1. Biology 351 Comparative Anatomy Dr. Tony Serino Misericordia Univ.
Introduction
Biology 351
Comparative Anatomy
Dr. Tony Serino
Misericordia Univ.

2. Comparative Anatomy
The study of morphology between species to understand evolutionary trends.
Evolutionary Morphology
Uses both living and extinct species
Can be combined with Comparative Physiology

3. Darwin’s Theory (1859)

4. Darwin’s Observations
All species over produce
Most populations are normally stable
Natural resources are limited

5. Darwin’s Observations
Individuals of a population vary from one another
Much of this variation is inheritable

6. Darwin’s Inferences
Over reproduction leads to a struggle (competition) for resources and survival with only a fraction surviving to reproduce successfully
Those who are better fitted (adapted) to their environment more often succeed to survive and reproduce
This results in the population changing to increase the frequency of those alleles which increase the survival rate.

7. Evolution- Descent with modification by means of natural selection to better adapt to their environment
Differential success in the survival and reproduction of individuals in a population changes the frequency of alleles in the gene pool such that the population adapts to its environment (increases its fitness)

8. Descent with Modification

9. Evidence of Evolution
Biogeography –study of the geographic distribution of populations

10. Evidence of Evolution
Comparative Anatomy & Physiology –study of common characteristics, processes, and/or behaviors
Homologous Structures
Vestigial organs

11. Evidence of Evolution
Fossil Record

12. Fossils

13. Evidence of Evolution
Comparative Embryology –study of animal development

14. Evidence of Evolution
Molecular Biology -study of important molecules in living cells; degree of conservation of molecular structure indicates relatedness between species

15. Microevolution
Generational changes in allele frequency in a population over time.
May lead to formation of new species
Darwin in 1874

16. Mechanisms for Microevolution
Genetic drift –random changes in small gene pool survival based on random chance (seeds happen to fall on fertile ground)

17. Genetic Drift: Founder Effect
Small random number of individuals move to a new location
Chance alone dictates what alleles moved to start new population
Ex. Galapagos finches – a storm blew a completely random number of birds from the main land to the islands.

18. Genetic Drift: Bottleneck Effect
Large environmental change that randomly kills off most of the population

19. Other Mechanisms for Microevolution
Gene flow –change in gene pool frequencies due to migration of individuals between populations
Mutation –change in gene structure changes allele frequency (only mechanism that can create new alleles)
Non-random mating –changes allele frequency due to choices in mating; ex. Inbreeding, assortative mating, sexual selection
Natural Selection –change in allele that adapts the population better to its environment

20. Types of Natural Selection

21. Speciation –generation of new species
Two types:
Anagenesis –one species evolves into another
Cladogenesis –one species evolves into several new species (like, in adaptive radiations); forms a lineage or clade

22. Cladogenesis Requires reproductive isolation to occur
Behavior, Temporal, Mechanical, Gametic, etc.
Main modes for reprod. isolation:
Allopatry –geographical isolation leading to reproductive isolation
Sympatry –reproductive isolation arising within the parent’s population habitat

23. Grand Canyon Ground Squirrels
The formation of the Grand Canyon 10,000 ya led to allopatric isolation of the rims squirrel populations eventually forming new species

24. Macroevolution –refers to large scale patterns, trends and rates of change in groups of species over time
Two theories on rate of evolution: Gradualism and Punctuated Equilibrium
Related concepts:
Pre-adaptation –pre-existing structures used to fulfill new role (biological role vs. function)
Ex: feathers (as insulator and later flight),
Some fish fins  tetrapod limbs for walking

25. Heterochrony –evolutionary changes in the timing or rate of developmental growth
Tree dwelling salamanders have shorter more webbed feet; growth of the foot ends sooner.

26. Heterochrony –change in timing of developmental development; may result in:
Allometric Growth –differential growth of body regions results in the adults shape

27. Paedomorphosis (Neoteny)
Heterochrony –change in timing of sexual development; may result in:
Paedomorphosis (Neoteny)
Retention of juvenile characteristics in the adult

28. Plate tectonics

29. Continental Drift

30. Adaptive Radiations

32. Geological Time Scale

33. Geologic Timeline of Earth *mya –millions of years ago
Era
Period
Time (mya)*
Important Events
Cenozoic (Age of Mammals)
Quaternary
1.8
Historical time; Ice age, Humans appear
Tertiary 65
Mammals, Teleosts, Birds, Insects and angiosperms undergo major radiation
Mesozoic (Age of Dinosaurs)
Cretaceous
144
Cretaceous extinction (includes dinosaurs), angiosperms appear
Jurassic
206
Dinosaur and gymnosperms dominate
Triassic
245
Major radiation of dinosaurs and gymnosperms; extinction near end of period of many early dinosaur groups
Paleozoic (Age of Fish)
Permian
290
Permian Mass Extinction (half of all life forms become extinct); radiation of reptiles
Carboniferous (Pennsylvanian and Mississipian periods) (Age of Amphibians)
363
Amphibians and vascular plants dominate, first reptiles and seed plants appear
Devonian (Age of Teleosts)
409
Radiation of bony fish, first amphibians and insects appear; extinction of many jawless fish
Silurian
439
Diversity of jawless fish and early vascular plants; first jawed fish appear
Ordovician
510
Marine alga abundant, colonization of land by arthropods and plants
Cambrian
543
Radiation of most modern animal phyla (Cambrian Explosion)
Precambrian
4600
Formation of Earth and its biosphere, Life begins (Archaebacteria) about 3800 mya; Oxygen begins to dominate atmosphere about 2700 mya; 600 mya soft-bodied invertebrates and algae thrive (Pre-cambrium Explosion)
Geologic Timeline of Earth *mya –millions of years ago

34. Types of Macroevolution: Convergent Evolution

35. Types of Macroevolution: Co-evolution
-ants and acacia tree -lions, prey, and scavengers

36. Types of Macroevolution: Divergent Evolution

37. Phylogeny –course of evolution
Dendrograms –branching “tree” diagrams depicting possible phylogeny usually by assorting organism by their similarities or common features
Systematics –study of biological diversity in an evolutionary context; links groups together is some logical pattern
Traditional systematics –places organisms in same taxon (group) if they share homologous structures
Phylogenetic systematics (cladistics) –places organisms in the same clade (lineage) (all the organisms in that lineage plus their common ancestor)
Example of Lungfish –traditional may put with other organisms with lung; Cladistics would group only with fish

38. Hierarchal Classification
-usually only group organisms together by morphological structures
Binomial system for naming species

39. Cladistics –uses multiple characters to group organisms
-may include morphology, fossils, molecular data, etc.
Cladograms allow us to explore relationships easily, but can lead to redundant terminology

40. Cladistic Relationships
Monophyletic taxons include an ancestor and all of its descendants
Paraphyletic taxons include a common ancestor but only some (not all) of its descendents (an artificial grouping)
Polyphyletic taxons place animals together for non-homologous similarities (an artificial grouping)

41. Similarity Comparisons
Other Important Anatomical Concepts
Similarity Comparisons
Homology –structures in two different species are homologous if they can be traced back to a feature in a common ancestor
Analogy –structures which share a common function
Homoplasy –structures with similar appearance
Note: primitive vs. derived

42. Symmetry

43. Body Planes

44. Anatomical Directions

47. Segmentation (metamerism)