An Introduction to Life on Earth

1. An Introduction to Life on Earth 1 0

2. Why Study Biology? • Biology helps you to understand your body. • How behavior affects health • How diseases do their damage • Biology helps you to become an informed citizen. • Pollution • Modified foods • Extinction • Cloning • Human stem cell research • Cures for diseases • Population control • Career opportunities • Biotechnology, pharmaceuticals, medical equipment • Allied health • Wild life manager, forester, environmental consultant • Law (environmental, patent, medical malpractice) • Research • Teaching • Biology can enrich your appreciation of the world.

3. Chapter 1 At a Glance • 1.1 What Is Life? • 1.2 What Is Evolution? • 1.3 How Do Scientists Study Life? • 1.4 What Is Science?

4. 1.1 What Is Life? Biology comes from the Greek words “bio” meaning “life” and “logy” meaning “the study of.” Organisms share common characteristics that, taken together, define life. Organisms: • Acquire and use materials and energy • Actively maintain organized complexity • Perceive and respond to stimuli • Grow • Reproduce • Have the capacity to evolve, collectively

5. 1.1 What Is Life? • Organisms acquire and use materials and energy • Materials and energy are required for organisms to maintain organization, to grow, and to reproduce • Important materials (minerals, water, & other simple chemical building blocks) are acquired from the air, water, soil, and bodies of other living things • Organisms use energy continuously to sustain themselves

6. Figure 1-2 Properties of life • The waterflea is alive. Antennae and eyes: living things respond to stimuli Gut: living things acquire nutrients Eggs: living things reproduce • This waterflea is both organized and complex.

7. 1.1 What Is Life? • Characteristics of living things • This wave is complex but not organized. • It is not alive.

8. 1.1 What Is Life? • Organisms acquire and use materials and energy (continued) • Organisms obtain energy in two ways, coming directly or indirectly from the sun • Photosynthesis is the process by which plants and some single-celled organisms capture sunlight • Other organisms consume energy-rich molecules in the bodies of other organisms

9. Figure 1-3 The flow of energy and the recycling of nutrients

10. 1.1 What Is Life? • Organisms actively maintain organized complexity • Living things use energy on a continuous basis to self-sustain • Cells pump chemicals in and out for appropriate chemical reactions to occur • Organisms maintain relatively constant internal conditions or homeostasis

11. Figure 1-4 Organisms maintain relatively constant internal conditions

12. 1.1 What Is Life? • Organisms perceive and respond to stimuli • Organisms sense and respond to internal and external environmental stimuli • Sensory organs in animals can detect and respond to external stimuli such as light, sound, chemicals, etc. • Internal stimuli in animals are perceived by stretch, temperature, pain, and chemical receptors • Plants and bacteria respond to stimuli as well (e.g., plants grow toward the light, and bacteria move toward available nutrients in a medium)

13. 1.1 What Is Life? • Organisms grow • 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 divide in half to reproduce after genetic material is copied • Growth involves the conversion of acquired materials to molecules of the organism’s body

14. 1.1 What Is Life? • Organisms reproduce • Organisms reproduce by dividing in half, producing seeds, bearing live young, and laying eggs • Organisms give rise to offspring of the same type • The parent’s genetic material (DNA) is passed on to the offspring, creating continuity of life

15. Figure 1-6 Organisms reproduce Panda with its baby Dividing Streptococcus bacterium Dandelion producing seeds

16. Figure 1-7 DNA

17. 1.1 What Is Life? • Organisms, collectively, have the capacity to evolve • Evolution is the process by which modern organisms descended, with modifications, from preexisting forms of life • Changes in DNA within populations occur over the course of generations, which results in evolution • Populations are groups of the same type of organism living in the same area

18. 1.2 What Is Evolution? • Evolution explains the diversity of life on Earth • Evolution provides an explanation for the similarities found among different types of organisms • Chimpanzees and people have various physical features in common • DNA of humans differs from that of chimpanzees by less than 5%

19. Figure 1-8 Chimps and people are closely related

20. Levels of biological organization Fig. 1-10

21. 1.3 How Do Scientists Study Life? • Life can be studied at different levels • 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

22. 1.1 What Is Life? • The cell is the basic unit of life • It is separated from its surroundings by a membrane • It encloses a variety of structures and chemicals in a fluid environment

23. Figure 1-1 The cell is the smallest unit of life nucleus cell wall plasma membrane organelles

24. 1.3 How Do Scientists Study Life? • Life can be studied at different levels (continued) • Some forms of life consist of single cells • In multicellular forms, cells combine to form tissues • Tissues combine to form organs, which can be united as organ systems • Multicellular organisms are composed of multiple organ systems

25. 1.3 How Do Scientists Study Life? • Life can be studied at different levels (continued) • Organisms of the same type that are capable of interacting and 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 environment is an ecosystem • The entire surface of Earth, including living and nonliving components, is the biosphere

26. 1.3 How Do Scientists Study Life? • Biologists classify organisms based on their evolutionary relationships • Scientists generally categorize organisms into three major groups, or domains • Bacteria • Archaea • Eukarya • The fundamental differences among cell types in organisms are reflected in classifications

27. Figure 1-11 The domains and kingdoms of life DOMAIN BACTERIA FIRST CELLS DOMAIN ARCHAEA Protists Plants DOMAIN EUKARYA Fungi Animals

28. 1.3 How Do Scientists Study Life? • Biologists classify organisms based on their evolutionary relationships (continued) • Bacteria and Archaea are single, simple cells • Eukaryotic organisms have one or more extremely complex cells • The domain Eukarya contains four subdivisions or kingdoms • Fungi • Plantae • Animalia • Protists

29. 1.3 How Do Scientists Study Life? • Biologists classify organisms based on their evolutionary relationships (continued) • Three characteristics underlie the classification of an organism into a domain and kingdom • There are exceptions to any simple set of rules used to distinguish the domains and kingdoms, but three characteristics are particularly useful • Cell type—simple or complex • The number of cells in each organism—unicellular or multicellular • Energy acquisition

30. 1.3 How Do Scientists Study Life? • Cell type distinguishes the Bacteria and Archaea from the Eukarya • All cells share common features • Plasma membrane is a thin sheet of molecules surrounding the cell • Organelles are specialized structures that carry out specific functions • All cells contain DNA, the hereditary material

31. 1.3 How Do Scientists Study Life? • Multicellularity occurs only among the Eukarya • Unicellular (single-celled) organisms are found in • Bacteria • Archaea • Multicellular (many-celled) organisms are found in Eukarya, within the kingdoms • Fungi • Plantae • Animalia

32. 1.2 What Is Evolution? • Three natural processes underlie evolution • Genetic variation among members of a population due to differences in their DNA • Inheritance of those variations by offspring of parents carrying the variation • Natural selection of individuals whose survival and enhanced reproduction are due to the favorable variations they carry

33. 1.2 What Is Evolution? • Mutations are the original source of differences in DNA • Variations are due to the differences in genes, which are components of DNA and the basic units of heredity • Mutations occur when changes in genes are mistakenly copied • Mutations can also result from DNA damaged by • UV rays from sunlight and toxic chemicals from cigarette smoke

34. 1.2 What Is Evolution? • Some inherited mutations help individuals survive and reproduce • Natural selection is the process by which organisms with certain inherited traits survive and reproduce better than others in a particular environment • Organisms that best meet environmental challenges leave the most offspring • Natural selection preserves genes that help organisms flourish

35. Figure 1-9 A fossil Tyrannosaurus rex

36. 1.4 What Is Science? • Science is the systematic inquiry – through observation and experiment – into the origins, structure, and behavior of living and nonliving environments

37. 1.4 What Is Science? • The scientific method is an important tool of scientific inquiry • The scientific method consists of six interrelated elements • Observation • Question • Hypothesis • Prediction • Experiment • Conclusion

38. 1.4 What Is Science? • The scientific method is an important tool of scientific inquiry (continued) • Scientific inquiry is a rigorous method for making observations • The scientific method for inquiry follows six steps

39. 1.4 What Is Science? • The six steps of scientific inquiry 1. Observation of a specific phenomenon 2. The observation, in turn, leads to a question 3. The question leads to formulation of a hypothesis, based on previous observations, which is offered as an answer to the question

40. 1.4 What Is Science? • The six steps of scientific inquiry (continued) • The hypothesis leads to a prediction, which isthe expected outcome of testing if the hypothesis is correct • The prediction is tested by carefully designed additional observations or carefully controlled manipulations called experiments • The experiments produce results that either support or refute the hypothesis, allowing the development of a conclusion

41. 1.4 What Is Science? • Biologists test hypotheses using controlled experiments • Two types of situations are established • A baseline or control situation in which all possible variables are held at a constant • An experimental situation in which one factor, variable, is manipulated to test the hypothesis to determine that this variable is the cause of an observation • Science is useless unless communicated • The scientific method is illustrated by experiments by Francesco Redi and Malte Andersson

42. Figure E1-1 The experiment of Francesco Redi illustrates the scientific method Observation: Flies swarm around meat left in the open; maggots appear on the meat. Question: Where do maggots on the meat come from? Hypothesis: Flies produce the maggots. Prediction: IF the hypothesis is correct, THEN keeping the flies away from the meat will prevent the appearance of maggots. Experiment: Obtain identical pieces of meat and two identical jars Place meat in each jar Experimental variable: Cover the jar with gauze Leave the jar uncovered gauze prevents the entry of flies Controlled variables: Leave covered for several days Leave exposed for several days time, temperature, place Flies swarm around and maggots appear Flies are kept from the meat; no maggots appear Results Experimental situation Control situation Conclusion: The experiment supports the hypothesis that flies are the source of maggots and that spontaneous generation of maggots does not occur.

43. Figure E1-2 The experiment of Malte Andersson Observation: Male widowbirds have extremely long tails. Question: Why do males, but not females, have such long tails? Hypothesis: Males have long tails because females prefer to mate with long-tailed males. Prediction: IF females prefer long-tailed males, THEN males with artificially lengthened tails will attract more mates. Experiment: Divide male birds into four groups Manipulate the tails of the males Experimental variable: Do not change the tail Cut the tail and re-glue in place Cut the tail to half of the original length Add feathers to double the tail length length of tail Controlled variables: Release the males, wait a week, count the nests Release the males, wait a week, count the nests Release the males, wait a week, count the nests Release the males, wait a week, count the nests location, season, time, weather Average of about one nest per male Average of about one nest per male Average of less than half a nest per male Average of About two nests per male Results Experimental groups Control groups Conclusion: The hypothesis that female widowbirds prefer to mate with long-tailed males (and are less likely to mate with short-tailed males) is supported.

44. 1.4 What Is Science? • Scientific theories have been thoroughly tested • A scientific theory is a general and reliable explanation of important natural phenomena that has been developed through extensive and reproducible observations and experiments • A scientific theory is best described as a natural law, a basic principle derived from the study of nature, which has never been disproven by scientific inquiry

45. 1.4 What Is Science? • Scientific theories are formulated in ways that can potentially be disproved • Basic principles of science are referred to as theories because theories can be disproved or falsified • Falsifying theories is distinctly different between scientific theories and faith-based beliefs • “Each creature on Earth was separately created” cannot be subjected to scientific inquiry because it is a belief rooted in faith

46. 1.4 What Is Science? • Science is a human endeavor • Human personality traits are part of “real science” • Scientists, like other people, may be driven by pride, ambition, or fear • Scientists sometimes make mistakes • Accidents, lucky guesses, intellectual powers, and controversies with others contribute strongly to scientific advances

47. 1.4 What Is Science? • Science is a human endeavor (continued) • In the 1920s, bacteriologist Alexander Fleming grew bacteria in cultures • One of the bacterial cultures became contaminated with a mold • Fleming was about to destroy the culture when he noticed the mold (Penicillium) inhibited bacterial growth in the culture

48. 1.4 What Is Science? • Science is a human endeavor (continued) • Fleming hypothesized that the mold produced an antibacterial substance • Further tests using broth from pure Penicillium cultures lead to the discovery of the first antibiotic, penicillin

49. Figure 1-12 Penicillin kills bacteria A Petri dish contains solid growth medium Bacteria grow in dense red colonies on the growth medium A substance diffuses from the mold and kills the bacterial colonies, which lose their color as they die A colony of the mold Penicillium

50. 1.4 What Is Science? • Science is a human endeavor (continued) • Fleming continued beyond a lucky “accident” with further scientific investigation to a great discovery • “Chance favors the prepared mind” Louis Pasteur