Unit 2 : Diversity of Life

1. Unit 2 : Diversity of Life

2. Classification of Living Things

3. Classification - Concepts and Principles • Scientists have identified 1.5 million kinds of living organisms. To deal with this huge number, biologists classify the organisms according to anestablished international system. This system allows biologists to identify an organism and place it in the correct group with related organisms. • The branch of biology that deals with classification and naming of living organisms is called taxonomy.

4. Taxonomy • naming and placing of all organisms into groups. • science of classifying organisms

5. Early Classification Schemes • placed all organisms into one of two groups

7. Classification by Aristotle and Theophrastus • Aristotle classified animals according to where in the environment they lived. • Theophratus classified plants according to their stem structure

10. The early schemes were based mainly on structural similarities.

11. In 1866 Ernst Haeckel added a third Kingdom - Protista • Was a dumping ground to help deal with organisms that were neither animals or plants • Ex. Euglena- had characteristics of both plant and animals so placed in Protista • As scientist learned more about structure and function of different organism more kingdoms were added. • Kingdom Fungi was proposed. Organisms from this kingdom were originally classified as plants, but fungi are not photosynthetic and are heterotrophic so they became a separate kingdom.

12. Robert Whittaker (1969) • Proposed a 5 Kingdom classification system base upon the following: • A) n umber of cells • B) presence or absence of a nucleus • C) Mode of Nutrition

13. Today • 6 Kingdom classification • Kingdom Animilia • Kingdom Plantae • Kingdom Fungi • Kingdom • Protista • Kingdom Bacteria or Monera • Kingdom Archaea

14. Three Domains( Largest Classification Group) • All six kingdoms are separated into 3 domains • A) Domain bacteria-Kingdom bacteria or Monera • B) Domain Archaea- Kingdom Archaebacteria or Archaea • C). Domain Eukarya-Kingdom Animalia, Plantae, Protista, and Fungi • Domain Eukarya originates from the word Eukaryotic meaning having a nucleus

15. Classification Categories • Within any Kingdom there are many levels of classification.

16. Carl Linnaeus • Linnaeus attempted to classify all known species of his time (1753). • Linnean hierarchical classification was based on the premise that the species was the smallest unit, and that each species (or taxon) nested within a higher category

17. Classification Categories • Kingdom • Phylum • Class • Order • Family • Genus • Species E.g.Humans • Animalia • Chordata • Mammalia • Primates • Hominidae • Homo • Homosapiens

18. Every single type of organism belongs to one kingdom, one phylum, one class, one order, one family, one genus, and one species.

19. Every Organism on earth is placed into each of the classification categories

22. Humans • Kingdom Animalia • Phylum Chordata • Class Mammalia • Order Primates • Family Hominidae • Genus Homo • Species Sapien

23. Domestic Dog • Kingdom Animalia • Phylum Chordata • Class Mammalia • Order Carnivora • Family Canidae • Genus Canis • Species familaris

24. Wolf • K. Animalia • P. Chordata • SubP. Vertebrata** • C. Mammalia • O. Carnivora • F. Canidae • G. Canis • S. lupus (Latin for wolf)

26. Naming Organisms • The system for naming things is called binomialnomenclature. It consists of naming each species with two names. The first is the genus name, the second is the species name. • This system was developed at a time when Latin was the language of scholars, and therefore the names are in Latin. Newly discovered organisms are still named using the Latin language. • Genus has first letter capitalized, species all lower case • underlined or italicized

27. Examples • Homo sapiens - Humans • Canis familaris - dog

28. The scientific name is used worldwide by all scientists, regardless of the language they speak. • The present classification system consists of 6 kingdoms. • The 6 kingdom system of classification is the best and most widely accepted system in use today because of the following reasons:

29. 1. It is generally able to deal with the discoveries of new life forms. • 2. Its ability to cope with changing ideas about those characteristics of greatest importance in classifying organisms. • 3. Able to account for the evolutionary and biochemical relationships that have been discovered among organisms.

30. Common Names • organisms may also be given common names.

31. Common names can cause confusion • StarFish - not a fish • green pepper is also referred to as a bell pepper, sweet pepper

32. Common names also vary from language to language • Dog - perro - inu • Cougar, Mountain Lion, Puma

33. Today’s Classification Schemes • Taxonomy centers around evolutionary relationships

35. Taxonomic Keys • A taxonomic key is a guide or blueprint to identifying organisms already classified by taxonomists. Such keys move from general to specific descriptions. • The keys are dichotomous, consisting of a series of paired statements that describe alternate possible characteristics of the organism. These paired statements usually deal with the presence or absence of characteristics or structures that are easily seen. As each pair of statements gets more specific, a smaller grouping of organisms is produced until the species is identified.

36. Sources of Evidence That We Use When Classifying Organisms: • 1. From fossils • 2. From living things

37. 1. Evidence from Fossils • Fossils are one of the strongest sources of evidence of evolution. • Definition: A fossil is any remains or signs of remains of an organism that lived in the past. • There are 4 major methods of fossil foundation:

38. (A) Preservation of the actual organism. They are usually preserved in a single substance. These include: • (i) Ice - some animals are permanently frozen in ice (e.g. Wooly Mammoth) • (ii) Amber - amber is the resin (gum) from some trees. The resin traps insects. • (iii) Tar Pits - naturally occurring in warmer climates. Animals fall into these pits and their skeletal remains are solidified along with the tar before they can decompose. (e.g. sabre toothed tiger) • (iv) Volcanic Ash - during volcanoes a tremendous amount of ash is produced. This ash covers over organisms and acts as a preservative. (e.g. reptiles)

39. (B) Petrifaction • The organism becomes covered in water containing a high mineral content. Gradually, the original substances of the organism dissolve and are replaced by minerals from the water. The remains of the organism are turned into stone. (e.g. petrified tree)

40. (C) Carbonization • Carbonization is a process whereby large carbon deposits of oil, coal and gas are produced. It is the result of large groups of organisms that are compacted together before they can decay. In coal deposits it is not uncommon to find the fossils of the organisms that produced the coal fields.

41. (D) Molds and Casts • Mold - sediment in which an organism is embedded hardens, preserving the shape of the organism after the remains decompose. • Cast - a mold becomes filled with minerals and then hardens, producing a copy of the external features of an organism.

42. (E) Imprint • An imprint is formed when an impression made in mud by a living organism is preserved when the mud is transformed into rock.

43. TRANSITIONAL FOSSILS LINKING PAST AND PRESENTBasilosaurus (ancient whale

44. Dating Fossils • It is important to know the age of fossils. This is done in two major ways: • (i) Relative Dating by Deposition of Sediment • (ii) Absolute Dating by Radioactive Dating

45. (i) Relative Dating by Deposition of Sediments • Most fossils are formed in sedimentary rocks. Examining layers of sedimentary rock gives the relative age of fossils. The relative age is determined by a fossil’s position in the sedimentary layers. The fossils in the layers on the bottom are assumed to be the oldest, and in the top layers are assumed to be the youngest; unless the geology of the area suggests otherwise. • Scientists have discovered it takes approximately 1000 years of sediment to produce 30 cm of rock. By knowing the fossil’s depth, one can determine the relative age of the fossil. • Example: 150 cm deep means a relative age of 5000 years.

46. (ii) Absolute Dating by Radioactive Dating • Radioactive dating of fossils or the rock in which it is found gives an absolute age. This method is based on the rate of radioactive decay in isotopes of particular elements. Living organisms accumulate certain radioactive isotopes when they are living. Once these organisms die, the radioactive isotopes start to break down. • The rate of the breakdown is called the half-life. This is the time it requires to breakdown half of the originally accumulated radioactive isotopes. Every isotope has a unique half-life. When the half-life of an isotope is known along with its proportion in a fossil-bearing rock, it is possible to calculate the age of the sample.

47. Isotopes Used for Radioactive Dating

48. 2. Evidence from Living Things • Living organisms provide us with evidence that development patterns, body structures and chemical processes show similarities that suggest a common design among some organisms. There are four branches of science that provide evidence which support the concept of evolution.

49. (A) Comparative Embryology • An embryo is an organism that is in the early stages of development. Scientists compare the structures of the embryos of different organisms. These comparisons of the embryological development of different species provide evidence of their relationship. The closer the resemblance between the embryos, the greater the evolutionary relationships.