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IB Biology Chapter 4-EcologyI. Species, communities, and ecosystems
A. Interdependence of Living Organisms1980-eruption @ Mt St. Helen’s-see p.172
B. What is a species? Defined as a
_________________________________________________________________________
Made up of organisms that-1. Have similar physiological and morphological (i.e.
Size and shape of an organism and/or its parts) characteristics that can be observed or measured
2. Have the ability to interbreed and produce fertile offspring
3. Are genetically distinct from other organisms4. Have a common phylogeny (i.e. family tree)
Challenges to this definition:Sometimes members of separate but similar species mate and succeed in hybrid offspring-eg.horse+zebra-produces---zebroids-both parents belong to Equidae family-related but not same species-do not have same # c’somes-why offspring usually infertileSome populations may be able to interbreed,but do not do so because they are in different niches or separated by long distancesHow do we classify organisms that reproduce asexuallyWhat about infertile offspring-Do we exclude humans unable to reproduce from species?What about in vitro fertilization
Domesticated dogs-while different breeds-are same species and can interbreed
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Hybrids To understand fertile offspring-♀(female) horse
+ ♂(male) produce_____-mules cannot mate to make more mules-mule is ∴ called_____________________________________
♂lion and ♀ tiger produce liger hybrid Challenges hybrids face cont as a population
inc.infertilty, Other hybrids:
♀ horse + ♂ donkey=mule♀ horse + ♂ zebra=zorse♀ tiger + ♂ lion=liger
C. Populations can become isolated Grp from a species separated from rest of species
may evolve differently when compared w/rest of population-eg.mice have inadvertently crossed oceans on board ships-as they searched for food-may even end up islands away-mice produced on new islands are reproductively isolated-may end up w/ a different frequency of certain alleles-eg fur color
Other things can produce isolation-such as mt. ranges-tree snails in Hawaii-present on only one side of volcano
Also temporal isolation-early migrating birds may have genes isolated from later arrivals
Behavioral isolation-such as different mating calls from same species of birds
Over time-some of these may result in speciation-_________________________________(refer to ch 10.3)
D. Autotrophs and heterotrophs1. Autotrophs-capable of
__________________________________________-synthesize organics from simple inorganics-usually by photosynthesis- Because the food they make is eaten by others
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__________- Examples-cyanobacteria,algae,grass,trees
2. Heterotrophs—cannot make own food from inorganics-but must get from other organisms-from autotrophy and heterotrophy-called ____________________because rely on others, ingest organic matter-Examples-zooplankton, fish, sheep, insects
E. Consumers Heterotrophs-whether we from autotrophs or
products of other heterotrophs Take in energy-rich C-compounds, such as
sugars,proteins,and lipids Only part of human’s diet that we synthesize is
Vitamin D -cholesterol molecule in our skin is modified by light into Vitamin D
E. Detritivores Eat non-living organic matter-dead leaves, feces,
carcasses-eg. Earthworms,woodliceF.Saprotrophs
Live on or in non-living organic matter, secreting enzymes and absorbing the products of digestion
Fungi, some bacteria-decomposersF. Communities
Group of populations living and interacting with each other in an area
1 species may interact by feeding on another or being eaten
May provide vital nutrients for another(e.g.-N-fixing bacteria)
One species may provide protection for another-e.g.-aphids protected by ants
One may rely on another for its habitat-e.g.-parasites
G. Ecosystems
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______________-non-living components of environment(air,water,rocks)-such measurements include _____________________________________-often using electronic probes and data-logging techniques
These things have a large influence on living things
________________-living factors Random sampling using quadrats(to determine the
frequency and distribution of a species)-see page 178
Systematic sampling-using a transect= aline traced from one environment to another-may be a1,25-50 m long-may set up quadrat every meter along transect or at specific intervals along transect-counting the organisms that hit each quadrat and then counting organisms found in each quadrat-no random numbers….see p. 179
H. Where do autotrophs get their nutrients? From inorganic surroundings Photosynthetic organisms-
phytoplankton,cyanobacteria,and plants---photosynthesis
Producers and start of food chainI. Nutrient Cycling
Find need nutrients w/in own habitat-C,N,etcDecomposers
Accessing nutrients through decay Saprophytes and detritivores break down body
parts of dead organisms Digestive enzymes convert organic matter into
more usable forms for themselves and other organisms-e.g. proteins from dead organisms are broken down into ammonia(NH3) and then, in turn ammonia has its N converted into nitrates(NO3-) by bacteria.
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This recycles nutrients so they are available to other organisms-instead of locked into carcasses or waste products
Decomposers help w/formation of soil ________-rich black layer composed of organic
debris and nutrients released by decomposers Decomposers form humus in compost piles
J. The sustainability of ecosystems Through recycling of nutrients, ecosystems can
contribute to be productive and successful for long periods of time
Convert CO2 to C6H12O6-by producers-used then to make complex carbs-like cellulose –or lipids and proteins
Consumers eat producers, and digest the complex organic compounds into simple building blocks---amino acids and sugars,eg,for growth and energy
When the consumers die,their cells and tissues are broken down by decomposers-minerals ret’d to soil---for producers ,once again-completing cycle
N-cycle-N important for nucleotides and amino acids—essential to DNA and proteins-essential to existence
Cycle starts w/ N in gas form in atmosphere(N2)—Plants and animals can’t use N2—some bacteria transform it by N-fixing Then absorbed by plant roots(some plants have N-fixing nodules attached to roots)----Plants and animals return N to soil in variety of ways—e.g. ,ret’d by decomposition,by urine,feces
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II. Energy FlowA. Importance of sunlight to ecosystems
Best studied ecosystems on earth’s surface, relying on sunlight-are the focus here
All life relies directly or indirectly on sun B. Role of photosynthesis
Take CO2 and convert to C6H12O6 Light energy converts into chemical energy(food)-
rich in energy due to chemical bonds between C and other atoms
Chemical energy measured in calories or kilocalories(kilocalories on pkg’ing)
Release energy by digesting,also to burnC. Food chains
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Consumers use the chemical energy from producers—to grow and maintain health
Pattern of feeding=_______________ Flow of
energy=_____________________________________ Write down which organism eats which w/ an
e.g. herring seal indicates seal eats herring
Food chain defined as ____________________________________________-arrow shows direction of energy flow
Trophic level=indicates how many organisms the energy has flowed through
1st trophic level has autotrophs or prodcers;next level primary consumers; next secondary consumers
D. Cellular respiration and heat As grasshoppers consume grass, chemical energy
is used for cellular respiration/glucose converted to CO2 and H2O
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This takes a sm amount of heat in each of grasshoppers cells…heat lost to environment/thee nutrient and energy passed on to next consumers
Cells of decomposers also do cellular respiration and thus release heat to environment
E. Heat cannot be recycled Heat not actually lost due to law of conservation of
energy, but cannot be used again as biological energy source
F. Where does the heat go? Heat lost from ecosystem, radiates into
surrounding environment/ecosystem cannot take back heat to use it-not recycled like nutrients
Food chain only adversely affected by the lost heat if sun is lost-thus affecting food chains
Only chemical energy can be used by next trophic level and only a small amount of energy absorbed is converted into chemical energy
No organism can use 100% of energy in organic molecules-typically only 10-20% used from previous step…~ 90% lost
Main reasons not all energy in n organism can be used by all other trophic levels:
1. Not all of an organism is swallowed as a food source-some parts rejected and decay
2. Not all food swallowed can be absorbed and used in body(e.g.-owl pellets
3. ______________________________________________________________________________________________
4. There is considerable heat loss from cellular respiration @ all trophic levels-most animals have to move-requiring more energy than plants-Warm blooded animals use much more
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see p.188
G. Pyramid of energy Used to show how much and how fast energy flows
from one trophic level to the next in a community Units=energy per unit area per time=kilojoules
per square meter per year(kjm-2yr-1)—take into account rate of energy produced as well qty
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Because energy is lost-each level smaller than previous—cannot have higher level wider than lower level
H. Food webs and energy levels in trophic levels # of organisms in a chain as well as qty sunlight
energy available @ start decide length of chain Biomass of a trophic level=estimate of mass of all
organisms w/in that level-expressed in mass units, but also take into account area or volumeeg.3tons acre-1yr-1Amount of sunlight reaching fields affects biomass, therefore sunnier region produce more biomass wheatSome molecules along the way cannot participate in biomass because they re lost-e.g. CO2 lost in cellular respiration, water during transpiration evapoartion from skin,uurea lot in excretion-
∴not all energy passed to next trophic level and not all biomass passed on
Sometimes foodweb rather than chain is used because there may be many feeding relationships going on
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III. Carbon cycling Crucial element to life Life on earth is referred to as C-based In biosphere as carbs, lipids, nucleic acids and proteins Also in atmosphere as CO2 and lithosphere -
________________________________________ Petroleum-from which gasoline, kerosene, and plastics are
made-rich in C having come from decomposed organisms of millions of years ago
Constantly cycled between living organisms and inorganic processes making C available-e.g. C atoms composing the flesh of a giraffe come from the vegetation it ate
When cellular respiration is complete-CO2 released into atmosphere
When organisms die, scavengers eat decomposers break down—which release CO2 back into atmosphere from cellular respiration
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-also see p.192A. Role of autotrophs in the C cycle
Photosynthetic autotrophs take CO2 from atmosphere and converts into carbs
Sugar a source of food-for the plant, but also for its consumers
The CO2 –not usable as food-emphasizes dependence on sun From glucose, autotrophs manufacture other compounds-
e.g.-fructose and galactose Plants also use it to make starch-energy stored as starch
granules, tubers or seeds Cellulose also made-for cell walls
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Glucose also starting point for other organics-e.g. lipids and amino acids-which go into cell membranes and proteins-enzymes
Other elements added to glucose-such as NB. C in aquatic ecosystems
CO2 water soluble Absorbed by bodies of water Organisms living in water also produce CO2 (by
cellular respiration) ___________________________________________________
__________________________________CO2+ H2O H2CO3 (carbonic acid)H2CO3 H+ + HCO3- (hydrogen carbonate)
The H+ influences pH The HCO3 – important inorganic C-based molecule
that participates in C-cycleC. Cycling of CO2
Absorbed by photosynthetic autotrophs such as bacteria, phytoplankton, plants, and trees. They are eaten by consumers, using C in their bodies
Cellular respiration (hereby abbreviated as cr) from all trophic levels produce CO2-releasing it back into environment
Diffuses into atmosphere or into water D. Methane in C-cycle
Members of Archaea include methanogens-anaerobic
__________________________________________________________________________________________
Methanogens also common in wetlands, where they produce marsh gas (may glow)
Also produce CH4 in digestive tract of mammals-inc. humans-hence the concern w/cattle herds-contribute to greenhouse effect (next section)
E. The oxidation of methane
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CH4 + 2 O2 2H2O + CO2-from burning of fossil fuels
CH4 main ingredient in fossil fuel-__________________
The C found in CH4 borrowed from CO2 molecule removed from atmosphere MYA-during photosynthesis, it then took CH4(g) millions of years to form and accumulate underground
When we burn natural gas, we return C to atmosphere as CO2
What would normally take millions of years to be cycled is thus released rapidly released
F. Peat as a fossil fuel ____________=partially decomposed plant matter Waterlogged, found in certain wetlands-e.g. Mires
and bogs in British Isles, Scandanavia, N. Russia, some of E. Europe, N. Canada, N. China, Amazon River basin, Argentina, N. USA9esp.Alaska), ans some of S.E Asia
Dark in color and only certain types of vegetation can grow on its surface-such as Sphagnum moss
Heterogeneous but at least 30% of its dry mass must be composed of dead organic material
Soil that forms peat is called a _______________-typically 10-40 cm thick
Spongy---The high levels of water on peatland force out the air that would normally be between the particles of soil-creates anaerobic conditions—This allows microorganisms to grow but prevents growth of microorganisms that would help in plant matter decomposition
∴ the energy rich molecules that would have been fed upon by decomposers are left behind and transformed, over thousands of years, into energy –rich peat.
pH of waterlogged histosol-very acidic
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not conducive to decomposers this contributes to the accumulation of non-
decomposed material within the pools of acidic water -in these wetlands
are unique organisms such as some aquatic beetles
to be usable as fuel, cut peat is dried out to reduce humidity. It is then cut into slabs, granules, or blocks and moved where needed
takes a long time to form and considered nonrenewable energy
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when oil prices are high, peat can be a competitive energy source
many wetlands have been drained to replace w/forests and farmland
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concern about wetland preservation has hindered some harvesting of peat…but also because of concern about unique species
also preserve because trapped pollen can reveal info about past climate
G. Oil and gas as fossil fuels When left in the correct conditions, partially
decomposed peat can be further transformed into coal
Over millions of years, sediments can accumulate above the peat and weight and pressure of those sediments compress it
Under ideal conditions, sedimentation cont. until C-rich deposits are both under huge pressure and exposed to high temperatures (since they have been pushed below Earth’s surface)
Pressure and heat cause chemical transformations associated w/lithification___________________________________
During lithification, the molecules are compacted and rearranged
The hydrocarbons-long chains-are of particular interest to industry due to the large amount of energy they hold-ready to be released by burning
Coal must be extracted from below ground to be used for energy-mining
Found in seams, where layers of sediments were deposited, covered, and then transformed and other twisted/deformed by geological forces over millions of years
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The C-H bonds hold a significant amount of energy, and because there is many-much energy to be released by burning
In addition to coal, the chemical transformations underground can produce other petro products such as crude oil and natural gas
During the __________________________period MYA, some places in the world that are now dry were underwater-hosted much aquatic or marine life-inc. algae and zooplankton
The dry deserts of Saudi Arabia used to be under the Tethys ocean-in the time of Pangea
At that time, under ideal conditions for petro formation, dead remains of organisms in the water did not fully decompose @ the bottom of the ocean-instead forming layers of sediment w/silt
In ________-no O2 conditions-the decaying material started to form sludge, as parts of organisms cells decayed and others didn’t-
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The lipid component of cells not easily broken down-the accumulated lipid trapped in sediments from a waxy substance called kerogen
Kerogen is also rich in hydrocarbons and also is transformed by pressure and heat as sediments accumulate above it and cause it to rearrange
Natural production of kerogen-long process Over millions of years and after geological
transformation, kerogen in porous sedimentary rock becomes crude oil or natural gas (in g state)-both being less dense than rock, rising through the cracks to the surface
World deposits of crude oil-see p.196
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Formation of gas and oil-see also p.197
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In order to be used by humans, petroleum products must be trapped and pooled under non-porous rock, preferably one bent by tectonic movement into a dome-as seen above-this allows large qty’s of useful gas and oil to collect together in a productive reservoir
Geologists study which parts of the world might contain exploitable gas and oil reserves
See explanation of fractionating tower on p. 198H.CO2 is produced when fossil fuels are used
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Substances rich in hydrocarbons can be oxidized using O2 gas from atmosphere when they are burned
Wood, animal dung, can be used-inc. for cooking Fresh, wet dung can be mixed w/other refuse from a farm
and put into lg container, where methane producing microorganisms will decompose and ferment it to produce CH4(g)-
Biofuels made in biogas generator take millions of years to form
In efforts to reduce fossil fuel consumption, some countries-
e.g. USA and Brazil-have introduced biofuel programs using ethanol made from crops like corn and soybeans
The plant material is fed to microorganisms that ferment it and release ethanol-which is added to gasoline for cars-reduces gasoline use
Standard vehicles cannot use more than 25% ethanol (need 75% or more gasoline)-gasohol
Esp. adapted vehicles can run solely on ethanol w/a different technique, biodiesel can be made from
vegetable oil or animal fat-such as from deep-fat fryers
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I. Limestone marine organisms remove CO2 from water and some is used
to make carbonate shells C can be in form of CO@ dissolved in water or HCO3- ions Coral polyps build coral reefs-they absorb 2 ions from
seawater to build the reef-HCO3-and Ca 2+---forming CaCO3(calcium carbonate)-basis for coral reef-sturdyCa2+ + 2 HCO3- CaCO3 + CO2 + H2O
Other organisms also use CaCO3 to build shells about their bodies-mollusks-snails, clams, oysters, and mussels—when they die their shells accumulate at bottom of ocean
Microscopic foraminifera are usually on ocean floor and build shells---their shells accumulating in sediment after millions of years through lithification—forming limestone
A bldg. material Carbon sequestration-taking C out of environment and
locking-up in a substance for an extended period of time—if natural its bio- sequestration-helps maintain balance in c –cycle
Through biosequestration-accumulation of foraminifera shells as sediment at bottom of ocean can trap C in limestone for millions of years
Making of cement by people sues limestone-releases C back to atmosphere as CO2
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IV. Climate Change Atmosphere plays vital role in regulating
temperature of earth’s surface Earth’s surface has an average temp of ~ 14°
C/fluctuations only rarely go below -80°C(Antarctica) or higher than 50 ° C (North Africa)
Note-moon ranges -150°C- 120°C-same d from the sun-but moon has basically no atmosphere
If the earth had no atmosphere average temp ~ 32° colder
A. The roles of CO2 and water vapor in the greenhouse effect
Greenhouse effect=planet’s ability to use its atmosphere _______________________________________________________________________________________________________________________________________________________.
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Greenhouse function and design =walls and roof made of glass, sunlight penetrates through glass, warming up plants inside (sunlight alone is made of short wavelengths-is not warm—rather it’s when sunlight hits an object that some of its energy transforms into heat-known as infrared radiation—which has longer wavelengths)-When sunlight goes through glass, warms up objects inside-radiating their heat to air inside, and some of the heat-not releasing like light –is trapped inside. Glass also plays major role in preventing warm air from rising through convection and dissipating the heat---Result= __________________________________________________________________________________________________
Greenhouse effect on a planet is caused by atmosphere’s ability to retain heat in a similar to that of greenhouse glass
Greenhouse gases(GHGs)-e.g. Water vapor and CO2 in atmosphere~ to the analogy of the glass
GHGs have ability to absorb and radiate infrared radiation (heat). These gases keep earth’s atmosphere warm by absorbing heat from warmed surface and re-radiating it in all directions-inc. back towards surface
CH4 and N-oxides are also GHGs to a lesser extent
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Climate experts at International Panel on Climate Change(IPCC)-confirmed earth undergoing global warming because of enhanced greenhouse effect (aka-runaway greenhouse effect)
Increasing levels of main GHGs-from human activities, such as burning fossil fuels-causing atmosphere to retain more and more heat
B. Different gases, different impacts 2 main factors that determine how much influence a gas
will have on the greenhouse effect1. The ability of the gas to absorb long-wave
radiation(heat)o CH4-eg-has a much greater potential to warm
the planet than CO2—however, CH4 has a shorter lifetime in the atmosphere (~12 years—whereas its ~ 50-200 yrs. for CO2)-CH4 can be broken down to other molecules, whereas
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CO2 is not very reactive, staying in atmosphere much longer
2. The concentration of that gas in the atmosphereo Studies of increases in concentrations of CO2
and CH4 gases over time show that CO2 conc’s increased ~ 40 %(since 1750) while CH4 have increased more than 150% in the same period-
o However, CH4 conc’s in Earth’s atmosphere are ~ 1700 ppb while CO2 conc’s ~ 400 ppb-∴ the conc of CO2 > 200x more than that of methane
o ∴ Environmental grps much more worried about CO2 conc’s than CH4 conc’s-but both do play a roleo N-oxides – just over 320 ppb, so they are about the a 5th the conc of methane-even though they have a global warming potential > 100 x that of CO2, their conc in atmosphere is 1000x < than CO2 conc’s
C. The warmed earth emits longer wavelength radiation (heat)
When sunlight enters a greenhouse and touches an object inside, some of the light energy is absorbed and converted into heat energy-i.e. long-wave infrared radiation
On earth, mts, forests, rivers, and oceans absorb some of the sunlight and are warmed, most of sunlight bounces off of the surface and ret’s to space-only sm amt converted into infrared to warm up the surface
_____________________________________________________________________________=albedo
Light-colored obj’s-eg ice and wt. sand-have high albedo-∴ little light is absorbed and such obj’s don’t heat up as much as dark obj’s (dark rocks and blk sand)
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D.How GHGs heat the atmosphere w/o an atmosphere the heat radiating from earth-from
low albedo obj’s would simply radiate back into space-and @ night it would be severely cold
However, this doesn’t happen because GHGs absorb and retain infrared coming from surface
GHGs then re-radiate the heat in all directions (like a radiator in a cold rm)
Some of the heat lost to space, but some of the long-wave rad will be directed down to surface, keeping it warm/rest radiate w/in atmosphere, -preventing nights that are too cold-whole process staring over w/sunrise in the morning
During the winter, days shorter and < of sunlight less direct, thus earth not warming up as much/in turn, days longer in summer, sunlight hits more directly and
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intensely---earth’s surface very hot during heat waves and nights are not cool enough to lower daytime temperatures
Fortunately, certain atmospheric gases filter more harmful UV rad-so does not get to such a max temp-like moon
Analogy of atmosphere as blanket-toning down daytime heat and nighttime cold
E. Global climate change is affected by greenhouse gases Climate=patterns of temp and precip,such as rainfall,
occurring over long time periods Weather can change frequently, but climates not usually
changing in our lifetime-rather 1000’s or millions of years
Climatologists and paleoclimatologists collect data about atmospheric conditions in recent decades and distant past (thermometers only been around for a few hundred yrs, so temps from so long ago must be inferred by proxies)_-see p.207(NOS)-e.g. using tree rings, coral reef growth, particularly fossils, etc…
Proxy data shows, that in N. hemisphere---15,000 years ago, it was very cold-under a glaciation period-ice age (periods of significant change in climate that produces
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sheets of ice hundreds of m thick-places where we now have cities-e.g.-Berlin
Last ice age ended about 10,000 years ago-we are now in an interglacial period-warmer temps
Does not take much of a temp drop to produce glaciation-~ 5° C drop from last ice age-we have had a succession of ice ages over millions of years
Factors believed to contribute to global temp changes over time inc. volcanic activity-w/particles suspended in air, qty of radiation from sun, position of continents, oscillations in ocean currents,Earth orbit fluctuations and inclination of axis, etc…See figure 4.2-p.207-There appears to be a strong correlation between temp increases and CO2 increase-clearly can lead to a warming of the atmosphere, since it increases the greenhouse effectIncrease of temp happens first and then CO2 conc rises-lag time partly explained by fact that, as oceans warm up, they release CO2-positive feedback to FURTHER increases in temp over time: warmer tempsmore CO2 even warmer temps even more CO2, etc…
F. The industrial revolution Since such happenings of 1800’s we have increased
qty’s of CO2 from factories, transport, use of fossil fuels-esp. coal and oil
Burning forests Estimates suggest that the level of CO2 in atmosphere
has increased by more than 35% compared to pre-industrial revolution
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Recent increases in atmospheric CO2 are largely due to increases in combustion of fossilized organic matter
Conc’s of major GHGs are naturally low, which prevent much heat retention#1 source of C emissions from humans is from _______________________________________________________________________________Also from deforestation, heating home w/fossil fuels, high meat diets (this industry highly dependent on fossil fuels)Purchasing goods transported long distances, travel from work to homeOut of -season produce from greenhouses heated by fossil fuelsDiet contributes to CH49cattle industry)Oxides of N produced burning fossil fuels using organic and commercial fertilizers, industrial processes
G. Threats to Coral reefsOrganisms sensitive to water temp, acidity, depth of water-all factors which are changingIncreased CO2 in air means an increase in ocean as well, lowering pH-death of coral polyps and algae—reefs-once dead-will not be rebuilt
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Color changes to bone whiteCoral reef death eliminates the home for many organisms
G. Are humans causing climate change?“climate-change deniers” have a # of criticisms about IPCC’s findings
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