Cells: Constructing Living Things

Cells: Constructing Living Things book cover — Table of Contents Life’s Amazing Mini Machines 4 Inside Every Cell A Cell’s Inner Workings 8 Prokaryotes vs Eukaryotes 15 Plant vs Animal 22 Building with Cells Cell Division 28 Building YOU 36 Tools of the Cell Trade 43 Glossary 46 Index 47 Show What You Know 47 Websites to Visit 47 About the Author 48

Cells: Constructing Living Things — page 1 — Life's Amazing Mini Machines What do a tree and an elephant have in common A trunk Jokes aside they are both made of cells So is every other living thing from the tiniest microbes to plants to humans to the marvelously giant whale Cells are like tiny machines carrying out all the work needed to keep us alive They are the smallest units of life capable of reproducing themselves Is It Alive How can you tell if something is alive For something to be considered an organism a living thing it has to display every single trait on this checklist It is made up of one or more cells It uses energy It maintains a steady stable internal environment It grows It reproduces It is capable of detecting and responding to changes in its environment What about viruses Are they alive The answer is no While they carry all the information needed to make more of themselves they can’t reproduce on their own Instead they have to infect a cell and force its machinery to do the job 4

Cells: Constructing Living Things — page 2 — Some organisms are unicellular meaning they are made up of a single cell Bacteria yeast and amoeba are all unicellular Other organisms are multicellular with bodies made up of more than one cell and sometimes trillions of cells Cells by the Numbers How many cells does an organism have Lactobaccillus a bacteria used to make yogurt 1 cell Simple roundworm 1,000 cells Adult human 37,000,000,000,000 37 trillion cells Yogurt Lactobaccillus 5

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