26 Inside Living Things-Mid

Inside Living Things Written by Ron Fridell

《生物内部》作者:Ron Fridell

Introduction Suppose you had microscopic X-ray vision. You would be able to take a deep look inside living things. What would you learn? What would you discover deep inside a rose, for example? Or an elephant? Or a human being like yourself? This book will explore these questions by looking deep inside living things.

假设你有显微镜下的x光视力。 你将能够深入观察生物的内部。 你会学到什么?例如，你会在玫瑰的深处发现什么? 还是一头大象?还是像你这样的人类? 这本书将通过深入观察生物的内部来探讨这些问题。

Cells All living things are made of cells. Cells are the smallest units of life. They produce the energy that makes living things grow and function. Some living things have only one cell. Tiny algae, diatoms and protozoa are examples of organisms that have only one cell. All of the activities needed for each organism's survival are carried on in its cell. Organisms with one cell live in a wide range of places. This includes ponds, rivers, and soil. Some one-celled organisms are even found inside the bodies of other living things. Other organisms have many cells. All of the cells work together so the organism can live. The bigger the organism, the more cells it usually has. An organism as big as a whale has trillions of cells.

所有生物都是由细胞组成的。 细胞是生命的最小单位。 它们产生能量，使生物生长和运作。 有些生物只有一个细胞。 小藻类、硅藻和原生动物都是只有一个细胞的生物。 每个有机体生存所需的所有活动都在其细胞中进行。 只有一个细胞的生物生活在广泛的地方。 这包括池塘、河流和土壤。 一些单细胞生物甚至在其他生物体内被发现。 其他生物有许多细胞。 所有的细胞共同工作，生物体才能生存。 生物体越大，通常拥有的细胞就越多。 像鲸鱼一样大的生物体有数万亿个细胞。

There are two basic types of cells: plant cells and animal cells. Let's look at an animal cell. The outer covering of an animal cell is called the cell membrane. This membrane is like a filter. It allows certain things to pass into and out of the cell. Nutrients are allowed to enter the cell. Waste is allowed to exit. Inside the cell membrane is a jellylike fluid called cytoplasm. Other cell parts float in the cytoplasm One important part is the nucleus. The nucleus is like the cell's brain It controls all the cell's activities.

细胞有两种基本类型:植物细胞和动物细胞。 让我们来看一个动物细胞。 动物细胞的外层被称为细胞膜。 这层膜就像一个过滤器。 它允许某些物质进出细胞。 营养物质被允许进入细胞。 废物被允许排出。细胞膜内部是一种叫做细胞质的胶状液体。 细胞的其他部分漂浮在细胞质中细胞核是一个重要的部分。 细胞核就像细胞的大脑，它控制着细胞的所有活动。

In many ways, plant cells are like animal cells. Both have a cell membrane, a nucleus, and cytoplasm. But they also have some parts that are different. A plant cell has a cell wall that surrounds the cell membrane. The cell wall supports the cell. Animal cells do not have cell walls. All cells turn food into energy. Mitochondria are cell parts that change energy, into forms that cells can use to do their jobs. Most cells also have several sac-like structures called vacuoles. These structures store food and water until the cell needs them. They also store waste until it can be removed from the cell. PLANT CELLS: FOOD AND STORAGE Animals have to eat food in order to live. However, plants can make their own food. Plants store a special material called chlorophyll. It is found in the plant's chloroplasts. Chlorophyll absorbs energy from light. The plant uses this energy with other materials from air and water to make food. This process is called photosynthesis. Animal cells do not have chlorophyll or chloroplasts.

在很多方面，植物细胞和动物细胞很像。 两者都有细胞膜、细胞核和细胞质。 但它们也有一些不同之处。 植物细胞有包围细胞膜的细胞壁。 细胞壁支撑着细胞。 动物细胞没有细胞壁。 所有细胞都把食物转化为能量。 线粒体是将能量转化为细胞可以利用的形式的细胞部分。 大多数细胞也有一些囊状结构，称为液泡。 这些结构储存食物和水，直到细胞需要它们。 它们还储存废物，直到可以从细胞中清除。 植物细胞:食物和贮藏动物为了生存必须吃东西。 然而，植物可以自己制造食物。 植物储存一种叫做叶绿素的特殊物质。 它存在于植物的叶绿体中。 叶绿素从光中吸收能量。 植物利用这种能量和空气和水中的其他物质来制造食物。 这个过程叫做光合作用。 动物细胞没有叶绿素或叶绿体。

Different Kinds of Cells Not all cells are alike. An organism's cells differ, depending on their function. To better understand how cells can differ, let's take a look at some kinds of cells found in animals. Most animals have many parts that work together. Each part is made up of different kinds of cells. There are muscle cells, nerve cells, blood cells, and hundreds of other types of cells. The cells must all work together to keep the body working correctly. Do You Know? Scientists estimate that there are about 75 trillion (75,000,000,000,000) cells in the human body, though the exact number changes. Cells are always growing, dying, and being replaced. These cells are very small. It would take ten thousand (10,000) cells just to cover the head of a pin.

不同种类的细胞并非所有的细胞都是一样的。 生物体的细胞因功能不同而不同。 为了更好地理解细胞是如何不同的，让我们来看看在动物身上发现的一些细胞。 大多数动物有许多部分共同工作。 每个部分都由不同种类的细胞组成。 有肌肉细胞、神经细胞、血细胞和数百种其他类型的细胞。 这些细胞必须一起工作以保持身体正常工作。 你知道吗?科学家估计，人体内大约有75万亿个细胞(75,000,000,000,000)，尽管确切的数字在变化。 细胞总是在生长、死亡和被替换。 这些细胞非常小。 光是覆盖一根针尖就需要一万个细胞。