Population Size And Ecology Flashcards
What are density dependant factors?
factors that INCREASE as pop. density increases.
all BIOTIC factors sow pop. growth eg disease, parasites
What are density independent factors?
factors that DO NOT INCREASE as pop. density increases.
effect is same regardless of pop. size as ABIOTIC factors cause pop. crash eg flood, fire
Describe population fluctuations
mainly due to BIRTH RATE and DEATH RATE.
hover around set point (above= density dependant increases death rate, below= environmental resistance relieved- death rate decreases)
Define abundance
measure of how many individuals exist in a habitat
Two ways to assess animal abundance
1) Capture- mark- recapture
2) Kick sampling (streams)
Two ways to assess plant abundance
1) quadrat- mean no. of individuals in several quadrats of known area (no/m^20
2) estimate percentage
Define distribution
Area or volume individuals are found
One way to measure plant distribution and what does it provide readings for?
1) Belt transect (tape through area & quadrat at regular intervals.
readings for: density of chosen species, % freq species, % area cover of species
One way to measure animal distribution
1) direct observation
Define species
group of organisms that share some characteristics and can interbreed to produce fertile offspring
Define population
group of organisms of same species which occupy particular habitat
Define birth-rate
no. of new organisms produced by reproduction per unit time
Define immigration
movement of population into same species
Define emigration
movement of individuals of one species out of population
Define equilibrium species
species that control pop. size by competition rather than reproduction or dispersal
factors that control pop size
1) energy flowing through ecosystem
2) biological cycles
3) succession
4) emigration
5) immigration
6) birth-rate
7) death-rate
8) new species
Describe the LAG phase
- slow growth
- time taken to adapt to environment
- BACTERIA- enzyme synthesis
Describe the LOG (exponential) phase
- birth-rate > death-rate
- BACTERIA- cell production > cell death
- rate does not continue to increase rapidly due to environmental resistance
Define environmental resistance
All factors that may limit the growth of a population ( BIOTIC OR ABIOTIC)
4 environmental resistance factors of bacteria in a flask
- food availability,
- overcrowding,
- intraspecific competition,
- toxic waste
4 environmental resistance factors of rabbits on a island
- predation
- parasitism
- disease
- intraspecific competition (food, nests)
Describe the STATIONARY phase
- birth-rate = death-rate
- BACTERIA- cell production = cell death
- carrying capacity reached- pop. fluctuates around this in response to environmental change
Define carrying capacity
Max. pop. size that can be maintained over a period of time by an environment
Describe the DEATH/ DECLINE phase
- environmental resistance slows growth until…
- birth-rate < death-rate
- BACTERIA- cell production < cell death
Describe the predator- prey cylcle (fluctuates around carrying capacity because….)
- large no of predator predates prey, prey pop decreases (INCREASE ENVIONMENTAL RESISTANCE FOR PREY)
- not enough food for predator, pop decreases (INCREASE ENVIONMENTAL RESISTANCE FOR PREDATOR)
- less predation on prey, pop increases (DECREASE RESISTANCE FOR PREY)
- more prey for predator, pop increases (DECREASE RESISTANCE FOR PREDATOR)
Define intraspecific competition
competition between individuals of SAME species
Define interspecific competition
competition between individuals of DIFFERENT species
- two species cannot occupy same niche of same habitat (GAUSIAN EXCLUSION PRINCIPLE)
Define community
Interacting populations of two or more species in the same place at the same time
Define ecosystem
Community of independent species interacting with the abiotic factors of their habitat
Define habitat
place where an organism lives
Define niche
role of a organism in its ecosystem, may include:
- may include microhabitat, food, nocturnal
- no two species have same niche- interspecfic competition leads to outcompeting one
Define producer
uses light energy to fix inorganic CO2 into organic molecules
-Phototrophs or chemoautotrophs
Define consumer
Obtains energy and complex organic molecules from tissues of other living organisms
- heterotrophs
Define biotic factor
ecological factor that is LIVING and may affect organisms in an ecosystem
-environmental resistance
Define abiotic factor
ecological factor that is NOT LIVING and may affect organisms in an ecosystem
- soil pH, temp, soil nitrate conc
Define edaphic factor
aspects of soil that may affect an organism in ecosystem
- pH, % humus, nitrate level
Define food chain
diagram showing simple, unbranched feeding relationship with only one organism at each position
Define trophic levels
position of an organism in food chain
- T1= producer= plant
- T2= primary consumer= herbivore
- T3= secondary consumer= carnivore
What do food chains NOT SHOW?
- all species at each trophic level
- detrivores and decomposers often greater biomass
- omnivores or organisms feeding at multiple tropic levels
Food webs show these
Define biomass
mass of biological material in living or recently living organisms
Describe biomass transfer
- Photosynthetic organisms convert sunlight into chemical energy which passes between organisms
- energy available to tropic level contributes to biomass
Define decomposition and give examples of decomposers
when dead energy remains in organic compounds
- detrivores & decomposers are SAPROBIONTS (get organic molecules from dead/ decaying organisms)
Define detrivores
eg earthworms
feed on small fragments of remains of dead organisms
Define decompers
eg bacteria, fungi
obtain nutrients from organisms and animal waste
Define photosynthetic efficiency
measure of how much light energy a plant captured by the sun
What is the typical loss between each trophic level?
10%
Why is photosynthetic efficiency not 100%
- reflected
- passes through
- absorbed by non-photosynthetic parts
- much is wrong wavelength
Define Gross Primary Productivity (GPP)
rate of production of chemical energy by photosynthesis
GPP= Plant respiration + NPP
Define Net Primary Productivity (NPP)
energy left in plants biomass and available to primary consumers
NPP= GPP - plant respiration
define primary productivity
rate at which producers convert energy into biomass
define secondary productivity
rate at which consumers convert chemical energy into biomass
define secondary production
total energy transferred to biomass
4 reasons energy is lost between trophic levels
1) inedible tissue. 2)
4 reasons energy is lost between trophic levels
1) inedible tissue. 2) indigestible food. 3) respiration. 4) excretory products
what is the pyramid of numbers?
No of organisms at each trophic level of food chain (proportional to size of group)
what is the pyramid if biomass?
dry mass of organisms present at each trophic level (usually actually pyramid shaped)
define succession
change in structure and species composition over time in a community
define primary succession
succession on land that has not been previously colonised. stages= seral stages. one seral stage improves environment for next
define pioneer species
first species to colonise new area
define climax community
final, stable community has reached equilibrium with environment- no further change
Describe primary succession on bare rock
- sere on dry environments= xerosere
- pioneer species= algae and lichens
- able tolerate desiccation and nutrients
- slowly erodes rock—> soil
Describe the process of primary succession
1) bare rock
2) spores allow mosses to gow
3) dies and forms soil- roots for plants
4) deeper soil= more water
5) over time, large trees–> climax community
ANIMAL BIODIVERITY CONSTANTLY INCREASES
What increases as xerosere progress?
- soil thickness
- humus, water, mineral content
- biomass
- biodiversity
Define secondary succession
Series of community changes that takes place on a previously colonised habitat that has been disturbed or damaged
Why is secondary succession quicker than primary succession?
- existing seed bank
- vegetable reproductive organs
- root systems
- fertility and structure of soil
How do humans impact succession?
DISCLIMAX
human interference may deflect natural climax community
- deforestation, planting fast growing trees
- grazing animals or moving
- farming and planting monocultures
final disclimax= golf courses, lawns, managed moor land, hedgerows
How is moorland managed? use grouse and grazing as an example
- fire= standard way of deflecting succession
- pre climax habitat preserved so specialised plants and animals preserved
GROUSE
-feed on young heather
1) pioneer stage (growing from seed)
2) building stage (rapid growth)
BURN TO RESTART GROWTH
3) mature stage (growing but gaps- not good for nests)
4) degenerate stage (branches break/ plant dies)
GRAZING
rabbits- prevent succession on chalk land
sheep- maintain open habitats
Define migration in terms of ecosystems
- arrival of spores, seeds, animals
- vital for succession
- non- native species have huge effect
When does competition occur in the development of habitats?
- all seral stages
- leads to one species outcompeting another (2 species cannot occupy same niche)
- best advantage wins
What is meant by facilitation? what are the two types?
POSITIVE INTERACTION BETWEEN ORGANISMS
1) mutualism
- interaction between species that benefit BOTH
2) commensalism
- interaction between species that BENEFITS ONE AND LEAVES OTHER UNAFFECTED
Describe the role of minerals in food chains
- short supply as from finite resources in crust/ atmosphere
- taken up by plants, manufactures biochemical molecules
- passed along food chain through trophic levels
- minerals released from dead organisms by decomposers
Describe the process of organic breakdown
- one organism source of nutrition for another
- detrivores & decomposers break down organism–> nutrients and minerals return to soil for plants to take up again
- saprobionts secrete enzymes onto organism matter to digest it & free minerals in process
LEARN CARBON CYCLE DIAGRAM
LEARN CARBON CYCLE DIAGRAM
Describe the 5 processes in the carbon cycle
1) PHOTOSYNTHESIS
- CO2 removed by plants to form C compound
2) RESPIRATION
- CO2 returned to atmosphere (plants, animals, decomposers)
3) DECOMPOSTION
- CO2 released from dead organisms by saprobionts
4) FOSSILISATION
- formation of fossil fuels from dead organisms which have not decayed
- limestone from skeletons and shells
5) COMBUSTION
- C from fossil fuels released as CO2
What is the greenhouse effect?
- radiation usually reaches earth from sun and some is reflected back to space
- radiation that reaches earth is absorbed and reemitted as a longer wavelength
- absorbed by greenhouse gases (CO2, CH4)
- contributes to global warming
Four factors that are increasing CO2 levels
1) CFC’s
2) DEFORESTATION
3) COMBUSTION OF FOSSIL FUELS
- increasing pop. 70% increase
4) METHANE
- rice crops (anaerobic respiration)
- cattle
- rotting material in landfill sites
What are the consequences of global warming?
- melting polar ice caps and thermal expansion of water (flooding)- increased droughts, hurricanes, forest fires
- serious effects on food production- reduction of grain crops, economic and political consequences
Define and describe carbon footprint
TOTAL AMOUNT OF CO2 RELEASED BY AN INDIVIDUAL PER YEAR
either:
- direct (home/ transport)
- indirect (CO2 resulting from goods and services consumed)
LEARN NITROGEN CYCLE DIAGRAM
LEARN NITROGEN CYCLE DIAGRAM
Name and describe the four stages in the nitrogen cycle
1) NITROGEN FIXATION
- converts atmospheric O2 into ammonia or ammonium compounds
- achieved by: nitrogen fixing bacteria, haber process, lightening
2) AMMONIFICATION
- decomposers secrete protease which hydrolyses decaying compounds into amino acids
- also secrete deaminase to produce ammonia then reduced to ammonium ions
3) NITRIFICATION
- ammonium ions—> nitrite ions by nitrosomonas
- nitrite ions—> nitrate ions by nitrobacter
- oxidation (o gained)
4) DENITRIFICATION
- nitrates lost from ecosystems and converted back to N2 by pseudomonas
- reduction
- bad for farming- anaerobic conditions- water logged soil lacks oxygen
What are the two types of nitrogen fixing bacteria and what do they do?
1) free living in soil (AZOTOBACTER)
- N2–> ammonium ions
- reduce nitrogen ions
- make own amino acids
- aerobic conditions but still reduction as high metabolic rate so low O2
2) mutualistic (RHIZOBIUM)
- root nodules of legumes
- synthesise nitrogenase
- combine ammonium ions with organic acids to form amino acids- translocated
- leg-haemoglobin- formed by nodules and absorb oxygen. keeps O2 partial pressure low for nitrogenase to carry out reduction, oxygen would inhibit reduction
