FORS2355 Vertebrate Natural History -- Lecture 3 (August 31, 2021)
The Geological Time Scales
Eon -- broadest time C Era Period . Epoch
History of the Earth
3 Geological Eons o Archean Eon -- began 4.6 billion years ago. Not many food resources. Molten rock cooling down. - Not much life at all. Proterozoic Era -- began 2.5 billion years ago. Formation of large continental land masses. Shallow seas Uptake in oxygen being produced and available in atmosphere. o Proterozoic Eon Eukaryotes appear around 2 billion years ago. Major diversification around 1 billion years ago. 15t animals appeared 600 million years ago. o Phanerozoic Eon -- 542 million years ago. Paleozoic Era Cambrian Period Smaller land masses Shallow seas Explosive radiation of animals. Diversification of arthropods (trilobites) : 15t appearance of chordates 1st appearance of vertebrates Sun heating seas More life Photosynthesis Productive Ecosystem Diversification Many rocks in shallow waters dissolved from water which created minerals for life Cambrian Period -- ca. 542-488 million years ago Globally milder climate; no glaciation Shallow-water reefs more extensive. Life restricted to marine waters. No terrestrial plants and animals Little to no freshwater life
o "Cambrian Explosion" : Widespread diversification over short time. Diversification of arthropods (trilobites) Chordates Vertebrates o Phanerozoic Era -- 542 million years ago - Rise of trilobites (had shells) Life co-opting minerals for evolutionary advantage Life began using minerals for bones, teeth, etc. : Allowed for even larger animals to develop. o Paleozoic Era - Ordovician period (488 million years ago) Stable Climate Major radiation of marine animals Jawless fishes
1st land plants
o Vertebrates -- 480 million years ago Higher taxonomy (all vertebrates) Kingdom = animalia or Metazoan Phylum = Chordata Subphylum = Vertebrata (or Craniata because development of cranium). Common Characteristics: Kingdom Animalia: Multicellular Increased complexity Heterotrophic -- obtains energy for life from food they eat. Herbivores, carnivores, omnivores, etc. Cannot produce own food internally like plants. Phylum Chordata: Notochord Dorsal stiffening rod; support for locomotion Hollow nerve cord Dorsal, usually with enlarged anterior brain Postanal tail extending beyond gut. Pharynx slits Throat region = Characteristics present at some point of development the ontogeny (aka development). Postanal tail is present. Subphylum Urochordata: Filter feeders "Tadpole" larvae Subphylum Cepinalocordata Lancelets Gill slits for feeding Open circulatory system
Subphylum Vertebrata
Prominent head with complex sense organs Cranium -- skull surrounding brain; bony, cartilaginous or fibrous Neural Crest -- important tissue forms unique structures in vertebrates Enlarged, tripartite brain (based on fossil evidence and physiology of extant forms, the 15t vertebrates arose in marine environments) Agnathans or Jawless Vertebrates Most primitive (oldest) of living vertebrates Hagfish (no vertebrae) Lampreys -- simple (primitive); cartilaginous structures = arcualia Fully formed vertebrae only formed in gnathostomes or jawed vertebrates. o Centrum surrounds notochord o Nerve cord passes through vertebral foramen (hole). Since cranium is common to all vertebrae, but vertebrae are not, some prefer to use Subphylum Craniata, but vertebrata more familiar. Anatomical structures/functions unique to vertebrates likely a result of 2