Ecology

Frage	Antworten
Ecology definition	The study of living things and their interactions with each other and their environment.
Population definition	An interbreeding group of organisms of the same species occupying a particular habitat
Ecosystems definition	A characteristic community of interdependent species interacting with the abiotic components of their habitat.
Birth rate definition	The reproductive capacity of a population; the number of new individuals derived from reproduction per unit time
Population definition	All the members of one species in an area that can breed with each other.
Community definition	All the members of all species in an area.
Habitat definition	The place in an ecosystem where an organism lives.
Immigration definition	The movement of individuals into a population of the same species
Equilibrium species definition	Species that control their population by competition rather than by reproduction and dispersal
Ecosystem changes	An ecosystem is not a static component; things change all the time. The source of energy for ecosystems is the sun. In temperate climates, the duration and intensity of sunlight changes over the course of a year, so the energy that flows through the ecosystem is subject to change.
Ecosystem changes pt 2	Nutrient cycles depend on fungi and bacteria, and their population growth is dependent on temperature (amongst other abiotic and biotic factors), so nutrient cycling varies throughout the year- ( cyclic pathway by which nutrients pass-through, in order to be recycled and reutilised. The pathway comprises cells, organisms, community and ecosystem.)
Factors controlling population size	Intensity of energy flowing through an ecosystem varies Biological cycles eg nitrogen cycle vary the mineral availability Habitats change over time as succession occurs New species arrive and some are no longer present Climate change alters habitats
Ecosystem changes pt 3 population	Community composition can change over time, for example, ponds silt up and land plants become established, this is known as succession. Population sizes change over time.
Things affecting population size	The population size is dependent on 4 factors – the reproduction rate, the death rate, immigration and emigration. In a stable population these are balanced and can be expressed as an equation: Reproduction + immigration = death + emigration This is because reproduction and immigration increase the size and death and emigration decrease the size of the population.
What determines population size	Birth rate, Immigration= increase pop Death rate or mortality,Emigration= decrease pop When combined effects of birth and immigration exceed death and emigration pop increases
Population size- fugitive/ equilibrium	Different strategies for population growth are used by different species, depending on characteristics- there's fugitive and equilibrium species
Fugitive	Fugitive species are poor at competition- instead rely on large capacity for reproduction/ dispersal to increase numbers- invade a new environment rapidly
Equilibrium species	Control population by competition in a stable habitat- usual pattern of growth is sigmoid- s shaped- curve called one step growth curve
Diagram of pop growth	p64
Niche definition	The role of an organism in an ecosystem, generally a feeding role.
Biotic	All the living and organic components of an ecosystem.
Abiotic	All the non-living parts of an ecosystem.
Population size- lag phase	Initially pop doesn't increase - period of slow growth- period of adaptation/ preparation for growth- rehydration and intense metabollic activity, especially enzyme synthesis- in sexually reproducing organisms- lag phase represents time for individuals o reach sexual maturity, find a mate and gestate young
Growth curve- what is it	Populations colonizing new environments undergo a characteristic series of stages that can be presented graphically as a growth curve. When writing about animals we tend to use the term birth rate rather than reproduction – careful not to use this for bacteria or fungi.
One step growth curve- bacteria	Bacteria in a nutrient broth first go through a lag phase. They are synthesising enzymes and replicating DNA. The numbers of individuals rise slowly. As food availability is high, the growth becomes exponential. Therefore, the cells divide rapidly, reproduction exceeds death rate and the population doubles for each unit of time. This is the log phase.As nutrients start to run out or get depleted, the reproduction and deaths in the population stabilise, this is the stationary phase. Death and reproduction are equal.Eventually the toxins in the broth build up to such an extent that deaths exceed reproduction and the population decreases in the death phase. Death could also be caused by nutrients running out in the broth.
But...	However, in less artificial situations other factors play a part- same factors apply but are additional biotic factors eg predation, parasitism/ disease as increased pop density allows infection to spread more rapidly, competition w/ other species for nesting sites and food- also abiotic factors eg temperature, light intensity (eg plants).
One step growth curve- animals- lag/ log phase	The lag phase is when the animal first arrives in an area, e.g. when grey squirrels were first introduced to Britain. The population increases slowly at first, there are not many individuals to breed and time is needed for enough individuals to reach sexual maturity. Log/ exponential phase- With plenty of food, the population increases exponentially.
One step growth curve- animals-stationary phase	Competition for food, territory and habitats is low; this is the log phase. Eventually the population reaches a maximum, called the carrying capacity- this number depends on resources available eg more food increased carrying capacity- pop= not absolutely constant fluctuates around cc in response to environmental changes
One step growth curve- animals-death phase	The factors that slow pop growth at end of log phase become more significant- pop size decreases until death rate is greater than birth rate- graph has negative gradient
Environmental resistance and carrying capacity	Predators= usually larger than prey and tend to kill before eating- abundance of prey limits no. predators and no. predators affects no. prey- predator-prey relationship causes both populations to oscillate (back and forth)-- oscillations limited by negative feedback (the effect that change in one part of an ecosystem or social system has on the very same part after passing through a chain of effects in other parts of the system)-
Negative feedback example	eg predators cause no. prey to decrease--- lack of prey- predators decrease--- lack of predators prey increases--- more prey predators increase- population numbers at carrying capacity can depend on numbers in other species
Calculating pop increase from a graph	When pop increase is very large- eg pop of bacteria in test tube- range of numbers is too great to plot on a linear scale- A log 10 scale is therefore used- each mark on pop size is ten times previous mark- shift log to see what population actually is- growth rate- no. species at certain time- no.species at another time (pop growth)/ time- no.species at both times antilogged to get proper amount
other calculations	for less than 1000 in pop: Birth rate: increase in pop/ original pop - to get to percentage- divide to 100- same structure for death rate over 1000- (Number of live births / Total population) * 1,000- will give you per 1000- eg if 4000- times no. by 4 net migration rate-: N = (I - E) / M X 1,000 N = Net migration rate I = Number of immigrants entering the area E = Number of emigrants leaving the area M = Mid-year population
Factors that regulate population increase- density dependent	Some environmental factors have more effect on given population if given area is larger- factors affect greater amount of population if pop is denser- called density dependent factors- biotic factors- include disease, parasitism and depletion of food supply
Factors that regulate population increase- density independent	Effect of abiotic factors in environment does not depend on population density- effect is same regardless of size of population- usually due to a sudden change in an abiotic factor eg flood/ fire
Populations fluctuate in numbers	Balance between birth rate and death rate regulates the size of a population- doesn't stay stay constant- in equilibrium species - usually fluctuations aren't large or erratic- numbers in populations fluctuate around a set point- if population rises above set point density dependent factor increases mortality or reduces breeding to extent that pop declines If pop falls below set pointr- environmental resistance is relieved for a bit- pop rises again
look at diagram for negative feedback	p69 lol
Abundance and distribution of organisms in a habitat	The study of species abundance and distribution= biogeography- Alfred R Wallace was first to model biogeographic regions- defined 6- when studying birds and other vertebrates- saw mountain ranges marked boundaries of many species' ranges and saw different animals in similar habitats- didn't correspond with prevailing exp that all organisms were created to suit particular environment
New habitat	When new habitat is assessed- physical features eg soil type and temp are described first- determine no./ type of plants that live there- also dependent on weather that usually occurs- animals in a habitat depend on plants- so in new habitat- plants described before animals
Measuring abundance	Abundance- no. individuals in a species in a given area or volume- can be assessed by: capture, mark, release, kick sampling in a stream and counting aquatic invertebrates
Measuring abundance plant species	Using quadrat to calculate the mean number of individuals in several quadrats of known area to find the density eg no./metre^2 Estimating % cover of a plant in which individuals are hard to recognise- estimating % frequency
Measuring distribution	Distribution- the area or volume in which an organism is found If habitat is uniform- (organisms are spread out in a fairly regular pattern)- positions of outermost plants= marked on map and area they surround can be measured- small area may indicate species is under threat of extinction- used to assess distribution of threatened plant species- mining companies and road building authorities can be lobbied to protect specific sites
measuring distribution pt 2	If habitat is non uniform- transect is useful for displaying variation in organisms and its correlation with a changing abiotic factor- a transect is line along which abundance is assessed- shows the organisms that lie on a line, at measured intervals A belt transect shows abundance data for given area at measured distances along transect- quadrat placed at each co-ordinate can show- density of chosen species, % frequency of chosen species, % area cover for all species
Kite diagram	shows % area cover for species across belt transect- to draw- draw x axis for length and y axis for 5 cover with 50% above and below x axis At each co-ordinate- place data points above and below x axis- each representing half of the % area cover join last two data points with a vertical line join data points above and below the axis
Ecosystems	Ecosystem= A characteristic community of independent species interacting with abiotic components of their habitat Community is many specie living and interacting together- interactions of organisms together and non living factors in their environment= ecosystem- biotic and abiotic factors are linked by energy flow and cycling of nutrients
Ecosystems can be...	Small- eg human large intestine and community of microorganisms Very large- Seas- some consider earth to be one large ecosystem Temporary- puddle left after rain Lasts millions of years-
Ecosystem examples	Ecosystem- Marine Example- Pacific ocean Abiotic features- aquatic- high mineral ion concentration Characteristic organisms- fish, algae,echinoderms Ecosystem- Artic Tundra Example-Canada, Siberia Abiotic features- temp change between -50C and +12C, 15-25 cm rainfall a year, windy Characteristic organisms- low growing plants, reindeer, arctic hare
Energy and ecosystems	Energy= no changes happen until energy changes occur- functionings of an ecosystem can be thought as a sequence of energy changes in which energy flows through components of an ecosystem Subject to certain rules- described as laws as thermodynamics
Energy and ecosystems pt2	Many possible energy sources on earth eg geothermal, electrical and chemical Been suggested: energy derived from unequal distributionof protons allowed the non living systems in the cavities of alkaline hydrothermal vents to make the transition into living systems early organisms used energy released by chem reactions to make carbohydrates by chemosynthesis...
Continuation of theory	...The electrons they need to reduce CO2 or methane to sugar are from the oxidation of inorganic molecules eg hydrogen or hydrogen sulphide. Some archea and bacteria still do- but tend to inhabit marginal ecosystems most significant energy source for ecosystems now is light energy radiation from the sun - light energy source for photosynthesis
Biotic components of an ecosystem- habitats	A habitat= The place in which an organism lives ecological or environmental area inhabited by a living organism- provides means of survival- food, water, soil, appropriate temp/ PH Not necessarily geographical area- part of 1 organism may be habitat for another eg human duodenum for tapeworms Microhabitat= very small area- differs from its surroundings has the features make it suitable for specific species
Biotic components of an ecosystem- Communities	Communities= Interacting populations of 2 or more species in the same habitat at the time -members of a species living and interacting in a habitat forms population- populations interact to form community-
Community ecology	community ecology studies interactions of the species related to distribution and abundance and their genotypic and phenotypic differences. Considers food web structure/ predator-prey relationships
Biotic components of an ecosystem- biomass transfer	Biomass- The mass of biological material in living or recently living organisms Ultimate source of energy for most ecosystems= sunlight- photosynthetic organisms convert light energy into chemical energy- passes from organism to another through food chain- the study of the flow energy through ecosystem= ecological energetics- energy available to a trophic level contributes to its biomass- Food chains can be thought as transferring biomass
Food chains	Producers- green plants, cyanobacteria, some Protoctista- incorporate suns energy into carbohydrates- this is food and so energy source for successive organisms in food chain- trap solar energy and synthesize sugars from inorganic compounds by photosynthesis-
Why does only small proportion of energy reach plant as light is incorporated into plants tissues	h
Food chains pt2	herbivores= primary consumers- carnivores= secondary/ tertiary and higher consumers Each of these groups operates at a feeding or trophic level with energy passing to a higher as material is eaten Energy in the food consumed is incorporatedinto molecules of the consumer As energy is passed along the food chainthere's a loss from the food chain at each level- energy flowing through ecosystem reduces- ultimately energy leaves system as heat
Decomposition	When producers/ consumers die- energy remains in organic compounds of which they are made- detritivores and decomposers feed as saprobionts- derive energy from dead/ decaying organisms- contribute to recycling of nutrients-
Difference- detritivores and decomposers	Detritivores- organisms eg earthworms, woodlice and millipedes- feed on small fragments of organic debris- this is detritus= the remains of dead organisms/ fallen leaves Decomposers - micrrobes such as bacteria and fungi that obtain nutrients from dead organisms and animal waste- complete the process of decomposition stated by detritivores.
Food web chains and their length	Food web shows how organisms in a community interact through food they eat-food chain is linear sequence of organisms in a food web producer (1st trophic level)---> primary consumer (2nd trophic)--->secondary consumer (3rd trophic)---> tertiary consumer (4th trophic)
Food chain pt 2	Energy lost at each link along food chain- after 4 or 5 levels not enough energy to support another one - no. links in a chain= limited Actual length depends on interacting factors: - More energy that enters food chain in first trophic level- eg more energy fixed in photosynthesis- longer food chain is-tropical food chains usually longer than arctic ones How efficiently energy is transferred between trophic levels Predator and prey populations fluctuate- affects chain length How large ecosystems is 3 dimensional environments eg aquatic systems have longer food chains than 2 dimensional habitats eg grasslands
look at diagram photosynthetice efficiency	p74
Photosynthetic efficiency- maths	Energy flowing from 1 organism to another- in food chain originatees as sunlight- about 60% of light energy that falls on plant may not be absorbed by photosynthetic pigments- could be; wrong wavelength, reflected, transmitted straight through leaf Photosynthetic efficiency= ability of plant to trap light energy PE= (quantity of light energy incorporated into product/ quantity of energy falling on plant ) x 100 wild plants may be low but higher in crop plants - selectively bred for high productivity- PE depends on plants genotype/ environmental factors
Primary productivity	Gross Primary productivity- rate of production of chemical energy in organic molecules by photosynthesis in given area, in a given time- kJ m-2y-1 A substantial proportion of gross production= released by respiration of the plant to fuel processes eg protein synthesis Remains= net primary productivity- represents energy in plants biomass= food available to primary consumers or in crops= yeild that can be harvested
Primary productivity pt 2	equation: GPP-respiration= NPP Both GPP and NPP are higher if plants have high PE - unlike crop plants- many plants less productive and not grown in deal conditions- so common figure for GPP is around 0.2- 2% of incident radiation and 0.1-1% for NPP
Energy flow through food chains	Primary productivity= rate at which producers convert energy into biomass- secondary productivity is rate at which consumers accumulate energy from assimilated food in biomass in their cells or tissues- secondary production occurs in heterotrophs eg animals, fungi, some bacteria, some protoctista
Why is energy lost along food chain	- energy molecules egested- eg cellulose not digested in cows gets excreted- however energy not lost from ecosystem- used by decomposers- carnivore's diet more digested- less energy lost -energy lost as heat following processes fuelled by the energy generated in respiration including muscle contraction - energy remains in molecules in parts of an animal that may not be eaten eg horns, fur and bones
Herbivores vs carnivores	herbivores- conversion efficiency of around 10% so only 10% of of plant material digested is incorporated into their biomass- so only part of NPP of whole ecosystem is transferred to primary consumers- also herbivores won't eat all vegetation available to them when grazing- carnivores are more efficient at energy conservation- foodeasily digestedmore easily
Fate of energy in consumers	Heat loss from reactions of respiration- P= 30% (ingested energy in consumer), S=60% In excreted and egested waste products-P= 60%, S= 20% Secondary production= P=10%, S=20%
Calculating efficiency of enregy transfer	efficiency of energy transfer: (energy incorporated into biomass after transfer/ energy available in biomass before transfer) x 100% eg 1609 kjm-2 in primary consumers ingessted by secondary- 193 kjm-2 transferred to detritivores and 88 kjm-2 transferred to tertiary (88+193/1609)x 100%
Ecological pyramids	Ecological pyramid is a diagram that shows a particular feature of each trophic level in an ecosystem- producers are drawn at bottom and succesive trophic levels are above- no. organisms, energy or biomass at each trophic level is represented by bar for each level- known as pryramids of numbers, energy or biomass depending on what's show
Ecologocal pyramids- pros and cons	Useful in describing ecosystems + Do not take account of fact some organisms operate at more than one trophic level at same time- eg human is omnivore can eat producers eg plant- primary or secondary eg eating egg from chicken look at diagrams p77
Pyramid of numbers pros and cons	- relatively easy to construct + does not take into account actual size of organisms range of no.s may be so large may be difficult to draw scale pyramid may be inverted if 1 trophic level has more organisms than previous trophic level look at diagram p78
Pyramid of energy	Most accurate way of representing feeding relationships- shows energy transferred from one trophic level to next per unit area or volume, per unit time as you go through food chain- energy lost from ecosystem- so area of bars decreases accordingly energy pyramids never inverted- easy to compare efficiency of energy transfer between trophic levels in different communities
Pyramid of biomass pt 1	Energy = incorporated into macromolecules that make up biomass of an organism- if available energy is greater, more biomass can be supported- so pyramid of biomass is closely related to energy passing through an ecosystem
pyramid of biomass judgement	Pyramids of biomass effectively represent energy flow through an ecosystem Difficult to measure accurately eg all plant's roots must be included Don't indicate productivity or amount of energy flowing through ecosystem pyramids may be inverted
pyramid of biomass judgement pt 2	trophic level may seem to contribute more to next trophic level than it actually does as organisms contain structures with mass that will not transfer to next trophic level eg bones/ beaks Species with similar biomass may have different lifespans- direct comparison of total biomass is therefore misleading
Inverted pyramid of biomass	In aquatic ecosystem phytoplankton= major producers- lots of energy flows through first trophic level and phytoplankton reproduce very quickly- some are eaten immediately- leaving just enough to maintain pop so their standing crop eg mass of individuals present at given time is lower than biomass of zooplankton which eat them- look at diagram- 78

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