5.1.1
Define Species, habitat, population, community, ecosystem and ecology
Wendy Choi IB Biology
Species – A group of organisms which can interbreed and produce fertile offspring Habitat – location within which a species normally lives Population – a group of same-species organisms who live in the same area at the same time Community – populations of different species in the same area interacting Ecosystem – A community and its abiotic environment Ecology – study of the relationship btwn living organisms and btwn others in their environment 5.1.2
Distinguish between autotroph and heterotroph
Mutual in existance
5.1.3
Distinguish between consumers, detritivores and saprophytes. saprophytes.
Consumers – an organism that ingests other organic matter that’s living/ recently dead
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An organism that generally obtains food by feeding on other organisms or organic matter due to lack of the ability to manufacture own food from i norganic sources; a heterotrophy Any of of the organis organisms ms in all trophic trophic levels levels in a food chain, chain, excep exceptt for produ producers cers In a foo food d chain chain,, the the leve levels ls of of cons consume umers rs are: are: ○ ○
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primary consumers – herbivores that feed on producers secondary consumers – consumers that feed on primary consumers and/or producers tertiary consumers – consumers that feed on secondary and primary consumers consumers,, as well as on producers
Detritivores – an organism that ingests non-living organic matter –
also also know known n as detriv detrivore ores s or detrit detritus us feede feeders rs
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animals and plants that consume detritus (decomposing organic organic material)
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Speed up decomposition and recycling of nutrients by increasing the surface area available to detritvoric bacteria Ex: millipedes, woodlice, dung flies, many terrestrial worms and burying beetles Most detritivores live in mature woodland, though the term can be applied to certain bottom-feeders bottom-feeders in wet environments; play a crucial role in benthic ecosystems, forming essential food chains and participating in the nitrogen cycle
Saprophytes – an organism that lives on/ in non-living organic matter – –
Secrets Secrets digest digestive ive enzym enzymes es into into and absorbing absorbing the produ products cts of of digestion digestion obtains obtains its nutrients nutrients from from non-living non-living organic organic matter matter,, usually dead dead and decaying decaying plant plant or animal animal matter, matter, by absorbing soluble organic compounds
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Saprotrophs consume external food sources rather than make their own food = heterotrophy Suffix -phyte = "plant".
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5.1.4
no truly saprotrophic organisms that are embryophytes, and fungi and bacteria are no longer placed in the Plant Kingdom. Plants once considered saprophytes, such as non-photosynthetic orchids and monotropes, are now known to be parasites on fungi. These species are termed myco-heterotrophs myco-heterotrophs Choi 2 Describe what is meant by a food chain, giving here examples, each with three linkages (4 organisms)
A feeding hierarchy in which organisms in an ecosystem are grouped into trophic (nutritional) levels and are shown in a succession to represent the flow of food energy and the feeding relationships between them. The directional flow of materials and energy from one organism to another is graphically represented by arrows. Most food chains have only about four to five links since too many links in a food chain will result in high demand, less supply of food (and therefore energy). Food Chain examples:
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Primary Producers Primary Consumers Quaternary Consumers
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Plant
5.1.5
→
→
Herbivore
Phytoplankton Grasses Grass
→
→
→
→
Zooplankton
Beetles
Slugs
→
Grass Dead
→
Carnivore
→
Grass
→
Slugs
Algae
→
Protozoa
→
→
→
Carnivore
Carnivore →
Secondary Consumers →
→
→
Tertiary Consumers
→
Carnivore
Carnivore
→
Carnivore
Hawk
Mountain Lions
Woodlice
Small Birds →
→
Small Birds
Badger
Grass
→
→
→
→
Shrew
→
Fox
Hawks
Oligochaeta
→
Northern Eider
→
Arctic Fox
Describe what is meant by a food web.
Food Web is basically interconnecting food chains in an ecological community
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Direct steps in any f ood chain seldom reflect reality, whereas a food web makes it possible to show much bigger animals (like a seal) eating very small organisms (like plankton).
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The food food web web has a number number of adva advantag ntages es over over a food food chains chains includi including: ng: ○ Shows the much more complex i nteractions between species within a community/ ecosystem ○
More than one producer supporting a community
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A single producer being a food source for a number of primary consumers
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That a consumer may have a number of different food sources on the same or different trophic levels That a consumer can be an omnivore, feeding as a primary consumer and as a consumer at higher trophic levels
Food sourc sources es of most most species species in an ecosys ecosystem tem are much much more more diverse, diverse, resultin resulting g in a complex complex web web of relationships. (Below is an example of an Antarctic food web)
Choi 3
5.1.6
Define trophic level .
The trophic level of an organism = the feeding relationship of that organism to other organisms in a f ood.
A consumer can occupy a number of different trophic levels in the f ood web depending on its prey.
5.1.7
Deduce the Trophic Level of organisms in a food chain or food web (Use 5.1.4 and 5.1.8) Organism Grass Slugs Badger
Trophic Level 1 2 3 4
Mountain Lions
Grass Dead Grass Woodlice
1 1 2 3 4
Shrew Fox Grass Mice Hawk Fox
1 2 3 4
Algae Protozoa Oligochaeta
1 1 2 3 4
Northern Eider Arctic Fox
Separate Paper: Diagram 5.1.8 Construct a food web containing at least 10 organisms. organisms. 5.1.9
State that light is the i nitial energy source for almost all communities.
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To maintain maintain food food chains, chains, food webs, webs, commu communities nities and and all their their interacti interactions ons requires requires energy energy
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Sunlight is the source of this energy for most communities both aquatic and terrestrial
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Principle Principle trap of sunligh sunlightt energy energy = protein protein molecule molecule chlor chlorophy ophyll ll
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Other energy sources for deep ocean communities based on geothermal energy
Choi 4
5.1.10
Explain the energy flow in a food chain. chain.
a) Not all solar energy will will come into contact with chlorophyll chlorophyll and will therefore therefore not be trapped in the synthesis of organic compounds b) Phot Photos osyn ynth thes esis is c) Consumer Consumers s feeding feeding and and passing passing on energy energy in the food d) Loss of energy energy as heat heat from from respir respiration ation e) death and the the consumption of dead organisms by by detritivores. detritivores. Or as food not not assimilated because because of incomplete digestion. Energy Loss – – – 5.1.11
loss of of energy energy in undigested undigested food food which which will then then be used used by sapro saprophyte phytes/ s/ decompos decomposers ers loss loss of heat heat ener energy gy in in the reacti reactions ons of resp respira iratio tion n ultima ultimatel tely y all all ener energy gy will will be be lost lost has heat heat State that energy transformations are never 100% eff icient .
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The transfe transferr of energ energy y from from one one trophic trophic level level to the next is ineffici inefficient ent Approx Approx 10-20 10-20 % of the energy energy on on one trophic trophic level level will will be assimilat assimilated ed at the next next higher higher trophic trophic level level
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The volume of one layer is 10% of the layer below (loss of energy makes food chains relatively short)
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Extreme environments ○
Like arctic: low initial trapping of energy by producers
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Food chains are short.
In tropic rainforests ○ The trapping of energy = more efficient ○
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5.1.12
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5.1.13
Food chains are longer, webs are more complex.
Why Why are are big big sca scary ry pre preda dato tors rs rar rare? e? Energy and matter are lost at each stage of the food chain ○ ○ Number of organisms generally reduces at each step or link in the chain Organisms at higher trophic levels become less and less common ○ 'top carnivores' will have to feed over a wide area or territory simply to find food. ○ ○ Another reason: an organism population gets smaller becomes more vulnerable to 'catastrophes': environmental environmental changes or disease. therefore 'super top carnivores' unlikely & prone to extinction. Explain reasons for the shapes of pyramids of energy.
The narrowi narrowing ng shape shape illustrates illustrates the the gradual gradual loss loss of energy progre progressin ssing g along the the links of a food food chain to higher tropic levels The base of pyramid would have a scale = energy/ area/unit time e.g. kJ m -2 yr-1 Unlike pyramids of number (of organisms), a pyramid of energy cannot invert due to the second law of thermodynamics, thermodynamics, 'energy cannot be created nor destroyed'
Explain that energy enters and leaves ecosystems, but nutrients must be recycled .
(a) Energy flows: At each trophic level energy is lost as heat and gained by consumption of food sources: At the top of the pyramid of energy it tapers to a point showing how all energy is ultimately radiated to space as heat. (b) Matter recycles and is the subject of the carbon, nitrogen and water cycle: nutrient is a form of matter, which cannot be created: no new carbon, hydrogen or oxygen. Producers (autotrophs) take inorganic molecules and convert them to organic compounds. Consumers feed at different trophic levels taking i n organic matter and using it for their own growth.
Choi 5
5.1.14
State that saprophytic bacteria and fungi (decomposers) (decomposers) recycle nutrients nutrients..
Saprotrophic Saprotrophic bacteria and fungi recycle the nutrient (organic molecules) of dead organisms.
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Decomposition - complex process serves many functions ○ formation of soil, ○ ○ the recycling of nutrients stored in the organic materials the reduction of high energy carbon compounds. ○
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Decomp Decompos ositio ition n is is a biolog biologica icall pro proces cess s
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First: secretion of extra-cellular digestive enzymes produced by the saprophytic bacteria & fungi onto the dead organism
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Enzymes hydrolyze biological molecules of which dead organisms are composed
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hydrolyzed molecules are soluble and will then be absorbed by the fungi or the bacteria
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Organic molecules oxidized to release CO2 back to the atmosphere
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Organic molecule are oxidized to release nitrogen in form of nitrate, nitrite and ammonium.
The oxidation of these organic compounds produces energy for the saprophyte but returns the various forms of matter to the abiotic environment
Choi 6
5.3.1
Outline the population size is affected by natality, immigration, mortality and emigration. Factors that increase population size: Natality is recruitment to a population through reproduction Immigration from external populations e.g. Bird migration Factor reducing population size: Mortality which is the death rate from any source e.g. predation Emigration, where individuals leave the population for another habitat
Explain the reasons for the exponential growth phase, the plateau phase and the transitional phase between the two phases. phases.
5.3.3
a) Exponential Phase: Low or reduced limiting factors cause the population expands exponentially into the habitat. The population may be increasing at 2n where n= number of generations. The rate of natality + immigration is greater than Mortality + emigration. Note that it does not mean that death/ emigration= 0 This would be typical of a population of germinating annual plants in a new season. Another example would be a a bacterial population during the initial phases of an infection. The population of any species occupying a previously unoccupied unoccupied habitat (succession) b) Transition Stage: Stage: Resources are reduced and become limiting in the growth of the population: As a population grows then there will be increased competition between the individuals of that population for the same resources. This competition means that some individuals will obtain resources and survive and others will not. Overall the effect is to produce a lower rate of population increase that observed during the exponential phase. ecology + evolutionary theory: a reduced rate of population growth and selection (survival and reporduction) of individuals within the population best suited to using resources. ''........can we doubt (remembering that many more individuals are born than can possible survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and procreating their kind? On the other hand, we may feel sure that any variation in the least injurious would be rigidly destroyed. This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection' Darwin Selection' Darwin C. (1859) The Origin of Species c) The Population plateau is where the population remains constant over time/ generations A constant population means that Natality + Immigration = Mortality + Emigration The population size is determined by the carrying capacity of the habitat at that point in time 5.3.4
List three factors that set limits to population increase. increase. With unlimited resources the population would increase exponentially. In reality however environmental resistance limits the population growth and determines the carrying capacity of the habitat: shortage of food or prey predation or parasitism disease accumulation of waste Shortage of space or territory
Choi 7
G.1.1 Outline the factors that affect the distribution of plant species, including temperature, water, light, soil, pH, salinity and mineral nutrients.
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The climate of of a regionregion- temperature and water ○ determines whether a particular organism or group of organisms live in a certain area ○ partially determined by global climate patterns Terrestrial biomes are defined by the predominant type of vegetation ○ relies on the factors of temperature and rainfall. Curvature and tilt of the Earth result in an uneven distribution of light, creating tropical, temperate, and arctic areas Among the many soil properties, soil pH is one of the most i mportant. ○ provides a good indication of the chemical status of the soil and can be used in part to determine potential plant growth influences nutrient uptake and tree growth ○ ○ Many soil nutrients change form because of reactions in the soil that are largely controlled by soil pH pH values at the extremes (<4.0 and > 8.5) can make some nutrients toxic and others ○ unavailable to plants lower pH levels (<4.5), aluminum, iron, and manganese are readily available for plant ○ uptake. At high pH levels (>5.5), calcium and potassium are overabundant. Salinity is Salinity is the presence of salt in the land surface/ soil/ rocks/ dissolved in water in rivers/ groundwater ○ Can develop naturally but where human intervention has disturbed natural ecosystems, the movement of salt into rivers and onto land has been accelerated. Some species of plants are more salt tolerant than others ○ Evidence in FL by observing the vegetation differences near salt water environments. Plant health depends on essential nutrients Macronutrients—carbon, Macronutrients—car bon, oxygen, hydrogen, nitrogen, sulfur, phosphorus (together 98% of plant ○ dry weight) and potassium, calcium, magnesium (1.5% of plant dry weight) – Micronutrients—chlorine, Micronutrients—chlor ine, iron, manganese, boron, zinc, copper, nickel, molybdenum ○
Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply, and territory.
G.1.2
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The predominant vegetation & climate determine the animal species found in the ecosystem Several limiting factors regulate growth in natural populations, the most obvious being competition among members of the population for limited resources, such as a food supply Limited resource may be something other than food or nutrients In many vertebrates that defend a territory, the availability of space may limit reproduction. The space needed for breeding and finding sufficient food is included in this territory. Even when space is sufficient, suitable breeding sites may not be available. As a population’s density increases, factors such as limited food supply and increased disease or predation may increase the death rate, decrease the birth rate, or both. Most popula populations tions are are regulated regulated by by a mixture mixture of factors factors and and fluctuatio fluctuations ns in numbers numbers are are common. common.
G.1.3 Describe one method of random sampling, based on quadrat methods, that is used to compare the population size of two plant or animal species.
– Determine what kind of plants and animals are in a particular habitat, and how many there are of each species, it is usually impossible to count each and every organism present. – Usually solved by taking a number of samples from around the habitat, making the necessary assumption that these samples are representative of the habitat in general. – Samples usually taken using a standard sampling unit of some kind. This ensures that all of the samples represent the same area or volume (water) of the habitat each time. – Usual sampling unit is a quadrat Quadrat normally consist of square frame, the most frequently used size being 1m2 . ○ Purpose of using a quadrat: enable comparable samples to be obtained from areas of consistent size ○ & shape. Random sampling usually carried out ○ ○ Quadrat frame placed on the ground (or on whatever is being investigated) & the animals, &/ or plants inside it counted, measured, or collected, depending on what the survey is for. ○ Done many times at different points within the habitat to give a large number of different samples.
– Simplest form of random sampling: the quadrat is thrown to fall at “random” within the site. ○
Better method of random sampling: map the area lay a numbered grid over the map A (computer generated) random number table then used to select which squares to sample in
G.1.4 Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable.
– Another way to assess distribution of organisms within a habitat – Tape is laid along the ground between two poles. – In a line transect, sample is confined to describing all of the organisms that touch the line – In a belt transect, sampling is confined to a strip of fixed width such as 0.5 or 1 meter Explain what is meant by the niche concept, including an organism’s spatial habitat, its feeding activities and its interactions with other species.
G.1.5
– A habitat is where an organism organism lives, and an ecological niche is the role role an organism plays in its community, community, including its habitat and its interactions with other organisms. – The niche includes the resources resources an organism uses to meet meet its energy, nutrient, and survival survival demands. G.1.6 Outline the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism.
– Competit Compe tition ion (- -) ○
When members of different species try to use a resource that Is in limited supply
– Herbivory erbi vory ( + - ) When one organism (herbivore) (herbivore) feeds on a Predation ( + - ) plant ○ When one animal (predator) feeds on another living animal (prey) Interactions between predator and prey Interactions between prey and its own – Parasit Para sitism ism ( + - ) ○ Organism (parasite) derives nutrition from another organism (host) ○ Effects of parasites on hosts can range from slight weakening to actually killing the host ○ Parasite also uses the host as a habitat ○
– Commensal Comme nsalism ism ( + o ) ○
One species benefits, while the other neither benefits nor is harmed.
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– Mutu Mu tua alism li sm ( + + ) ○ ○ ○
Both organisms in this relationship receive a benefit Mutualistic relationships often help organisms obtain food or avoid predation Parasitism, commensalism, and mutualism are all types of symbiosis.
G.1.7
Explain the principle of competitive exclusion.
– Principle of competitive exclusion states that no two species can occupy the same niche at the same time – Demonstrated by by Gauss in cultures cultures of Paramecium species species – Definition of this principle in the Biology Course Companion states: ○ two species cannot coexist in the same habitat if their niches overlap ○ Either one species will lead to the decline and extinction of the other, or one or both of the competitors will narrow their niches to avoid competition. ○ Their realized niche will be narrower than their fundamental niche G.1.8
Distinguish between fundamental and realized niches. niches.
– An organism’s niche is affected by by both abiotic factors factors – such as as climate climate and habitat habitat – Biotic factors (such as competitors, parasites, and predators in the habitat)
– Because of this, ecologists distinguish between the fundamental and realized niches – An organism’s fundamental fundamental niche comprises all conditions conditions under which the organism can potentially potentially survive and reproduce. – The realized niche niche is the set of conditions conditions under which which it exists in nature. G.1.9
Define biomass.
– Biomass - dry weight of organic matter of a group of organisms found in a habitat – Biomass may refer to the entire community or to a single single trophic level of even to a single single individual G.1.10
Describe one method for the measurement of biomass of different trophic levels in an ecosystem. ecosystem.
– A number of ways to measure plant biomass with varying degrees of destructiveness. In the area set aside for biomass, randomly locate a quadrat. ○ Biomass can be assessed indirectly and completely nondestructively by counting the number of individuals of the target species. Randomly selecting a sample of individuals. Determining mean height within the sample (height will be an indirect measure of biomass). Multiply the mean height by the stem density (number of individuals). – A more destructive destructive method involves taking taking a sample of individuals of the target species species and cutting them at soil level. ○ Tag each individual with a label Dry it to a stable weight and weigh it ○ ○ Determine mean mass of plants in area ○ Multiply by the stem density in the area. ○
– A third method – ○ ○
completely harvest all the target species in the quadrat dry them to a stable weight and then determine the total biomass
– Herbivorous insects can be collected from a plant to determine their mass and then the biomass of the plant they are consuming can be determined
G.2.1
Define gross production, net production and biomass.
– Productivity = energy quantity fixed per unit area per unit time in an ecosystem by a particular trophic level – Gross Production = amount light energy converted to chemical energy by autotrophs in an ecosystem aka primary productivity reduced by the loss of energy through cellular respiration – Net Production = Energy Energy able to be passed on by producers to consumers consumers used to create the next level of an energy pyramid ○ ○ aka productivity pyramid ○ ○
G.2.2
Calculate values for gross production and net production using the equation: gross production – respiration = net production.
– Gross energy minus energy lost equals net energy – Might be asked to use thi s equation when interpreting or creating an energy pyramid – Primary production production can be used used to compare compare biomes. G.2.3
Discuss the difficulties of classifying organisms into trophic levels.
– “Discuss, giving examples, the difficulties of placing organisms in higher trophic levels.” 4 point question – In food webs, organisms often occupy two levels. – – – – –
Some organisms organisms eat prey from from different trophic trophic levels. Not all feeding habits habits of all organisms are known Feeding habits may vary seasonally seasonally or during the life cycle As you move move up the food chain, less energy is available Broad diet is needed to ensure ensure adequate energy energy intake.
G.2.4
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Explain the small biomass and low numbers of organisms in higher trophic levels.
The shortness of food chains chains can be attributed to the loss of energy energy between trophic trophic levels. In general, only about 10% of the energy energy from one trophic trophic level is available to the next trophic trophic level. This 10% rule of thumb also explains why few carnivores can be be supported in a food web web The amount of energy available available to top-level consumers consumers is small compared with that available available to lower-level consumers. Only a fraction of the energy from photosynthesis flows flows through a food chain to top-level top-level consumers. This explains why top-level top-level consumers such as lions and hawks hawks require so much much territory; it takes a lot of vegetation to support trophic levels that are many steps removed from the photosynthetic level. An energy pyramid pyramid also explains why meat is a luxury luxury for humans. Producing meat meat for human consumption means more land be cultivated; more water, fertilizers and pesticides are needed. Energy losses between trophic trophic levels also result in pyramids based on the number of organisms or the amount of biomass at each trophic level.
G.2.6 Distinguish between primary and secondary succession, using an example of each. – Biotic factors may actually change the abiotic abiotic factors in an environment the environment becomes limiting to them ○ ○ other species become more suited This is known as succession ○ – Primary succession succession occurs in areas where where there is no soil formation. – Secondary succession succession is the progression of communities where a pre-existing pre-existing climax community has been disturbed but the soil is already developed – During succession, initial changes are are often much more rapid than subsequent subsequent changes. – A pioneering group of plant species will arrive on the island contribute to the development of an ecosystem that will eventually stabilize with different dominant species – The change in dominant species species with will arrive on the island contribute contribute to time occurs as a result of the development of an ecosystem pioneering species altering the abiotic ○ ○ eventually stabilize with conditions such that other species different dominant species become more suited. ○
G.2.7
Outline the changes in species diversity and production during primary succession.
– Gross productivity productivity rises as small plants are replaced replaced by larger plants. plants. ○ Biomass increases. ○ Increase in productivity at autotroph level is transmitted to upper trophic levels Succession increases species diversity. ○
– Often the only life forms present are autotrophic bacteria ○ ○
Lichens and mosses grow f rom windblown spores Soil develops gradually as rocks weather and organic material accumulates.
Explain the effects of living organisms on the abiotic environment, with reference to the changes occurring during primary succession.
G.2.8
– Ecologists have studied primary primary succession on the rocky moraines left by retreating glaciers glaciers around Glacier Bay, Alaska, and have identified a predictable pattern of changes in vegetation and soil characteristics – Early pioneering species include Dryas, a mat-forming shrub, which is later replaced with stands of alder. Both of these species have symbiotic nitrogen-fixing bacteria, which improve the soil for later plant species. – Later spruce trees use the soil nitrogen and lower the soil pH as the trees’ acidic needles needles decompose. – By altering soil properties, properties, pioneer plant species species permit new species to grow, grow, and the new plants in turn alter the environment – By about 300 years after glacial glacial retreat, spruce-hemlock forest forest dominates the area. area. G.2.9
Distinguish between biome and biosphere.
– A biome is an ecological region dominated by a certain type of ecosystem characterized by certain precipitation and temperature conditions leading to a distinctive biological community adapted t those conditions – Our biosphere biosphere is composed composed of these biomes. biomes. Mader defines biosphere ○ “zone of air, land, & water at the surface of the Earth in which living organisms are found”. Atmosphere = air ○ Lithosphere = land ○ ○ Hydrosphere = water G.2.10
Explain how rainfall and temperature affect the distribution of biomes. biomes.
– The distribution of biomes is determined determined by physical physical factors such as climate (principally temperature temperature and rainfall), which varies according to latitude and altitude. G.2.11
Outline the characteristics of six major biomes.
– Des Desert ert ○ ○ ○
Temperature Moisture (rainfall) Vegetation
– Grassl Grassland and – Shrubl Shrubland and – Temperat Temperate e Deciduous Deciduous Forest – Tropical Rainforest
– Tundra
