12/27/2022 0 Comments What is the smallest unit of life![]() In the 1670s, van Leeuwenhoek discovered bacteria and protozoa. Despite the limitations of his now-ancient lenses, van Leeuwenhoek observed the movements of single-celled organism and sperm, which he collectively termed “animalcules.” In a 1665 publication called Micrographia, experimental scientist Robert Hooke coined the term “cell” (from the Latin cella, meaning “small room”) for the box-like structures he observed when viewing cork tissue through a lens. The microscopes we use today are far more complex than those used in the 1600s by Antony van Leeuwenhoek, a Dutch shopkeeper who had great skill in crafting lenses. In spite of their enormous variety, however, all cells share certain fundamental characteristics. Each of these cell types plays a vital role during the growth, development, and day-to-day maintenance of the body. And red blood cells carry oxygen throughout the body. Cells of the immune system fight invading bacteria. For example, bone cells help to support and protect the body. Just as a home is made from a variety of building materials, the human body is constructed from many cell types. Your body has many kinds of cells, each specialized for a specific purpose. Like a brick wall, your body is composed of basic building blocks and the building blocks of your body are cells. What is the basic building block of that wall? It is a single brick, of course. Cell TheoryĬlose your eyes and picture a brick wall. It includes land, water, and portions of the atmosphere. At the highest level of organization, the biosphere is the collection of all ecosystems, and it represents the zones of life on Earth. An ecosystem consists of all the living things in a particular area together with the abiotic, or non-living, parts of that environment such as nitrogen in the soil or rainwater. For instance, all of the trees, flowers, insects, and other populations in a forest form the forest’s community. For example, each tree in a forest is an organism.Īll the individuals of a species living within a specific area are collectively called a population. A community is the set of different populations inhabiting a common area. For example vertebrate animals have many organ systems, such as the circulatory system that transports blood throughout the body and to and from the lungs it includes organs such as the heart and blood vessels. Organisms are individual living entities. An organ system is a higher level of organization that consists of functionally related organs. In most multicellular organisms, cells combine to make tissues, which are groups of similar cells carrying out the same function. Organs are collections of tissues grouped together based on a common function. Organs are present not only in animals but also in plants. (credit “molecule”: modification of work by Jane Whitney credit “organelles”: modification of work by Louisa Howard credit “cells”: modification of work by Bruce Wetzel, Harry Schaefer, National Cancer Institute credit “tissue”: modification of work by “Kilbad”/Wikimedia Commons credit “organs”: modification of work by Mariana Ruiz Villareal, Joaquim Alves Gaspar credit “organisms”: modification of work by Peter Dutton credit “ecosystem”: modification of work by “gigi4791″/Flickr credit “biosphere”: modification of work by NASA) From an atom to the entire Earth, biology examines all aspects of life. As discussed in more detail below, all living things are made of one or more cells. ![]() Organelles are small structures that exist within cells and perform specialized functions. In plants, animals, and many other types of organisms, molecules come together in specific ways to create structures called organelles. Atoms combine to form molecules, which are chemical structures consisting of at least two atoms held together by a chemical bond. It consists of a nucleus surrounded by electrons. The atom is the smallest and most fundamental unit of matter. Living things are highly organized and structured, following a hierarchy of scale from small to large (Figure 1). 2.3 A Cell is the Smallest Unit of Life Levels of Biological Organization
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