Biology: Evolutionary History of Arthropod Body Plan

What is the likely outcome of the origin of Ubx and abd-A Hox genes in the arthropod body plan?

Increased complexity of body segments (correct)
No effect on body segment diversity
Simplification of body segments
Loss of segmentation in arthropods

Which group of invertebrates was used to test the hypothesis about the origin of Ubx and abd-A Hox genes?

Arthropods
Ecdysozoans
Onychophorans (correct)
Nematodes

What is the difference between arthropods and onychophorans in terms of body segment diversity?

Arthropods have diverse body segments, while onychophorans have identical body segments (correct)
Arthropods have fewer body segments than onychophorans
Onychophorans have more body segments than arthropods
Onychophorans have diverse body segments, while arthropods have identical body segments

What is the function of Ubx and abd-A Hox genes in arthropods?

Influence segmentation (C) Signup and view all the answers

What is the likely ancestral relationship between onychophorans and arthropods?

Onychophorans and arthropods share a common ancestor (A) Signup and view all the answers

What is the significance of studying the evolutionary history of arthropods?

To understand the diversity of species on Earth (D) Signup and view all the answers

What is the primary driver of body segment diversity in arthropods?

Changes in the sequence or regulation of existing Hox genes (A) Signup and view all the answers

What is the significance of studying Hox genes in onychophorans?

To test whether arthropod body plan diversity arose from new Hox genes (A) Signup and view all the answers

What is a characteristic feature of modified appendages in arthropods?

They are paired and jointed (B) Signup and view all the answers

What did Carroll and colleagues find in their study of Hox genes in the onychophoran Acanthokara kaputensis?

The presence of all arthropod Hox genes, including Ubx and abd-A (D) Signup and view all the answers

What is a possible outcome of changes in the sequence or regulation of developmental genes such as Hox genes?

Changes in form and body plan (D) Signup and view all the answers

What is a close relative of arthropods that was studied to understand the evolution of body segment diversity?

Onychophorans (A) Signup and view all the answers

What is the significance of the fossil record of the Cambrian explosion in understanding arthropod evolution?

It reveals the gradual evolution of arthropods from lobopod ancestors. (C) Signup and view all the answers

What is a key feature of early arthropods such as trilobites?

They showed little variation from segment to segment. (D) Signup and view all the answers

What is the likely reason for the great diversification of arthropods?

The evolution of specialized appendages for different functions. (B) Signup and view all the answers

What is the significance of the extinction event 250 million years ago?

It led to the extinction of all trilobite species. (A) Signup and view all the answers

What is a characteristic of lobopods, which are thought to be the ancestors of arthropods?

Most of their body segments were identical to one another. (B) Signup and view all the answers

What is a key innovation that contributed to the success of arthropods?

Their segmented body plan and jointed appendages. (A) Signup and view all the answers

What is a fundamental feature of animal body plans that helps explain why most animals are not a hollow ball of cells?

Gastrulation (C) Signup and view all the answers

What is the main difference between radial symmetry and bilateral symmetry in animals?

Radial symmetry has no front and back ends, while bilateral symmetry has two axes of orientation (B) Signup and view all the answers

What is a characteristic feature of sponges that distinguishes them from other animals?

They lack symmetry altogether (B) Signup and view all the answers

What is the likely outcome of changes in the molecular control of gastrulation over millions of years?

It would remain unchanged for millions of years (A) Signup and view all the answers

What is the significance of studying animal body plans in the context of evolution?

It reveals the diversity of body forms that have evolved independently in different lineages (D) Signup and view all the answers

What is the likely reason for the observed differences in body features between closely related species?

It is due to the loss of body features over the course of evolution (B) Signup and view all the answers

What do animal body plans primarily describe?

Morphological and developmental traits (D) Signup and view all the answers

What is the term 'body plan' meant to imply?

A particular set of integrated morphological and developmental traits (A) Signup and view all the answers

What is the significance of studying animal body plans?

To compare and contrast key animal features (B) Signup and view all the answers

What is a characteristic of the ancestors of the human species?

Adapting to open woodlands and savannas (D) Signup and view all the answers

What is a characteristic of the evolutionary history of biological diversity?

A gradual and steady evolution of species over time (C) Signup and view all the answers

What is the context of the concept of body plans in the study of evolution?

Evo-devo, the interface between evolution and development (A) Signup and view all the answers

What is a characteristic feature of bilateral animals?

The ability to move actively from place to place (D) Signup and view all the answers

What is the significance of the process of gastrulation in animal body plans?

It allows for the formation of true tissues in the body (C) Signup and view all the answers

What is a key difference between radial and bilateral symmetry?

The number of imaginary cuts that divide the animal into mirror-image halves (C) Signup and view all the answers

What is the primary characteristic of animal body plans that have true tissues?

The formation of true tissues through membranous layers (D) Signup and view all the answers

What is the significance of the fossil record in understanding the evolution of bilateral symmetry?

It provides evidence for the origin of bilateral symmetry 550 million years ago (B) Signup and view all the answers

What is the primary characteristic of eumetazoan body plans?

The presence of true tissues (D) Signup and view all the answers