EcosystemEcosystemV.SanthanamV.Santhanam

Department of Department of chemistry chemistry

SCSVMVSCSVMV

EcosystemEcosystem• A dynamic community of organisms A dynamic community of organisms

living in a particular environment and living in a particular environment and the physical elements in that the physical elements in that environment with which they interact.environment with which they interact.

• HabitatHabitat: A site where a plant or : A site where a plant or animal naturally lives and grows animal naturally lives and grows (within an ecosystem).(within an ecosystem).

• Ecological NicheEcological Niche: The functional role : The functional role of a given species within an ecosystem.of a given species within an ecosystem.

Scientist have expressed concern that:Scientist have expressed concern that:• Human activities are straining the natural Human activities are straining the natural

resource system.resource system.• Exceeding the crucial limits called Exceeding the crucial limits called

THRESHOLDSTHRESHOLDS..• Resulting in instability and usually Resulting in instability and usually

environmental deterioration.environmental deterioration.

Living organisms:Living organisms:• Exist in natureExist in nature• In a state of balance with one another.In a state of balance with one another.

Law of Limiting FactorsLaw of Limiting Factors: :

- All organisms require minimum quantity - All organisms require minimum quantity of essentials such as nutrients, heat, light, of essentials such as nutrients, heat, light, space etc.space etc.

- The size of any population is ultimately - The size of any population is ultimately limited by one or more environmental limited by one or more environmental factors.factors.

• Excessive change imposes a serious threat Excessive change imposes a serious threat to existence.to existence.

• Complex web of Interrelationships.Complex web of Interrelationships.

Ecosystem: Ecosystem: • Living elementsLiving elements• Non-Living elementsNon-Living elements

Living Elements:Living Elements:• Producers: PlantsProducers: Plants• Consumers: AnimalsConsumers: Animals• Decomposers: Bacteria, Fungi, InsectsDecomposers: Bacteria, Fungi, Insects

Non-Living ElementsNon-Living Elements::• Energy Source: SunEnergy Source: Sun• Chemicals: Carbon, Nitrogen, Chemicals: Carbon, Nitrogen,

Oxygen, Phosphorous, Hydrogen, Oxygen, Phosphorous, Hydrogen, Sulfur Sulfur – Critical components of all biological lifeCritical components of all biological life

• Elements: Wind and WaterElements: Wind and Water

BIOGEOCHEMICAL BIOGEOCHEMICAL CYCLES CYCLES

• Include a variety of biological, Include a variety of biological, geological and chemical processesgeological and chemical processes

• Earth as a closed system – all Earth as a closed system – all elements needed for life were elements needed for life were present when Earth formedpresent when Earth formed

• Cycle through Earth’s systems – Cycle through Earth’s systems – from a few days to millions of yearsfrom a few days to millions of years

Ecological successionEcological succession

• Succession is a scientific term describing Succession is a scientific term describing the long-term progression of biological the long-term progression of biological communities that occurs in a given area. communities that occurs in a given area.

• Ecological succession breaks down into Ecological succession breaks down into three fundamental phases: primary and three fundamental phases: primary and secondary succession, and a climax state. secondary succession, and a climax state.

• The study of ecological succession The study of ecological succession generally focuses on the plants present on generally focuses on the plants present on a particular site. But animal populations a particular site. But animal populations also shift over time in response to the also shift over time in response to the changing habitat.changing habitat.

Mechanisms of successionMechanisms of succession

• F.E. Clement (1916) developed a F.E. Clement (1916) developed a descriptive theory of succession and descriptive theory of succession and advanced it as a general ecological advanced it as a general ecological concept. His theory of succession had a concept. His theory of succession had a powerful influence on ecological thought. powerful influence on ecological thought. Clement's concept is usually termed Clement's concept is usually termed classical ecological theory. According to . According to Clement, succession is a process Clement, succession is a process involving several phases.involving several phases.

Stages of successionStages of succession

• Primary successionPrimary succession• Secondary successionSecondary succession• Intermediate stateIntermediate state• Ecological climaxEcological climax

• NudationNudation: Succession begins with the development of : Succession begins with the development of a bare site, called Nudation (disturbance).a bare site, called Nudation (disturbance).

• MigrationMigration: It refers to arrival of propagules.: It refers to arrival of propagules.• EcesisEcesis: It involves establishment and initial growth of : It involves establishment and initial growth of

vegetation.vegetation.• CompetitionCompetition: As vegetation became well established, : As vegetation became well established,

grew, and spread, various species began to compete grew, and spread, various species began to compete for space, light and nutrients. This phase is called for space, light and nutrients. This phase is called competition.competition.

• ReactionReaction: During this phase autogenic changes affect : During this phase autogenic changes affect the habitat resulting in replacement of one plant the habitat resulting in replacement of one plant community by another.community by another.

• StabilizationStabilization: Reaction phase leads to development : Reaction phase leads to development of a climax community.of a climax community.

Primary SuccessionPrimary Succession

• Primary succession occurs when organisms Primary succession occurs when organisms colonize an area devoid of life, usually after a colonize an area devoid of life, usually after a catastrophic natural event that leaves the land catastrophic natural event that leaves the land barren. barren.

• Often the first organisms to take hold are algae, Often the first organisms to take hold are algae, fungi and simple plants such as lichens and fungi and simple plants such as lichens and mosses. mosses.

• Over time a thin layer of soil builds up so that Over time a thin layer of soil builds up so that more advanced plants, such as grasses and ferns, more advanced plants, such as grasses and ferns, can take root. can take root.

• Along with the successful colonization of plants Along with the successful colonization of plants come animals such as insects, birds and small come animals such as insects, birds and small invertebrates. invertebrates.

Secondary SuccessionSecondary Succession

• Most ecological change occurs as secondary Most ecological change occurs as secondary succession. In fact, most biological succession. In fact, most biological communities are in a continual state of communities are in a continual state of secondary succession. secondary succession.

• This term describes the process in which an This term describes the process in which an established community is replaced by a established community is replaced by a different set of plants and animals. different set of plants and animals.

• Secondary succession is gradual, always Secondary succession is gradual, always moving toward the climax community. moving toward the climax community.

• Most ecosystems, however, experience Most ecosystems, however, experience disturbances -- either natural events such as disturbances -- either natural events such as wildfires or flooding, or man-caused events wildfires or flooding, or man-caused events such as logging -- that set back the progress of such as logging -- that set back the progress of succession.succession.

Intermediate StagesIntermediate Stages

• An ecosystem undergoes many intermediate An ecosystem undergoes many intermediate stages of succession. These changes form a stages of succession. These changes form a continuum between the two endpoints, with the continuum between the two endpoints, with the actual stages being merely a fixed glance at the actual stages being merely a fixed glance at the never-ending progression of plants and animals. never-ending progression of plants and animals.

• The emergence of the climax state of succession The emergence of the climax state of succession may occur more quickly in some ecosystems, may occur more quickly in some ecosystems, and likely never occur in other biomes that and likely never occur in other biomes that experience routine disturbances. experience routine disturbances.

• Examples of quickly forming climax communities Examples of quickly forming climax communities are the short-grass and long-grass prairiesare the short-grass and long-grass prairies

• A seral community is an intermediate stage A seral community is an intermediate stage found in an ecosystem advancing towards its found in an ecosystem advancing towards its climax community. .

• In many cases more than one seral stage In many cases more than one seral stage evolves until climax conditions are attained.evolves until climax conditions are attained.

•   A A prisereprisere is a collection of seres making up the  is a collection of seres making up the development of an area from non-vegetated development of an area from non-vegetated surfaces to a climax community. Depending on surfaces to a climax community. Depending on the substratum and climate, a seral community the substratum and climate, a seral community can be one of the following.can be one of the following.

• HydrosereHydrosere– Community in freshwaterCommunity in freshwater

• LithosereLithosere– Community on rockCommunity on rock

• PsammoserePsammosere– Community on sandCommunity on sand

• XerosereXerosere– Community in dry areaCommunity in dry area

• HalosereHalosere– Community in saline body (e.g. a marsh)Community in saline body (e.g. a marsh)

Climax CommunitiesClimax Communities

• Climax communities are relatively stable and Climax communities are relatively stable and can vary widely in a given region, especially can vary widely in a given region, especially when the landscape consists of high when the landscape consists of high mountains and low valleys. mountains and low valleys.

• In such cases, the final biological matrix of In such cases, the final biological matrix of plants and animals can cover vast tracts of plants and animals can cover vast tracts of land or be limited to a very small pocket land or be limited to a very small pocket within the landscape. within the landscape.

• Overall, a climax community is very Overall, a climax community is very dependent on rainfall, soil, altitude and dependent on rainfall, soil, altitude and temperature. temperature.

BiomesBiomes

• A biome is the largest terrestrial A biome is the largest terrestrial ecological unitecological unit

• Characterized by interaction of flora and Characterized by interaction of flora and fauna and abiotic factors.fauna and abiotic factors.

• The land mass is divided into different The land mass is divided into different biomes according to location, biomes according to location, temperature and rain fall.temperature and rain fall.

• A biome is getting the name from the A biome is getting the name from the dominating /climax plant form. Ex grass dominating /climax plant form. Ex grass biome is where grasslands predominates.biome is where grasslands predominates.