60 Questions
Which type of heart has no neural control to regulate pumping?
Three-chambered heart
What is the main difference between the circulatory system of open and closed systems?
Extent of the capillary system
How do O2 and CO2 mainly get transported in organisms with no blood specifically involved in their transport?
Via diffusion
What is the function of flame cells in nonvertebrate chordates?
Cellular filtration
In ancestral vertebrates, how are body fluids different from those of nonvertebrate chordates?
Different ionic composition
What is the role of archinephric ducts in ancestral vertebrates?
Excreting waste to the cloaca
What is the main difference in development between vertebrates and invertebrates?
Vertebrates use inductive interactions between developing structures to determine cell types, while invertebrates have predetermined cell lineages.
What is the role of Hox genes in development?
Regulate the expression of a network of other genes
Which germ layer forms the nervous system, including most of the sense organs?
Ectoderm
How many Hox genes do vertebrates typically have?
Thirteen
Which germ layer forms the rest of the digestive tract's lining as well as the glands associated with the gut?
Endoderm
What distinguishes vertebrates in terms of Hox genes?
They have undergone duplications of the entire Hox complex
When did the first duplication event of the Hox complex occur?
Start of vertebrate evolution
What does the mesoderm germ layer form?
Muscles, skeleton, connective tissues, circulatory system, and urogenital system
Which gland is formed by the endoderm germ layer?
Liver
What role does Neural Crest tissue play in embryological development?
Forms novel structures, especially in the head region
Why is the mesoderm germ layer considered significant in development?
It is the last layer to appear in animal evolution.
How did the doubling and redoubling of the Hox gene sequence impact vertebrates?
Allowed for more structural complexity
What type of tissue layer lies between the dermis and the fascia overlying the muscles in tetrapods?
Hypodermis
What is the main function of the subcutaneous fat stored in the hypodermis of tetrapods?
Generating heat
Which type of mineral is unique to vertebrates and provides resistance to acid, especially during anaerobic metabolism?
Hydroxyapatite
Why might vertebrates have evolved a skeleton made of hydroxyapatite instead of calcite?
To resist blood acidification during anaerobic metabolism
What are the hydroxyapatite crystals aligned on in the mineralized tissues of vertebrates?
Matrix of collagenous fibers
In which region of tetrapods are subcutaneous striated muscles found?
Hypodermis
What is another term used to refer to the pharyngeal arches?
Visceral arches
Which term is used to describe the gill arches in the passage?
Visceral arches
What is the embryonic name for the structures that are referred to as gill arches in adults?
Pharyngeal arches
What does the term 'branchial arches' mean?
Arch bearing gill tissue
What is the relationship between the splanchnocranium and neural-crest tissue?
Splanchnocranium is formed only from neural-crest tissue
In which group of organisms is a structure functionally equivalent to the vertebrate splanchnocranium present?
Cephalochordates and hemichordates
What is the main role of the kidney in volume regulation in freshwater environments?
Regulating volume and concentration of body fluids
Which ions are primarily regulated by the gills?
Monovalent ions
What is the main function of the notochord in vertebrates?
Provides support for body muscles
What is the significance of myomeres in vertebrates?
They have a more complex W shape
Which fins are absent in the initial stages of development?
Lateral fins and median fins besides the tail fin
What is the presence of dorsal fins indicative of in vertebrates?
They are present in all vertebrates except hagfishes
What is the significance of neural crest tissue in vertebrate embryonic development?
Neural crest tissue is a fourth germ layer unique to vertebrates that gives rise to a variety of structures, including pigment cells, and plays a crucial role in shaping the vertebrate body plan.
How does neural-crest tissue in vertebrates differ from a similar population of cells found in amphioxus?
In vertebrates, neural-crest cells migrate throughout the body and differentiate into different cell types, while in amphioxus, these cells do not migrate or change into different cell types.
What are placodes and how do they contribute to vertebrate development?
Placodes are epidermal thickenings that give rise to sensory organs like the nose, eyes, and inner ear in vertebrates.
What morphological feature shared between tunicates and vertebrates may indicate a precursor to the vertebrate neural crest?
The presence of cells resembling migratory neural-crest cells in the larval stage of a tunicate species, which differentiate into pigment cells.
What implications would the presence of eyes and a muscular pharynx in the Cambrian chordate Haikouella have in terms of neural crest evolution?
The presence of eyes and a muscular pharynx in Haikouella would imply the presence of neural crest in this animal.
How do neural-crest cells contribute to the formation of structures in vertebrates?
Neural-crest cells migrate throughout the body and differentiate into various cell types, contributing to the development of structures like pigment cells, craniofacial bones, and peripheral nervous system components.
What is the exception in the genes coding for the vertebrate brain found in amphioxus?
those directing formation of the telencephalon
What reinforces the belief that differences in gene expression are as important as differences in gene presence?
the presence of vertebrate brain genes in amphioxus
What are two unique vertebrate features mentioned in the text?
multilayered epidermis and endothelium-lined blood vessels
What are the main systems contrasted between vertebrates and nonvertebrate chordates in Table 2-1 and Figure 2-4?
heart, brain, and circulatory system
What are some structures found in a generalized chordate like amphioxus?
cerebral vesicle, notochord, nerve cord, pharynx, atrium, gill slit
What is the significance of the tripartite brain in hypothetical primitive vertebrates?
It represents an early stage of brain evolution
What is the function of the subcutaneous striated muscles found in the hypodermis of mammals?
Enable them to flick the skin to get rid of a fly
Why is hydroxyapatite preferred over calcite in vertebrates' mineralized tissues?
Hydroxyapatite is more resistant to acid, making it suitable for anaerobic metabolism.
Describe the composition of vertebrate mineralized tissues.
Complex matrix of collagenous fibers, cells secreting a tissue matrix, and hydroxyapatite crystals aligned on collagenous fibers.
Explain the structure of hydroxyapatite crystals in vertebrate mineralized tissues.
Aligned on the collagenous fibers in layers with alternating directions, similar to plywood.
Where is subcutaneous fat stored in tetrapods?
Hypodermis or subcutaneous tissue layer
What type of tissue layer contains collagenous and elastic fibers in tetrapods?
Hypodermis or subcutaneous tissue layer
What is the structure from which teeth form in jawed vertebrates?
Dermal papilla
How are teeth of jawed vertebrates structurally composed?
Inner layer of dentine and outer layer of enamel or enameloid around a central pulp cavity
What controversial debate exists regarding the origin of dental tissues?
Whether they are always derived from the ectoderm or can form from the endoderm
What is the embryonic origin of teeth in some fishes, contrary to the general belief?
Endoderm
Describe the basic structure of teeth in jawed vertebrates.
Inner dentine layer, outer enamel/enameloid layer, central pulp cavity
What is the structure from which shark scales (dermal denticles) form?
Dermal papilla
Study Notes
Vertebrate Characteristics
- Vertebrates have a closed circulatory system with a heart that pumps blood throughout the body.
- Heart has three chambers: sinus venosus, atrium, and ventricle.
- No neural control of the heart in early vertebrates, but present in all except hagfishes.
Circulatory System
- Closed circulatory system without blood sinuses, except in hagfishes and lampreys.
- Extensive capillary system present in vertebrates.
- Blood involved in the transport of respiratory gases (O2 and CO2) with the help of hemoglobin.
Excretion and Osmoregulation
- Specialized glomerular kidneys present in vertebrates for ultrafiltration of blood.
- Kidneys lead to the outside via the archinephric ducts to the cloaca.
- Body fluids are more dilute than seawater, except in hagfishes.
Development and Germ Layers
- Vertebrates have three germ layers: ectoderm, endoderm, and mesoderm.
- Ectoderm forms the outermost layer, including skin and nervous system.
- Endoderm forms the digestive tract and associated glands.
- Mesoderm forms muscles, skeleton, and circulatory and urogenital systems.
Skeletal System
- Hydroxyapatite, a complex compound of calcium and phosphorus, is unique to vertebrates.
- Skeleton made of hydroxyapatite is resistant to acidification of the blood.
- Hydroxyapatite crystals are aligned on collagenous fibers in layers with alternating directions.
Hox Genes
- Hox genes regulate the expression of a hierarchical network of genes controlling development from front to back along the body.
- Vertebrates have more Hox genes than other animals, with duplications of the entire Hox complex.
Neural Crest
- Neural crest is a new tissue in embryological development that forms novel structures in vertebrates, especially in the head region.
- Neural-crest cells originate at the lateral boundary of the neural plate and migrate throughout the body to form various structures.
Placodes
- Placodes are epidermal thickenings that give rise to complex sensory organs, including the nose, eyes, and inner ear.
- Placodes are similar to neural crest but have a different origin.
Explore the role of Hox genes in regulating the hierarchical network of genes that control development from front to back along the body. Learn about the unique characteristics of vertebrates in terms of Hox gene duplication and complexity.
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