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Ecosystem V.Santhanam Department of chemistry SCSVMV
Ecosystem• A dynamic community of organisms living in a particular environment and the physical elements in that environment with which they interact.• Habitat: A site where a plant or animal naturally lives and grows (within an ecosystem).• Ecological Niche: The functional role of a given species within an ecosystem.
Scientist have expressed concern that:• Human activities are straining the natural resource system.• Exceeding the crucial limits called THRESHOLDS.• Resulting in instability and usually environmental deterioration.Living organisms:• Exist in nature• In a state of balance with one another.
Law of Limiting Factors: - All organisms require minimum quantity of essentials such as nutrients, heat, light, space etc. - The size of any population is ultimately limited by one or more environmental factors.• Excessive change imposes a serious threat to existence.• Complex web of Interrelationships.
Non-Living Elements:• Energy Source: Sun• Chemicals: Carbon, Nitrogen, Oxygen, Phosphorous, Hydrogen, Sulfur – Critical components of all biological life• Elements: Wind and Water
BIOGEOCHEMICAL CYCLES• Include a variety of biological, geological and chemical processes• Earth as a closed system – all elements needed for life were present when Earth formed• Cycle through Earth’s systems – from a few days to millions of years
Ecological succession• Succession is a scientific term describing the long-term progression of biological communities that occurs in a given area.• Ecological succession breaks down into three fundamental phases: primary and secondary succession, and a climax state.• The study of ecological succession generally focuses on the plants present on a particular site. But animal populations also shift over time in response to the changing habitat.
Mechanisms of succession• F.E. Clement (1916) developed a descriptive theory of succession and advanced it as a general ecological concept. His theory of succession had a powerful influence on ecological thought. Clements concept is usually termed classical ecological theory. According to Clement, succession is a process involving several phases.
• Nudation: Succession begins with the development of a bare site, called Nudation (disturbance).• Migration: It refers to arrival of propagules.• Ecesis: It involves establishment and initial growth of vegetation.• Competition: As vegetation became well established, grew, and spread, various species began to compete for space, light and nutrients. This phase is called competition.• Reaction: During this phase autogenic changes affect the habitat resulting in replacement of one plant community by another.• Stabilization: Reaction phase leads to development of a climax community.
Primary Succession• Primary succession occurs when organisms colonize an area devoid of life, usually after a catastrophic natural event that leaves the land barren.• Often the first organisms to take hold are algae, fungi and simple plants such as lichens and mosses.• Over time a thin layer of soil builds up so that more advanced plants, such as grasses and ferns, can take root.• Along with the successful colonization of plants come animals such as insects, birds and small invertebrates.
Secondary Succession• Most ecological change occurs as secondary succession. In fact, most biological communities are in a continual state of secondary succession.• This term describes the process in which an established community is replaced by a different set of plants and animals.• Secondary succession is gradual, always moving toward the climax community.• Most ecosystems, however, experience disturbances -- either natural events such as wildfires or flooding, or man-caused events such as logging -- that set back the progress of succession.
Intermediate Stages• An ecosystem undergoes many intermediate stages of succession. These changes form a continuum between the two endpoints, with the actual stages being merely a fixed glance at the never-ending progression of plants and animals.• The emergence of the climax state of succession may occur more quickly in some ecosystems, and likely never occur in other biomes that experience routine disturbances.• Examples of quickly forming climax communities are the short-grass and long-grass prairies
• A seral community is an intermediate stage found in an ecosystem advancing towards its climax community.• In many cases more than one seral stage evolves until climax conditions are attained.• A prisere is a collection of seres making up the development of an area from non-vegetated surfaces to a climax community. Depending on the substratum and climate, a seral community can be one of the following.
• Hydrosere – Community in freshwater• Lithosere – Community on rock• Psammosere – Community on sand• Xerosere – Community in dry area• Halosere – Community in saline body (e.g. a marsh)
Climax Communities• Climax communities are relatively stable and can vary widely in a given region, especially when the landscape consists of high mountains and low valleys.• In such cases, the final biological matrix of plants and animals can cover vast tracts of land or be limited to a very small pocket within the landscape.• Overall, a climax community is very dependent on rainfall, soil, altitude and temperature.
Biomes• A biome is the largest terrestrial ecological unit• Characterized by interaction of flora and fauna and abiotic factors.• The land mass is divided into different biomes according to location, temperature and rain fall.• A biome is getting the name from the dominating /climax plant form. Ex grass biome is where grasslands predominates.