Quadrat Sampling
Creators: name: Sanyal, Tanmay
Publisher: name: Zenodo
Year: 2025

description: Slide 1: Title Slide

This slide introduces the presentation topic, "Quadrat Sampling," prepared by Dr. Tanmay Sanyal, Assistant Professor in the Department of Zoology, Krishnagar Government College.

 

Slide 2: Introduction to Biodiversity



Biodiversity refers to the variety of different organisms present in an ecosystem and their interactions.

Estimation of biodiversity involves measuring species richness (number of species) and abundance (number of individuals per species).

Statistical representations of biodiversity include aspects such as richness, evenness, and dominance.


 

Slide 3: What is Biodiversity?



Diversity accounts for both the number of species and their evenness or equitability.

Species richness is the total number of species in a community.

Evenness reflects how individuals are distributed across species, highlighting balance in a community.


 

Slide 4: Biodiversity Indices



These indices quantify biodiversity.

Key types of indices include: 



Species Richness Indices: Measure total species present.

Evenness Indices: Determine how evenly species are distributed in a community.



 

Slide 5: Why is Biodiversity Measured?



Measurement helps assess ecosystem health, indicating richness and evenness.

High biodiversity correlates with greater stability, productivity, and resilience to disturbances.


 

Slide 6: Types of Biodiversity



Alpha Diversity: Diversity within a specific area or ecosystem, measured by counting taxa at the species level.

Beta Diversity: Comparison of species diversity between ecosystems, identifying unique taxa in each.

Gamma Diversity: Overall diversity across multiple ecosystems in a region.


 

Slide 7: Simpson's Index



Developed in 1949, this index measures the probability of two randomly chosen individuals belonging to the same species.

Formula: D=∑(nN)2D = \sum \left( \frac{n}{N} \right)^2, where nn is the number of organisms of a particular species and NN is the total number of organisms.

Index values range from 0 to 1: 



0: No diversity.

1: Infinite diversity.



 

Slide 8: Shannon-Weiner Index



Proposed by Claude Shannon in 1948, this index incorporates species richness and evenness.

Formula: H=−∑(piln⁡pi)H = -\sum \left( p_i \ln p_i \right), where pip_i is the proportion of individuals of a species.

Higher values indicate greater uncertainty and diversity.


 

Slide 9: Evenness Index



Highlights how evenly species are distributed in a community.

Calculated using Pielou's Evenness Index (JJ): 



Formula: J=HHmaxJ = \frac{H}{H_{max}}, where HH is Shannon's Index, and HmaxH_{max} depends on species richness.

Values range from 0 (low evenness) to 1 (maximum evenness).

A low JJ indicates dominance by one or few species.



 

Slide 10: Fish Community Assessment Parameters



Key metrics include: 



Species composition and richness.

Presence of intolerant species.

Proportions of omnivores, insectivores, top carnivores.

Incidence of anomalies like diseases, tumors, or fin damage.



 

Slide 11: Acknowledgment



Acknowledges Mr. Aloke Saha and Mr. Pronoy Mukherjee for their assistance in preparing the presentation.