Botany Notes: 004 Chapter 1

Chapter 1: An Introduction Botany is the scientific study of plant life. Plants differ from one another in size, structure, manner of life, and other features and over the years, man has accumulated tremendous amounts of information about them. Yet, we still have so much more to learn about them. Botany will enrich your own life by helping you understand the fascinating diversity of these organisms that share this planet with us. Before we go into any actual study of any plant, it is first essential for us to understand this definition of botany. What do we mean by “scientific”? What are the characteristics of living things? What are plants? What differentiates them from other living things?

Science Science is a process for evaluating experimental and observed knowledge (the scientific method), a global community of scholars, and the organized body of knowledge gained by this process and carried by this community (and others). Natural sciences study nature; social sciences study human beings and society. The basic commitment of science is to collect objective data (facts that are observable and measurable) and then reach conclusions and formulate generalizations by analyzing such data. Scientists collect data either by observation or by controlled experiments. Scientists must ensure that the data are as free as possible of subjective bias, recorded and analyzed instrumentally when possible, and extensive enough so that such factors as range of variability can be defined, preferably statistically. When collecting data, scientists begin by asking questions, which they then try to answer. Hypotheses are often tested by means of a controlled experiment, in which one or more experimental groups are compared with one or more control groups, under conditions that are held standard except for one factor, the variable. The number of organisms used is important: an experiment based on only a few test organisms is apt to be non-predictive and unreliable. Upon reaching a conclusion, the scientist tries to form a generalization and compares this generalization to others. A generalization that represents a cohesive statement of principle is known as a theory. It should be pointed out that no matter how firm the database upon which a scientific theory rests, the theory must always remain subject to revision in the light of additional data.

The Scientific Method “Scientific” study involves a system that scientists use to get to the bottom of things. The observation of living things has generated a lot of questions about them. How they came to be? How are plants constructed? How do animals move? Why are animals and plants important? Scientists answer these and other questions by using an experiment-based process called the scientific method. The scientific method is a systematic way to describe and explain phenomena based on observing, comparing, reasoning, predicting, testing concluding, and interpreting. This is what science is all about. Rather than just being a set of facts that describe and explain the universe, science is a dynamic process wherein the excitement lies in the intriguing observations and carefully crafted experiments devised to help us learn more about the world around us. The scientific method begins with observations that prompt us to ask the cause of these observations. These causal questions lie at the heart of the scientific method. Science is fundamentally about finding answers to these kinds of questions. To find answers to these questions,

scientists use past experiences, ideas, and observations to propose hypotheses that may produce predictions. To determine if these predictions are accurate, scientists collect data by observation or performing experiments. If the experimental results match the predictions of a hypothesis, the hypothesis is accepted; if they don’t, the hypothesis is rejected. The effect of this is to make scientific progress by revealing answers piece by piece. By testing a single hypothesis, a scientist has not ruled out other possible causes for an observation. To do so, he would have to devise alternative hypotheses, make predictions for them, and obtain experimental results to compare with the predictions. By this process, he may be able to reject all his hypotheses. Either way, he makes progress by testing several hypotheses, not just one. Although the scientific method is a powerful tool for answering some kinds of question, it is not foolproof. Most experiments do not distinguish other possible interpretations. Most of the time, it is impossible to recreate conditions in the laboratory or consider all factors that influence the occurrence of events. Any conclusion marks an end to the scientific method for a particular experiment but it seldom ends the process of scientific inquiry. To the curious scientific mind, a conclusion is never the final answer. There is always something more to study, something new to learn.

Characteristics of Living Things Living things have common themes that separate them from non-living things. All living things have organization, undergo metabolism, growth and reproduction, respond and adapt to changes in the environment. Organization. All living things are made up of cells. Some organisms are made up of only one cell (unicellular) while others are made up of more than one (multi-cellular). In multi-cellular organisms, each cell has specific functions and specific roles in keeping the organism alive. Even within cells, specific structures have their own functions and roles. Even beyond the organism level, we find that organisms often group themselves into populations. Populations of different species make up a community which is part of an ecosystem which makes up the biosphere. Metabolism. All living things undergo metabolism. Metabolism is the collective term for all the essential biochemical processes that goes on inside the body. Digestion, respiration, photosynthesis, and the elimination of waste materials are only some of the processes constantly in progress. There are two phases of metabolism. Anabolism is the constructive or building up phase while catabolism is the destructive or breaking down phase. Growth. Living things grow and develop. Growth involves an increase in size for unicellular organisms or an increase in the number of cells for multi-cellular animals. Development involves change in shape and form. Reproduction. Living things reproduce. Reproduction is necessary for the perpetuation of the species. Reproduction can be asexual (without sex cells) or sexual (recombination of genes from two interacting sex cells). Irritability. Irritability is defined as the ability of an organism to respond to stimuli. The stimulus may be simple, such as in bacteria moving away from or toward a heat source. It may be complex i.e. a bird responding to a complicated series of signals in a courtship ritual. Adaptation. Adaptation is the ability of an organism to change in response to the environment. The process of changing to promote survival includes: adaptability of the individual 3

organism in direct response to some specific challenge and mutability (alteration) of genes and chromosomes producing a range of variability in offspring. Each species, whether plant or animal, exhibits an adaptation to the environment distinct from other organisms.

Plants Living things are classified on the basis of evolutionary relationships that exist among them. Modern scientists usually recognize five major kingdoms that represent all known species of living things. The table below shows the five kingdoms and the major differences that exist between them. Kingdom Monera

Type of Cell Prokaryotic

Protista

Eukaryotic

Plantae

Eukaryotic with walls Eukaryotic

Fungi

Cell Organelles No membrane around organelles, no plastids, no mitochondria All cell organelles Present but cells simpler

Cellular Organization Unicellular and/or colonial

Representative Blue-green algae, bacteria

Unicellular and/or colonial Multicellular with tissues

Protozoa

Lack plastids and Syncytial photosynthetic pigments Animalia Eukaryotic without Lack plastids and Multicellular with tissues walls photosynthetic pigments Table 1.1. Characteristics of five kingdoms (Modified from Storer et al, 6th Ed., 1979)

Higher plants Mushrooms, molds Any animal

Plants vs. Animals What are plants? What makes a plant different from an animal? Although the basic unit of structure and function of both plants and animals is the eukaryotic cell and plant and animal cells are so much alike as to strongly suggest a common ancestor, there are two salient points of difference: plant cells have chloroplasts and plant cells are enclosed in cell walls. Other differences are noted in the Table 1.2. Animals Heterotrophic (do not photosynthesize, lack chloroplasts) Determinate Absent Present in most Mostly mobile Glycogen (multiply branched glucose chain), saturated fats CO2 and nitrogenous wastes, kidneys needed in most animals

Plants Autotrophic (carry out photo synthesis, Mode of nutrition contain chloroplasts) Indeterminate Extent of Growth Made up of cellulose, rigid, inert Cell Wall Absent Nervous System Mostly immobile Mobility Primary Food Starch (unbranched glucose chain), Reserve unsaturated oils O2 from photosynthesis, CO2 from Waste Products metabolism, kidneys not needed since nitrogenous wastes not generated Table 1.2. Some major differences between animals and plants (Modified from Glinoga)

Importance of Botany Plants are very important to people. Understanding how they function enables one to make wise decisions about many things that affect the individual, family, and the community. The use of organisms to produce consumer needs is called biotechnology. Use of bacteria to turn milk into cheese or the use of live yeast to make bread rise are techniques of biotechnology. Farming, pest control, livestock management, nutrition, food processing, and food preservation also involve biotechnology. Plants provide us with oxygen, food, non-edible economic products, biomedical products, research material. They also have ecological, aesthetic, and affectional value. 4

Oxygen. Green plants and algae generate the oxygen that sustains life on earth. Remove all animal life on earth and plant life will go on and new organisms will eventually evolve. Remove all plant life on earth and it becomes a barren rock. Food. Plants also generate sugars essential to life. 95% of our food comes from only 20 species of plants. Rice, corn, wheat, barley, oats and potatoes are our major sources of carbohydrates. Vegetables and fruits remain a vital source of nutrients to supplement our diet. Spices like pepper, onion, garlic make our food more tasty. Beverages like coffee, tea, chocolate, beer, whisky, rum, and fruit juices all come from plants. Non-edible economic products. We use cotton, flax, and ramie for clothing. Fibers of hemp are used for rope, sisal for brooms and brushes, cotton and flax for paper money. Different types of wood are used for shelter and furniture, paper and fuel. Plants extracts are used to make paint, plastics, soap, oils, adhesives, natural rubber, waxes, and dyes. These are only some non-edible economic products that plants provide for us. Biomedical products. Drugs such as morphine, cocaine, aspirin, caffeine, codeine, digitoxin, quinine, vinblastine, and most antibiotics come from plants. On the negative side, plants also have toxins that can damage crops, cause allergies, and poison us. Research. The foundations of genetics were based on research made by Gregor Mendel on peas. Cells were first described on cork tissue by Robert Hooke. Matthias Schleiden, a botanist, first postulated that all plants were made up of cells before Theodor Schwann postulated the same thing on animals. The tobacco mosaic virus was the first virus to be described. At present, research continues to identify secondary metabolites that plants secrete which may be of beneficial for human use. Ecological value. Besides providing us with oxygen that we need, plants form an integral part of the ecosystem. Plants trap energy from the sun to make carbohydrates. Plant eaters (herbivores) are a source of food for carnivores (meat eaters) and ominivores (plant and meat eaters). Aesthetic value. Plants are used by people to beautify their surroundings. People maintain gardens, grow flowering and ornamental plants. People have also shown their fascinations with plants by sculpting them into various shapes, incorporating them into logos and names, and naming children after them. Plants also serve as inspiration in literature and the arts. Affectional value. People take pride in their ability to grow plants. Some talk to plants not only to grow them better but to alleviate stress. We also give plants and flowers to signify our affection. We give different flowers to show our love for others, to show our concern when they are sick and even our sorrow when people pass away.

Branches of Botany Since botany presents a wide range of topics, scientists often choose a specific category to study. Some botanists, for example, devote their time to studying plants belonging to one particular taxonomic group. Others study one or more aspects of plant structure, function, or behavior, often using a comparative approach. Here are only a few of the branches of science that fall under the scientific study of plant life: Taxonomy – classification and naming of plants and animals Botany – scientific study of plant life Agronomy – soil management and crop production Bryology – bryophytes (mosses, liverworts, and related plants) Lichenology – scientific study of lichens 5

Mycology – scientific study of fungi Phycology – scientific study of algae Forestry – developing, caring for, or cultivating forests; management of growing timber Horticulture – growing fruits, vegetables, flowers, or ornamental plants Biotechnology – the use of organism to produce consumer needs Pharmacology – drugs including Materia Medica, toxicology, and therapeutics Toxicology – scientific study of poisons Biochemistry – chemical compounds and processes in living organisms Molecular biology – molecules and processes in cells Cytology – cell structures and function often at electron microscopy level Histology – organs and tissues at the microscopic level Gross anatomy – non-microscopic structures of organisms Physiology – body functions of the entire organism Genetics – hereditary traits and their transmission Ecology – relationships between biotic (living) and abiotic (physicochemical) environments

Important Contributors to Botany Our present knowledge about this subject is based on previous works of past scientists. Botany would not be as advanced as it is today if not for the great pioneers of the science. Here are only some of the scientists who contributed greatly to the scientific study of living things. Theophrastus of Eresus ~300 B.C. – description of nearly 500 plants and their uses Dioscorides ~100 B.C. – De Materia Medica included 600 medicinally useful plants Robert Hooke 1665 – coined the term “cell” describing the texture of cork using magnifying lenses Anton von Leeuwenhoek 1667 – microscopic discovery of bacteria, protozoa and spermatozoa Carolus Linnaeus 1735 – basis for modern classification of living Fig. 1.1 Theophrastus of Eresus things; binomial nomenclature Matthias Schleiden (a botanist) and Theodor Schwann (a zoologist) 1839 – put forth the thesis that cells were the units of structure in plants and animals. Rudolf Virchow 1855 – stressed the role of the cell in pathology and stated that all cells came from preexisting cells “Omni cellulae e cellula” Charles Darwin and Alfred Wallace 1859 – foundation of modern theory of evolution Louis Pasteur 1860 – conclusive experimental refutation of the theory of spontaneous generation Gregor Mendel 1865 – foundations of genetics James Watson and Francis Crick, 1953 – discovered the structure of DNA Fig. 1.2 Watson and Crick

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