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1.1 The Secret Life of Earth
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  1. 1.1 The Secret Life of Earth • Human activities are profoundly changing life on Earth • Hundreds of new species are discovered each year – about 20 species become extinct every minute in rain forests alone • What is a species, and why should discovering a new one matter to anyone other than a scientist? • These questions are part of biology, the scientific study of life

  2. Same Parts, Different Organization • Complex properties, including life, often emerge from the interactions of much simpler parts

  3. A Pattern in Life’s Organization • Atoms • Fundamental building blocks of all substances • Molecules • Consisting of two or more atoms • Cell • The smallest unit of life • Tissue • Specialized cells organized to perform a collective function

  4. A Pattern in Life’s Organization • Organ • Structural unit of interacting tissues. • Organ system • A set of interacting organs • Multicelled organism • An individual consisting of one or more cells

  5. A Pattern in Life’s Organization • Population • Individuals of the same species in the same area • Community • Populations of all species in the same area • Ecosystem • A community and its environment • Biosphere • All regions of the Earth where organisms live

  6. ANIMATED FIGURE: Life’s levels of organization To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  7. Take-Home Message: How do living things differ from nonliving things? • All things, living or not, consist of the same building blocks—atoms; atoms join as molecules. • The unique properties of life emerge as certain kinds of molecules become organized into cells. • Higher levels of life’s organization include multicelled organisms, populations, communities, ecosystems, and the biosphere. • Emergent properties occur at each successive level of life’s organization.

  8. 1.3 How Living Things Are Alike • Continual inputs of energy and the cycling of materials maintain life’s complex organization • Organisms sense and respond to change • All organisms use information in the DNA they inherited from their parent or parents to develop and function

  9. Energy and Life’s Organization • Energy • The capacity to do work • Not cycled; flows through the world of life in one direction • Nutrients • Atoms or molecules essential in growth and survival that an organism cannot make for itself • Cycled between organisms and the environment

  10. Producers and Consumers • Producers • Acquire energy and raw materials from the environment • Make their own food (photosynthesis) • Consumers • Cannot make their own food • Get energy by eating producers and other organisms

  11. Organisms Sense and Respond to Change • Organisms sense andrespond to change both inside and outside the body • The body’s internal environment consists of all body fluids outside of cells • The internal environment must be kept within certain ranges of composition, temperature, and other conditions • By sensing and adjusting to change, organisms keep conditions in the internal environment within a range that favors cell survival (homeostasis)

  12. Organisms Use DNA • DNA is the basis of similarities in form and function among organisms • Details of DNA molecules differ – the source of life’s diversity • DNA • Deoxyribonucleic acid • Carries hereditary information that guides development and functioning

  13. Development and Growth • DNA guides ongoing metabolic activities that sustain the individual through its lifetime • Development • Multistep process by which the first cell of a new individual becomes a multicelled adult • Growth • In multicelled species, an increase in the number, size, and volume of cells

  14. Reproduction and Inheritance • All organisms receive their DNA from one or more parents • Reproductionincludes various processes by which individuals produce offspring • Inheritancerefers to the transmission of DNA to offspring

  15. Take-Home Message:How are all living things alike? • A one-way flow of energy and a cycling of nutrients sustain life’s organization. • Organisms sense and respond to conditions inside and outside themselves; they make adjustments that keep conditions in their internal environment within a range that favors cell survival, a process called homeostasis. • Organisms develop and function based on information encoded in their DNA, which they inherit from their parents. DNA is the basis of similarities and differences in form and function

  16. Organisms With No Nucleus • Bacteria and archaea are two types of organisms whose DNA is not contained within a nucleus • Bacteria • The most diverse and well-known group of single-celled organisms that lack a nucleus • Archaea • Single-celled organisms that lack a nucleus but are more closely related to eukaryotes than to bacteria

  17. Eukaryotes • Eukaryotes are organisms whose DNA is contained within a nucleus • Some eukaryotes live as individual cells; others are multicelled • Eukaryotic cells are typically larger and more complex than bacteria or archaea

  18. The Three-Domain System

  19. The Six-Kingdom System

  20. 1.5 Organizing Information About Species • Each type of organism, or species, is given a unique name • We define and group species based on shared traits • Taxonomy is the science of naming and classifying species

  21. The Binomial System • Carolus Linnaeus standardized a two-part naming system that we use today • The first part is the genus, a group of species that share a unique set of features • The second part is the specific epithet • Genus name plus specific epithet designate one species • Example: the dog rose Rosa canina

  22. Taxonomic Classification

  23. A Rose by Any Other Name . . . • A species is assigned to higher taxa based on some subset of heritable traits it shares with other species • Morphological traits (observable characteristics) • Physiological traits (functional characteristics) • Behavioral traits (responses to certain stimuli)

  24. Traits • Traits vary a little within a species • There can be tremendous differences between species; such species look very different, so it is easy to tell them apart • Species that share a more recent ancestor may be harder to tell apart

  25. The Biological Species Concept • Evolutionary biologist Ernst Mayr defined a species as groups of individuals that potentially can interbreed, produce fertile offspring, and do not interbreed with other groups • This “biological species concept” is useful in many cases, but it is not universally applicable • For now it is important to remember that a “species” is a convenient but artificial human construction

  26. Four Butterflies, Two Species

  27. The Scientific Method

  28. Peacock Butterfly Defenses Against Predatory Birds

  29. Probability • In cases like flipping a coin, it is possible to calculate probability of an expected result • Probability • The measure, expressed as a percentage, of the chance that a particular outcome will occur • Depends on the total number of possible outcomes • Analysis of experimental data often includes calculations of probability

  30. Statistical Significance • If a result is very unlikely to have occurred by chance alone, it is said to be statistically significant • Statistically significant refers to a result that is statistically unlikely to have occurred by chance • In science, every result – even a statistically significant one –has a possibility of being incorrect

  31. “Theories” and “Laws” • A scientific theoryis a long-standing hypothesis that has not been disproved after many years of rigorous testing • Like all hypotheses, a scientific theory can be disproven by a single observation that falsifies it • A law of nature describes a phenomenon that has been observed to occur consistently, but for which we do not have a complete scientific explanation