Comparative Anatomy of Vertebrates Z441 Lecture 1 PDF

Comparative Anatomy of the Vertebrates ‫تشريح الفقاريات المقارن‬ Z441 Credit hours: 3 Introduction Lecture 1 Chapter 1 Aim of the course  A study of the structural and functional evolution of selected organ systems in representative vertebrates.  Structures...

Comparative Anatomy of the Vertebrates ‫تشريح الفقاريات المقارن‬ Z441 Credit hours: 3 Introduction Lecture 1 Chapter 1 Aim of the course  A study of the structural and functional evolution of selected organ systems in representative vertebrates.  Structures and their organization are interpreted in terms of their embryological development, phylogeny, and functional adaptations. Topics 1- Definition of Anatomy, Comparative Anatomy. Brief history of Comparative Anatomy. Method of studying Comparative Vertebrate Anatomy. 2- Integumentary system 3- Nervous system 4- Skeletal system What is Anatomy?  The branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts. What is Comparative Anatomy?  The science of comparative vertebrate anatomy is the study of similarities and differences in structural organization, entailing detailed comparisons of the data and derivation of general principals from which deductive conclusions can be drawn.  The purpose of such an analysis is to construct logical explanations to the variations in the structures of the bodies of vertebrates and their close relatives. Why is Comparative Vertebrate anatomy important?  Comparison of structures throws similarities and differences into better relief.  Comparison emphasizes the functional and evolutionary themes vertebrates carry within their structures.  Comparison also helps formulate the questions we might ask of structure. Comparative Vertebrate Anatomy  Different fishes have different tail shapes.  In the homocercal tail, both lobes are equal in size, making the tail symmetrical. In the heterocercal tail, found in sharks and a few other groups, the upper lobe is elongated.  Why the tail is different?  Why an animal is constructed in a particular way is related to the functional requirements the part serves?  Functional morphology is the discipline that relates a structure to its function. Definitions of Biological Disciplines  Evolution—change through time  Biodiversity—variety of living forms & their habits  Anatomy & Physiology—structure & function  Behavior—how animals do things  Ecology—interactions of animals with each other & their physical environments Levels of Organization  How molecules within cells Interact—molecular Biology  how cells function— Cell Biology  how tissues/organs of an individual organism function & interact—Physiology Levels of Organization  how individuals w/in a species interact— Population Biology intraspecific level  how different kinds of organisms interact—Community Ecology interspecific level  Relate levels of organization when comparing organisms to better understand evolutionary trends. Phylogeny The course of evolutionary change within a related group of organisms. The course of evolution.  Also, a graphical representation or evolutionary tree of that change.  Often represented by a diagram of bifurcating branches.  Within the amphibian limb are the structural reminders of its fish-fin ancestry; within the wing of a bird are the evidences of its derivation from the reptilian forelimb.  Each modern group living today carries forward mementos of the evolutionary course traveled by its ancestors.  Phylogeny  Historical relationship between organisms or lineages  Ancestry shown by phylogenetic tree  Phylogenetic Systematics- shows relationships from past to present ◦ Shows evolutionary relationships Figure 2.1  Major Vertebrate Groups Figure 2.2 History  The idea of change through time in animals and plants dates back to ancient schools of Greek philosophy. Linnaeus Swedish biologist devised a system for naming animals and plants which is still the basis for modern taxonomy. (species do not change).  Darwin termed the mechanism now determining which organisms survive and which do not natural selection, nature’s way of weeding out the less fit.  In this struggle for existence, those with superior adaptations would, on average, fare better and survive to pass on their successful adaptations. Thus, descent with modification resulted from the preservation by natural selection of favorable characteristics.  Lamarck’s view. It has been called evolution by means of the inheritance of acquired characteristics.  Characters were “acquired” to meet new needs and then “inherited” by future generations.  Today we know the answers to this paradox. Mutations in genes produce new variations.  Genes carry characteristics unaltered and without dilution from generation to generation.  Morphology is the central theme in evolutionary biology. Cuvier- considered morphology to be integration of form and Figure 1.8. Fruit fly wing and pteranodon function wing analogous and homoplastic structures but not homologous.  Morphological concepts Similarities, symmetry, and segmentation. Similarities  Ancestry, function , or appearance. Similarities  Homologous structures – share common ancestry – may have different functions Ex: Birds wings and mole forearm. tracing their common ancestry to reptiles. Homology recognizes similarity based upon common origin. Serial homology – means similarity between successively repeated parts in the same organism. The chain of vertebrae in the backbone, the several gill arches, or the successive muscle segments along the body are examples Analogous structures – same function – may have different ancestry ex: bat wing & butterfly wing. On the other hand, turtle and dolphin forelimbs function as paddles (analogy) and can be traced historically back to a common source (homology).  Similarities  Homoplastic Structures look similar but distantly related (may or may not be homologous or analogous). Ex: In addition to sharing a common origin (homology) and function (analogy), turtle and dolphin flippers also look superficially similar; they are homoplastic.  Morphology is the central theme in evolutionary biology. Figure 1.8. Fruit fly wing and pteranodon wing analogous and homoplastic structures but not homologous.  Figure 1.9. Forelimb bones. Homology in type of bones present (e.g., carpals, humerus, etc.) Adaptations give a variety of functions (e.g., walk, fly, swim, etc.) Natural Selection- variations in organisms result in varying degrees of success in competition (i.e., survival of the “reproductive” fittest)  Vertebrate embryos are structurally similar in early embryonic stages. Figure 1.10. Vertebrate embryo development.  Birds: Loss of digits, some bones fused Bats: 5 digits, elongated metacarpals and phalanges Figure 1.7. Wing morphology. Pterosaurs: elongated fourth digit  Homology- two or more structures that share common ancestry  Analogy- structures have similar functions  Homoplastic- structures look similar but distantly related Symmetry ‫التماثل‬  Radial symmetry: refers to a body that is laid out equally from a central axis, so that any of several planes passing through the center divides the animal into equal or mirrored halves.  Saggital symmetry bilateral symmetry, only the midsagittal plane divides the body into two mirrored images, left and right  Symmetry  Anterior refers to the head end (cranial), posterior to the tail (caudal).  Dorsal to the back, and ventral to the belly or front.  The midline of the body is medial; the sides are lateral.  An attached appendage has a region distal (farthest) and proximal (closest) to the body.  The pectoral region or chest supports the forelimbs; the pelvic region refers to hips supporting the hindlimbs.  Symmetry  Frontal plane ‫(أمامي‬cononal plane) divides a bilateral body into dorsal and ventral sections.  Sagittal plane ‫سهمي‬splits it into left and right portions.  Transverse plane‫ عرضي‬separates it into anterior and posterior portions. Because humans carry the body upright and walk with the belly forward, the terms superior and inferior generally replace the terms anterior and posterior  Segmentation or Metamerism ‫التقسيم‬  The process that divides the body into duplicated sections. Ex: Tapeworms (segmentation is the basis for amplifying output). Earthworm(segments for support and locomotion). Reference  Kardong, KV (2011). Vertebrates: Comparative Anatomy, Function, Evolution. 6th edition, McGraw-Hill Companies, Inc., New York, USA. p. 1-18. Thank you