Ecology 2 Flashcards
why are earthworms a farmers friend
. This is so because they help in the breakdown of complex organic
matter as well as in loosening of the soil
define decomposition? who doit?
Similarly, decomposers break
down complex organic matter into inorganic substances like carbon
dioxide, water and nutrients and the process is called decomposition.
Dead plant remains such as leaves, bark, flowers and dead remains of
animals, including fecal matter, constitute detritus, which is the raw
material for decomposition.
The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and
mineralisation.
The first three steps in decomposition operate simultaneously on the detritus . Humification and mineralisation occur during decomposition in the soil.
define:
i) fragmentation
ii) leaching
iii) catabolism
i) Detritivores (e.g., earthworm) break down detritus into smaller particles. This process is called fragmentation.
ii) By the process of leaching, water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
iii) Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism.
what is humus and humifications
Humification leads to accumulation of a dark coloured amorphous substance called humus
that is highly resistant to microbial action and undergoes decomposition
at an extremely slow rate. Being colloidal in nature it serves as a reservoir
of nutrients.
mineralisation
The humus is further degraded by some microbes and release
of inorganic nutrients occur by the process known as mineralisation.
what does rate of decomposition depend upon
- Decomposition is largely an oxygen-requiring process.
The rate of decomposition is controlled by chemical composition of detritus and climatic factors.
- In a particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars.
- Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes.
- Warm and moist environment favour decomposition whereas low
temperature and anaerobiosis inhibit decomposition resulting in build up of organic materials.
(i) Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix Sun’s radiant energy to make food from simple inorganic materials.
(ii) Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world. So, it is very important to know how the solar energy captured by plants flows through different organisms of an
ecosystem. All organisms are dependent for their food on producers, either
directly or indirectly. So you find unidirectional flow of energy from the
sun to producers and then to consumers.
2nd law of td
Further, ecosystems are not exempt from the Second Law of
thermodynamics. They need a constant supply of energy to synthesise the molecules they require, to counteract the universal tendency toward increasing disorderliness.
producers
The green plant in the ecosystem are called producers. In a terrestrial
ecosystem, major producers are herbaceous and woody plants. Likewise, producers in an aquatic ecosystem are various species like phytoplankton, algae and higher plants.
define food chain/ web
Starting from the plants (or producers) food chains or rather webs are formed such that an animal feeds on a plant or on another animal and in turn is food for another.
The chain or web is formed because of this interdependency.
No energy that is trapped into an organism remains in it for ever.
The energy trapped by the producer, hence, is either passed on to a consumer or the organism dies.
consumers
All animals depend on plants (directly or indirectly) for their food needs. They are hence called consumers and also heterotrophs.
- If they feed on the producers, the plants, they are called primary consumers, and if the animals eat other animals which in turn eat the plants (or their produce) they are called secondary consumers.
- Likewise, you could have tertiary
consumers too. - Obviously the primary consumers will be herbivores.
Some common herbivores are insects, birds and mammals in terrestrial
ecosystem and molluscs in aquatic ecosystem.
primary carnivore and secondayr carnivore
The consumers that feed on these herbivores are carnivores, or more
correctly primary carnivores (though secondary consumers). Those animals that depend on the primary carnivores for food are labelled secondary carnivores.
detritus food chain
The detritus food chain (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria.
They meet their energy and nutrient requirements by degrading dead organic matter or detritus.
These are also known as
saprotrophs (sapro: to decompose).
Decomposers secrete digestive
enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them.
Grazing food chain
i) In an aquatic ecosystem, GFC is the major conduit for energy flow.
ii) As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the GFC.
iii) Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural
ecosystem, some animals like cockroaches, crows, etc., are omnivores.
These natural interconnection of food chains make it a food web.
define trophic level
Organisms occupy a place in the natural surroundings or in a
community according to their feeding relationship with other organisms.
Based on the source of their nutrition or food, organisms occupy a specific
place in the food chain that is known as their trophic level. Producers
belong to the first trophic level, herbivores (primary consumer) to the
second and carnivores (secondary consumer) to the third
