[Flourella]

Textbook confusing me :

"Values of D range from 0 to 1. A Diversity Index value of 1 represents very low species richness. A value of 0 represents very high species richness -- the value you get if there is only one species present, for example."

If species richness is "the number of different species per unit area" then surely only one species present would amount to LOW species richness? Is there a mistake in the textbook somewhere, or am I being thick?

Later on it says "the higher the number we get for D, the greater the diversity." I would have thought that this generally means a high species richness, as in lots of different species present (though I realise it depends on the abundance of each species too, not just species richness), so in the first extract I posted have they just got "low" and "high" the wrong way round? Oh I don't know, I give up, if anyone could de-confuse at all me I'd be grateful!

[Coursework.info]

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[clad in armour]

ill post to keep your thread alive but im doing AS biology as well and I havnt got on to that yet
OCR by any chance?

[Kam1992]

Hey,

The Simpson's Diversity Index is a measure of biodiversity.
In order to measure biodiversity, we must consider ''evenness'' and ''species richness''.
Evenness is a measure of the relative abundance of individuals in each species. In other words, it's how many of each species there are. A habitat where there are even numbers of individuals in each species is likely to be more diverse than one in which individuals of one species outnumber all the others
Species richness is just how many different species there are in a habitat.
A high Simpson's Diversity Index number indicates a diverse habitat. Simpsons diversity is just an equation used to work out the assumed biodiversity of an area. A high number happens to represent a biodiverse habitat..

hope thats useful :-)

[Flourella]

Yep, OCR

(Original post by Kam1992)
Hey,

The Simpson's Diversity Index is a measure of biodiversity.
In order to measure biodiversity, we must consider ''evenness'' and ''species richness''.
Evenness is a measure of the relative abundance of individuals in each species. In other words, it's how many of each species there are. A habitat where there are even numbers of individuals in each species is likely to be more diverse than one in which individuals of one species outnumber all the others
Species richness is just how many different species there are in a habitat.
A high Simpson's Diversity Index number indicates a diverse habitat. Simpsons diversity is just an equation used to work out the assumed biodiversity of an area. A high number happens to represent a biodiverse habitat..

hope thats useful :-)

Thank you very much for your help So would you say my textbook was just talking nonsense where it said a high species richness would be only one species present?

[harishharidas]

Yeah the green books messed up. Its because the formula they use is
D = 1-(Σ(n/N)^2)

So if you have a low diversity and for example just have 10 dogs in a certain area with no other species. n/N = 1 and so D = 0.

So 0 represents a low diversity and 1 represents a high diversity. If the formula didn't have 1- then a value of 0 would represent high diversity as it represents the probability that two random organisms picked are from different species.

But yeah the book confused me too.

[Ishraq Tarafdar]

(Original post by Flourella)
Textbook confusing me :

"Values of D range from 0 to 1. A Diversity Index value of 1 represents very low species richness. A value of 0 represents very high species richness -- the value you get if there is only one species present, for example."

If species richness is "the number of different species per unit area" then surely only one species present would amount to LOW species richness? Is there a mistake in the textbook somewhere, or am I being thick?

Later on it says "the higher the number we get for D, the greater the diversity." I would have thought that this generally means a high species richness, as in lots of different species present (though I realise it depends on the abundance of each species too, not just species richness), so in the first extract I posted have they just got "low" and "high" the wrong way round? Oh I don't know, I give up, if anyone could de-confuse at all me I'd be grateful!

Haha, I'm confused on what the book says as well. Surely it is a load of bull, right? Or am I being very blind or something?