Post on 30-Sep-2015
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Taxonomic relationships based on phylogenies - considerations
Phylogenies are hypotheses can be falsified as new data comes in
When is a character derived vs. ancestral? Need a good outgroup (closest relative of the ingroup)
Vertebrate phylogeny reconstruction A continual process Allows us to formulate hypotheses about the sequence of evolution of vertebrates
Fossils and evolutionary hypotheses
Evolution of parental care in crocodiles and birds (closest living relatives to dinosaurs) did dinosaurs have parental care? (not universal in earlier evolved, living vertebrate groups)
1.5
Other challenges to determining phylogenetic relationships Homoplasy similarities in characters that are not indicative of a common ancestry
Convergent evolution, parallel evolution characters that have evolved independently in separate evolutionary lineages (but impression of common evolutionary origin)
Phylogenetics and conservation
Important tool for endangered species conservation e.g. Clouded leopards
1.6a
Phylogenetics and conservation
Important tool for endangered species conservation, but should not be the only tool, e.g. Polar bears and brown bears
1.6b
History of the Earth and vertebrate evolution
Continental shifts Climate change Coalescing, fragmentation of vertebrate faunas
Paleozoic Cambrian Ordovician Silurian Carboniferous Permian Triassic
Mesozoic Jurassic Cretaceous
Cenozoic Tertiary Quaternary
(oldest to
youngest periods in descending
order)
Vertebrate structure
Vertebrates in relation to other animals Metazoans
Early embryo forms hollow ball of cells (blastula) Sex cells formed in special organs
Sponges
Cell layers and tissues, nervous system with neurons
Cnidarians ectoderm, endoderm
Triploblasts ecto/meso/endoderm; bilaterally symmetrical gut; anterior head
Coelomates
Coelom: split in mesoderm forms inner body cavity
Protostomes Blastopore (1st opening in the embryo) becomes the mouth Mollusca Annelida Arthropoda
Deuterostomes Blastopore becomes the anus (second opening: mouth)
Chordata Echinodermata Hemichordata
Chordata Distinct features 1) Notochord-dorsal stiffening rod 2) Dorsal hollow nerve cord 3) Segmented, post-anal tail 4) Endostyle ciliated, glandular groove on the floor of the pharynx - secretes mucus for trapping food particles (generally homologous with the vertebrate thyroid gland) Other shared features 5) Pharynx feeding or respiration (fishes) 6) Bilaterally symmetrical (one side mirror of other) 7) Left-to-right symmetry (e.g. Heart (l) & liver(r))
Vertebrates Urochordates (tunicates) Small marine animals
Cephalochordates Small marine animals
Three subphyla:
Urochordata (tunicates)
Filter food particles from seawater Free-swimming larva have chordate features Most adults are sedentary (probably a derived form)
2.2
Cephalochordates Fish-like locomotion due to (i) sequential contraction of myomeres (striated muscle fibres on the sides of the body) and (ii) incompressible notochord (prevents body from shortening when myomeres contract) Respiration through the skin surface; gill slits used to filter feed Shared features with vertebrates (but different from tunicates): 1) Myomeres 2) Analogous circulatory system 3) Specialized excretory cells (podocytes) 4) Vertebrate-like tail fin
myomeres
2.2
What is a vertebrate animal? Animals that have vertebrae serially arranged to form a spinal column*; these replace the notochord after embryonic period
Other distinguishing features of vertebrates: 1) Cranium (bony or cartilaginous, surrounding the brain)
*Jawless fishes lack true vertebrae, and some jawed fishes retain the notochord as adults (e.g. Sharks)
2) Prominent head with complex sense organs 3) Embryonic feature: neural crest a unique germ layer
that forms many new structures (e.g. head)
4) Large brains having three parts: forebrain, midbrain and hindbrain
Basics of vertebrate structure Whole-animal level transition from non-vertebrate chordate
Increased body size and activity
Need organ systems that can carry out physiological processes at a greater rate
Evolution towards larger head, muscular pharynx, bigger brain, sensory system
Need muscles and skeleton (mobility)
2.4
Vertebrate embryology gill pouch stage
Segmentation
Lining in other vertebrates: Thymus, parathyroid glands, tonsils
Grooves: gills (fish)
Ventral part of mesoderm: Vascular system, heart, reproductive system
Kidneys
Dorsal mesoderm: skin, muscle , vertebral column, ribs, limb muscles in tetrapods
Similar laying down of different anatomical structures
2.5
Vertebrate adult tissue types Organs comprised of epithelial, connective, vascular, muscular, and nervous tissues
Mineralized tissues hypoxyapatite (Ca + P) (unique to verts.) cartilage, bone, enamel, dentine, enameloid (many fishes), cementum
Integument external covering skin, glands, scales, dermal armour, hair epidermis: protection, exchange, sensation
Vertebrate skeletomuscular system
Notochord and gill skeleton
Cranium
Vertebrae, ribs, median fin supports
Appendicular skeleton (limb skeleton bones, limb girdles)
Chondrocranium cartilage around the brain Splanchnocranium gill supports
Dermatocranium skin as an outer cover
Lamprey Chondrichthyan
Osteichthyan
Cranium-cross-sectional view
teeth notochord gular bones
chondrocranium
dermatocranium
Otic capsule
Lower jaw Branchial basket
2.8
Axial muscles sequential muscle blocks overlap, produce body undulations when they contract
Vertebrate skeletomuscular system
2.10
Vertebrate energy acquisition, metabolism
Feeding/digestion 1) Mouth, pharyngeal processing: chemical and physical components 2) Enzymes produced by the liver and pancreas 3) Cloaca: common opening for urinary and digestive systems
Respiration/ventilation Through thin skin (many amphibians) Gas exchange over large surface areas (gills, lungs)
Blood -Oxygen and nutrients through arteries+veins connected by capillaries closed circulatory system) -Removes CO2 and metabolic wastes
Vertebrate cardiovascular system
2.11
Excretory and reproductive systems
Kidneys Dispose waste products; regulate bodys minerals and water
Reproduction Gametes (eggs/sperm) Usually two sexes but some unisexual fishes, amphibians and lizards
No specialized tubes/passages for gametes (lampreys)
Deposited eggs may develop inside/outside the body Intromittent organs by which sperm are inserted into female reproductive tracts (e.g. claspers)