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.
Here are 30 one-line questions with answers based on your notes:
What is a trophic level in an ecosystem?
The position an organism occupies in a food chain.What does an ecological pyramid represent?
The relationship between different organisms in an ecosystem.What are the three types of ecological pyramids?
Pyramid of biomass, pyramid of number, and pyramid of energy.What does the pyramid of biomass show?
The amount of biomass per unit area at each trophic level.In which ecosystems can the pyramid of biomass be inverted?
In aquatic ecosystems.What does the pyramid of number represent?
The number of individuals per unit area at each trophic level.Where is an upright pyramid of number found?
In the grassland and polar ecosystems.What type of pyramid is found in a tree ecosystem?
Inverted pyramid of numbers.What does the pyramid of energy represent?
The flow of energy through each trophic level in an ecosystem.What is the 10% rule in ecological pyramids?
Only 10% of energy is transferred to the next trophic level.Why is the pyramid of energy always upright?
Because energy decreases with successive trophic levels.What is ecological productivity?
The primary fixation of solar energy by plants and its use by organisms.How is ecological productivity measured?
In grams of organic matter per square meter per year.What is primary productivity?
The productivity of producers like green plants and phytoplankton.What is gross primary productivity (GPP)?
The total amount of energy fixed by producers.How is net primary productivity (NPP) calculated?
NPP = GPP - energy lost to respiration.Which regions have high ecological productivity?
Tropical rainforests, coral reefs, and wetlands.What is ecological succession?
The process by which the structure of a biological community evolves over time.What is a sere in ecological succession?
A series of communities characteristic of a given site during succession.What is a pioneer species?
The dominant species in the first stage of ecological succession.What is primary succession?
Succession in a totally lifeless area without soil.What is secondary succession?
Succession that occurs in areas where a community has been removed.What is autogenic succession?
Succession caused by the community itself as it reacts to environmental changes.What is allogenic succession?
Succession driven by external conditions like glacial retreat.What is a species niche?
The role a species plays in its ecosystem, including its interactions and environmental requirements.What is a specialist species?
A species with a narrow niche, like pandas and koalas.What is a generalist species?
A species with a broad niche that can survive in varied conditions, like humans and rats.What is mutualism?
A biotic interaction where both species benefit, like coral polyp and zooxanthellae.What is parasitism?
A biotic interaction where one species benefits at the expense of the other, like worms and host organisms.What is predation?
A biotic interaction where one species hunts and feeds on another, like a lion hunting a deer.
Q10: What is negative interaction? Comment on the various types of negative interaction with examples. (150 words/10 Marks)
Negative interactions occur when one or both species involved in the interaction are harmed or disadvantaged in some way. In ecosystems, negative interactions help regulate population dynamics and competition among species.
The main types of negative interactions are:
Parasitism: One organism benefits, while the host is harmed. Example: Tapeworms in the intestines of animals.
Predation: One organism (the predator) kills and feeds on another organism (the prey). Example: A lion hunting a zebra.
Ammensalism: One species is harmed while the other is unaffected. Example: The banyan tree, which blocks sunlight for smaller plants.
Competition: Species compete for the same resources, resulting in reduced fitness for both. Example: Lions and cheetahs competing for prey.
These interactions shape species evolution and resource allocation within ecosystems, maintaining ecological balance.
Q11: Write a note on the functions of an ecosystem. (150 words/10 Marks)
An ecosystem performs various essential functions to maintain ecological balance and support life on Earth. These functions include:
Energy Flow: Energy flows through an ecosystem in a unidirectional manner via food chains and food webs, starting from primary producers to various consumers.
Nutrient Cycling: Ecosystems recycle essential nutrients like carbon, nitrogen, and phosphorus through biogeochemical cycles, ensuring the continuous availability of these elements.
Decomposition: Decomposers break down organic matter, returning nutrients to the soil, which is vital for plant growth.
Regulation of Climate and Atmosphere: Ecosystems influence climate by regulating greenhouse gases, maintaining air quality, and stabilizing temperatures.
Supporting Biodiversity: Ecosystems provide habitats that support diverse species, allowing interactions like pollination and seed dispersal.
Overall, ecosystem functions sustain life by ensuring the balance between biotic and abiotic components, promoting environmental health.
Q1: Explain the concept of ecological succession with examples. (10 Marks/150 Words)
Ecological succession is the gradual process through which ecosystems change and develop over time. It involves the sequential replacement of one biological community by another until a stable climax community is established.
There are two types of ecological succession:
Primary Succession: This occurs in lifeless areas where no soil exists initially, such as on newly formed volcanic islands or glacial retreats. Pioneer species like lichens and mosses colonize the area first, breaking down rocks and creating soil, eventually allowing larger plants to grow. Over time, a mature forest or ecosystem develops.
Secondary Succession: This occurs in areas where a pre-existing community has been disturbed but soil remains intact, such as after a forest fire or agricultural abandonment. The process is faster because the soil already contains seeds and nutrients. Pioneer species like grasses and shrubs grow first, followed by trees and larger plants.
Both types of succession contribute to ecosystem development and biodiversity enhancement, leading to a balanced climax community.
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