Ecology

Ecology is the scientific study of interactions among organisms and their environment, such as the interactions organisms have with each other and with their abiotic environment. Abiotic: Physical, or nonliving, factor that shapes an ecosystem. Examples include rocks, climate, pressure and humidity. Biotic: Living factors such as plants, animals, fungi, protist and bacteria are all biotic or living factors. Habitat: the area where an organism lives, including the biotic and abiotic factors that affect it. Niche: describes the relational position of a population or species in an ecosystem. The niche describes how population reacts to the abundance of its natural resources and enemies.

Organization of ecosystem

Individual: An individual is any living thing or organism. Individuals do not breed with individuals from other groups. Population: A group of individuals of a given species that live in a specific geographic area at a given time. Populations include individuals of the same species, but may have different genetic makeup. Community: This includes all the populations of organisms of different species in a specific area at a given time. Ecosystem: Ecosystems include more than a community of living organisms (biotic) interacting with the environment (abiotic eg rocks, water, air and temperature). Biome: A biome is a set of ecosystems in a geographic area. Eg grasslands, tropical forests, deserts etc. Biosphere: A biosphere is the sum of all the ecosystems established on Earth.

Trophic levels of Food Chain

Some more Definitions… Trophic level: Step in flow of energy through an ecosystem: – Plants (First trophic level) – Herbivores (Primary consumers) – Carnivores (Secondary consumers) – Omnivores – Decomposers Producers: trap sunlight for photosynthesis to conert inorganic matter into organic matter. Consumers: obtain energy in the form of organic matter. Food Chain: Sequence of organisms feeding on one another. Food web: Interaction of many food chains

Pyramids for characterizing Ecosystems Pyramid of Energy There is about 90% loss of energy as we proceed from one trophic level to the next higher level.

Pyramid of Numbers Can lead to inverted pyramids: Eg. A large number of insects feeding on leaves of single tree.

Pyramid of Biomass 90% loss at each trophic level

Community Interactions Predation: occurs when one organism captures, kills and eats other organisms for food. This is a positive-negative (+ -) interaction in that the predator species benefits while the prey species is harmed. Parasitism: Interaction in which one organism is harmed (Host) while other is benefitted (Parasite). Parasite generally derives nourishment and shelter from host. Example: tapeworm is a parasite in humans. Mutualism: Mutualism is a symbiotic interaction between species in which both benefit. Examples include Rhizobium bacteria growing in nodules on the roots of legumes and insects pollinating the flowers of plants.

Commensalism: is a type of relationship among organisms in which one organism benefits while the other organism is neither benefited nor harmed. The organism that benefited is called the commensal while the other organism that is neither benefited nor harmed is called the host. For example, an epiphytic orchid attached to the tree for support benefits the orchid but neither harms nor benefits the tree. Amensalism: an interspecific relationship in which a product of one organism has a negative effect on another organism. Example antibiotics production by bacteria and fungi. Competition: Interaction in which both organisms are harmed to some extent. Competition can be for food, shelter, nesting sites, water or mates. Eg. Competition of crop plants with weeds.

Cycling of Matter in Ecosystem Biogeochemical cycle or substance turnover or cycling of substances is a pathway by which a chemical substance moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. It tells us about the biological, geological and chemical factors which are involved in recycling of matter. The circulation of chemical nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, and water etc. through the biological and physical world are known as biogeochemical cycles.

Hydrological/Water cycle

Carbon Cycle

Nitrogen Cycle g20_nitrogen.swf