Question

Describe how superposition is used to determine the order of taxon origination. Are all extant taxa from an era expected to be discovered in rock layers from that era?

Answer 1

Describe how superposition is used to determine the order of taxon origination.

Taxon means a group of organisms. There may be one or more kind of population in that group.

Superposition of rock units is used for relative age determination. It is a very simple method.

The principle of superposition states that in a group of under formed sedimentary rocks,

the beds which are oldest will be seen at the bottom and the youngest of those beds can be seen at the top.

There are two assumptions here:

1. Layers were originally deposited horizontally.
2. Beds are not overturned.

So, one can easily determine the order of taxon origination through this method as mentioned above.

Are all extant taxa from an era expected to be discovered in rock layers from that era?

Extant Taxa refers to species,genera and families that are still alive.

There is a method called Biostratigraphy. It is used for correlating and assigning relative ages of rock strata by using fossil remains contained in those rocks.The aim of this method is to show that extant taxa from an era is discovered in rock layers from that era. Fossil remains from the rock is very essential and crucial here. because, sediments of the same age may look different due to local environmental variations. If fossil species are recorded properly, era determination will be perfect.