Anatomical and Evolutionary Concept

1. Anatomical and Evolutionary Concept Ma.Luisa V. Cuaresma Biological Sciences Department

2. Taxonomic Principles What if they discovered an unknown organism? How do they begin with their classification? • Biologists classify organisms into different categories mostly by judging degrees of apparent similarity and difference that they can see.  Assumption: The greater the degree of physical similarity = the closer the biological relationship.

3. Researchers begin their classification by: • looking for anatomical features that appear to have the same function as those found on other species.  • determining whether or not the similarities are due to an independent evolutionary development or to descent from a common ancestor.  • If the latter is the case, then the two species are probably closely related and • should be classified into the same or near biological categories.

4. Similarities: Homology, Analogy and Homoplasy Homology • features of two or more organisms sharing common ancestry. • anatomical features, of different organisms, that have a similar appearance or function because they were inherited from a common ancestor that also had them.  • The wing of a cat, bat, whale and your arm have the same functional types of bones as did our shared reptilian ancestor.   Therefore, these bones are homologous structures. • The more homologies twoorganisms possess, the more likely it is that they have a close genetic relationship.

5. Homologous Structures The bones are color-coded to demonstrate that all of the organisms in the picture must have evolved from a common ancestor. Homology (shared characteristics among different species) is presented as solid evidence for biological evolution.

6. Analogy • anatomical features that have the same form or function in different species that have no known common ancestor.  • established through behavioral and biomechanical analysis • may or may not be homologous • Examples: insect wing & bird's wing,Fish fin; whale flipper Analogousstructures: wing of an insect, bird bat and pterosaur

7. Homoplasy • features of two or more organisms are related by similarity of appearance • similarities cannot be explained by either homology or analogy • nonhomologous structural similarities between species.  In these cases, the common ancestor did not have the same anatomical structures as its descendants.  Instead, the similarities are due to independent development in the now separate evolutionary lines.  • misleading similarities. • Homoplastic structures can be the result of parallelism, convergence, analogies, or mere chance. • Ex: Sail fish and Pelycosaur ; Mimicry & camouflage

8. Mimicry or Camouflage

9. Ancestry Appearance 1 2 4 3 Function 5 7 6 The Distinctions and Relations among Common Ancestry (Homology), Common Function (Analogy) and Common Appearance (Homoplasy) Legend: 1-Same ancestor; Diff. fxn.; Diff. appearance 2-Same ancestor; same fxn.; diff. appearance 3-Same ancestor; same fxn.; same appearance 4-Same ancestor; diff. fxn.; same appearance 5-Diff. ancestor; same fxn.; diff. appearance 6-Diff. ancestor; same fxn.; same appearance 7-Diff. ancestor; diff. fxn.; same appearance

10. Homoplastic structures can be the result of parallelism, convergence, analogies, or mere chance. Parallelism, or parallel evolution, is a similar evolutionary development in different species lines after divergence from a common ancestor that did not have the characteristic but did have an initial anatomical feature that led to it.  Convergence, or convergent evolution, is the development of a similar anatomical feature in distinct species lines after divergence from a common ancestor that did not have the initial trait that led to it. 

11. Linnaean scheme of Classification • Lumps organisms together based on presumed homologies.   Assumption : • The more homologies two organisms share, the closer they must be in terms of evolutionary distance.  • The higher, more inclusive divisions of the Linnaean system are created by including together closely related clusters of the immediately lower divisions. 

12. The result is a hierarchical system of classification with the highest category consisting of all living things. 

13. Cladistics • This involves making a distinction between derived and primitive traits when evaluating the importance of homologies in determining placement of organisms within the Linnaean classification system.  • Derived traits are those that have changed from the ancestral form and/or function. • An example is the foot of a modern horse.  Its distant early mammal ancestor had five digits.  The bones of these digits have been largely fused together in horses giving them essentially only one toe with a hoof.  • .  In contrast, primates have retained the primitive characteristic of having five digits on the ends of their hands and feet.  Animals sharing a great many homologies that were recently derived, rather than only ancestral, are more likely to have a recent common ancestor. 

14. Development: Ontogeny & Phylogeny • Ontogenesis • Developmental history of an organism affected by genes; emb; embryogenic changes due to aging and ends at death. • Single lifetime

16. Phylogenesis • Evolutionary history of a Taxon (family or group of organisms) by relation to an evolutionary (ancestral) lineage. • 100T to 100M of years

17. Symmetry and Segmentation • describes the way in which the body of the animal meets the surrounding environment. • is the balanced distribution of duplicate body parts or shapes. Body Symmetry: orientation of the animal body in relation to environment.

18. Radial Symmetry • Body is laid equally from a central axis; any several planes passing through divides the animal into equal halves. • Ex: Body of Starfish

19. Bilateral Symmetry-Body is laid equally from a mid-sagittal plane; divides the body into two, mirror halves.Ex: Vertebrate Animal

20. Midsagittal and Sagittal(lengthwise) • -Divides the R & L parts • Coronal (frontal planes) • -Divides the ventral (anterior) and dorsal (posterior) parts. • Transverse (horizontal) • -Divides the body into superior (upper) & inferior (lower) parts.

21. Superior – structures higher or going cranial • Inferior – structures lower or going caudad • Posterior – structures located dorsally or back part • Anterior – structures located ventrally or front (belly) part * In a 4-legged animal (anterior-cranial; posterior-caudal; dorsal-vertebral location; ventral-belly location)

23. Directional Terms Anterior: In front of, front Posterior: After, behind, following, toward the rear Distal: Away from, farther from the origin Proximal: Near, closer to the origin Dorsal: Near the upper surface, toward the back Ventral: Toward the bottom, toward the belly

24. Superior: Above, over Inferior: Below, under Lateral: Toward the side, away from the mid-line Medial: Toward the mid-line, middle, away from the side Rostral: Toward the front Caudal: Toward the back, toward the tail

25. Segmentation • segmentation(metamerism) - Division of the body along the anteroposterior axis into a serial succession of segments. • Divides the body into duplicated sections or metamerism • Metamere – segment or unit section • More evident in invertebrates (ex: worms) than vertebrates. • Ex: Backbone; Muscles of the fish; Teeth

26. Body Regions • Head/Cranium • Neck/Cervical • Thorax / Pectoral region • Abdomen/Peritoneum • Hip/Pelvis • Urogenital/Perineum • Upper extremity • Appendages of pectoral or chest region • Lower extremity • Appendages of pelvic or hip region

27. Cranial cavity • -Oral/buccal cavity; Nasal cavity; Orbits; Middle-ear cavity (auditory ossicles / ear bones) • Vertebral cavity • Thoracic / Pectoral cavity -Mediastinum – breast plate -Pleural cavity – encases the lungs -Pericardial cavity – encases the heart • Abdominal or Peritoneal cavity • Pelvic / Hip cavity – encases reproductive parts • Perineum – encases urogenital parts Body Cavity

29. End of Presentation!!!!