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Chapter 1 An Introduction to Life on Earth
Basic Biology (BIOL 111)
Campbell University
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Chapter 1: An Introduction to Life on Earth ● Life can be studied at different levels: ○ Atom ○ Molecule ○ Cell ○ Tissue ○ Organ ○ Organ System ○ Multicellular Organism ○ Population ○ Species ○ Community ○ Ecosystem ○ Biosphere ● Levels of organization ○ All matter is formed of elements ■ An atom is the smallest particle of an element retaining the properties of an element. ■ Atoms combine to form molecules. ■ Molecules provide the building blocks for cells, the smallest unit of life. ■ Some forms of life consist of single cells. ■ In multicellular organisms, cells combine to form tissues ■ Tissues combine to form organs, which then can be connected as organ systems ■ Organisms of the same that are capable of interbreeding are called a species ■ A group of organisms of the same species living in a given area is a population ■ Interacting populations make up a community. ■ A community and its nonliving components is an ecosystem ■ The entire surface of the Earth, including living and nonliving components, is the biosphere ● How do Scientists Study Life? ○ Scientific principles underlie all scientific inquiry. ■ Natural causality is the principle that all events can be traced to natural causes.
■ Natural laws apply to every time and place ● Natural laws are uniform in space and time ● The principle is key to understanding biological events before humans record them. ● Creationism is contrary to the principle of uniformity- in-line and natural causality. ○ Creationists hold the different species were created one at a time by the direct intervention of God, contrary to events we see happening today. ○ Scientific inquiry is based on the assumption that people perceive natural events in similar ways ○ Historical approaches to studying life ■ The belief that some actions happen through supernatural forces (e., the supernatural) ■ The belief that all events can be traced to natural causes that we can comprehend (natural causality) ● Corollary: evidence gathered from nature that has not been deliberately distorted to fool us ○ People have similar perceptions ■ This is based on the assumption that all human beings perceive natural events in fundamentally the same way ■ Common perception allows us to accept observations of other humans as reliable ■ Common perception is usually not found in appreciation of art, poetry, and music, nor between cultures or religious beliefs ● Value systems are subjective ● Science requires objectively gathered data ● The scientific method-the basis for scientific inquiry ○ Scientific inquiry is a rigours method for making observations ○ The scientific method or inquiry follows six steps
- Observation of a specific phenomenon
- The observation, in trunks, leads to a question
- The question leads to formulation of a hypothesis, based on previous observations, that is offered as an answer to the question
- The hypothesis leads to a prediction, typically expressed in “if...
substance ○ Further tests using broth from pure Penicillium cultures lead to the discovery of the first antibiotic, penicillin ○ Fleming continued beyond a lucky “accident” with further scientific investigation to a great discovery ○ “Chance favors the prepared mind” Louis Pasteur ● Scientific theories have been thoroughly tested ○ A scientific theory diffes in definition from that of everyday usage ■ Many people use the word theory to mean hypothesis or an “educated guess” ○ A scientific theory is a general explanation for important natural phenomena ■ It is extensively and reproducibly tested ■ It is more like a principle or natural law (e., the atomic, gravitational, and cell theories) ■ If compelling evidence arises, a theory may be modified ○ New scientific evidence may prompt radical revision of existing theory ■ Example: Discovery of Prions ● Prusiner’s Prions ● Before 1980, all known infectious diseases contained DNA or RNA ● In 1982, Stanley Prusiner showed that the infectious sheep disease scrapie is caused by a protein (a “protein infectious particle,” or prion) ● Prions have since been shown to cause “mad cow disease” and diseases in humans ● The willingness of scientists to revise accepted belief in light of new data was critical to understanding and expanding the study of prions ● Science is based on reasoning ○ Deductive Reasoning: applying the (already existing) rule is the process of generating hypotheses based on well-supported generalizations ■ Example: Based on Cell theory, any newly discovered organism would be expected to be composed of cells ○ Inductive reasoning: creating the rule is used in the development
of scientific theories, or ■ A generaltization is created from many observations ■ Example: cell theory arises many observations that all indicate a cellular basis for life ○ DIGS ■ D - Deductive ■ I - is ■ G - General to ■ S - Specific ● Evolution: The Unifying Theory of Biology ○ Evolution is the process by which modern organisms descended, with modifications, from preexisting forms of life ■ Abdundant evidence has been found to support evolutionary theory since Charles Darwin and Alfred and Wallace proposed it in the mid-1800s ■ Those who see evolution as “just a theory” don’t understand the scientific definition of a theory ■ Evolution explains how diverse forms of life originated through changes in their genetic makeup ● Modern organisms descended with modification from preexisting organisms ○ Darwin and Wallace formulated the basis of our modern understanding of evolution ○ Evolution arises as a consequence of three natural processes ■ Genetic variation among members of a population due to differences in their DNA ■ Inheritance of those variations by offspring of parents carrying the selection ■ Natural Selection of individuals whose survival and enhanced reproduction are due to the favorable variations they carry. ● Genetic variability ○ Genetic variation arises from segments of DNA ○ Changes in genes (mutations) alter the informational content ○ Mutations arise from a number of sources ■ Mutations can occur from irradiation ■ Mutations occasionally arise from copying mistakes in DNA during cellular reproduction
unit of life ○ Single cell has an elaborate internal structure ○ All cells contain ■ Genes that provide information to control the life of the cell ■ Organelles, which are small, specialized structures that perform specific functions ■ A plasma membrane that encloses the fluid cytoplasm and organelles from the outside world ● Living things maintain relatively constant internal conditions through homeostasis ○ Organisms must maintain homeostasis ○ Example: organisms regulating body temperature ○ Homeostasis mechanisms include: ■ Sweating in hot weather or dousing oneself with cool water ■ Metabolizing more food, basking in the sun, or turning up the thermostat in cold weather ○ Organisms still grow and change maintaining homeostasis ● Living things response to stimuli ○ Sensory organs in animals can detect and response to external stimuli like light, sound, chemicals, etc ○ Internal stimuli in animals are perceive by stretch temperature, pain, and chemical receptors ○ Plants and bacteria response to stimuli as well (e., plants grow towards the light, and bacteria move toward available nutrients in a medium. ● Living things acquire and use materials and energy ○ Materials and energy is required for the organism to maintain organization, grow, and reproduce
○ Important materials (nutrients) are acquired from the air, water, soil, or other living things ○ Nutrients are incorporated into the bodies of organisms ○ Nutrients are continuously recycled among the living, and nonliving things ○ Organisms obtain energy in two ways ■ Plants, and some single-celled organisms capture sunlight in photosynthesis ■ Other organisms consume energy-rich molecules in the bodies of other organisms ○ All energy that sustains life comes directly or indirectly from the sun ● Living things grow AND DEVELOP ○ Every organism becomes larger over time ■ Plants, birds, and mammals grow by producing more cells to increase their mass ■ Bacteria grow by enlarging their cells; they also divide to make more individuals ○ Growth involves the conversion of acquired materials to molecules of the organism’s body ● Living things reproduce themselves ○ Organisms give rise to offspring of the same type ○ The parent’s genetic material (DNA) is passed on to the offspring, creating a continuity of life. ● Living things, collectively, can evolve. ○ The genetic composition of a whole species changes over many generations ○ Mutations and variable offspring allow a species to evolve ● How do Scientists categorize the Diversity of Life? ○ Scientists generally categorize organisms into three major groups or domains. ■ Bacteria ■ Archaea
● Members of different kingdoms have different ways organisms acquire energy ○ Autotrophs (“self-feeding”) photosynthetic and chemosynthesis ■ Photosynthetic organisms that capture sunlight and store it in sugar and fats ■ Includes plants, some bacteria, and some protists ○ Heterotrophs (“other-feeding”) ■ Organisms that acquire energy through ingesting molecules in the bodies of other organisms ■ Includes many archaeans, many bacteria, many protists, all the fungi, and all the animals ■ The size of the food eaten varies from individual food molecules to the ingestion and digestion of whole chunks.
Chapter 1 An Introduction to Life on Earth
Course: Basic Biology (BIOL 111)
University: Campbell University
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