Evolution and Our Heritage

Transcription

1 BIOLOGY OF HUMANS Concepts, Applications, and Issues Fifth Edition Judith Goodenough Betty McGuire 22 Evolution and Our Heritage Lecture Presentation Anne Gasc Hawaii Pacific University and University of Hawaii Honolulu Community College

2 Evolution and Our Heritage OUTLINE: Evolution of Life on Earth Scale of Evolutionary Change Evidence of Evolution Human Evolution

3 Evolution of Life on Earth Evolution Descent with modification from a common ancestor Earth is estimated to be 4.5 billion years old Environment of early Earth was very different from that of today Hot, volcanic crust Intense UV radiation Almost no gaseous oxygen Physical and chemical evidence suggests that life has existed for 3.8 billion years

4 Figure 22.1 Representation of the early Earth.

5 Evolution of Life on Earth Chemical evolution Life evolved from chemicals increasing in complexity over about 300 million years Possible steps in chemical evolution Inorganic molecules Small organic molecules Macromolecules Early cells Prokaryotic Eukaryotic Multicellular organisms

6 Small Organic Molecules Inorganic molecules form small organic molecules Favored by low-oxygen atmosphere Oxygen attacks chemical bonds Energy provided by lightning and intense UV radiation Tested by several groups of scientists Small organic molecules formed larger molecules Possibly proteins or nucleic acids First genetic material could have been RNA or DNA

7 Figure 22.2 Apparatus used by Miller and Urey.

8 Macromolecules and Early Cells Organic macromolecules (proteins and genetic material) aggregated into droplets Precursors to living cells Earliest cells Prokaryotic cells about 3.8 billion years ago Eukaryotic cells about 1.8 billion years ago

9 Macromolecules and Early Cells Endosymbiont theory Some organelles within eukaryotic cells were once free-living prokaryotes Mitochondria may be descendants of once free-living bacteria Multicellularity Evolved in eukaryotes about 1.5 billion years ago Eventually led to organisms such as plants, fungi, and animals

10 Figure 22.3 Possible steps in the origin of life on Earth.

11 Scale of Evolutionary Change Microevolution Changes at the genetic level within a population over a few generations Macroevolution Larger-scale evolutionary change over longer periods of time Origin of groups of species Mass extinctions

12 Microevolution Basic terms in microevolution Population: group of individuals of the same species living in a particular area Gene pool: includes all of the alleles of all of the genes of all individuals in a population

13 Microevolution Variation in populations: sexual reproduction shuffles alleles already present in population Gametes of an individual are variable (crossing over and independent assortment) Combination of gametes at fertilization Mutation: produces new genes and new alleles Occurs at low rate in any set of genes

14 Microevolution Some processes that lead to microevolution Genetic drift Gene flow Mutation Natural selection

15 Microevolution Genetic drift Allele frequencies within a population change randomly because of chance alone Usually negligible in large populations Two mechanisms that facilitate Bottleneck effect Founder effect

16 Genetic Drift Bottleneck effect A change in the gene pool that occurs when there has been a dramatic reduction in population size Individuals are killed at random Alleles in survivors may not be representative of the original population

17 Genetic Drift Founder effect Genetic drift in new, small colonies A few individuals leave their population and establish themselves in a new, isolated place Genetic makeup of the colonizing individuals is probably not representative of the population they left

18 Gene Flow Occurs when individuals move into and out of a population and interbreed with the resident population Cessation of gene flow can be important in formation of new species

19 Gene Flow Species A population or group of populations whose members are capable of successful interbreeding under natural conditions Speciation Formation of a new species When populations become separated, they may become genetically distinct and no longer capable of successful interbreeding Can result in a new species

20 Natural Selection Charles Darwin On the Origin of Species (1859) Species are not specially created, unchanging forms Modern species are descendants of ancestral species Evolution occurs by natural selection

21 Natural Selection Individual variation exists within a species, and some of this variation is inherited Some individuals leave more surviving offspring than others because their particular inherited characteristics make them better suited to their local environment Evolutionary change occurs as the traits of successful individuals become more common in the population

22 Natural Selection Fitness Compares the number of reproductively viable offspring among individuals Individuals with greater fitness have more of their genes represented in future generations Adaptation Through natural selection, populations become better suited to their environment

23 Natural Selection Natural selection does not lead to perfect organisms Can act on available variation only Can modify existing structures only Organisms cannot be perfect at everything Face many competing demands, so adaptations are often compromises

24 Natural Selection Web Activity: Agents of Change

25 Macroevolution Large-scale evolutionary change over long periods of time Linnaeus developed the Latin binomial scheme for naming organisms The genus name is followed by the specific epithet; both are italicized Example: Homo sapiens

26 Macroevolution Linnaeus also developed a system for classifying organisms into a series of increasingly broad categories Species Genus Family Order Class Phylum Kingdom Domain added later as the most broad category

27 Figure 22.5 Categories in the classification of living organisms.

28 Phylogenetic Trees Branching diagrams that depict hypotheses about evolutionary relationships among species or groups of species Begin by constructing a character matrix

29 Figure 22.6 A phylogenetic tree depicts hypotheses about evolutionary relationships among organisms.

30 Evidence of Evolution Comes from several sources Fossil record Biogeography Comparison of anatomical and embryological structures Molecular biology

31 Fossil Record Fossils preserved remnants and impressions of past organisms Provide strong evidence of evolution Biased sampling of past life Fossilization Occurs as hard body parts such as bones, teeth, and shells become impregnated with minerals from surrounding water and sediment Eventually the sediments may be uplifted by geological processes, exposing the fossil

32 Figure 22.7 A sampling of past life in fossils.

33 Figure 22.8 A typical sequence for fossilization.

34 Fossil Record Fossils of extinct organisms show similarities to, and differences from, living species Transitional forms link ancient organisms to modern species Example: whale evolution

35 Fossil Record Biogeography Study of the geographic distributions of organisms Geographic distributions often reflect evolutionary history and relationships Related species are more likely to be found in the same geographic area than are unrelated species

36 Figure 22.9 The evolution of whales as revealed by transitional fossils.

37 Geographic Distributions and Comparative Molecular Biology New distributions of organisms occur by two basic mechanisms Dispersal Organisms move to new areas Areas occupied by organisms move or are subdivided Comparative anatomy Homologous structures Structures that are similar and that probably arose from a common ancestry

38 Geographic Distributions and Comparative Molecular Biology Web Activity: Biogeography and Continental Movement

39 Figure The story of marsupials and Australia.

40 Figure Homologous structures.

41 Evidence of Evolution Comparative molecular biology Molecular clock hypothesis Based on the assumption that point mutations in DNA occur at a constant rate The more differences in the DNA sequences between two organisms, the more time has elapsed since the common ancestor

42 Figure Resemblance early in development indicates common descent.

43 Comparative Anatomy and Embryology Convergent evolution When two organisms evolve similar structures because of similar ecological roles and selection pressures Analogous structures Structures that are similar because of convergent evolution Common embryological origins can be considered evidence of common descent Example: all vertebrate embryos look very similar early in development

44 Evidence of Evolution Web Activity: Principles of Evolution

45 Human Evolution Human roots trace back to the first primates Primates probably arose from an insect-eating mammal that lived in trees, like a modern tree shrew

46 Human Evolution Primate characteristics reflect an arboreal lifestyle specialized for manual capture of insects Flexible, rotating shoulder joints Sensitive pads on ends of digits Nails instead of claws Grasping feet and hands Forward-facing eyes Large brain Small litter size

47 Figure A tree shrew.

48 Human Evolution Order Primates Suborder Lemurs, lorises, and pottos Retain ancestral features Suborder Monkeys, apes, and humans Family Hominidae now includes apes and humans ( hominids) Subfamily Hominidae includes human lineage ( hominins)

49 Figure Examples of modern primates.

50 Figure Monkeys and apes are placed with humans in another suborder.

51 Figure Hypothesized relationships among living primates.

52 Comparisons of Human and Chimp Skeletal Anatomy Many aspects of human skeletal anatomy reflect our terrestrial lifestyle and upright stance while walking Bipedalism walking on two feet S-shaped spine Large patella Arms shorter than legs Toes not opposable

53 Figure Some major differences in skeletal anatomy and teeth between chimpanzees and humans.

54 Misconceptions Humans descended from chimpanzees Fact: humans and chimpanzees represent separate phylogenetic branches that diverged about 6 million years ago Modern humans evolved in an orderly stepwise fashion Fact: more than one species of hominin existed simultaneously at several points in the past Different parts of the human body evolved at the same rate Fact: different traits evolved at different times and rates ( mosaic evolution)

55 Figure Hominin footprints from Laetoli, Tanzania.

56 Trends in Hominin Evolution Bipedalism Shortening of jaw and flattening of face Reduced sexual dimorphism in body size Increased brain size along with tool use Language and behavioral complexity

57 Australopithecines Ardipithecus ramidus Oldest hominin remains About 4.4 million years old Discovered in 1994; descriptions published in 2009 Facultative bipedalism May have given rise to Australopithecus

58 Australopithecines Species within the genus Australopithecus (from earliest to most recent) A. anamensis About 4 million years old A. afarensis Lucy About 3.2 million years old May have led to Homo A. africanus About 3 million years old

59 Figure Fossilized remains and reconstruction of Lucy.

60 Homo habilis Species within the genus Homo (from earliest to most recent) Homo habilis ( handy man ) About 2.5 million years ago First member of the modern genus of humans Differed from A. afarensis in having a larger brain size May have used stone tools and been capable of speech

61 Homo ergaster, Homo erectus, and Homo heidelbergensis Homo ergaster ( working man ) About 1.9 million years ago Remains traditionally classified as H. erectus Homo erectus ( upright man ) Diverged from H. ergaster about 1.8 million years ago First hominin to migrate out of Africa May have used fire

62 Homo ergaster, Homo erectus, and Homo heidelbergensis Homo heidelbergensis 800,000 to 30,000 years ago May have given rise to H. sapiens and H. neanderthalensis

63 Homo sapiens thinking man Oldest fossil evidence for modern humans comes from Africa about 130,000 years ago Characteristics Larger brain Flat forehead Absent or small brow ridges Prominent chin Very gracile body form

64 Homo neanderthalensis Neanderthals Known from Europe and Asia from about 200,000 to 30,000 years ago Lived in caves Features reflect adaptations to cold climates Had social structure Now have first version of Neanderthal genome Modern humans may have bred with Neanderthals in the Middle East

65 Homo neanderthalensis Cro-Magnons (form of H. sapiens) Accomplished hunters and artists Lived in groups

66 Figure Relatively recent representatives of the genus Homo.

67 Table 22.1 Review of Some Milestones in Human Evolution

68 Figure The major hominin species.

69 Human Evolution Two hypotheses for the evolution of modern humans Multiregional hypothesis ( multiple origins) H. sapiens evolved independently in Europe, Asia, Africa, and Australia from distinctive local populations of earlier humans Out of Africa hypothesis ( single origin) H. sapiens evolved from earlier humans in Africa and later migrated to Europe, Asia, and Australia

70 Human Evolution Evolution and Faith

71 You Should Now Be Able To: Describe the evolution of life on Earth Understand the scale of evolutionary change Know the evidence of evolution Understand human evolution