Science of Zoology and Evolution of animal diversity

1. Chapter 1 Science of Zoology and Evolution of animal diversity

3. Science of Zoology • Zoology: The scientific study of animal life Phylogeny or phylogenetic tree is a diagram whose branches represent evolutionary lineages and depicts the common descent of species or higher taxa

4. Principles of Science • Nature of science: • Science is guided by natural law • Science has to be explained by reference to natural law • Science is testable against the observable world • The conclusions of science are tentative and therefore not necessarily the final word • Science is falsifiable

5. Principles of Science • Scientific Method • Hypothetico-deductive Method: Scientific process of making a conjecture or assumption and then seeking empirical tests that potentially lead to its rejection

6. Principles of Science • Hypothesis: • Potential answers to questions being asked • Derived from prior observations of nature or from theories derived on such observations • Often constitute general statements about nature that may explain a large number of diverse observations • If a hypothesis is very powerful in explaining a wide variety of related phenomena, it attains the level of a theory

7. Principles of Science The scientific method may be summarized as a series of steps: Observation Question Hypothesis Formation Empirical Test Controlled Experiment Includes at least 2 groups Test Group Control Group Conclusions Accept or reject your hypothesis Publications 1-7

8. Principles of Science • Experimental vs. Evolutionary Sciences • Experimental Sciences: • Seek to explain the proximate or immediate causes that underlie the functioning of biological systems at a particular time and place • Goal: To explain how animals perform metabolic, physiological, and behavioral functions at the molecular, cellular, organismal, and populational levels

9. Principles of Science • Example: • How do birds navigate when migrating long distances? • What mechanism allows a jellyfish to sting? • How does population density affect the physiology and behavior of organisms? Biological sciences that investigate proximate causes are called experimental sciences because they use the experimental method which includes a control

10. Principles of Science • Example: Studying processes by which animals maintain their body temperature under different environmental conditions, digest food, migrate to new habitats, or store energy Experimental sciences: Molecular biology, cell biology, endocrinology, immunology, physiology, developmental biology, and community ecology

11. Principles of Science Evolutionary Sciences: addresses questions of ultimate causes that have molded biological systems and their properties through evolutionary time • Example: • Why do different species of animals have different numbers of chromosomes in their cells? • Why do some animal species maintain complex social systems, whereas other species have solitary individuals?

12. Principles of Science • Evolutionary sciences require comparative method rather than just experimentation. • Systematics is the ordering of organism according to their inferred evolutionary relationships for comparative study. • Evolutionary Sciences: Comparative Biochemistry, Molecular Evolution, Comparative Cell Biology, Comparative Anatomy, Comparative Physiology, and Phylogenetic Systematics

14. Origins of Darwinian Evolutionary Theory • Pre-Darwinian Evolutionary Ideas • Early Greek philosophers, Xenophanes, Empedocles, and Aristotle • Developed idea of evolutionary change • Recognized fossils as evidence of former life

15. Origins of Darwinian Evolutionary Theory • Lamarckism: The First Scientific Explanation of Evolution • Jean Baptiste de Lamarck (1744 – 1829) • Authored 1st complete explanation of evolution in 1809 • Made convincing case that fossils were remains of extinct animals

16. Origins of Darwinian Evolutionary Theory • Proposed an evolutionary mechanism • Inheritance of acquired characteristics • Organisms strive to meet demands of the environment • Acquire adaptations and pass them by heredity to offspring • Individual organisms transform their characteristics to produce evolution • This hypothesis was rejected.

18. Origins of Darwinian Evolutionary Theory • Darwin’s evolutionary theory • Differs from Lamarck's in being a variational not a transfromational theory • Evolutionary change is caused by differential survival and reproduction among organisms differing in hereditary traits

19. Origins of Darwinian Evolutionary Theory • Charles Lyell and Uniformitarianism • Sir Charles Lyell (1797-1875) • Geologist • Principle of Uniformitarianism • Guides scientific study of the history of nature • Laws of physics and chemistry have not changed throughout earth’s history • Past geological events occurred by natural processes similar to those observed today

21. Origins of Darwinian Evolutionary Theory • Lyell’s studies led him to conclude that the earth’s age must be measured in millions of years • Claims left important marks on Darwin’s evolutionary theory

22. Origins of Darwinian Evolutionary Theory • Darwin’s Great Voyage of Discovery • Charles Robert Darwin • Presented the first credible explanation of evolutionary change • Made extensive collections and observations on a 5 year voyage (1831-1836) on the H.M.S Beagle • Published his findings in On the Origin of Species by Means of Natural Selectionin 1859

26. Theories of Evolution and Heredity • Ernst Mayr (Harvard University) proposed that Darwinism should be viewed as five major theories: • Perpetual Change • Common Descent • Multiplication of the Species • Gradualism • Natural Selection

27. Theories of Evolution and Heredity • Perpetual Change The living world is neither constant nor perpetually cycling, but is always changing • The varying forms of organisms undergo measurable change across generations throughout time • Documented by the fossil record • Theory upon which the remaining 4 are based

28. Theories of Evolution and Heredity • Common Descent All forms of life descend from a common ancestor through a branching of lineages • Life’s history has the structure of a branching evolutionary tree, known as a phylogeny • Serves as the basis for our taxonomic classification of animals

30. Theories of Evolution and Heredity • Multiplication of Species The evolutionary process produces new species by splitting and transforming older ones

31. Theories of Evolution and Heredity • Gradualism Large differences in anatomic traits that characterize disparate species originate through the accumulation of many small incremental changes over very long periods of time

32. Theories of Evolution and Heredity • Natural Selection A creative process that generates novel forms from the small individual variations that occur among organisms within a population • Adaptation An anatomical structure, physiological process, or behavioral trait that evolved by natural selection and improves an organism’s ability to survive and leave descendants

33. Evidence for Darwin’s Five Theories of Evolution • Perpetual Change • Evidenced by the fossil record • Fossil: remnant of past life uncovered from the crust of the earth • Many organisms left no fossils

34. Figure 1_10a

35. Figure 1_10b

36. Figure 1_10c

37. Evidence for Darwin’s Five Theories of Evolution • Interpreting the Fossil Record • The fossil record is biased because preservation is selective • Vertebrate skeletons and invertebrates with shells provide more records • Soft-bodied animals leave fossils only in exceptional conditions • Fossils form in stratified layers • New deposits are on top of older material

39. Evidence for Darwin’s Five Theories of Evolution • “Index” or “guide” fossils are “indicators” of specific geological periods • Layers often tilt and crack, and can erode or be covered with new deposits • Under heat and pressure, rock becomes metamorphic and fossils are destroyed

41. Evidence for Darwin’s Five Theories of Evolution • Geological Time • Sedimentary Rock Layers • The Law of Stratigraphy • Dates oldest layers at the bottom and youngest at the top • Time is divided into eons, eras, periods and epochs • Radiometric Dating (late 1940s) • Method for determining the age of rocks • Radioactive decay of naturally occurring elements is independent of heat and pressure

42. Evidence for Darwin’s Five Theories of Evolution • Evolutionary Trends • Trends are directional changes in features and diversity of organisms • Fossil record allows observation of evolutionary change over broad periods of time. • Animals species arise and become repeatedly extinct. • Animal species typically survive 1–10 million years

43. Evidence for Darwin’s Five Theories of Evolution • Horse evolution shows clear trend • Change occurred in both features of horses and numbers of species • Trends in fossil diversity are due to different rates of species formation and extinction

45. Evidence for Darwin’s Five Theories of Evolution • Common Descent • Darwin proposed that all plants and animals descended from a common ancestor • Life’s history forms a branching tree called a phylogeny • All forms of life, including extinct branches, connect to this tree • Phylogenetic research is successful at reconstructing the history of life

46. Evidence for Darwin’s Five Theories of Evolution • Homology and Phylogenetic Reconstruction • Darwin saw homology as major evidence for common descent • Richard Owen described homology as “the same organ in different organisms under every variety of form and function” • Vertebrate limbs show the same basic structures modified for different functions • Darwin’s central idea that apes and humans have a common ancestor was explained by anatomical homologies

48. Evidence for Darwin’s Five Theories of Evolution • Branches of the tree combine species into • Nested hierarchies of groups within groups • The pattern of nested hierarchies • Forms the basis for classification of all forms of life

49. Evidence for Darwin’s Five Theories of Evolution • Ontogeny, Phylogeny, and Recapitulation • Ontogeny • History of the development of an organism through its entire life • Recapitulation (biogenetic law) • Ontogeny recapitulates phylogeny • Flawed notion • Based on Lamarck’s concept of the inheritance of acquired traits