UNIT 2

THE ECOSYSTEM

2.1.1 COMPONENTS OF AN ECOSYSTEM

AND LEVELS OF ORGANIZATION

A group of organisms that share similar physical characteristic and genetic traits that interbreed and produce fertile offsprings.

The basic unit of ecology or the basic unit of an ecosystem.

Sea lamprey( Petromyzon marinus)

POPULATION

• A group of organisms of the same species living in the same place at the same time and which are capable of interbreeding.

COMMUNITY

• A group of populations living and interacting with each other in a common habitat.

• Habitat: The environment or place where normally or usually an individual lives.

ECOSYSTEM

• A community of interdependent organisms (biotic factors) and the physical environment (abiotic factors) they inhabit.

• The environment where biotic factors (living things) interact and abiotic factors ( non living things) are interconnected.

TYPES OF ECOSYSTEMS

ECOLOGICAL NICHE

• Role or funtion of the specie in its environment.

• Where it lives ( habitat ), when and how it lives, and what it does (predator – prey relationship, mating, etc.)

• For example: The sea lamprey eats fish blood (parasite) and is eaten (probably) by lake trout

FOOD CHAIN• WHO EATS WHO AND HOW ENERGY FLOW.

KEY CONCEPTS

SPECIES-organisms with similar characteristics that are able to reproduce fertile offspring.

POPULATION-organisms of the same specie that live together in a place and interact with each other.

COMMUNITY-group of populations living and interacting with each other.

KEY CONCEPTS

NICHE – describes the role of an organisms or population in its community or ecosystem. In other words, the function of an organisms in its living environment.

HABITAT - is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism. It is the natural environment in which an organism lives, or the physical environment that surrounds (influences and is utilized by) a species population.

Key Concepts

Ecosystem - Is a community of interdependent organisms and the physical (abiotic) environment which they inhabit.

Ecosystems may be of varying sizes from a drop of rainwater to a forest.

Human ecosystems may include a household or a school or a nation.

Ecosystems interact to make a biosphere.

Key Concepts

Biome – is a collection of ecosystems sharing common climatic conditions, e.g. tundra, desert, tropical rain forest.

Key Concepts

Biosphere - is that part of the Earth inhabited by organisms. It is a thin layer that extends from the upper part of the atmosphere down to the deepest parts of the oceans which support life – 11 km below sea level to 10 km above.

From an ecological point of view, the biosphere is the "global ecosystem", comprising the totality of biodiversity on earth and performing all manner of biological functions, including photosynthesis, respiration, decomposition, nitrogen fixation and denitrification.

COMPONENTS

Abiotic FactorsThe non-living, physical and chemical components.

Include:

• The atmosphere: humidity, temperature range, gases, clouds, air pressure, greenhouse gases, ozone layer, etc

• Climate: light intensity or light exposure; temperature range; precipitation; humidity; pressure, wind speed and direction, etc.

• Soil structure and chemistry: moisture, pH, nutrients, components, temperature, etc

• Water chemistry: pH; salinity; dissolved nutrients; dissolved oxygen, turbidity, etc

• Seasonality

• Level of pollutants

Biotic FactorsThe living components of an ecosystem.

Living organisms or their products that directly or indirectly affect an organism in its environment.

Includes organisms such as plants, animals, protista like algae, euglena, amoebas, rotifers, diptera, etc, in general phytoplankton and zooplankton. Also fungi like mushrooms, yeasts, and molds. Bacterias and archae too. But is also includes predation, parasitism, commensalism, mutualism, etc.

Biotic factors interact as: producer, consumer, detritivore, scavenger, decomposer, parasite, host, predator, prey, competitor, herbivore, carnivore, omnivore, mutualist, and pathogen.

COMPONENTSBiotic Factor

COMPONENTSAbiotic Factors

LIMITING FACTORS

• Case study in commercial farming.In Scotland, until the 1970´s, large areas of scottish blanket blog were viewed as a place for commercial forestry operations. It was too wet for Sitka Spruce, the predominant cash wood crop to grow and too expensive to drain. Then it was discovered that if a nurse crop of lodgepole pine was planted ahead of the Sitka, even though the lodgepole pine would die in the very wet conditions, they would dry the soilm enough to allow the Sitka to succeed. Thus, the drying of the area and closing in of the canopy trees with trees planted very close in rows would prevent growth of sphagnum moss.

Factors that prevent the growth or limit the size of a population, a community or organism growing larger.

Biotic factors such as predation or competition or parasitism are limiting factors.

Abiotic factors such as nutrients, soil chemistry, water quality, dissolved oxygen, temperature, etc can restrict the growth of population.

Sitka spruceLodgepole pine Sphagnum moss