Ecological Pyramids
An ecological pyramid is a graphical representation of the relation between various trophic levels of organisms in a food chain.
Ecological Pyramids are of 3 types
1. Pyramid of number.
2. Pyramid of Biomass.
3. Pyramid of Energy.
1. Pyramid of Numbers
- This deals with the relationship between the numbers of primary producers and consumers of different levels.
Types of Pyramid of Numbers
Upright pyramid-
- In this Pyramid the Number of producers is higher in number than the consumers present in other trophic levels.
- Number of individuals in each trophic level decrease when we go from bottom to top in a pyramid.
- Example- Grassland ecosystem.
Grass → Insect/grass hopers → Sparrow → Snake → Hawk.
Inverted pyramid
- In this pyramid, the number of individuals is increased from lower level to higher trophic level.
- Example- A count in a forest would have a small number of large producers, for e.g., few number of big trees.
Mixed or spindle shaped pyramid-
- In this type of pyramid producers (lowest level) and top carnivores (top level) have less population and middle portion have large population.
- Example-Forest ecosystem.
2. Pyramid of Biomass
- Biomass is the total dry weight of the animals as well as plants present in the ecosystem at any point of time.
- Like pyramid of numbers, it may be upright one or inverted one.
- In case of a forest and grass land ecosystem it is upright and in cases of a pond ecosystem inverted pyramids are observed.
It is further divided as follows-
Upward pyramid -
- In this pyramid lowest tropic level have highest biomass and its tarts decreasing as we move towards Higher Trophic level.
- Example- It is found in most of the ecosystem like-Forest ecosystem, Grassland ecosystem etc.
Inverted Pyramid-
- In this pyramid, the mass of individuals is increased from lower level to higher trophic level.
- Example- Aquatic Ecosystem-It have phytoplankton’s as producers and have low biomass as comparison to higher tropic level.
3. Pyramid of Energy
- It gives detail regarding transfer of energy from one trophic level to next trophic level.
- Energy transfer from lower trophic levels to upper ones decreases.
- As a result, the taller the pyramid, the less energy will reach the organisms in the highest trophic level.
- Only 10% of the energy is being transferred to the subsequent upper trophic level organisms.
- For example, if the producers generate 1000 kilo calorie amount of energy, the primary consumers will receive 100 kcal, the secondary consumer will get 10 kcal and only 1 kcal amount of energy will reach to the tertiary or topmost level of consumers.
Two basic features of this Pyramid
1. Energy flow is unidirectional and irreversible.
2. There is gradual decrease of energy level when we move from lower trophic level to higher trophic level
Some limitations of ecological pyramids.
- Ecological pyramids have some limitations to their use.
- Certain organisms may occupy different positions within an ecological pyramid, depending on the ecosystem being studied.
- Seasonal changes are not taken into consideration when studying ecological pyramids.
- Detritivores, which play an important role in ecosystem function, are not represented in ecological pyramids.
Some concepts related to Energy flow in any ecosystem
Productivity of any Ecosystem-
The relationship between the amount of energy accumulated and the amount of energy utilized within one trophic level of food chain
Types of productivity
1. Primary Productivity-
- Primary productivity is the rate at which green plants accumulate solar energy in organic forms as chemical energy.
- It is the first and basic form of energy storage in the food chain.
- The fraction of fixed energy a trophic level passes on to the next trophic level is called production.
Sub-Types-
Gross primary productivity (G.P.P.)-
- Gross primary productivity (GPP) refers to the total amount of solar energy that is captured in food material through the process of photosynthesis.
Net primary production (N.P.P.) or plant growth-
- Net primary production (N.P.P.), also known as plant growth, refers to the amount of energy stored in organic matter per unit area and time that remains after respiration in plants.
Net productivity of energy = gross productivity—energy lost in respiration
2. Secondary Productivity-
- Secondary productivity is the term used to describe the rate at which heterotrophic organisms produce energy-yielding substances.
Sub-Types-
Net secondary production-
- "Net secondary production" is the scientific term used to describe the amount of energy that is stored in the tissues of consumers or heterotrophs.
Gross secondary production-
The total plant material ingested by herbivores is grass secondary production.
Efficiency of an Ecosystem-
Before discussing efficiency ,there are Some Basic terms and they are as given below-
- Ingestion -It indicates the quantity of food or energy taken by trophic level.
- Assimilation- It indicates the amount of food absorbed and fixed into energy rich organic substances which are stored or combined with other molecules to build complex molecules such as proteins, fats etc..
- Respiration- It indicates the energy lost in metabolism.
Efficiency
1. Exploitation efficiency = Ingestion of food/prey production.
2.Assimilation efficiency = Assimilation / ingestion.
3. Net production efficiency = Production / assimilation.
4. Ecological efficiency = Exploitation efficiency × Assimilation efficiency × Net production efficiency; = Consumer production/prey production;
or
Ecological Efficiency= Production/ingestion.
Standing Corp -
- The term "standing crop" refers to the quantity of living matter present in a given trophic level or population component, encompassing both plants and animals.
- It includes Both, Number and biomass of any organism or non-living thing in any area
Energy flow Models-
- Energy flow models represents the pattern through which energy is transferred between different tropic levels.
Different Types of Energy Flow models-
1. Single Chain Energy Flow Model-
- This type of energy flow works as per the food chain of the ecosystem.
- For example, In a grassland ecosystem, the producers are the grasses.
- Grasses fix carbon dioxide from the atmosphere to produce carbohydrates as the gross productivity.
- This represents a one-way direction of energy flow.
2. Y – Shaped Energy Flow Model-
- The Y-model describes the relationship between a grazing food chain and a detritus food chain.
- In addition to the single chain model, there is another way of energy transfer that exists in nature.
- The food web provides a more complex and realistic depiction of energy flow with various combinations, which reflects this type of model.
Important One Liner on Ecological Pyramids.
What are ecological pyramids?
Ecological pyramids are graphical representations of the trophic levels (feeding hierarchy) of an ecosystem.
What are the three types of ecological pyramids?
The three types of ecological pyramids are the pyramid of numbers, pyramid of biomass, and pyramid of energy.
What does the pyramid of numbers show?
The pyramid of numbers shows the number of individuals at each trophic level in an ecosystem.
What does the pyramid of biomass show?
The pyramid of biomass shows the amount of living organic matter (biomass) at each trophic level in an ecosystem.
What does the pyramid of energy show?
The pyramid of energy shows the flow of energy through the trophic levels in an ecosystem.
Why is the pyramid of numbers inverted in some cases?
The pyramid of numbers can be inverted in some cases when the producers are very small in size but have a high rate of reproduction.
What is the significance of the pyramid of biomass?
The pyramid of biomass shows the total mass of organisms at each trophic level, and thus provides a better estimate of the amount of energy available in an ecosystem.
What is the difference between the pyramid of biomass and the pyramid of numbers?
The pyramid of biomass shows the amount of living organic matter at each trophic level, whereas the pyramid of numbers shows the number of individuals at each trophic level.
What is the significance of the pyramid of energy?
The pyramid of energy shows the flow of energy through the trophic levels in an ecosystem, and thus helps in understanding the efficiency of energy transfer between trophic levels.
How does the pyramid of energy change with each trophic level?
The pyramid of energy becomes smaller with each trophic level, as energy is lost as heat during metabolic processes.
What is meant by the 10% rule in ecological pyramids?
The 10% rule states that only 10% of the energy available at one trophic level is transferred to the next trophic level.
What is a standing crop?
A standing crop is the total amount of living organic matter at a given point in time in an ecosystem.
How can ecological pyramids help in understanding the health of an ecosystem?
Ecological pyramids can help in understanding the health of an ecosystem by providing information on the trophic structure, energy flow, and nutrient cycling.
What are some limitations of ecological pyramids?
Some limitations of ecological pyramids include the assumption of a simple food chain, the difficulty in accurately estimating biomass, and the exclusion of decomposers.