How does synthesis of the leading strand differ from synthesis of the lagging strand during dna replication?

DNA replication is a process where the DNA is copied and replicates to produce the 2 identical copies of the molecule. Strands of DNA molecule work as a template for the production of complementary strands. The DNA splits synthesizing a fork. A new DNA is always synthesized in a 5' prime to 3' prime manner. Replication of both the DNA strands goes in two different ways.

1) Leading strands: It is a strand which is goes to the direction same as the replication fork movement and synthesized in 5'-3' prime direction. This strand formation is occurred as nucleotides are continuously added to the 3' prime end after polymerase reads the DNA template (original).

2) Lagging strands: It is a strand which is goes to the opposite direction as the replication fork movement and synthesized in 3'-5' prime direction. It is synthesized in fragments which are known as okazaki fragments. Lagging strand synthesis needs RNA primase.

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?