Ecologie
Inleiding..................................................................................................................................................2
Fysische omgeving..................................................................................................................................3
Climate...............................................................................................................................................3
Terrestrial environment......................................................................................................................4
Soil..................................................................................................................................................4
Aquatisch milieu.................................................................................................................................5
Organismen en hun omgeving................................................................................................................7
Plant adaptations to the environment...............................................................................................7
Adaptaties van dieren aan hun omgeving..........................................................................................9
Populaties.............................................................................................................................................12
Eigenschappen van populaties.........................................................................................................12
Populatiegroei..................................................................................................................................12
Levensgeschiedenis..........................................................................................................................13
Soorten-interacties...............................................................................................................................16
Intra- en interspecifieke competitie.................................................................................................16
Parasitisme en mutualisme..............................................................................................................25
Gemeenschapsecologie........................................................................................................................26
Gemeenschapsstructuur...................................................................................................................26
Dynamiek in gemeenschappen.........................................................................................................28
Ecosysteemecologie.............................................................................................................................28
Energetica.........................................................................................................................................28
Decompositie....................................................................................................................................29
Biogeochemical cycles......................................................................................................................30
1
,Inleiding
Ecologie is de studie van de relaties en interacties die bestaan tussen organismen onderling, en met hun
abiotische omgeving (niet levend: fysische en chemische samenstelling van water, bodem en atmosfeer).
Soorten zijn aangepast aan het klimaat: temperatuur en neerslag bij terrestrische systemen en licht en nutriënten
beschikbaarheid bij aquatische systemen bepalen waar de dieren leven.
Tropische regenwouden zijn het best geschikt voor leven en hebben dus de grootste diversiteit, de temperatuur
en neerslag blijven stabiel gedurende het jaar. Een Woestijn heeft bijna dezelfde temperatuur maar er is een
beperkte neerslag. Aquatische systemen zijn veel stabieler, koraalriffen zijn ondiep en veranderen niet rap, er is
voldoende nutriënten recyclage dus er is hier veel diversiteit. Daar waar er geen licht is leven organismen die
aangepast zijn, de nutriënten zijn hier totaal verschillend.
Temperaturen kunnen enorm verschillen binnen het systeem zelf (hoogte), vochtigheid, concentratie van gassen
(verbruik van moleculen), lichtintensiteit varieert op aarde (dag-nacht, seizoenen), nutriënten. Interacties met
andere organismen: symbiose en predator-prooi interactie. Omgeving waarin een organisme leeft is een fysieke
locatie in tijd en ruimte die aquatisch of terrestrisch kan zijn en stabiel of tijdelijk (vb: poel wanneer depressies
onder water komen te staan die in de zomer uitdrogen).
Vb: bosecosysteem: in de late zomer weinig neerslag en temperatuur in wintermaanden lager, klimaat bepaald
vegetatietypen en dit is dan een typisch loofbos. Veel schimmels en fungi die instaan voor de recyclage,
bodemprofiel aanwezig, bovenste lagen bevatten meer organisch materiaal.
Hiërarchie in ecologische systemen
Ecologen bestuderen patronen en processen op verschillende niveaus: individu, populatie, gemeenschap,
ecosysteem (nadruk op energie), landschap, globale schaal (biosfeer).
Een landschap is een mozaïek van geconnecteerde ecosystemen, hier wordt gefocust op de uitwisseling van
energie, materialen en organismen tussen meerder ecosystemen.
De biosfeer is het globale ecosysteem: de som van al de ecosystemen en landschappen op de planeet.
Echinacea is een grasplant uit de prairies ver van de zee dus weinig neerslag, Hoe zit het met de populatie?
Fluctueert die veel en hoe komt dat? Plant staat in een community met andere organismen die aangepast zijn
aan de graslandsteppes, indien rekening houdend met bodem en neerslag dan kijken naar ecosysteem.
Bomen komen niet voor bij weinig neerslag of koude temperaturen (boomgrens in de bergen). Eekhoorn zijn
aangepast aan bossen, populatiegrootte verschilt tussen bostypes (meer in loofbossen en minder in naaldbos)
fluctuaties van een populatie binnen een ecosysteem.
Bij ecosystemen ligt de nadruk op de energie-en nutriëntenstromen, hoe snel worden ze omgezet in biomassa/
voortplanting ? Hoe snel worden ze afgebroken, inclusief ontbinding na de dood ? Systeem van recyclage gaat
heel traag bij droogte en vooral bij lage temperatuur. Dood organisch materiaal stapelt op naarmate dat men naar
de polen gaat, hier kunnen dus bijvoorbeeld turfbodems ontstaan. Bij terrestrische systemen verloopt de
recyclage veel sneller dat in aquatische systemen. In open grasland savannes zijn Acacia’s die veel proteïnen
hebben dus hier komt veel predatie op, de giraffen eten hier van en ze ontlasten ver weg van de planten zodat de
stikstof uit de planten in graslanden terecht komt. Graslanden kunnen wel makkelijk afbranden en hierdoor
verdwijnt de stikstof.
Biomen kennen en kenmerken die erbij horen kunnen opnoemen, deze worden bepaald door het klimaat.
Terrestrische biomen: tropisch bos, savanne, woestijn, chaparral, graslanden, breedbladig bos, naaldbos,
toendra, hoge bergen, pool ijs.
2
,Fysische omgeving
Climate
Weather occurs at a specific place/time and is a combination of specific factors such as temperature, humidity,
precipitation. Climate is a long-term average pattern of weather and there are differences across the globe.
Solar radiation is electromagnetic energy (shorter wavelength = higher energy, long wavelength = lower energy).
The hotter an object, the shorter the wavelength of energy it emits. Surface temperatures reflect the difference
between incoming and outgoing radiation: short wave radiation comes to earth from the Sun and is reflected back
into space, lighter places will reflect more light. Albedo = fraction of light that a surface reflects, an albedo of 1
means all is reflected. Greenhouse gases such as methane, carbon dioxide and water vapor absorb most energy
in de atmosphere, they help to keep the surface of the Earth warm.
Net radiation = incoming solar (shortwave) radiation minus outgoing terrestrial (longwave) radiation
determines the Earth surface temperature. It differences around the globe: highest on the equator, lowest
around the poles. (goes from -280 to 280). The variation comes from the angle how the solar radiation arrives on
Earth and thus the area will be larger at the poles but the amount radiation stays the same.
Average net radiation of Earth = 0, there are areas with negative radiation (poles) and positive radiation (equator).
There is seasonal variation in temperature during the year. On the equator are less seasonal differences because
the Earth’s axis is tilted. Earth faces the sun with one off the poles and that pole gets more sun, around the
equator is not much difference so there is almost no seasonal variation. The imbalance results in a global pattern
of heat redistribution from the equator to the poles: warm surface air at the equator rises and moves north and
south, at the poles the air cools down and descends to the surface where it moves back towards the equator.
Earth rotates around its axis so the equator moves faster than the poles: Coriolis effect, air is deflected towards
the pole areas and in opposite directions in the north (right) and south (left). There is also compression of the air
and where air becomes more dense (when latitude increases) it is spread to areas where it is less dense: cells
around the earth with permanent wind in a certain direction (trading winds): polar cell, Ferrell cell, Hadley cell.
Currents are patterns of water movement, global wind patterns affect these currents and the ocean currents are
modified by presence of land. Gyre = a large system of rotation ocean movements, gyres dominate water
movement in the oceans (clockwise in the Northern hemisphere, counter clockwise in the Southern hemisphere).
Moisture content of air and precipitation.
When water evaporates: energy is absorbed so evaporation requires energy. Condensation releases energy.
When air is saturated with water, water will condensate. Saturation vapor pressure (VP) = water vapor capacity of
air, the amount of pressure exerted by water at saturation, if this is exceeded the condensation occurs.
Relative humidity = (current VP/saturation VP) x 100
If the relative humidity increases when saturation vapor pressure is reduced, it will rain.
The dew point = the temperature at which saturation VP occurs.
Precipitation is not evenly distributed across Earth: lower in the polar areas and deserts (around the equator).
Pattern is linked to air circulation: peaks in rainfall correspond to rising air masses: when air is going up in a cell
switch because the air cools down, decreases in rainfall are associated with descending dry air masses.
Precipitation has seasonal variation because the Intertropical Convergence Zone (ITCZ) shifts.
Proximity to the coastline influences climate: near the coast are smaller temperature fluctuation during the year
and more precipitation.
Topography influences regional and local patterns of climate: mountains affect climate, the climates on the
different sides of the mountain will be different. The direction of the wind will be more wet, the clouds are blocked
by the mountain. Air wants to move so it is pushed up: air cools down and precipitation happens, then the air is
cold so it goes down over the mountain and warms back up, because it does not have any water it picks moisture
up from the area behind the mountain.
3
, Terrestrial environment
Functioning of an ecosystem is contained by its physical environment.
Organism living in terrestrial environment need some kind of support structures because of gravity.
Only resistance from the air while moving.
Water availability: desiccation (loss of water to the environment), water evaporates from the surface of the cells
through diffusion unless the air is saturated. Water balance: the difference in water concentration between the
organism and its environment. Hydration: replacing water that has been lost to the air.
Plants acquire water through roots (osmosis) and in desserts it takes water through the leaves (diffusion).
Diffusion = movement of substances from areas of high concentration to areas of low concentration.
Osmosis = diffusion of water through the cells.
Plants reduce water loss by having a waxy cuticle (outside of plant) and stomata that allow oxygen to leave and
carbon dioxide to enter.
Gravity: exoskeleton or endoskeleton for animals, cell walls of chitin for fungi and cell walls of cellulose for plants.
Environmental variability: terrestrial environments are highly variable in temperature and precipitation.
Climate variability: different ecosystems, climate fluctuations have short-term effects on metabolic processes and
long-term effects on distribution of organisms and ecosystems.
Light availability: light reaches the earth and is partly absorbed and partly reflected back. Absorption depends on
the vegetation type: forests are more efficient in light absorption (more layers of leaves) than a meadow.
Leaf area index (LAI) = area of leaves per unit of ground area, this is better than counting the number of leaves
that effect the light levels because leaves vary in size and shape.
Different types of radiation that plants can detect and utilize: PAR (photosynthetically active radiation), R (red
radiation) and FR (far red radiation). The transmittance of light varies depending on the wave length.
Plants adapt their leaf size and leaf orientation depended on water availability, the angle of the sun and the
season.
Soil
= the biologically active, porous medium that has developed in the uppermost layer of the Earth. It evolved
through weathering processes driven by biological, climatic, geologic and topographic influences. Soil is a
dynamic mixture of minerals, organic matter, water and air but time is also an important factor.
Soil forming factors (state factors) are major environmental controls of soil forming processes such as parent
material (PM), topography/relief (R), climate (Cl) and biota (B).
S = measurable soil property = f(PM, R, Cl, B) x time.
3 main rock families: igneous rock formed though cooling and solidification of magma or lava (plutonic or
volcanic), sedimentary rock formed by accumulation or deposition of small particles on the floor of water bodies or
glaciers, metamorphic rock: rocks modified by heat, pressure and chemical processes.
Climate affects soil formation through impacts on biota, impacts on weathering (temperature, precipitation, wind)
and impacts on water/element cycles.
A soil horizon is a layer parallel to the soil surface which differs from the layers above and beneath: O (organic
layer, decomposed organic material), A (topsoil, mineral soil and humus), B (subsoil, clays and salts), C
(substratum, parent material), R (bedrock).
Climate controls evaporation processes and therefore the amount of water in the soil which in turn controls the
forming of soil horizons.
Topography affects water movement on and in the soil: moisture increases as you move from the ridgetop down
the slope to valleys and streams.
Biota is a source of organic matter and a mean of forming of organic matter: decomposition, melanization
(development of soil as a consequence of the incorporation of organic matter), pedoturbation (mixing of soil
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