Question

EVOLUTION CONNECTION Living members of a vertebrate lineage can be very different from early members of the lineage, and evolutionary reversals (character losses) are common. Give examples that illustrate these observations and explain their evolutionary causes.

Short answer

Due to natural selection, the living members are different from the early members in the vertebral lineage. One of the examples can be penguins. Like birds, the early vertebrates could fly, but the living member penguin could not fly and are adapted for swimming.

Another example is the frog that does not possess teeth in its lower jaw. The ancestral frogs had teeth in their lower jaw, which helped them catch prey.

Step-by-step solution

Vertebrates

Vertebrates are the organisms that belong to the phylum Chordata. The ancient species was closely linked to one of the most successful animals ever who could swim, walk, glide, or fly called the vertebrates.

Vertebrates get their name from the vertebral column, or backbone, consisting of a series of bones called vertebrae.

For more than 150 million years, vertebrates were confined to the oceans, but the emergence of limbs in one branch of vertebrates around 365 million years ago paved the way for these vertebrates to colonize the land.

Evolutionary reversals

Reverse evolution refers to transforming a character state into one that resembles an ancestral state in appearance and includes both reversion and regression patterns. Reversal can happen when a new structure develops because of loss of function mutations that mirror the original structure or loss of a gene.

Examples of the evolutionary relationship between the living and ancestral organisms of vertebral lineages.

Penguins and birds can be considered as an example of this observation. The ancestral vertebrates of penguins, like birds, could not fly. Penguins also have wings, but they do not fly; instead, they use their wings to swim.

The habitat where penguins live has affected their ability to swim. Penguins can catch their prey more effectively by swimming instead of flying.

Today's living frog does not possess teeth in their lower jaw; they are present only in the upper jaw in most frogs. The teeth of the frogs fall and grow multiple times throughout their lifetime. The ancestral frogs had thousands of small hooked teeth that helped them catch their prey.

The frogs without sharp and hooked teeth today help them survive in a different environment. They used their sticky tongue to catch prey and did not require teeth for this purpose.

Natural selection is the cause of this evolutionary change in organisms. Due to natural selection, penguins and frogs underwent a substantial change, and now the penguins could swim, and the frog can survive different ecosystems as they are not a threat to other organisms.

Thus, natural selection is the evolutionary cause of the difference between living vertebrates and ancestral vertebrates like penguins and frogs.