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Chapter One: What is Plant Biology?. Introduction. 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
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Introduction • 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
Introduction • 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
Plant Survival Needs • 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
Early Plants • The first plants evolved from an organism much like the multicellular green algae living today. • Green algae are protistsnot 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
Divisions • 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?
Relationship of Humans with their Environment • Human and Animal Dependence on Plants • Oxygen production • Food products • Lumber, paper, clothing • Coal, oil • Methane gas from decomposed plants and animal manures • Gasohol
Plants and the Future • Cultivation of food plants • Use of plants in cleaning polluted water • Algae and space exploration • Identification and preservation of medicinal plants
Botany as a Science • 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
Botany as a Science • 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)
Microscopes • Anton van Leeuwenhoek (1632-1723) • Development of primitive microscopes • First to describe bacteria, sperm, and other microbes • Primitive microscopes • Led to the discovery of plant cells (1665)
Botanical Disciplines • Plant Anatomy: internal structure of plants • Marcello Malpighi (1628-1694) • Discovered various tissues in stems and roots • Nehemiah Grew (1628-1711) • Structure of wood
Botanical Disciplines • Plant Physiology: plant function • J. B. van Helmont (1577-1644) • Flemish physician and chemist • Famous willow branch experiment
Botanical Disciplines • Plant Taxonomy: identifying, naming, and classifying plants • Oldest branch of plant study • Carolus Linnaeus (1707-1778) • Wrote Species Plantarum (1753) • Pteridologists: study ferns • Bryologists: study mosses and other similar plants
Botanical Disciplines • Plant Geography: how and why plants are distributed, 19th century • Sir Joseph Hooker • Charles Darwin
Botanical Disciplines • 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
Botanical Disciplines • Plant Morphology: form and structure of plants, 19th century
Botanical Disciplines • 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)