36 Life Cycles-High

Life Cycles Written by Ned Jensen

《生命周期》作者:Ned Jensen

Introduction Most living things, or organisms, go through several stages during their lives. During each stage, these organisms change. When they reach the adult stage, they often produce new living things of their own type. The adult stage ends when an organism dies. The stages an organism goes through are called its life cycle. All plants and animals go through changes from the very beginning of their lives to the end of their lives. They all have life cycles. You, too, are an organism. You have gone through stages of change. And you will continue to change as you grow older.

大多数生物或有机体在其一生中会经历几个阶段。 在每个阶段，这些生物体都会发生变化。 当它们到达成年阶段时，它们通常会产生自己类型的新生物。 成体阶段在有机体死亡时结束。 有机体所经历的阶段被称为生命周期。 所有的植物和动物从生命的开始到生命的结束都会经历变化。 它们都有生命周期。 你也是一个有机体。 你已经经历了改变的阶段。 随着年龄的增长，你会继续改变。

Organisms of the same type go through the same stages of change. Humans, cats, dogs, cows, and bears are similar organisms. They are called mammals. Mammals go through similar stages. Different types of animals, such as birds, frogs, and snakes, have different kinds of life cycles. They go through different stages of change. Plants have life cycles that are different from all animal life cycles. This book is about the life cycles of different organisms. As you read you will learn how the life cycles of these organisms are different.

同一类型的生物经历相同的变化阶段。 人、猫、狗、牛和熊都是类似的生物。 它们被称为哺乳动物。哺乳动物也经历了类似的阶段。 不同类型的动物，如鸟类、青蛙和蛇，有不同的生命周期。 他们经历了不同的变化阶段。 植物的生命周期不同于所有动物的生命周期。 这本书讲的是不同生物的生命周期。 在阅读过程中，你将了解到这些生物的生命周期是如何不同的。

Human Life Cycle Let's begin by looking at a life cycle that is important to you— the human life cycle. The human life cycle begins with a tiny egg. This egg grows inside a mother organism. The egg soon becomes a small embryo. An embryo is a bunch of cells that are just starting to grow into a baby organism. After about two months, the human embryo begins to look like a human. It is still very small, but it has a head, arms, legs, and other human body parts. For another seven months, the human organism develops inside the mother's body.

人类生命周期让我们从一个对你很重要的生命周期开始——人类的生命周期。 人类的生命周期始于一个小小的卵子。 这个卵生长在母体内。 卵子很快就变成了一个小胚胎。 胚胎是一堆刚刚开始成长为婴儿有机体的细胞。 大约两个月后，人类胚胎开始长得像人。 它还很小，但它有头、胳膊、腿和其他人体部位。 在接下来的七个月里，人类的有机体在母亲的体内发育。

After nine months inside the mother, the baby is born. At this time, the stage is called infancy, and the organism is called an infant. An infant depends on its mother for everything. It cannot walk, talk, or feed itself. Word Wise Here are three prefixes that represent numbers. tri = 3 quad = 4 quint = 5 A mother may have more than one egg growing inside her at the same time. If two eggs are growing, twins will be born. Three eggs will produce triplets. Four eggs will produce quadruplets. And five eggs will produce quintuplets.

在母体内9个月后，婴儿出生了。 在这个时候，这个阶段被称为婴儿期，有机体被称为婴儿。 婴儿事事依赖母亲。 它不能走路，不能说话，也不能自己吃饭。 这里有三个代表数字的前缀。 tri = 3 quad = 4 quint = 5一位母亲可能同时有一个以上的卵子在她体内生长。 如果两个卵子在生长，双胞胎就会诞生。 三个鸡蛋会生三胞胎。 四个卵子将产生四胞胎。 五个卵子会生五胞胎。

At around two years of age, an infant leaves the infancy stage and enters a stage called childhood. Childhood lasts for about 10 years. Then a child enters a stage called adolescence. In this stage, a human develops the ability to make a baby. A human is an adolescent until about 18 to 20 years of age. The adolescent then becomes an adult. The adult is the longest stage in the human life cycle. A human is an adult for the rest of his or her life. Do You Know? The oldest known human was a French woman who lived 122 years.

在大约两岁的时候，婴儿离开婴儿期，进入童年期。 童年大约持续10年。 然后孩子进入一个叫做青春期的阶段。 在这个阶段，人类发展出了制造婴儿的能力。 一个人在18到20岁之前都是青少年。 然后，青少年成长为成年人。 成人是人类生命周期中最长的阶段。 一个人的余生都是成年人。 你知道吗?已知最长寿的人类是一位法国妇女，她活了122岁。