Honours / Core Course (CC)
INTRODUCTION TO CHORDATES
►General characteristics and outline classification of Phylum Chordata (Young, 1981)
Q.’Notochord acts as a hydrostatic skeleton’—justify the statement.
Sometimes fluid is held within swell cells and other time resides between core cells of the notochord. The fluid that normally fills the fibrous sheath remains static and does not flow. Such mechanical structure, in which the outer wall encloses a fluid core , are called hydrostatic skeleton. It lies along the body axis to allow lateral flexion but prevents collapse of the body during locomotion.
Functional significance—Upon muscle relaxation, the springy notochord straightens the body. Thus, the notochord prevents the collapse or telescoping of the body and acts as the muscle’s antagonist in order to straighten the body. As a result, alternating side muscle contractions in partnership with the notochord generate lateral waves of body undulation. This form of locomotion may have been the initial condition that first favored the evolution of the notochord.
►General characteristics and classification of sub-phylum Urochordata and Cephalochordata
up to Classes (Young, 1981).
Q.What are the vanadocytes?
i)Tunicate blood has some unusual features. In some species of Ascidiidae and Perophoridae, it contains high concentrations of the transitional metal vanadium and vanadium-associated proteins in vacuoles in blood cells known as vanadocytes.
ii)Some tunicates can concentrate vanadium up to a level ten million times that of the surrounding seawater. It is stored in a +3 oxidation form that requires a pH of less than 2 for stability and this is achieved by the vacuoles also containing sulphuric acid….
Dr. Friedrich Wolfgang Martin Henze (1873∼1956) who first found out high levels of vanadium in the blood cells (coelomic cells) of an ascidian in 1911 at Stazione Zoologica di Napoli.
►Metamorphosis in Ascidia.
►Chordate Features, structure of pharynx and feeding in Branchiostoma
Q.State the feeding mechanism involved in Amphioxus.
Cilia present in stigmata beat to drive out water current from pharynx to atrium to exterior to maintain water current through mouth.
Trapping of food particles: By sticky secretion of mucous cells from endostyle..
Passage of food rope: Mucous entangled food – peripharyngeal ciliary groove – epipharyngeal grooves --esophagus, as a food rope.
Resisting entry of unwanted large particles: By buccal cirri around the mouth.
Receptor for testing water current: Receptor organs, located on velum and atrium.
Regurgiation of unwanted water-current: Performed by closing the atriopore and contracting the pharyngeal musculature.
Nervous regulation: Afferent and efferent nerve fibers regulated by beating of cilia.
►General characteristics and classification of cyclostomes up to order (Young, 1981)
Q.Mention the systematic position of Sphyrna sp.
Sub Phylum: Vertebrata
Sub Class: Elasmobranchii
►General characteristics and classification up to living sub classes (Young, 1981)
Q.What is labyrinthine organ?
A labyrinth fish is one that has a special organ, known as the labyrinth, which allows the fish to breathe air from the surface of the water. The air is forced into the labyrinth organ, to allow the oxygen to be absorbed. Within the labyrinth, cavities are many small maze-like compartments of thin boney plates called lamellae. The lamellae are covered with extremely thin membranes, so thin that oxygen can pass through. Blood within the membranes absorbs the oxygen and carries it throughout the body.
►Accessory respiratory organ
Q. “Swim bladder acts as lung”—justify the statement.
The wall of the swim bladder in many cases (Amia sp) is sacculated and resembles lung. In Polypterus sp the swim bladder is more lung like and gets a pair of pulmonary arteries arising from the last pair of epibranchial arteries.
►Migration in fishes
►Parental care in fishes
Q.How does Betta sp perform parental care?
The male Siamese fighting fish (Betta sp) secrete excessive mucus and blows air bubble through it forming a surface bubble nest where the eggs are deposited by male on collecting it in their mouths. The after care is taken over by males, who defend it to death.
►Swim bladder in fishes.
►General characteristics and classification up to living Orders (Young, 1981)
Q.Distinguish between Anura and Caudata.
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Metamorphosis is iodothyronine-induced and an ancestral feature of all chordates.
Q.What is heterochrony?
This is a change in the timing of events during development. A vertebrate lineage that retained juvenile characteristics when it was sexually mature would have a proportionally larger head and eyes than normal for its sister group (Alberch et al. 1979; McKinney and McNamara 1991).
Example—The oral disk of Lampreys enlarges early in their larval ontogeny. However, in a few parasitic forms remain small until later at sexual maturity, where it enlarges.
►Parental care in Amphibia
Q.State with reason whether viviparity exists in amphibian parental care.
This mode of parental care exists in some representatives. This extreme modification is observed in Salamandra atra and Salamandra maculosa. The eggs are placed inside the uterine cavity where entire tadpolehood is completed. Two eggs are laid at a time. The larvae remain attached with the uterine wall by membrane which functions physiologically in the manner of a primitive placenta. The broad and vascular tail also helps in metabolic exchanges.
►General characteristics and classification up to living Orders (Young, 1981)
►Poison apparatus and Biting mechanism in Snake.
Q.What does proteroglyph mean?
Snakes those have permanently erect grooved poison fangs, with ordinary teeth behind them in the jaws. It includes the cobras, Kraits, and the sea snakes (Elapidae). It includes the following features—
i.Location of Poison groove – all along the surface.
ii.Located in front of maxilla & oftenly with several small solid teeth behind the fangs.
iii.Fangs are extremely and permanently erect.
iv.The fangs are each connected by a venom duct to a venom gland.
v.They use muscular contraction of the venom gland to inject the venom into the prey.
vi.Rigid fangs fit into pockets in the outer gum of the lower jaw.
►Poisonous & Non-Poisonous snake.
Q.Give scientific names of two poisonous and two nonpoisonous snakes found in India.
i)Common Krait (Bungarus caeruleus), ii)Indian cobra (Naja naja), iii)Russell’s Viper (Vipera russelli)
i)heckered keelback or Asiatic water snake (Xenochrophis piscator), ii) The buff striped keelback (Amphiesma stolatum).
►General characteristics and classification up to living Sub-Classes (Young, 1981).
Q.What is pterylosis?
Pterylosis refers to the arrangement of feathers and how they are implanted in the skin, while ptilosis refers to the properties of the feathers themselves. Each feather originates from the epidermal layer of the skin and are arranged in definite tracts called pterylae, which are separated from the featherless tracts, called apteria.
►Exoskeleton and migration in Birds
►Principles and aerodynamics of flight
Q.What do you mean by aerodynamic drag?
This is the force opposite to the direction of motion and hence the source of energy loss in flight. The drag foce can be separated into two portions. Lift –induced drag, which is inherent in the wing (primarily arising from wingtip vortices) and parasitic drag , including skin friction drag from the friction of air and body surfaces and form drag from the bird’s frontal area. The streaming of bird’s body and wing reduces these forces.
►General characters and classification up to living sub classes (Young, 1981)
►Exoskeleton derivatives of mammals
Q.Distinguish between horn and antler.
►Adaptive radiation in mammals with reference to locomotory appendages
►Echolocation in Micro chiropterans
Q.What is Doppler effect? Briefly illustrate how echolocation in bats is dependent on Doppler effect?
An increase (or decrease) in the frequency of sound, light or other waves as the source and observer move towards each other. The effect causes the sudden change in pitch noticeable in a passing siren, as well as the red shift seen by astronomers.
The echoes coming back from any insect show the Doppler effect, which is if a sound source is moving toward us, the sound will have a higher pitch. If it is moving away, the sound will be of lower pitch. The horseshow-noses bat emits a signal at 83.4 kHz. If echoes coming back from the insect (prey) are at 83.4 kHz then according to the effect the horseshoe-nosed bat that the insect is flying away from it at the same speed that the bat is travelling (For further information follow contact).