Organisms that later became good index fossils lived over a

wide geographic area and existed for a short geologic time.

Explanation:

Index fossils are the type of fossil that are used to define periods of geologic time.

Geologic time can simply be explained as the extensive interval of time occupied by the geologic history of Earth. And it is known to be the main factor determining the degree of rock compaction.

In this case, the index fossils are known to be widely distributed, but are limited in time span, or geologic time.

the diploid number of chromosomes is sometimes represented by the symbol 2n. for the fruit fly, the diploid number is 8, which can be written as 2n = 8, where n represents twice the number of chromosomes in a sperm or egg cell.

an organism's phenotype is the  form of a trait  that it  displays. for  flowercolor, a pea  plant  can  display  a phenotype of purple or white flowers. an organism's  genotype  is the alleles of a gene it contains. based on his data, mendel concluded that a phenotype can be  determined  by more than one  genotype.