"Natural Science 4" is an interactive encyclopedia that includes scientific information in the understanding of fourth grade students, wonderfully illustrated and animated.
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* Chapter 1 Lesson 3 *
* Animal life cycle *
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Animals are living organisms that are born, grow , develop, reproduce and die. During their life, their body undergoes several changes in shape, size, color, passing through several stages of growth and development. These stages in a being's life form a life cycle.
The life cycle as well as its duration differs from one species to another. Some animals have very short life cycles. Mayflies, for example, live only one day as adults. But enough to breed and lay eggs. Other species are able to give birth only a few months after birth. For example, a house rabbit becomes an adult 5-6 months after birth and can breed. There are also very long-lived animal species. You've surely heard of the Galapagos tortoise. It lives over 150 years.
Returning to insects, they are the most numerous living things on the surface of the earth. They reproduce through eggs.
The butterfly has a very interesting life cycle. It includes a series of spectacular transformations of appearance and lifestyle. The totality of these transformations is called metamorphosis.
The adult butterfly lays eggs on a leaf. They are about the size of pinballs. From each egg, after a few days, a very small larva or caterpillar will emerge. The caterpillar consumes a large amount of leaves and grows in size. This is the reason why she molts several times, that is, she changes her skin. After a few weeks, the caterpillar stops eating, looks for a safe place, usually under a leaf, hangs on to it and begins to build a cocoon, pupa or chrysalis. It is a stage where the butterfly will sleep for a long time and molt for the last time. At some point, it will start to pierce the cocoon and instead of a caterpillar, a beautiful butterfly will emerge.
Like insects, birds reproduce through eggs.
Inside the egg is the embryo, that is, the future chick. Most birds have a strong maternal instinct. They incubate their eggs for several weeks, warming them with their own bodies. During this time, the embryo develops using the nutrients contained in the egg. Chicks will emerge from them, which are cared for and fed by the parents. Once mature, the young birds are ready to lay eggs as well.
But how do fish reproduce? Of course, also through eggs.
The female lays a lot of spawn in the shallower but vegetated water. Fish eggs are shellless. Although they are not hatched, . From these will come out the young that look like their parents, only they are smaller in size.
Reptile eggs can be encased in either a thick shell or a leathery shell.
The female lays her eggs on the ground or buries them in the sand, to hatch with the help of the sun. The incubation period varies from a few days to several months.
The life cycle of amphibians, of which group frogs are also a part, includes three stages: egg, larva and adult. The transition from the larval stage to the adult stage involves a radical transformation.
Amphibian eggs do not have a shell, but are housed in a gelatinous mass. Each egg will hatch into a small larva, called a tadpole. It differs greatly from the adult in terms of appearance, food and lifestyle, being similar to a fish. It lives and breathes only in water, through its gills. After a while, the tadpole transforms. Following this transformation, the adult amphibian appears.
Mammals give birth to live young that they feed with their own milk.
In most mammals, the embryo develops in the mother's abdomen over a different period of time, depending on the species. This can vary from 16 days, in the case of the hamster, to 660 days, in the case of the elephant. During this period, the embryo (i.e. the fetus) begins to develop and is nourished by the mother's blood. At the end of this period, the female gives birth to one or more cubs, which resemble their parents in appearance. A female can give birth several times during her lifetime.
But not all mammals give birth to fully developed young. Marsupials continue their growth even after birth, in the mother's pouch. This is an outer pocket where the milk-producing mammary glands are also located. This category includes kangaroos, koalas and opossums.
Describe the life cycle of your favorite animal!