In the $Rivet$ $Popper$ hypothesis,what do the rivets represent?

Which of the following is true for species diversity?

How many varieties of rice have been estimated to be present in India?

Given below is the representation of the extent of global diversity of vertebrates. What groups do the portions represent?

Identify the correct statements :
$1.$ According to $\text{IUCN} (2004)$,the total number of described species is slightly more than $1.5$ million.
$2.$ Robert May estimated the total species diversity on Earth to be around $7$ billion.
$3.$ Insects make up more than $70 \%$ of all recorded animal species.
$4.$ India,with $2.4 \%$ of the world's land area,contributes $8.1 \%$ to global species diversity.

$A$: Taxonomic diversity represents the maximum level of species diversity.
$R$: It represents species of taxonomically different groups occurring in equal balance.