Problem 23 - Biology

Question

The sister taxon of the Chordata is the ___________. a. Mollusca b. Arthropoda c. Ambulacraria d. Rotifera

Step-by-Step Solution

Answer

c. Ambulacraria

Step 1: Understand the Question

Identify what is being asked. In this case, the question is asking for the sister taxon of Chordata.

Step 2: Define 'Sister Taxon'

A sister taxon is the closest relative of a group in a phylogenetic tree, sharing a common ancestor.

Step 3: Analyze the Options

Consider the provided taxa: a. Mollusca, b. Arthropoda, c. Ambulacraria, and d. Rotifera.

Step 4: Compare Phylogenetic Relationships

Chordata is a group that includes vertebrates. Compare each option to determine which is the sister group based on evolutionary relationships.

Step 5: Select the Correct Answer

Ambulacraria, which includes Echinoderms and Hemichordates, is the closest relative to Chordata. Thus, the sister taxon to Chordata is Ambulacraria.

Key Concepts

phylogenetic tree

A phylogenetic tree is a visual representation of the evolutionary relationships among various groups of organisms. Imagine it like a family tree but for species.
Each branch point represents a common ancestor, and the branches show how different species or groups evolved from that ancestor.

When reading a phylogenetic tree, the tips of the branches represent the current species, while the nodes (where branches split) represent common ancestors. Here's an important tip: the closer the branches are, the closer the evolutionary relationship between those species.

Phylogenetic trees can help us understand a lot about how different organisms are related and how they have diversified over time.

evolutionary relationships

Evolutionary relationships describe how different groups of organisms are related based on shared traits and common ancestry.
These relationships are often depicted in phylogenetic trees to make them easier to visualize.

Let's break this down a bit:

• Organisms that share a recent common ancestor are closely related. They are more likely to have similar characteristics.
• Organisms that diverged a long time ago are less closely related. They have had more time for their traits to evolve differently.

A key term here is 'sister taxa.' Sister taxa are groups that share an immediate common ancestor. This means they evolved from the same branch point on the phylogenetic tree.
For example, in the problem you looked at, Chordata's sister taxon is Ambulacraria, which means they share a recent common ancestor.

Ambulacraria

Ambulacraria is a supergroup of marine animals that includes two main groups: Echinoderms (like starfish and sea urchins) and Hemichordates (like acorn worms).
These animals have some common features like a larval stage and a simple nervous system.

Ambularcaria is important in evolutionary biology because of its close relationship to the Chordata, the group that includes all vertebrates. Together, Chordata and Ambulacraria form the larger group called Deuterostomes.

Studying Ambulacraria can help scientists understand more about the early evolution of animals, including how more complex systems in vertebrates evolved from simpler beginnings.