ACLOSER LOOK AT LIVING THING plants algae insects protozoa fungi monera bacteria and similar animals forms other viruses Scientists have discovered nearly 2 million different species or kinds of living things Most of these species are animals About halfof all spe cies are the animals known as insects Encyclopaedia Britannica Inc and animals can replace a body part that has been lost a tail for example through a process called regeneration A living organism also has to be able to cre ate more of its kind through
INTRODUCTION Living things reproduce either sexually with two parents or asexually where an organism creates new life on its own The final test that every living thing must pass is the ability to get rid of waste and toxic substances through excretion These unwanted and potentially harmful materials E TF are produced in plants animals and humans in the process of living Plants release waste gases into the air through their stomata Animals and humans sweep waste and toxins out of their bodies primarily through sweat urine and feces The ability to do just one or a few of the functions listed here is all well and good but that doesn t mean that something is alive All seven characteristics must be present for an organism to be considered a true living
CHAPTER 1 THE CHARACTERISTICs OF LIVING THINGS Eas HOSE IN iving things include many kinds of organisms from the plants ani mals fungi and algae that can be readily seen in nature to the multitude of tiny creatures known as protozoa bacte ria and archaea that can be seen only with a microscope Living things can be found in every type of habitat on Earth on land and in lakes rivers and oceans Although all these organisms are very different from one another they all have two things in common They are descended from a single ancient ancestor and they are alive Most scientists believe that the first living organism on Earth probably evolved within a billion years of Earth s formation which occurred roughly 4 5 billion years ago This belief is based on evidence from the fossil record Fossil remains of microorganisms resembling cyanobacteria a group of micro organisms formerly known as blue green algae were discovered embedded in rocks that were roughly 3 5 billion years old A A IO
THE CHARACTERISTICS OF LIVING THINGs The colors of Morning Glory Pool a hot spring in Yellowstone National Park are the result of different types ofcyanobacteria which are micro organisms that thrive in harsh environments Shutterstock com The early Earth was very different from the Earth of today The atmosphere was rich in hydrogen which was critical to the chemi cal events that later took place According to one scientific hypothesis soupy mixtures of elements important to life such as carbon II
