Ecology and Sustainable Development – 2009-2010 Hand-outs Nurmukhanbetova G.A. Cand.Sc.

Topic 2: Autecology – the ecology of single species.

NB! The main idea: Note how living organisms are adapted to the various climatic and geographic conditions found on the earth.

Lecture outline:

1. Ecological factors: classification

2. Limiting factors:

• Liebig’s law of the minimum

• Shelford’s principle of tolerance limits

3. Ecosystems diversity. Earth’s biomes:

1. Ecological factors: classification

Classification of ecological factors:

Abiotic factors - the nonliving components of an ecosystem.

Biotic factors - the living components of an ecosystem.

Anthropogenic factors – factors that are caused by human activities.

Ecological factors
Abiotic Meteorological (climatic) (t0, humidity, pressure, wind) Geophysical (radiation, relief, magnetic) Chemical (components of atmosphere, water, soil chemistry and structure, acidity)	Biotic Zoogenic (animals relationships) Phytogenic (plants relationships) Microorganismic (microorganisms relationships)	Anthropogenic Economical (using natural resources for survival) Technogenic (using machines and complex technical equipment to reach definite purposes)

Ecological factors interactions:

Some factors affect organisms directly: t, wind, pH, and salinity; others act as resources: nutrients, light and water.

Abiotic factors can interact with one another: Rains  Flood  Changes of the chemical soil composition.

Living organisms also affect abiotic factors: plants replenish oxygen in the atmosphere by the process of photosynthesis:

H₂O + CO₂ + Sun light energy  C_n (H₂O)_n + O₂

Water Carbon dioxide Sugar Oxygen

Abiotic and biotic factors in ecosystems also interact with each other: climate and soil conditions determine which plants will live in a certain area. Plant life in turn affects the distribution of animals.

Climate + Soil  Plants  Animals

The influence of humans (anthropogenic factor) on abiotic variables may be substantial:

For example, increasing CO₂ output from the burning of fuels and deforestation may cause global CO₂ levels to increase so much that the world’s climate might change (so-called global warming).

Other anthropogenic changes include increased SO₂ (sulfur dioxide) output from fossil fuel burning (coal, oil, natural gas), leading to acid rain, acid lakes, and acid streams.

Biotic relationships:

Biotic factors interact in many ways: Competition, Predator – Prey system, Parasitism (Parasite–Host), Symbiosis.

Competition – a kind of antagonistic relationship within a community - a struggle between two or more groups for a limited resource such as light, food, or space.

Intraspecific – competition among members of the same species.

Interspecific – competition between members of different species.

Predation – a kind of relationship when one organism (predator) feeds directly upon another living organism (prey).

Parasitism – a kind of relationship when one organism (parasite) feeds on another living organism (host) or steals resources from it without killing it.

Symbiosis – the non-antagonistic relationship between different species living in close association with one another.

Mutualism – a type of symbiosis in which both organisms benefit from living together.

Commensalism – a type of symbiosis in which one member benefits and the other is neither benefited nor harmed.

2. Limiting factors: critical limiting factor and tolerance limits

Critical limiting factor – is the single factor closest to the survival limits, that determine area where a particular organism can live.

Liebig’s law of the minimum (1840):

The major environmental factor, affecting an organism is that one is in the minimum.

Shelford’s principle of tolerance limits (1913):

Each environmental factor has both minimum and maximum levels called tolerance limits, beyond which a particular species cannot survive or is unable to reproduce.

Range of tolerance – the range of conditions to which an organism is adapted.

Environmental gradient includes:

- the optimum range, where organisms do best

- zones of physiological stress, where survival and reproduction are possible but not optimal

- zones of intolerance, where life for that organism is impossible.

Tolerance limits – limits of organisms stability to effect of ecological factors.

Any factor, which affects an organism, is either optimal or limiting depending on its strength.

Examples of limiting factors:

- for terrestrial organisms: temperature, moisture, and nutrient availability.

- for aquatic organisms: sunlight, oxygen supply, salinity, gradient (water current).

Sometimes the requirements and tolerances of species are useful indicators of specific environmental characteristics – environmental indicators (trout, lichens etc.).

Homeostasis – the biological balance between an organism and its environment.

Adaptation - an genetically determined structural, functional, or behavioural characteristic of an organism that increases its chance of survival in a particular environment.

Different ecological groups:

• Eyrobionts – are organisms with large range tolerance to an ecological factor.

• Stenobionts – are organisms with narrow range tolerance to an ecological factor.

• Xerophytes – are organisms that are adapted to drought and environmental water shortage.

• Homeothermics – are organisms with constant temperature not depending on environmental temperature.

• Poikilotehermics – are organisms with body temperature depending on environmental temperature.

• Endemics - species that are localized and may have just one population that inhabits a small area.

3. Ecosystems diversity: Earth’s biomes:

Biome - a large area of biosphere characterized by a distinct climate and by the presence of dominant plants and animals adapted to it.

The earth’s biomes are primarily controlled by temperature and precipitations.

• Terrestrial, or Land biomes:

• Polar – biomes found at the earth’s coldest extremes.

• Tundra – a treeless biome blanketed by snow in the winter.

The limiting factor is permafrost – a permanently frozen layer of ground over 500 m thick.

• Coniferous Forest – is a biome that is dominated by conifers, cone-bearing evergreen trees such as pines, firs, spruces, and cedars (boreal forest, or taiga).

• Deciduous forest – is a biome characterised by the presence of trees that lose their leaves in the fall.

• Grassland – is a biome dominated by grasses.

Grasslands are known by various names in different regions of the world:

Prairie (North America), Steppes (Asia), Pampas (South America), Veldt (South Africa), Savannah (grassland with scattered trees found in tropical and subtropical areas in Africa).

• Desert – is an area where rainfall averages less than 25 cm per year.

The limiting factor is low level of water.

• Rain forests

• Tropical rain forest biome – is found near the equator where rainfall and sunlight abound.

• Temperate rain forest extends along the west coast of North America.

• Aquatic, or Water biomes:

Marine biome: ocean, sea

• Ocean (3.5% salt)

• Oceanic zone – the deep water of the open ocean, is less populated (animals of this zone feed on sinking plankton and dead organisms).

• Neritic zone – extends over the continental shelf (light penetration, minerals from the ocean bottom support the greatest amount of marine life).