ECOSYSTEM

CONCEPT• Everything in the natural world is connected.

• Plants and animals depend on each other to survive. This connection of living things to each other is called biodiversity.

• These plants and animals within an area interact with each other and with the non-living elements of the area, such as climate, water, soil and so on.

• An ecosystem, short for 'ecological system', is a community of living and non-living things that work together.

• An ecosystem is a community of living organisms (plants, animals and microbes) in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system.

Ecosystem defined• An ecosystem is a community of plants,

animals and smaller organisms that live, feed, reproduce and interact in the same area or environment.

• An ecosystem is a community of living and nonliving things considered as a unit.

• Ecosystem is a complex set of relationships among the living resources, habitats and residents of an area. It includes plants, trees, animals, fishes, birds, micro-organisms, air, water, soil and people.

• An ecosystem is a self regulating group of biotic communities of species interacting with one another and with their non-living environment exchanging energy and matter.

• Ecosystems are dynamic interactions between plants, animals, and microorganisms and their environment working together as a functional unit. Ecosystems will fail if they do not remain in balance.

Ecosystem defined

Ecology• Term Coined by Earnst Haeckel in 1869.• Derived from greek words: OIKOS(Home)

+LOGOS(Study)• So, Ecology is the study of organisms in their

natural home interacting with their surroundings.• Ecology is the scientific study of the

relationships that living organisms have with each other and with their natural environment.

• Ecology is the study of ecosystems.

Functions of ecosystem

• Habitat functions: ecosystems provide habitat to wild plants and animals and thus conserve biological and genetic diversity. It supports different food chains and food chains.

• Production function: production of wide range of goods ranging from food to raw materials.

• Regulatory functions: ecosystem regulates essential ecological processes and life support systems and renders stability. Responsible for cycling of nutrients between biotic and abiotic components(biogeochemical cycles). Also, it provides many services that have direct and indirect benefits to humans (i.e., clean air, water and soil). Soil formation, climate regulation, etc.

• Every ecosystem regulates and maintains itself and resists any stresses or disturbances upto a certain limit. This is known as cybernetic system.

Functions of ecosystem

• Informational function: ecosystems provide an essential 'reference function' and contribute to the maintenance of human health by providing opportunities for spiritual enrichment, cognitive development, recreation and aesthetic experience. 

Functions of ecosystem

Structure of Ecosystem

Biotic Components of Ecosystem

• Different living organisms constitute the biotic components of an ecosystem.

• This refers to large life-forms such as trees or mammals, small life-forms such as insects and algae, and microscopic life-forms such as bacteria.

• Biotic, meaning of or related to life, are living factors. Plants, animals, fungi and bacteria are all biotic or living factors.

Producers• Most important components of ecosystem.• Producers are organisms which are able to manufacture

organic compounds from inorganic substances from their environment.

• Food is produced both for themselves and for other organisms.

• They depend directly on the abiotic component for their survival and production of nutrients.

• Producers are also known as autotrophs (derived from Greek words: “autos” meaning self and “trophe” meaning nourishment)

• They induce into the ecosystem, the energy required for its biological processes.

• Producers extract nutrients from soil or ocean and manufacture their own food using photosynthesis, in the presence of carbon dioxide and sunlight and so energy from sun powers the base of food chain. Producers are also, thus known as primary producers.

• An exception occurs in deep-sea hydrothermal ecosystems where there is no sunlight. Here, the primary producers manufacture food through a process called chemosynthesis.

• Chemosynthesis is a process certain organisms use to produce energy, akin to photosynthesis, but without the utilization of sunlight. The energy comes from the oxidization (burning) of chemicals which seep up from the Earth's crust.

• So, producers are either photo-autotrophs or chemo-autotrophs.

Producers

• Consumers are organisms that obtain nutrients by consuming other organisms.

• These organisms are formally referred to as heterotrophs (derived from Greek words “heteros” meaning another/ different and “trophe” meaning nourishment.

• A heterotroph is an organism that cannot synthesize their own food and must obtain it ready made.

• They can be herbivores, carnivores, omnivores or detritivores.

Consumers

Herbivores• Animals who derive their required energy

directly from consuming the plants and plants only.

• Also known as primary consumers.

• Herbivores have special digestive systems that let them digest all kinds of plants, including grasses.

• Eg. Rabbit, cattle, horse, sheep, insects, etc.

Carnivores • Animals that feed on other animals.

• Carnivores generally eat herbivores (secondary consumers), but occasionally eat other carnivores also (tertiary consumers).

• Eg: lion, tiger, cats, birds of prey, sharks, frogs, etc.

Predators

• A predator is an organism that hunts and kills other organisms for food.

• Eg: lions, tigers, sharks, wolves, snakes, etc.

Scavengers

• Scavengers eat the food that has been killed and left behind by predators.

• Eg: vultures, racoons, hyena,etc.• Scavengers play an important role

in the ecosystem by consuming the carcass of of animals that have been left to decompose. Decomposers and detritivores complete this process, by consuming the remains left by scavengers.

Omnivores• Animals that feed on both plants and animals.• Omnivores often are opportunistic, general

feeders with neither carnivore nor herbivore specializations for acquiring or processing food, and are capable of consuming and do consume both animal protein and vegetation.

• Many omnivores depend on a suitable mix of animal and plant food for long-term good health and reproduction.

• Eg, humans, bear, etc.

Detritivores • They feed on dead plant and animal matter, but

perform an additional function which is to return essential nutrients back to the ecosystem in the process.

• Detritivores actually eat organic matter.• They are essential for recycling of nutrients:

without them dead plant material would not be returned to the soil for new growth

• Eg: worms, millipedes, sea stars, crabs, dung flies.

• Detritivores consume dead organic material such as carcasses, fallen leaves, dead plants, animal droppings and shed skins.

• Having consumed the material, the organism then excretes or egests waste.

• This waste contains nutrients which are thus returned to the soil, facilitating new plant growth, or made easier for other organisms to consume. By breaking down dead matter into smaller pieces, detritivores speed up the process of decomposition.

Detritivores

Decomposers/ Saprobes • These are micro-organisms which break-down organic

matter into inorganic compounds and derive their nutrition in the process. Decomposers break down complex compound into simpler compounds without eating them.  

• For example, fungi can grow on organic matter, such as a dead tree trunk or a piece of bread, and breaks it down and absorbing the nutrients without eating the wood or the bread.

• These are organisms that aid in decomposition of already dead or dying organisms.

• Decomposers secrete enzymes to digest organic matter and then absorb resulting molecules.

• Eg: bacteria, fungi, etc.

• The nonliving materials in an ecosystem, such as minerals, gases, liquids and chemicals are referred to as abiotic or non-biotic factors.

• Abiotic, meaning not alive, are nonliving factors that affect living organisms. Environmental factors such habitat (pond, lake, ocean, desert, mountain) or weather such as temperature, cloud cover, rain, snow, hurricanes, etc. are abiotic factors.

Abiotic Components of Ecosystem

• An abiotic factor is a nonliving condition or thing, such as climate or habitat, that influences or affects an ecosystem and the organisms in it.

• Abiotic factors can determine which species of organisms will survive in a given environment.

Abiotic Components of Ecosystem

Abiotic Components of Ecosystem

• Flow of energy in an ecosystem is governed by following cycles:

Water CycleCarbon CycleOxygen CycleNitrogen CycleEnergy Cycle

ENERGY FLOWS IN AN ECOSYSTEM

Water cycle

• The carbon, which occurs in organic compounds, is included in both the abiotic and biotic parts of the ecosystem.

• Carbon is a building block of both plant and animal tissues.

• In atmosphere, carbon occurs as carbon dioxide.

• Through photosynthesis, plants form carbohydrates that contain carbon and emit oxygen which is used by animals for respiration.

• Plants are consumed by animals for derivation of energy.

• Both plants and animals release carbon dioxide during respiration.

• Carbon is returned to soil in form of wastes from animals and plants and in the form of dead matter when decomposed.

Carbon cycle

Carbon cycle

Oxygen Cycle

Nitrogen Cycle

• About 78% of Earth’s atmosphere is Nitrogen, in free form.

• Living things require nitrogen in compound form (not in free form), to build proteins and other important chemicals.

Nitrogen Cycle

• Not all the nitrogen that gets fixed is used by plants and animals.

• Some of it is returned to the atmosphere through a process called denitrification

• Bacterial species such as Pseudomonas and Clostridium perform denitrification of nitrates in anaerobic conditions (absence of oxygen).

• They use the nitrate in the place of oxygen during respiration.

• Effectively, they breathe nitrate and exhale nitrogen gas back into the atmosphere. 

Nitrogen Cycle

ENERGY CYCLE

• The ultimate source of energy (for most ecosystems) is the sun.

• The ultimate fate of energy in ecosystems is for it to be lost as heat.

• Energy and nutrients are passed from organism to organism through the food chain as one organism eats another.

• Decomposers remove the last energy from the remains of organisms.

• Inorganic nutrients are cycled, energy is not.• Flow of energy in an ecosystem is uni-directional.

ENERGY CYCLE

• Flow of energy in an ecosystem is governed by laws of thermodynamics, which are:

Energy cannot be created or destroyed (but it can be transformed into stored energy & heat)

Energy is lost as energy is transformed.

ENERGY CYCLE

ENERGY CYCLE

Integration of Cycles in Nature

• All these cycles are responsible for maintenance of life on earth.

• If mankind disturbs these cycles beyond the limits that nature can sustain, they will eventually break down and lead to a degraded earth on which man will not be able to survive.

Food chain

• Every living organism/ thing requires energy to survive, whether it be plants, animals or humans.

• Energy is required by living beings to grow.

• Plants get their energy from photosynthesis.

• Animals get energy from the food they consume.

• A food chain is the sequence of who eats whom in a biological community (an ecosystem) to obtain nutrition.

• A food chain shows how each living thing gets food, and how nutrients and energy are passed from creature to creature.

• A simple food chain can be seen below:

Food chain

Food Chain

• A food chain starts with the primary energy source and end with top predators,animals that have little or no natural enemies.

• When any organism dies, it is eventually eaten by detrivores (like vultures, worms and crabs) and broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues.

Food Chain

• Food chains make a full circle, and energy is passed from plant to animal to animal to decomposer and back to plant!

• There can be many links in food chains but not TOO many.

• If there are too many links, then the animal at the end would not get enough energy.

Food Chain

• The further along the food chain you go, the less food (and hence energy) remains available.

• Most food chains have no more than four or five links.

• In a food chain each organism obtains energy from the one at the level below.

• A change in the size of one population in a food chain will affect other populations. 

Food Chain

Types of Food Chains

Grazing food chains

• Start with green plants and culminate with carnivores.

(a)Predatory food chain – begins with plants and proceeds from small to large animals.

E.g.- crops - field mice – owls

(b) Parasitic food chain – Begins with plants and proceeds from large to small animals.

E.g.- producers - herbivores– parasites

Detritus/ saprophytic food chains• They start with dead organic matter.• Death of organism is the beginning of the

detritus food chain.• Eg: leaf litter in a forest – fungi – bacteria• Bacteria and fungi, however, are eaten by

organisms and they in turn are eaten by other organisms.  Since the source of energy is not the sun but detritus, this linear feeding relationship is called a detritus food chain. 

• In nature, food chain relationships are not isolated; rather they are complex, because one organism may form the food source of many organisms.

• Thus, instead of a simple linear food chain, there is a web like structure formed by these interlinked food chains.

• Such interconnected matrix of food chains is called 'food web'.

• Food webs are indispensable in ecosystems as they allow an organism to obtain its food from more than one type of organism of the lower trophic level.

Food Web

Food Web• Food chains are generally found to be

interlinked and inter-woven as a network and are known as food web.

• Food Web a system of interlocking and interdependent food chains in a given area.

• A food web is several food chains connected together.

• A food web is many food chains linked together to show a more accurate model of all possible feeding relationships of organisms in an ecosystem.

Food web

Food web

Trophic Levels

• These are the various steps in a food chain or food web.

• Level1: producers (autotrophs)

• Level2: primary consumers (herbivores)

• Level3: secondary consumers (carnivores/omnivores)

• Level4: tertiary consumers (top carnivores)

Ecological pyramids• An ecological pyramid is an

illustration of the reduction in energy as you move through each feeding level in an ecosystem.

• Each feeding level of the ecosystem is called trophic level.

• Producers form the base of the pyramid.

• Consumers form the upper layers.

• Diagram that shows the relative amount of energy or organisms contained within each trophic level of a food chain or web.

Ecological pyramids

• Ecological pyramids are graphs which illustrate the trophic levels in a community.

• Most ecological pyramids are large at the base and narrow at the top.

• Less Energy

• More energy

Ecological pyramids

Ecological pyramids

Ecological pyramids• An ecological pyramid is a diagram that

shows the amounts of energy or matter contained within each trophic level in a food web or food chain.

Pyramid of biomass• The total amount of matter present in organisms

of an ecosystem at each trophic level is biomass.

• In other words, the total amount of living or organic matter in an ecosystem at any time is called 'Biomass'.

• Biomass means the mass of living material at a stage in a food chain. The biomass at each stage goes down as you go from one stage to the next, just like the amount of energy.

• Pyramid of biomass is the graphic representation of biomass present per unit area of different trophic levels, with producers at the base and top carnivores at the top.

• Pyramid of biomass records the total dry organic matter of organisms at each trophic level in a given area of an ecosystem.

• A pyramid of biomass is a chart, drawn to scale, that shows the biomass at each stage in a food chain. The bars become narrower as you reach the top.

• Typical units for a biomass pyramid could be grams per meter2 or calories per meter2.

Pyramid of biomass

• This demonstrates the amount of matter lost between trophic levels.

• There are two types of biomass pyramids: upright and inverted.

• An upright pyramid is one where the combined weight of producers is larger than the combined weight of consumers. An example is a forest ecosystem.

• An inverted pyramid is one where the combined weight of producers is smaller than the combined weight of consumers. An example is an aquatic ecosystem.

Pyramid of biomass

• In a terrestrial ecosystem, the maximum biomass occurs in producers, and there is progressive decrease in biomass from lower to higher trophic levels. Thus, the pyramid of biomass in a terrestrial ecosystem is upright.

Pyramid of biomass

• In an aquatic habitat the pyramid of biomass is inverted or spindle shaped where the biomass of trophic level depends upon the reproductive potential and longivity of the member.

Pyramid of biomass

Pyramid of numbers• A pyramid of numbers is a graphical representation of

the numbers of individuals in each population in a food chain.

• The pyramid of numbers represents the number of organisms in each trophic level.

• Pyramid of numbers can be used to examine how the population of a certain species affects another.

• Often, the autotrophic level in a pyramid of numbers is much larger than any of the higher trophic levels, and the numbers decreases upon ascending the pyramid. There are exceptions, however. For example, in a tree community, a single tree could support many different populations of larger numbers.

Pyramid of Numbers

Pyramid of energy• The pyramid of energy represents the total

amount of energy consumed by each trophic level.

• An energy pyramid is always upright as the total amount of energy available for utilization in the layers above is less than the energy available in the lower levels. This happens because during energy transfer from lower to higher levels, some energy is always lost.

• Measured in joules or calories.

Pyramid of energy

• Ecosystem is not static, its dynamic and changing constantly.

• Its structure and function change over time.• These changes are in order and are capable of

being predicted.• One type of community gets totally replaced with

another type of community over a period of time and this causes several changes.

• This is ecological succession.

Ecological succession

Ecological succession• It is the slow and gradual process, by which ecosystems

change and develop over time.• Ecological succession is the changing sequence of

communities that live in an ecosystem during a given time period.

• In simple words, it is the gradual replacement of one community by another through natural processes over time.

• It refers to the natural gradual changes in the types of species that live in an area.

• Ecological succession is the gradual process by which ecosystems tend to change and develop over a period of time.

• For example, a bare patch of ground will not stay bare. It will rapidly be colonized by a variety of plants.

• It is the transition that takes place when one biotic community gives way to another biotic community.

Ecological succession

Why succession takes place• Succession takes place because through the

processes of living, growing and reproducing, organisms interact with and affect the environment within an area, gradually changing it.

• Each species is adapted to thrive and compete best against other species under a very specific set of environmental conditions. If these conditions change, then the existing species will be outcompeted by a different set of species which are better adapted to the new conditions.

PIONEER ORGANISMS• A pioneer organism is an organism that populates a

region after a natural disaster or any other event that may have caused most life in that area to disappear.

• It is the first organism formed on the lifeless ground.• Over time, dead material from pioneer species forms

humus, and the soil which results is colonized by other species.

• Common pioneer organisms include lichens and algae.• A pioneer species are the species dominating a

community in the first stage of succession.

Features of Pioneer Species

• High growth rate

• Small size

• Wide dispersal

• Fast population growth

CLIMAX COMMUNITY

• An ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment.

• A climax community is the final stage of succession, remaining relatively unchanged until destroyed by an event such as fire or human interference.

• A stable, mature and final community that undergoes little or no succession, when left undisturbed.

Features of Climax Community

• Slower growth rate

• Larger size

• Lower rates of dispersal

• Lower rates of colonization

• Longer lives

Stages of Ecological Succession• Process begins with establishment of few

pioneer species which get replaced by species of increasing complexity.

• Establishment of pioneer species at a bare site causes changes in soil structure and nutrient content, followed by changes in physical environment.

• Existing species get replaced by new species due to changed physical factors.

• These changes are often accompanied by introduction of animal species into the area.

• This cyclic process ends after reaching a stabilized community called climax community.

• At this stage ecosystem is in a state of balance, until disturbed by external factors.

• Disturbances destroy existing climax community and then process of succession starts anew.

Stages of Ecological Succession

Clement’s Theory of Succession/ Classical ecological theory

• Published by  Frederic Clements in 1916.• According to Clements, succession is a

process involving several phases:Nudation: development of a bare site,

uninhabited by any organisms, as a result of disturbances.

Invasion/Migration: arrival of seeds, spores and other reproductive propagules for establishment of species.

Ecesis/ colonization: It involves establishment and initial growth of vegetation. Dependent on soil structure. This is the stage where pioneer species survive.

Aggregation: Increase in the population of established species.

Competition: As vegetation became well established, grew, and spread, various species began to compete for space, light and nutrients. This also happens for animal species.

Clement’s Theory of Succession/ Classical ecological theory

Reaction: Environmental conditions get modified by the action of species occupying the habitat and this triggers displacement and replacement of one species by another.

Stabilization: Process by which climax community gets established. Reaction phase leads to development of a climax community, which is mature, self-sustaining and stable. It is the final stage of succession. Climax community continues until another disturbance steps in.

Clement’s Theory of Succession/ Classical ecological theory

Types of Ecological Succession

• Primary succession is the series of community changes which occur on an entirely new habitat which has never been colonized before.

• Primary succession occurs in essentially life-less areas where no ecosystem existed before.

• It begins on a barren surface.• For example: on new islands created by volcanic

eruptions, bare rocks, rocks exposed by glacier retreats, etc.

Primary Succession

• In primary succession pioneer species like lichen, algae and fungus as well as other abiotic factors like wind and water start to "normalize" the habitat.

• The primary succession is important in pioneering the area to create conditions favorable for the growth of other forms of plants and animals.

• Pedogenesis or the formation of soil is the most important process.

• http://youtu.be/vNHnwHaSolA

Primary Succession

Primary Succession

Secondary Succession

• Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat.

• For example: after felling trees in a woodland, land clearance or a fire.

• Secondary succession begins in an area that already has soil.

Process of secondary succession is much faster……why????

• Secondary succession is usually faster than primary succession as:

Soil is already present, so there is no need for pioneer species;

Seeds, roots and underground vegetative organs of plants may still survive in the soil.

Secondary Succession

• An example of Secondary Succession by stages:1. A stable deciduous forest community2. A disturbance, such as a wild fire, destroys the forest3. The fire burns the forest to the ground4. The fire leaves behind empty, but not destroyed, soil5. Grasses and other herbaceous plants grow back first6. Small bushes and trees begin to colonize the area7. Fast growing evergreen trees develop to their fullest, while shade-tolerant trees develop in the understory8. The short-lived and shade intolerant evergreen trees die as the larger deciduous trees overtop them. The ecosystem is now back to a similar state to where it began.

Secondary Succession