What defines homologous organs in biology?
They have different forms but a similar structural plan and body position from a common ancestor.
What characterizes analogous organs?
They share a function without necessarily sharing morphology or ancestry.
Why are insect and bird wings considered analogous?
Because they perform flight but do not share the same anatomical origin.
Who presented an evolutionary theory of homology in 1866?
Haeckel presented it in 1866.
Who discussed the evolutionary theory of homology in 1872?
Darwin discussed it in 1872.
What defines an organ in the body?
A distinct body part with specific structure, shape, position, and function.
What happens during rudimentation of an organ?
An organ loses its function but remains after embryonic development.
What is afanizia in organ development?
An organ appears during embryogenesis and later disappears completely.
What does ontogeny describe in biology?
The individual development relationships of an organism.
What does phylogeny describe in biology?
The historical evolutionary development relationships of an organism.
What three features characterize chordates?
A notochord, a dorsal hollow nerve tube, and a respiratory region in the anterior intestine.
What are the three chordate subphyla?
Cephalochordata, Urochordata, and Vertebrata.
Name one of the five shared chordate characteristics.
The notochord.
Name another shared chordate characteristic besides the notochord.
Pharyngeal slits.
What is the dorsal hollow nerve tube in chordates?
A shared chordate characteristic.
In which phylum is Amphioxus classified?
Chordata
Which genus does Amphioxus belong to?
Branchiostoma
How many Branchiostoma species occur worldwide?
Approximately 9 species
Where can Branchiostoma species be found?
In all oceans and the Mediterranean Sea
What is the body shape of Amphioxus?
Lance-shaped
What is the size range of Amphioxus?
5–8 cm
Which fin folds does Amphioxus have?
Dorsal, caudal, and ventral fin folds
What is the amphioxus notochord?
An elastic axial structure beneath the nerve tube extending along the entire body.
How does water flow through amphioxus's body?
From mouth to pharynx, through pharyngeal slits and atrial cavity, exits via atriopore.
Where does the digestive tract of amphioxus end?
At the anus.
Does amphioxus have a differentiated heart?
No, it does not have a differentiated heart.
What drives circulation in amphioxus?
A venous sinus and dorsal and ventral vessels connected through branchial vessels.
What type of excretory organs does amphioxus have?
Numerous nephridial organs with nephrostomes opening into the coelomic cavity.
Where do the outlets of amphioxus nephridial organs open?
Into the atrial cavity.
What are three functions of the integumentary system?
Protection, material exchange, and thermoregulation.
Which germ layers form vertebrate skin?
Ectoderm forms the epidermis and mesoderm forms the dermis.
What are the four principal epidermal cell types?
Keratinocytes, melanocytes, Langerhans cells, and Merkel cells.
What type of connective tissue is the papillary dermis?
Loose areolar connective tissue.
What type of connective tissue is the reticular dermis?
Thicker dense irregular connective tissue.
What are the main functions of the vertebrate skeleton?
Body support, organ protection, movement, mineral and fat storage, and blood-cell formation.
Through which stages does the vertebrate endoskeleton develop?
Connective-tissue, cartilaginous, and bony stages.
Does the sequence of endoskeleton development stages vary among vertebrate groups?
Yes, the sequence varies among groups.
What type of ossification forms bone directly from mesenchyme?
Intramembranous ossification.
Which ossification type forms bone on a hyaline-cartilage model?
Endochondral ossification.
What is the first step in endochondral ossification?
Cartilage-model formation.
What follows bone-collar formation in endochondral ossification?
Primary ossification center formation.
What is the final step in endochondral ossification?
Growth-plate closure.
What are the three vertebrate muscle tissues?
Smooth muscle, skeletal striated muscle, and cardiac striated muscle.
What is a key cellular feature of a skeletal-muscle myofiber?
It is multinucleate.
How do fast and slow skeletal muscle fibers differ in contraction and fatigue?
Fast fibers contract rapidly and fatigue quickly; slow fibers resist fatigue.
Why are slow skeletal muscle fibers darker than fast fibers?
They contain more myoglobin.
What is a sarcomere in muscle tissue?
The contractile unit of skeletal and cardiac muscle from one Z-disk to the next.
What filaments overlap within a sarcomere?
Actin and myosin filaments.
What does the central nervous system contain?
The brain and spinal cord.
What does the peripheral nervous system contain?
Nervous tissues outside the central nervous system.
What is a neuron?
The structural and functional unit of the nervous system.
How does a neuron conduct excitation?
Through its cell body, dendrites, and axon.
What is the role of neuroglia?
To support neurons physiologically, metabolically, and developmentally.
Which neuroglia insulate axons?
Oligodendrocytes and Schwann cells.
What cells line the central canal?
Ependymal cells.
What is the sequence of neurons in a vertebrate reflex pathway?
From sensory neuron to associative neuron to motor neuron.
Which parts organize the vertebrate digestive tract?
Mouth, pharynx, esophagus, stomach, small intestine, large intestine, and terminal anus or cloaca.
What are the three basic layers of the intestinal wall?
Mucosa, muscular layer, and serosa.
What is the main function of the small intestine?
It is the principal site of digestion and absorption.
What is the main function of the large intestine?
It mainly absorbs and processes residual material.
Which are the two principal accessory digestive glands in vertebrates?
The liver and pancreas.
What distinguishes internal from external respiration?
Internal respiration exchanges gases between tissues and cells; external respiration exchanges gases across respiratory surfaces with the environment.
What are the two fundamental vertebrate respiratory organs?
Gills and lungs.
From which embryonic layer do vertebrate gills and lungs develop?
Endodermal derivatives of the anterior intestine.
What structures separate pharyngeal slits in amphioxus?
Primary and secondary branchial septa.
What function do ciliated epibranchial and hypobranchial grooves serve in amphioxus?
They retain food particles in the water.
What is the swim bladder of bony fish?
A blind dorsal evagination of the esophagus that regulates specific body weight.
How do physostomous and physoclist fish differ in swim bladder structure?
Physostomous fish have an open swim bladder; physoclist fish have a closed one.
How do vertebrate lungs differ from gills in blood circulation?
Lungs receive pulmonary arteries and return oxygenated blood via pulmonary veins; gills are part of branchial arterial circulation.
Test your knowledge with 34 questions on Vertebrate Zoology.
1. What distinguishes homologous organs from analogous organs?
2. Why are insect wings and bird wings classified as analogous organs?
Review the complete course in the study sheet for Vertebrate Zoology.
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