Animals World

Some interesting facts about Animals:

  • Reproductive Modes of Frogs Gladiator frogs are large treefrogs that construct nests in which eggs are deposited. Nests are made by males, who pivot around in soft sand or mudat the edge of a pond or stream to make a depression that fills with water. Eggs are deposited as a surface film in the nest. Glass frogs deposit a small clutch of eggs on a leaf overhanging a small stream or river. When the eggs hatch, the tadpoles fall into the water below. Leptodactylus frogs construct foam nests for their eggs. An amplexing male and female rotate their legs rapidly and secretions emitted with the eggs and sperm are whipped into a meringuelike froth. Eggs and tadpoles develop entirely within the foam; most predators cannot enter the sticky foam. Poison frogs deposit their small clutches of eggs on land. The male (but sometimes the female) guards them. After the eggs hatch, the parent transports the tadpoles on his or her back to a small pool or stream where the tadpoles undergo the rest of their development. Eleutherodactylus frogs deposit small clutches of eggs on land. Development of the egg to a small froglet occurs entirely within the egg capsule. Gastric-brooding frogs swallow their eggs, and development of the tadpoles occurs in the mother's stomach. A chemical secreted by the developing tadpoles inhibits the production of gastric fluids so that the tadpoles are not digested.

  • Fly Wings In the fruit fly Drosophila, each wing develops froma packet of epithelial cells called the imaginal disk. The imaginal disk grows into a wide, baglike structure that flattens out to become a transparent wing only a few cells thick. Hemolymph-filled veins along the anterior wing margin and within the wing support the fragile wing and supply the wing cells with nutrients and water. Drosophila powers its single pair of wings quite differently than the more primitive dragonflies and grasshoppers that have two pairs of wings. Flies have internal dorsoventral (vertical) muscles on each side of the body that pull the top of the thoraxdownwhen they contract. This moves each of the wings up because the wing bases are inserted into the top of the thorax. Contracting longitudinal muscles (running along the length of the thorax) force the top of the thorax back to its original position. This causes each of the wings to move down. Wing movement in most advanced flying insects is associated with the extremely rapid deformation of the thorax. Houseflies can flap their wings up to two hundred times per second, whereas gnats can flap up to one thousand times per second. The wings of true flies not only flap up and downbut they also alter their angle of attack while moving forward during the down stroke and moving backward during the upstroke. These complex movements provide both lift and thrust and require a number of highly evolved muscle groups.

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