 Plants make up more than 98% of total biomass on Earth  They produce oxygen, produce food for all living things, and remove large amounts of CO2 from atmosphere  Life would not exist without plants  If all plants on Earth were wiped out, the oxygen in our atmosphere would run out within 11 years

 Plants belong to Kingdom Plantae  Multicellular eukaryotes  Cell walls made of cellulose  Carry out photosynthesis using green pigments chlorophyll a and b  Include trees, shrubs, grasses, mosses, and ferns  Most are autotrophs

 Because plants are stationary, living on land can be challenging  Plants must have:  Sunlight (photosynthesis)  Water and Minerals (photosynthesis and growth)  Gas exchange (bring in oxygen, dispose of CO2)  Transport of water and nutrients

 The first plants evolved from an organism much like the multicellular green algae living today.  Green algae are protists not plants  DNA sequences show that plants came from these green algaes  Oldest plant fossils ~ 450 mya  Similar to today’s mosses  Simple and grew in damp places

 Four main groups :  Bryophytes (mosses and relatives)  Seedless Vascular Plants (ferns and relatives)  Cone-bearing plants (gymnosperms)  Flowering plants (angiosperms)  Groups based on three important features:  Water-conducting tissues?  Seeds?  Flowers?

 Human and Animal Dependence on Plants  Oxygen production  Food products  Lumber, paper, clothing  Coal, oil  Methane gas from decomposed plants and animal manures  Gasohol

 Cultivation of food plants  Use of plants in cleaning polluted water  Algae and space exploration  Identification and preservation of medicinal plants

 Botany: the study of plants  Science: “a search for knowledge of the natural world”  Botanists: scientists who study plants  Scientific Method:  Observations and testing hypotheses  Principles and theories

 Hypothesis: tentative, unproven explanation for something that has been observed  Controlled experiment: an experiment in which only one variable is changed  Variable: specific aspect of an experiment  Independent: variable that you control  Dependent: variable that changes in response to independent (what you measure)

 Anton van Leeuwenhoek ( )  Development of primitive microscopes  First to describe bacteria, sperm, and other microbes  Primitive microscopes  Led to the discovery of plant cells (1665)

 Plant Anatomy: internal structure of plants  Marcello Malpighi ( )  Discovered various tissues in stems and roots  Nehemiah Grew ( )  Structure of wood

 Plant Physiology: plant function  J. B. van Helmont ( )  Flemish physician and chemist  Famous willow branch experiment

 Plant Taxonomy: identifying, naming, and classifying plants  Oldest branch of plant study  Carolus Linnaeus ( )  Wrote Species Plantarum (1753)  Pteridologists: study ferns  Bryologists: study mosses and other similar plants

 Plant Geography: how and why plants are distributed, 19 th century  Sir Joseph Hooker  Charles Darwin

 Plant Ecology: interactions of plants with one another and with their environments  Rachel Carson  Wrote Silent Spring (1962)  Increased public awareness of ecology with her publication

 Plant Morphology: form and structure of plants, 19 th century

 Other related sciences:  Genetics: heredity studied with plants, plant breeding for crops, genetic engineering for food, medicine, etc.  Cell biology: study of cell structure and function  Electron microscopy  Economic botany and ethnobotany: practical uses of plants and plant products (herbal medicine)