Question

What synapomorphy (shared, derived trait) distinguishes animals as a monophyletic group, distinct from choanoflagellates? a. multicellularity b. coloniality c. heterotrophy d. movement

Short answer

a. Multicellularity

Step-by-step solution

Understand the terms

To answer this question, we need to understand the following terms: 1. Synapomorphy: A characteristic that is shared among a group of organisms and is derived from a common ancestor. 2. Monophyletic group: A group of organisms that includes an ancestor and all of its descendants. 3. Choanoflagellates: A group of single-celled aquatic organisms that are considered the closest living relatives of animals.

Analyze each option

Let's analyze each option to find the shared derived trait that distinguishes animals from choanoflagellates: a. Multicellularity: Animals are multicellular, whereas choanoflagellates are single-celled. The emergence of multicellularity is a significant event for the diversification of animals. This is a strong candidate for the answer. b. Coloniality: While some choanoflagellates form colonies, animals are not exclusively colonial. This option is not unique enough to distinguish animals as a monophyletic group from choanoflagellates. c. Heterotrophy: Both animals and choanoflagellates are heterotrophic (they cannot produce their own food). This trait is shared but is not derived. d. Movement: Both animals and some choanoflagellates are capable of movement (though not all animals are motile in their adult form). This trait is not distinctive, as movement is observed in both groups.

Choose the correct answer

Among the given options, multicellularity is the only shared derived trait that is unique to animals, distinguishing them as a monophyletic group apart from choanoflagellates. As a result, the correct answer is: a. Multicellularity

Key concepts

Multicellularity

Multicellularity is a fundamental characteristic that distinguishes animals from their closest relatives, the choanoflagellates. Unlike single-celled organisms, multicellular organisms consist of many cells that work together to perform the complex functions required to sustain life. This evolution allowed for the specialization of cells, where different cells take on specific roles such as digestion, reproduction, and movement.
This organization increases efficiency and enables organisms to grow larger and become more complex.

• Multicellularity involves the division of labor among cells which allows for distinct tissue formation.
• It enables organisms to develop diverse structures and functions, increasing overall adaptability and survival.
• This trait was crucial for the emergence and diversification of the animal kingdom.

Monophyletic Group

A monophyletic group, also known as a clade, is a set of organisms that includes an ancestor and all of its descendants. This concept is important in understanding evolutionary relationships as it reflects the evolutionary history of life forms.
Organisms within a monophyletic group share specific genetic and morphological traits inherited from their common ancestor.

• Shared traits are known as synapomorphies, which are used to identify the group.
• Monophyletic groups provide insight into evolutionary processes and speciation events.
• They help in classifying and organizing biological diversity based on shared ancestry.

Animals are considered a monophyletic group because they all derive from a common multicellular ancestor that differentiates them from choanoflagellates, their closest through single-celled lineage.

Choanoflagellates

Choanoflagellates are fascinating organisms due to their position as the closest living relatives of the animal kingdom. They are simple, single-celled organisms found mostly in aquatic environments. Despite their simplicity, they provide significant insights into the evolution of multicellularity.
Choanoflagellates have a unique cell structure characterized by a flagellum surrounded by a collar of microvilli, which they use to feed on bacteria.

• Though unicellular, some choanoflagellates can form simple colonies, offering clues to how multicellularity might have evolved.
• Their genomics and cell processes have helped researchers understand the transition from single-celled to multicellular life.
• Studying choanoflagellates gives us a glimpse into the early ancestral forms of animals.

Animal Diversity

Animal diversity is one of the most fascinating aspects of biology, characterized by the incredible variety of forms and functions observed within the animal kingdom. This diversity stems from the ancient evolution of multicellularity, which set the stage for divergence into a multitude of life forms.
The animal kingdom ranges from simple organisms like sponges to more complex beings like mammals, illustrating wide-ranging adaptability.

• Diverse morphological features allow animals to occupy various ecological niches.
• The adaptability of animals has resulted in their presence in nearly every environment on Earth.
• This diversity is continually shaped by natural selection, leading to new species and forms.

Understanding animal diversity not only enriches our knowledge of life on Earth but also highlights the evolutionary processes that continue to shape organisms today.