Ecosystem- Important terms

Module 2-ECOSYSTEM 

34. Food chain

Food chain is the linear network of links in a food web starting from an autotroph such as grass  and ending with predator like bear or a detrivore like earthworm at its apex. 

A food chain shows how organisms are related to each other by the food they eat. Each level of food chain represents a different trophic level. A food chain starts at trophic level 1 with primary producers such as plants, can move to primary consumer at level 2 and typically finished with secondary or tertiary consumer at levels 3, 4 or 5.

Food chain is of 2 types. They are grazing food chain and detrious food chain.

Grazing food chain start from living plants and goes to grazing herbivores and then to carnivores and predators

Some examples of grazing food chain are:

Detrious food chain start from dead organic matters and goes to decomposers and then to predators.

A food chain can regulate and maintain the population size. As the living beings are eating and being eaten up each other, the overall population size is controlled. It is also balancing the ecology. All the nutrients are balanced equally.

35. Food web

Food web is a multi-directional food chain. It shows all the inter connection of food chain and is a graphical representation of what- eats-what in an ecological community. The complexity of the food web depends upon the diversity of the ecosystem. If the food web is more complex, the biodiversity is high and the ecosystem will be stable.

36. Ecological Succession

Ecological succession is defined as, A change in the community in which new populations of organisms gradually replace existing ones.

There are two types of ecological succession

1) Primary Succession

Occurs where there is no soil, e.g. after a   volcanic eruption or a glacial retreat.
Pioneer organisms
Simple plants first – no or shallow roots.
Gradual influx of more complicated and larger plants as the habitat changes
Unfavourable for life at first.
Ends with a “climax community” – ecosystem stays constant, provided there are no changes in abiotic influences.

2) Secondary Succession

Community development in the areas that were previously occupied by other community.

Occurs after a disturbance. E.g., loss of trees after disease, Fire or wind, deforestation etc.
Conditions are favourable, as soil and nutrients are already present.
More rapid than primary succession

37. Bio magnification

When non-degradable substances enter the food chain, they do not get metabolized or broken down and instead get transferred up the trophic levels of the food chain. During this process, they show an increase in concentration which is referred to as bio-magnification. This results in increased toxicity and may even be lethal. This phenomenon is well established for mercury and DDT.

38. Bio diversity

Biodiversity refers to the variety of life on Earth. This includes the number of species of plants, animals and microorganisms along with the diversity of genes in these species. Moreover, it embodies the different ecosystems on the planet, for example forests, deserts, coral reefs and wetlands.

39. Estuary

Estuary is the diverse ecosystem lies between the seas and continents. It is the area at the mouth of the river where the river joins the sea or ocean. The upper limit of an estuary is called as its head and the lower limit as its mouth. Between the fresh water head and the saline water mouth of the estuary, lie several zones corresponding to the intermediate salinity ranges.

The organisms that live in estuary must have ability to survive the varying salinity level. The turbidity, limit the depth of the light penetration and thus limiting photosynthesis and primary production. Most of the estuarine species are detrivores. Some of the dwellers of the estuaries spawn in the fresh water and feed and grow at sea. Some of the species on the other way spawn at sea and feed and grow in fresh water. Other than permanent dwellers, estuaries are host for visitors like migratory birds and fishes.

40. Biome

The terrestrial part of the biosphere is divisible into enormous regions known as biomes on the basis of climate and the abundance of plants and animal species found in each of it.

The most important climatic factors are temperature and rainfall.

Types of biomes

i) Tropical rain forest- high temperature and rainfall

ii) Temperate rain forest- little less temperature and high rainfall

iii)Savanna grassland

iv)Temperate grassland

v)  Desert-high temperature and very less rain

vi) Tundra- very less temperature and rainfall

41. Ecological pyramid and types

Ecological Pyramid

3 types of ecological pyramids based on what it represents are:
1. Pyramid of number
2. Pyramid of biomass and
3. Pyramid of energy

Pyramid of numbers

The number of individuals at the trophic level decrease from the producer to the consumer level. In croplands the crops are more in numbers. The grasshoppers feeding on crop plants are lesser in number. The frogs feeding on grasshopper are still lesser in number. The snakes feeding on frogs are fewer in number.

In grassland the grasses are large in numbers. The consumers decrease in the following order.

Crops  - > Grasshopper  - > Frogs  - > Snakes  - > Hawks.

2.Pyramid of biomass

Biomass refers to the total weight of living matter per unit area. In an ecosystem the biomass decreases from the producer level to the consumer level.
In grassland the biomass of grasses is the maximum and it gradually decreases towards the consumer level.
Grass -> Grasshopper  -> Garden Lizard  -> Hawk.
Grass -> Mouse  ->      Snake  -> Hawk.
Crops- > Grasshopper- > Frogs - > Snakes  - > Hawks.
In a forest, the biomass of trees is the maximum and the top consumer is the minimum. The decrease in weight occurs in the following order.
Plants ->    Deer   ->     Fox   -> Tiger.
Plants ->    Rabbit  ->   Fox   -> Lion

3. Pyramid of energy 

In an ecosystem, the energy flow from the producer to the consumer level will be decreasing. In grassland, grass plants trap the maximum sun light energy. The energy gradually decreases towards the top consumer level. The chemical energy is transformed into kinetic energy.
Grass -> Rabbit  -> Fox  -> Lion.
Grass -> Grasshopper  -> Garden Lizard  -> Hawk.
Grass -> Mouse  -> Snake

The graphical representation of different trophic levels in an ecosystem is known as ecological pyramid. When it is arranging the number of organisms or the biomass or the energy level of an ecosystem in an order from top to bottom or vice versa, automatically it will form the shape of a pyramid. At the bottom level of the pyramid will be the autotrophs or producers and tertiary consumers at its apex. Pyramid may be represented either in the form of triangle or rectangle. The area of each segment of pyramid will be proportional to the number or biomass or energy level of that ecosystem.