22. Why are spongin and spicules important to a sponge?
The spicules are made up of calcium and silica.
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23. What are the four characteristics common to most animals?
1) Cellular structure
2) The nature of coelom
3) Notochord
4) Segmentation or absence of segmentation
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24. List the features that all vertebrates show at some point in their development
1) Embryonic germ layer a) Endoderm, b) Ectoderm - Two germinal layers.
2) a) Ectoderm, b) Endoderm, c) Mesoderm - Three germinal layers
3) Organogenesis
i) Ectoderm - Skin, Hair, Nerve, Tooth, Nail
ii) Endoderm-Intestine lung, Liver
iii) Mesoderm - Muscle, Bones, Heart
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25. Compare closed and opened circulatory system
Open Circulation
i. There is no blood vessels
2. Blood remains filled in the tissue spaces.
3. (Eg.) Arthropods, Mollusca, Echinodermata.
Closed Circulation
i. Presence of blood vessels.
ii. Blood is circulated through blood vessels.
iii. (Eg.) Earthworm, Cephalochordates, Chordates
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26.Compare Schizocoelom with enterocoelom
Schizocoelomates
Body cavity is formed by spilitting of mesoderm.
(Eg.) Annelids, Arrthopods
Enterocoelomates
The body cavity is formed from the Mesodermal pouches or archenteron.
(Eg.) Echinodermata Chordates
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The archenteron becomes the digestive tract (or primitive gut) of the developing animal. Formed during the gastrulation stage of embryonic development, this hollow pouch eventually develops into the stomach, intestines, and other components of the gastrointestinal system
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a) Sea anemone
b) Radial symmetry
c) It is not a cephalized animal
d) Diploblastic animal
e) One
f)Yes
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Unrelated characters: Radial Symmetry
1) Notochord, Cephalization dorsal nerve chord, are characteristic features of chordate animals.
Radial Symmetry
This is the feature of invertebrate organism.
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Flatworms are called acoelomates because they completely lack a coelom—a fluid-filled, mesoderm-lined body cavity between the digestive tract and the outer body wall.
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Trochopore larva is seen in the Phylum - Annelida.
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1) The body is spindle shaped skin is covered by ganoid cycloid or Ctenoid scales.
2) They have four pairs of filamentous gills with operculam on either side.
3) Air bladder helps in gaseous exchange and for maintaining buoyancy.
4) Sexes are separate.
5) They have lateral line sense organs. The kidney is mesonephric.
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The air bladder (or swim bladder) in bony fishes is primarily a gas-filled hydrostatic organ that helps fish maintain neutral buoyancy. By adjusting the gas volume within this organ, fish can effortlessly float, sink, or hover at a specific depth without wasting energy
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1) The body of reptile is covered by dry and cornified skin with epidermal scales or scutes.
2) All are poikilotherms.
3) Most reptiles lay cleidoic eggs.
4) Excretion is by metanephric kidneys and are uricotelic.
5)
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No, the number of eggs or young ones produced by an oviparous and viviparous mother cannot be equal. The number of eggs laid by the oviparous animals are always more in number than the young ones produced by viviparous animals.
Viviparous animals: Viviparous animals are those animals in which both the fertilization (i.e. the fusion of male and female gametes) of egg that results in zygote and development of embryo take place inside the body of the female in the mother's womb.These animals give birth to young ones directly.Examples – mammals such as cows, goats, dogs, humans, etc.
Oviparous animals: Oviparous animals are those animals in which both the process of development of embryos take place outside the body of the female.In oviparous animals fertilization can occur inside the mother’s body or outside the mother’s body.Oviparous animals lay eggs outside their body. Example – birds, hen, frogs, etc
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