OVERVIEW OF THE PREVIOUS CLASS (05:12 PM)

ECOLOGICAL PYRAMID (05:29 PM)

• Trophic level is a position an organism occupies in a food chain.
• Trophic level represents a functional level, not a species as such.
• An ecological pyramid is a graphical representation of the relationship between different organisms in an ecosystem.
• Each bar in an ecological pyramid represents a trophic level, their order and the flow of energy.
• There are three types of ecological pyramids-
• a)PYRAMID OF BIOMASS
• It shows the amount of biomass present per unit area at each trophic level with producers at the base and top carnivores at the top.
• Biomass is measured using the dry weight of an organism. Each trophic level has a certain mass of biomass at a particular time called a standing crop.
• The pyramid of biomass can be upright as well as inverted. Example: Grassland ecosystem(Upright pyramid), Aquatic ecosystem(Inverted pyramid).
• b)PYRAMID OF NUMBER
• It represents the number of individuals per unit area of various trophic levels.
• An upright pyramid of numbers is found in the grassland ecosystem, a polar ecosystem near Antarctica.
• Inverted pyramid of numbers if found in tree ecosystem.
• c)PYRAMID OF ENERGY
• It represents the flow of energy through each trophic level of an ecosystem.
• The pyramid of energy is always upright, the amount of energy decreases with successive trophic levels and only 10% of energy is transferred to each trophic level from the lower ones. (10 % rule of Lindeman)
•  It is because of this the number of trophic levels in an ecosystem is limited 
• SIGNIFICANCE OF PYRAMID OF ENERGY
• Helps in understanding ecological productivity at each trophic level.
• Helps in understanding the efficiency of energy transfer.
• Helps in assessing the environmental impact of development.

ECOLOGICAL PRODUCTIVITY (06:07 PM)

• Ecological productivity refers to the primary fixation of solar energy by plants and the subsequent use of that energy by plant-eating herbivores, carnivores and detrivores.
• It is measured as grams of organic matter per square meter per year.
• The productivity of producers through photosynthesis is called primary productivity. Example: Productivity of green plants and phytoplanktons.
• Secondary and tertiary productivity refers to productivity at the level of primary consumers and secondary consumers respectively.
• Gross primary productivity (GPP) is the total amount of energy that is fixed by producers.
• Net primary productivity(NPP) is adjusted for energy loss due to respiration.
• GPP=NPP + Energy loss.
• Factors affecting ecological productivity include the abundance of sunlight, water and nutrients.
• Regions with high ecological productivity include tropical rainforests, coral reefs and wetlands.
• Regions with low ecological productivity include deserts, deep oceans, etc.

ECOLOGICAL SUCCESSION (06:25 PM)

• It is a process by which the structure of the biological community evolves over time.
• The developmental stages of a community are known as the seral stage.
• The series of communities that are characteristic of a given site is called a sere.
• A species dominant in the first seral stage is called a pioneer species.
• The community at the climax stage is called as climax community.
• TYPES OF SUCCESSION
• a)Primary succession
• Occurs in a totally lifeless area. It usually contains no soil. Examples: Newly formed volcanic island.
• 
• b)Secondary succession.
• It occurs in areas where a community that previously existed has been removed.
• It is faster than primary succession. Example:Regions of forest fire, abundant agriculture fields.
• 
• Autogenic succession
• It involves the succession of a community from itself as a result of its reaction to the environment causing its own replacement. for example: As herbivores decrease a grassland may gradually get converted into forest.
• Allogenic succession
• Replacement of the existing community with a new one under the influence of external conditions.Example: Glacial retreat resulting in land clearing and growth of new forest.

FUNCTIONS OF ECOSYSTEM (07:10 PM)

• It is the role played by an organism in a community of ecosystems.
• Species niche encompasses both the physical and environmental conditions. It requires interactions it has with other species.
• No two species can have the exact same niche if it occurs one species will dominate the other and the other has to adapt and change or become extinct.
• Species with a narrow or limited niche are called specialist species. Examples are pandas, the Koala beer of Australia, snow leopards, and lion-tailed macaques.
• Species with a broader niche is called as a generalist and it can survive in a wide variety of conditions. Examples: Goats, Rats, Human beings, and the house sparrow.
• SIGNIFICANCE (07:32 PM)
• Helps in understanding ecosystem functioning.
• Conservation of the ecosystem by understanding the ecological niche of different species.
• Biodiversity management.
• Invasive species management.
• Studying evolutionary ecology.

BIOTIC INTERACTION (07:34 PM)

• S.No	INTERACTION	SPECIES A	SPECIES B
  1.	Mutualism	+	+
  2.	Commensalism	+	0
  3.	Proto-Cooperation	+	+
  4.	Ammensalism	0	-
  5.	Parasitism	+	-
  6.	Predation	+	-
  7.	Cannibalism	+	-

• Mutulaism example:
• Coral polyp and Zooxanthellae.
• Dwarf mongoose and hornbill
• Proto cooperation example:
• Cattle and Egret.
• Commensalism example:
• epiphytes and trees.
• Ammensalism example:
• Banyan tree and small plants.
• Parasitism example:
• Lion hunting deer.
• Parasitic plants, worms etc.
• Predation example:
• Lion and deer.
• Competition example:
• Lions and cheetahs.

The topic for the next class: Biogeochemical cycles.