Problem 6 - Biology

Question

Which of the following is an example of a developmental homology seen in human embryonic development and other vertebrate species that are not mammals? a. gill ridges b. umbilical cord c. tail d. both a and c e. all of the above

Step-by-Step Solution

Answer

The correct answer is (d) both a and c.

Step 1 Identify the homologous structures

Embryonic developmental structures like gill ridges and tails are found in both humans during the embryonic stage and other vertebrate (non-mammalian) species. Therefore, these structures can be considered a homology.

Step 2 Exclude the irrelevant options

The umbilical cord is a characteristic feature of mammals including humans, so it is not a homology between human embryos and non-mammalian vertebrates. Therefore, the option (b) 'umbilical cord' and option (e) 'all of the above' are incorrect.

Step 3 Choose the correct answer

Based on the analysis in step 1 and step 2, the correct answer is (d) both a and c, which includes the gill ridges and tail, as these are the structures present in both humans (during embryonic development) and other vertebrates.

Key Concepts

Human Embryonic Development

Human embryonic development is a fascinating process that starts right after fertilization and lasts until the end of the eighth week of pregnancy. During this period, the embryo goes through many changes and forms basic structures that will develop into different parts of the body.
Although human embryos develop within a womb, in the early stages they display fascinating similarities with embryos of other vertebrate animals. These similarities can be attributed to our shared evolutionary ancestry. By studying human embryonic development, scientists can understand how common features in vertebrates develop and what roles they play.

Gill Ridges

Gill ridges are one of the intriguing structures found in the embryos of many vertebrates, including humans. In fish, gill ridges develop into gills which are used for breathing underwater. However, in humans, these structures are not used for respiration. Instead, they form different tissues and structures in the neck and face regions.
Gill ridges in human embryos are an example of developmental homology. They demonstrate our evolutionary past and how certain structures have evolved over time to support various functions in different species. Because we share a common ancestry with fish and other vertebrates, humans still exhibit gill ridges during early development.

Vertebrate Species

Vertebrate species are a diverse group of animals characterized by having a backbone or spinal column. This group includes mammals, birds, reptiles, amphibians, and fish. One of the remarkable aspects of vertebrates is that they share many developmental traits at the embryonic stage, which is evidence of their common evolutionary origin.
Despite their diversity, vertebrate embryos, including humans, go through similar stages of development, reflecting their relatedness. Studying these similarities allows scientists to trace the evolution of complex structures and understand how different species adapt to their environments over millions of years.

Tail

A tail is a common feature found in the embryos of many vertebrates, including humans. In human embryonic development, a tail is present in the early phases but regresses before birth. By the end of human embryonic development, the tail has either disappeared or contributed to the formation of the tailbone.
The presence of a tail in embryos is another example of developmental homology. It highlights our shared evolutionary lineage with other vertebrate animals that retain their tails into adulthood, such as reptiles, birds, and many mammals. Understanding why and how these structures evolve in different species helps scientists to explore the principles of developmental biology.

Homologous Structures

Homologous structures are anatomical features in different species that have a similar origin. These structures may serve different functions but show how species are connected through evolution. In the context of embryonic development, gill ridges and tails are examples of such structures.
During the embryonic stages, these homologous structures provide clues about the common ancestry of vertebrates. While humans and other mammals have evolved to adapt these features for different purposes, their presence highlights evolutionary connections across species. Investigating homologous structures gives valuable insight into how complex organisms have evolved and diversified.