Frogs belong to amphibians. They can live in water and land, but they are most suitable for wet environment, but they cannot reproduce without water. Therefore, if they are put in their hands for a short time, they will not die without hurting them wantonly.

Morphological characteristics

Frog body can be divided into three parts: head, trunk and limbs. Frog has four toes on its front foot, five toes on its back foot and webbed feet. There are two slightly bulging small bags on both sides of the frog's head. That's its eardrum. Frogs can hear through it. Frog's back is green, smooth and soft, with patterns, and its abdomen is white. You can hide it in the grass, which makes it easier to catch pests and protect yourself. Its skin can also help it breathe. Its airbag is only available to male frogs. Frogs hunt with their tongues, which contain mucus.

Head

Frog's head is flat, slightly triangular, and its snout is slightly pointed. The mouth is wide and transverse, and consists of upper and lower jaws. There is a pair of nostrils at the front end of the maxillary dorsal side, and the outer edge of the outer nostril has a nasal flap. Eyes are large and prominent, born on the left and right sides of the head, with upper and lower eyelids; There is a semi-transparent transient membrane on the inside of the lower eyelid. When the eyelids are closed, what happens to the position of the eyeball? There is a circular eardrum behind each eye (toad's eardrum is smaller. There are a pair of oval protuberances on the back and upper part of the eye and tympanic membrane, which are called posterior auricular glands. The male frog has a light brown membrane fold inside and behind the mouth corner, which is a sound sac, and it bulges when singing

The limbs < P > The forelimbs are short and consist of five parts: upper arm, forearm, wrist, palm and finger. 4 fingers, no webbed fingers. In the reproductive season, the male frog has an enlarged protuberance on the inside of the base of the first finger, which is called a marriage tumor for holding the right one. The hind limbs are long and developed, which are divided into five parts: thigh, tibia, tarsal, metatarsal and toe. 5 toes, webbed between toes. On the first toe. Nerve cells in frog's eye retina can be divided into five categories, one category only reacts to color, and the other four categories only react to a certain feature of the moving target, and can transmit the decomposed feature signals to the visual center of the brain-the optic tectum. There are four layers of nerve cells on the optic tectum. The first layer reacts to the contrast of moving objects. The second layer can extract the convex edge of the target; The third layer only sees the peripheral edges of the target; The fourth layer only cares about the light and shade changes of the dark front edge of the target. These four layers of features are like drawing on four pieces of transparent paper, overlapping together, which is a complete image. Therefore, among the fast-flying small animals of various shapes, the frog can immediately identify its favorite flies and moths, but has no response to other flying things and static scenery.