Summary Ecologie 2019 – part 1 (ECO 1 – 5)
Chapter 2: Climate (summary)
Earth gets solar energy in the form of shortwave radiation and emits energy back into
space in the form of longwave radiation.
The spin of Earth on its axis deflects air and water currents to the right in the
Northern Hemisphere (clockwise) and to the left in the Southern Hemisphere
(counter-clockwise).
The relative humidity is the amount of water in the air as a percentage of the
saturation vapor pressure (the maximum amount the air could hold at a given
temperature).
Land surfaces heat and cool more rapidly than water.
With El Nino, the trade winds give rise to unusually warm water off the coast of
western South America.
Chapter 3: The Aquatic Environment (par. 3, 4, 6 & 7 in
detail)
3.2 Properties of water (summary)
Water is a polar molecule because of the positive hydrogen and negative oxygen atoms.
3.3 Light
The amount of light that reflects from the surface of the water depends on the angle at
which the light strikes the surface. The light entering water is further reduced:
Suspended particles intercept the light and either absorb or scatter is.
Water itself absorbs light, first red light and next yellow light. Blue wavelengths
penetrate the deepest.
Only 10% of blue light reaches more than 100 m in depth.
Many organisms in the deep sea have adapted organs that produce light through chemical
reactions referred to as bioluminescence.
3.4 Temperature varies with water
depth
Warmer water at the surface moves downward and cooler
water from below moves up to the surface. The region of the
vertical depth profile where the temperature declines most
rapidly is called the thermocline. Above the thermocline lies
the epilimnion which is less dense and warmer, and below lies
the hypolimnion which is denser and colder.
In waters of the temperate zone, there is only a thermocline in the summer months. After
summer, the surface water cools down and the surface water becomes denser and sinks. As
the difference in water density between the epilimnion and hypolimnion decreases, winds
,can mix the vertical profile to greater depths. This process of vertical circulation is called
turnover.
3.5 Water as a solvent (summary)
Water can dissolve more substances than any other liquid, making it an excellent solvent.
Salinity is expressed in practical salinity units (‰, grams of chlorine per kilogram of water).
3.6 Oxygen
Oxygen and carbon dioxide can diffuse from the atmosphere into surface waters.
Solubility of gasses in water:
Higher solubility with lower temperature.
Higher solubility with higher atmospheric pressure (in great depths).
Higher solubility with lower salinity.
Oxygen absorbed by surface water mixes with deeper water by diffusion, turbulence and
internal currents. It is lost from the water when the temperatures rise or when aquatic life
takes up the oxygen.
Oxygen is also produced by photosynthesis in surface waters (because light is most available
at the surface).
Flowing water has a greater contact with the atmosphere, so the oxygen content of this
water is high.
3.7 Acidity has a widespread influence on aquatic
environments
Upon diffusing into the surface, carbon dioxide
reacts with water to produce carbonic acid
(H2CO3), which further dissociates into hydrogen
ion and bicarbonate ion (HCO3-). Bicarbonate
may further dissociate into another hydrogen
ion and a carbonate ion (CO32-):
CO2 + H2O ↔ H2CO3
H2CO3 ↔ HCO3- + H+
HCO3- ↔ H+ + CO32-
The dynamics of the carbon dioxide – carbonic
acid – bicarbonate system directly affects the
pH of aquatic systems. It functions as a buffer to
keep the pH of water within a narrow range.
As the pH drops, aluminium begins to dissolve. This aluminium is highly toxic to many
aquatic species, so they are unable to tolerate low pH conditions.
3.8 Water movement (summary)
As the equatorial currents move northward and southward, deep waters move up to the
surface, forming regions of upwelling. In coastal regions, winds blowing parallel to the coast
create a pattern of coastal upwelling.
, 3.10 Estuaries (summary)
The place where freshwater joins and mixes with salt water is called an estuary.
Issues & applications: Ocean acidification (summary)
Increased carbon dioxide concentrations lead to a decline in pH and reduced carbonate
concentrations. The reduction in carbonate concentrations has reduced calcium carbonate
mineral concentrations that are essential for calcifying marine species.
Chapter 4: The Terrestrial Environment (par. 6, 8, 9 &
quantifying ecology 4.1 in detail)
4.2 Light (summary)
Leaf density is expressed as leaf area index (LAI), the area of leaves per unit of ground area.
Quantifying ecology 4.1 Beer’s law and the attenuation
of light
Beer’s law describes the attenuation of light through a homogeneous medium (canopy of
leaves): ALi =e−LAI ∗k in which ALi is the light reaching position i as a proportion to the light
i
reaching the top of the canopy , LAIi is the LAI at height i and k is the extinction coefficient.
Beer’s law can also be used in aquatic environments: ALz=e−k ∗z in which k T is the total light
T
extinction coefficient and z is the water depth.
4.4 Weathering (summary)
In mechanical weathering, water, wind, temperature and plants break down rock. In
chemical weathering, the activity of soil organisms, the acids they produce and the rainwater
break down primary minerals.
4.6 Soils have certain distinguishing physical
characteristics
A soil’s texture is the percentage of sand, silt ad clay. Based on proportions of these
components, soils are divided into texture classes.
4.7 Soil horizons (summary)
Soils develop in layers called horizons.
O horizon: the organic layer.
A horizon: topsoil with accumulation of organic matter.
B horizon: subsoil in which mineral materials accumulate.
C horizon: unconsolidated material underlying the subsoil.
4.8 Moisture-holding capacity is an
essential feature of soils
If there is more water than the pore space can hold, the soil is
saturated and excess water drains from the soil. If water fills all the
pore spaces and is held there by internal capillary forces, the soil is at
field capacity. At the wilting point, plants can’t extract water from
