Lesson 13: Early Vertebrates

Vertebrata

• subphylum of the phylum chordata

• only ~2-5% of animal species

Biodiversity

• variety of different life forms on Earth, and the variations in the species

  • total genes, species, and ecosystems of a region

• taxonomic biodiversity: # of species

• ecological biodiversity: # of ecosystems

• morphological biodiversity: genetic diversity

Mass Extinctions

• high rate of extinctions at several points within history:

  • ordovician: 86% of species

  • devonian: 75% of species

  • permian: 96% of species

  • triassic: 50-75% of species

  • cretaceous: 75% of species

Human Induced Threats 

• Non-industrial human coinciding extinctions

  • 50, 000 years of vertebrate extinctions 

    • many large vertebrates in Australia: marsupials, dodo…

  • mastadons, mammoths, and giant sloths gone 10, 000 years ago

• Industrial human coinciding extinctions

  • world populations of vertebrates fell overall by 60% between 1970 and 2014

Neural Crest 

• “4th germ layer”

  • quadroblastic ?

• develops into tri-partite brain

  • forebrain houses the cerebral cortex, the main processing centre of the brain

Craniata

• a group of chordate animals that possess a skull, which can be bony or cartilaginous

  • includes all vertebrates

• mineralized tissue

  • cranium (skull) and vertebrate (surround and protect nerve cord)

• pair of semi-cirular canal 

• ectodermal placodes 

  • epidermis thickening → sensory systems 

Homeobox Genes

• “hox” genes

• a DNA sequence that encodes a DNA-binding motif in proteins, which act as transcription factors that regulate gene expression during embryonic development

  • head-tail plan 

Vertebrate Musculokeletal Modifications

• endoskeleton permits almost unlimited body size with much greater economy of building materials 

• forms excellent jointed scaffolding for attachment of segmented muscles 

Vertebrate Physiology

• modifications of digestive, respiratory, circulatory and excretory systems to meet increased metabolic demand 

Tripartite Brain

• forebrain 

  • olfactory system 

• midbrain 

  • ocular system 

• hindbrain 

  • balance, hearing, taste, touch, respiration, circulation 

Forebrain

• olfactory system 

Midbrain

• ocular brain 

Hindbrain

• balance

• hearing

• taste

• touch

• respiration 

• circulation 

Earliest Vertebrate

• Myllokunmingia 

• found in Chengjiang Fauna, China 

• vertebrate features: 

  • no vertebrae but a cranium, and segments out from notochord

    • similar to a hagfish 

  • cartilaginous gill supports 

    • similar to a lamprey