BI256 Study Guide - Midterm Guide: Myosin, Chagas Disease, Phylogenetics

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4 Apr 2017
Animals Midterm
Chapter 9: Animal Architecture
Cambrian Explosion: Period of rapid evolution and diversification
Occurred 500 MYA, had 100 phyla of animals emerging, now 34 living phyla today
Body Plan: regular arrangement of body structures relative to axis of the body [Grade of organization, body symmetry, number of
embryonic germ layers, and number of body cavities]
Body plans: Animal Symmetry
Body Plan
1. Asymmetry No body axis and no plane of symmetry
Example: Protozoan(Amoeba) and Poriferans (sponge)
2. Spherical Symmetry Infinite number of planes of symmetry, best for floating or rolling
Rare, found in only protozoans (radiolarians)
Sense and interact with environment from all directions
3. Radial Symmetry General form of a cylinder (tubular, vase or bowl shaped)
Biradial symmetry
Jelly fish, sea jelly have radial symmetry, comb jellies are Biradial symmetry
4. Bilateral Symmetry Animals divided alone sagittal plane into 2 identical portions (left and right)
Associated with cephalization (controlled mobility)
Dorsal (top), ventral (bottom), anterior (left) posterior (right) on cat model
5 Grades of Organization within Animals and Animal-like Groups
Grade of Organization
Protoplasmic Level of Organization All life functions within a single cell
Differentiated organelles that perform specific functions
Cellular Level of Organization Aggregation of cells exhibiting functional differentiation
Division of labour between cells (reproduction, nutrition)
Cell-Tissue Level of Organization Aggregation of cells into tissues (definite patterns/layers)
Tissue-Organ Level of Organization Aggregation of tissues into organs
Organs made up of more than one kind of tissue
Parenchyma and Stroma
Organ-System Level of Organization Organ work together as a system to perform a function
Systems associated with basic body function
Four Tissue Types
Tissue Type
Epithelial Free surface (e.g. human skin as well as the human gut)
Barrier function stops things from getting into the body as well as getting out
Muscle Contraction- by contraction the muscles are shortening
Majority of muscle mass is skeletal muscle, cardiac muscle, smooth muscle in the
intestinal wall
Nerve Involved in the transmission of impulses and has a control/regulatory function
Connective Support function, comes in loose connective (proper)m bone and blood
Complexity and Body Size
More complex grades of metazoan organization permit and promote evolution of a large body size
As the body size increases surface-area-to-volume ratios have important consequences for animal respiration, heat, ect
Surface area increases as the square of body length. SA=L2, volume increases as cube of body length V=L3
Benefits of Being Large
Buffers against environmental fluctuations (Temperature, ionic gradients)
Provides protection against predators and promotes offensive tactics, cost of maintaining body temperature is less per gram of
body weight than in small animals
Energy costs of moving a gram of body weight over a given distance less for larger animals
Body Cavities & Germ Layers
Development: series of progressive changes in an individual from is beginning to maturity, begins when a fertilized egg divides
mitotically, specialization occurs as a hierarchy of developmental “decisions”
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Blastula: a cluster of cells (few hundred to several thousand) created by the cleavage
Most multicellular animals, arranged in 1 layer of germ cells around a fluid-filled cavity- blastocoel, in mammal’s cell cluster is a
Gastrulation and Formation of Two Germ Layers
Gastrula- forms by invagination of one side of blastula Gastrocoel ( a new internal cavity) surrounded by 2 layers:
oAn outer layer of ectoderm
oAn inner layer of endoderm
Blastopore- opening into gastrocoel
Blind or incomplete gut- when the only opening into embryonic gut is the blastopore
Formation of a Complete Gut
The gut, an endodermal tube, forms by inward movement of archenteron until it reaches the ectodermal wall of the gastrula,
surrounded by the blastocoel
Has 2 openings: Blastopore and Second opening forms by merging of the archenteron tube in the ectoderm
Most develop a complete gut with a second opening
Protostomes: blastopore-mouth
Deuterostomes: blastopore-anus
Formation of Mesoderm
Diploblastic- animals with 2 germ layers, Triploblastic- animals with 3 layers
Mesoderm is the 3rd germ layer, initial mesoderm cells arise from endoderm, forms between endo&ectoderm
Forms in two ways
oProliferation of cells from near the lip of the blastopore (schizocoely)
oPushing of the central region of the archenteron wall (enterocoely)
Formation of the Coelom
Coelom- fluid filled body cavity surrounded by mesoderm, between outer body wall and gut in bilateral animals
Formed by either Schizocoely or Enterocoely
Upon completion of coelom formation, body has 3 germ layers and 2 cavities
Coelom- Advantages
oEnables internal organs to grow larger and become more sophisticated
oFluid cushions internal organs, preventing injury
oAct as a hydrostatic skeleton, providing support for soft-bodied animals
1. Acoelomate
No coelom, parenchyma (mesoderm)
2. Pseudocoelomate
Pseudocoel, tube within a tube
3. Eucoelomate
True coelom, lined with peritoneum
Schizocoelus developmental formation, enterocoelus developmental formation
Taxonomy and Phylogeny of Animals
Biologists organize animals in a nested hierarchy of groups within groups according to evolutionary relationships as revealed by
ordered patterns in their sharing of homologous features
>1.5 million species of animals named
Taxonomy: formal system of naming and classifying species
Systematics: broader science of classification (systematization) organisms based on similarity, biogeography
Zoologists have 3 goals:
oTo discover all species of animals
oTo reconstruct their evolutionary relationships
oTo classify (systematize) animals according to their evolutionary relationships via informative taxonomic system
Kingdom, Phylum, Class, Order, Family, Genus, Species
Animal “Species”: Criteria for Identifying Species
Common Descent : Central to nearly all modern concepts of species
oSmallest distinct groupings of organisms sharing patterns of ancestry and descent
Reproductive : Member of a species must form a reproductive community that excludes members of other species
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oSexually reproducing populations(interbreeding) and asexually reproducing populations (a particular ecological habitat in a
particular space_
Distribution (time and space ): Geographic range: distribution through space
oCosmopolitan: very wide distribution
oEndmic: very limited range
oEvolutionary duration- distribution through time
Modern Definition of “Species”
oNo single species concept accepted by all zoologists. All agree: a species should constitute a population lineage with a history of
evolutionary descent separate from other such lineages
Phylogenetic Reconstruction
oA major goal is systematics is to infer the evolutionary tree or phylogeny that relates all living and extinct species
oCharacters- organismal features used to construct a phylogeny [or evolutionary tree] (morphological, chromosomal, and
oHomology- character similarity resulting from common ancestry
oHomoplasy-(analogous) non-homologous similarity, misrepresents common ancestry (e.g. Evolutionary convergence of fusiform
shape or as a wing is butterfly, bat, and bird are analogous)
Using Character Variation to Reconstruct Phylogeny
oCladistics (Phylogenetic systematics)- classifies organisms into hierarchical monophyletic groups (reflects actual process of
oCladogram- nested hierarchy of clades presented as a branching diagram. Showing ancestral relationships between organisms.
Based upon sharing of derived characters (synapomorphies)
oClade- group consisting of a single organism and all its descendants
Potential Relationships between taxonomic groups
A. Monophyly: A monophyletic taxon includes the most recent common ancestor and all descendants of that ancestor
B. A taxon is paraphyletic if it includes the most recent common ancestor of all members of a group and some but not all descendants
of that ancestor
C. Polyphyly: a taxon is polyphyletic if it does not include the MRCA of all members of a group. Two sep origins
Protozoan Groups
oThe white cliffs of Dover are Ancient deposits of foraminifera (testate amoeba)
o250,000 protozoan species
oThey have a protoplasmic level of organization
1. Protozoan defy tidy classification
2. Plant-animal distinction not easily made
3. Despite apparent simplicity, protozoans are as complex as any metazoan
4. Few other groups rival protozoans in economic importance
Characteristics No cell wall
One motile stage in life cycle
Body Plan Unicellular (some colonial)
Specialized organelles (no organs or tissues)- protoplasmic
ALL symmetries represented
NO germ layer present (no embryonic stage)
Most naked some endoskeleton or exoskeleton
Pseudopodia, cilia and flagella
All types of nutrition: autotrophic (photosynthetic, e.g.Volvox), but mostly heterotrophic (holozoic feeders, feed
on solid particles, phagocytosis)
Saprozoic feeder- feed on soluble food, pinocytosis or transport
Reproduce asexually by fission, budding and cysts or sexually by conjugation (in ciliates “syngamy”-gametes
fertilized by another gamete)
Environment Aquatic or terrestrial environments, can survive only within narrow environmental ranges (important
Classification: Protozoans
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