Chapter 29, Problem 1U

Fossil evidence of eukaryotes dates back to

a. 2.5 BYA.

b. 1.5 BYA.

c. 2.5 MYA.

d. 1.5 MYA.

Summary Introduction

Introduction:

The fossils of eukaryotes were found around $1.5$ $\text{BYA}$(billion years back). The microfossils evolved $3.2$ $\text{BYA}$(billion years back) which led to the evolution of the eukaryotic organisms with nuclei from the prokaryotic organisms without nuclei.

Answer to Problem 1U

Correct answer:

The fossils of early eukaryotic organisms emerged $1.5$ $\text{BYA}$(billion years back). Therefore, option b. is correct.

Explanation of Solution

Reason for the correct statement:

The fossil record indicates the emergence and origin of the eukaryotes with the presence of true nuclei $1.5$ $\text{BYA}$(billion years back). These cells were much bigger in size as compared to the previous prokaryotes that had internal membranes.

Option b. is given as “ $1.5$ $\text{MYA}$”.

As, fossil records of the eukaryotic organisms dates back to “ $1.5$ $\text{BYA}$(Billion years back)”, is the right answer.

Hence, option b. is correct.

Reasons for the incorrect statements:

Option a. is given as “ $2.5$ $\text{BYA}$”.

Some species of bacteria evolved $2.5$ billion years back.  So, it is a wrong answer.

Option c. is given as “ $2.5$ $\text{MYA}$”.

Some species of humans evolved $2.5$ million years back in the evolutionary phylogenetic history like the Homo erectus species. So, it is a wrong answer.

Option d. is given as “ $1.5$ $\text{MYA}$”.

Some species of humans like Homo habilis evolved $1.5$ million years back. So, it is a wrong answer.

Hence, options a., c., and d. are incorrect.

Conclusion

The fossil record indicates the emergence of eukaryotes around $1.5$ $\text{BYA}$(billion years back).