The pygmy zebra octopus is a potential new model organism for understanding brain function in humans despite the independent evolution of high intelligence in both groups. Describe (or draw a phylogenetic tree to show) the relationships among humans (H. sapiens), the pygmy zebra octopus (O. chierchiae) and two other protostome model organisms in medicine: the fruitfly (D. melanogaster) and roundworm (C. elegans).

Verified step by step guidance

1. Identify the major taxonomic groups for each organism: Humans belong to the phylum Chordata, class Mammalia. The pygmy zebra octopus belongs to the phylum Mollusca, class Cephalopoda. The fruitfly belongs to the phylum Arthropoda, class Insecta. The roundworm belongs to the phylum Nematoda.
2. Understand the concept of a phylogenetic tree, which is used to show the evolutionary relationships among various biological species based upon similarities and differences in their physical or genetic characteristics.
3. Place the common ancestor of all these organisms at the base of the tree. This represents the last universal common ancestor (LUCA) from which all life on earth diverged.
4. Branch out from the LUCA to form two main groups: Protostomes (which include Mollusca, Arthropoda, and Nematoda) and Deuterostomes (which include Chordata). This division is based on the developmental process of the embryo.
5. Further divide the Protostomes into their respective phyla (Mollusca for the octopus, Arthropoda for the fruitfly, and Nematoda for the roundworm) and place the Deuterostome (Chordata for humans) on a separate branch. This will visually represent the evolutionary distance and relationships among the organisms.

Key Concepts

Phylogenetic Tree

A phylogenetic tree is a diagram that represents the evolutionary relationships among various biological species based on their genetic or physical characteristics. It illustrates how species diverged from common ancestors over time, allowing researchers to visualize the lineage and evolutionary history of organisms. In this context, constructing a phylogenetic tree helps to clarify the relationships between humans, the pygmy zebra octopus, and other model organisms.

Protostomes

Protostomes are a major group of animals characterized by their embryonic development, where the mouth forms before the anus. This group includes diverse organisms such as arthropods and mollusks, which are often used as model organisms in biological research. Understanding protostome biology is crucial for comparing the evolutionary pathways and functional similarities between species like the pygmy zebra octopus and other model organisms like fruit flies and roundworms.

Model Organisms

Model organisms are non-human species that are extensively studied to understand biological processes, disease mechanisms, and genetic functions that may be applicable to humans. They are chosen for their ease of maintenance, rapid reproduction, and genetic tractability. The fruit fly and roundworm are classic examples, providing insights into genetics and development, which can be compared to the potential insights gained from studying the pygmy zebra octopus.