A Closer Look at Plant Classifications, Parts, and Uses
A CLOSER LoOK AT PLANT CLASSIFICATIONS PARTS AND Us I2
CHARACTERISTICS OF PLANTS WHAT DISTINGUISHES PLANTS FROM OTHER LIVING THINGS Exactly what is a plant and how is it differ ent from other life forms Initially this may seem like a simple question Everyone knows that an elm tree is a plant whereas a dog is not Nevertheless the precise definition of plants is still a matter of debate among some scientists As recently as the late 1960s scientists believed that all organisms could be classified as members of either the plant or the animal kingdom Life forms that are green and that can synthesize their own food using light energy were put in the plant kingdom Those organisms that lack green pigment and are able to move about were considered to be animals As scientists made more detailed studies of certain organisms that were con sidered to be plants they recognized that they were quite different from plants and that they did not share an evolutionary his tory with them Herbivores like horses get many minerals from plants Hemera Thinkstock 13
A CLOSER LoOK AT PLANT CLASSIFICATIONS PARTS AND Us BIRE 14
CHARACTERISTICS OF PLANTS Today plants are recognized as multi cellular organisms that carry out pho tosynthesis This activity takes place in special structures or organelles called chloroplasts and makes use of a green chem ical compound called chlorophyll Another important characteristic of plant cells is that they have cell walls that are composed of cellulose the stiffening material in tree trunks twigs and the veins of leaves Plants are eukaryotes that is their cells contain a true nucleus and other membrane bound bodies This property distinguishes plants from bacteria and archaea which are prokaryotes organisms made up of a single cell that does not contain a true nucleus Eukaryotes have larger and much more complex cells than do prokaryotes Eukaryotes traditionally have been divided into four kingdoms Protista Fungi Animalia and Plantae Scientists distinguish between these kingdoms based on differences in the structure of the eukaryotes cells and tissues Most members of the kingdom Protista have only one cell The protists called Plant cell walls contain cellulose which makes tree trunks rigid Shutterstock com 15
