, called an algal bloom. The water becomes green, and light is unable to penetrate to any depth.
The plants in the deeper regions of the lake cannot photosynthesise and they die.
There is a general decrease in animal species diversity, as they rely on the plants for food and shelter.
The short-lived algae soon die and are decomposed by saprobiontic bacteria and fungi.(C cycle)
These are aerobic organisms and use a lot of oxygen, decreasing oxygen availability in the body of water.
Most of the water becomes deoxygenated. There is an increased biological oxygen demand. Fish and aquatic invertebrates die and are decomposed.
