Gnathostomes Flashcards

Questions and Answers

What are gnathostomes?

Jawed fishes.

What are the derived characteristics of gnathostomes? (Select all that apply)

Lateral line system (correct)

Feeding without teeth

Hox duplication (correct)

Jaw (correct)

How did the development of jaws help gnathostomes?

Provided a clamping motion for food, allowed for a broader diet range.

What does more hox duplication mean for an organism?

It means more complex morphology. Signup and view all the answers

What does genome duplication allow for in organisms?

Performing more complex functions. Signup and view all the answers

What is gene duplication?

A random mutation event during meiosis. Signup and view all the answers

What happens during nonfunctionalization of duplicated genes?

One duplicated gene loses its function. Signup and view all the answers

What is neofunctionalization in gene duplication?

One gene takes on a new function. Signup and view all the answers

What is subfunctionalization?

When the two genes have different functions. Signup and view all the answers

What is the lateral line system?

Vibration sensing organs on the body. Signup and view all the answers

Why did early gnathostome fossils outnumber jawless vertebrates?

They were excellent swimmers and eaters. Signup and view all the answers

What characterized Dunkleosteus?

Big, armored first vertebrate super predator. Signup and view all the answers

What are acanthodians also known as?

Spiny sharks. Signup and view all the answers

What are the derived characteristics of chondrichthyans?

Cartilaginous skeleton, placoid scales, well-developed paired fins. Signup and view all the answers

How do chondrichthyans respire without lungs or a swim bladder?

By ram ventilation. Signup and view all the answers

What are the copulatory organs of chondrichthyans?

Claspers. Signup and view all the answers

What is the diversity and ecology of chondrichthyans?

1000 species, mostly marine, successful predators. Signup and view all the answers

What distinguishes elasmobranchii?

Sharks, rays, and skates with oviparity and viviparity. Signup and view all the answers

What are holocephali?

Ratfish, mostly found in deep water. Signup and view all the answers

What are osteichthyans?

Bony fishes. Signup and view all the answers

What are the derived characteristics of osteichthyans?

Dermal fin rays, swim bladders. Signup and view all the answers

Study Notes

Gnathostomes Overview

Gnathostomes are jawed fishes, characterized by the development of jaws aiding in a broader diet.
Key derived characteristics include a jaw, four sets of Hox genes due to duplication, complete genome duplication, and the lateral line system.

Evolutionary Significance of Jaws

Jaws evolved from anterior rods of gill slits, providing a clamping action for feeding.
Allows grasping, shearing, and chewing, enhancing dietary options.

Genetic Adaptations and Duplications

Hox gene duplication allows for greater morphological complexity in organisms.
Genome duplication enables advanced functions and capabilities in species.
Gene duplication occurs through random mutation during meiosis, increasing mutation rates. Beneficial mutations can be passed on, leading to new functions or losses of function (nonfunctionalization).

Types of Duplicated Genes

Nonfunctionalization: one duplicated gene loses its function.
Neofunctionalization: one gene acquires a new function distinct from the ancestral gene.
Subfunctionalization: each gene takes on a different function, both originating from the ancestral gene.

Lateral Line System

A sensory system with mechanoreceptive hair cells that detect water movement.
Essential for detecting predators and prey.

Early Gnathostomes and Fossil Record

Early gnathostomes outnumbered jawless vertebrates due to superior swimming ability and feeding mechanics.
Initial marine species later adapted to freshwater environments.

Notable Groups of Gnathostomes

Placoderms (e.g., Dunkleosteus): Existed 450-360 million years ago, large and armored, known as early super predators with evidence of internal fertilization.
Acanthodians (Spiny Sharks): Lived 430-250 million years ago, characterized by stout spines supporting fins, resembling sharks.

Chondrichthyans (Sharks, Skates, Rays)

Key features: cartilaginous skeletons, placoid scales, well-developed paired fins, internal fertilization.
Respiration is achieved through ram ventilation; constant movement ensures water flows over gills.
Possess claspers for reproduction, located beside the cloaca.

Chondrichthyans Diversity and Ecology

Includes approximately 1000 species, thriving in marine environments globally.
They exhibit both predatory behaviors and filter feeding strategies.

Subclasses of Chondrichthyans

Elasmobranchii: This group includes sharks, rays, and skates. Features include oviparity and viviparity (exclusively in sharks), a sophisticated lateral line, strong chemoreception, and specialized vision with a reflective tapetum lucidum.
Holocephali: Includes ratfish primarily found in deep waters. Characterized by oviparity and males having tentaculums for reproduction, along with a unique jaw structure and grinding teeth for consuming crustaceans.

Osteichthyans (Bony Fishes)

Defined by bony skeletons, dermal fin rays, swim bladders for buoyancy, and color vision.
Adaptive reproductive strategies include internal fertilization among various species.

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Description

Explore the fascinating world of gnathostomes, the jawed fishes! This quiz covers key characteristics, including jaw development, genome duplication, and their evolutionary significance. Perfect for students studying marine biology and vertebrate evolution.