bio2 test 3 animal diversity vertebrates

Evolution of vertebrate diversity characteristics

• All vertebrates are chordates, but not all chordates are vertebrates 

• In addition to chordate characteristics, vertebrates have: 

  • Vertebral column 

  • Distinct, well-differentiated head 

  • Neural crest (ridge on embryo > nervous system) 

  • Endoskeleton 

•  Vertebrate phylogeny 

jawless fish

• Hagfishes and lampreys 

• Not very closely related 

• Have a head and notochord 

• No hinged jaws or paired fins 

• Scavengers, external parasites

Jawed Vertebrates

• Most vertebrates have hinged jaws 

• Evolved from skeletal supports of pharyngeal gill splits 

• capture/ processing of larger prey 

Jawed Fishes

• Chondrichthyans 

• Ray-finned fish 

• Lobe-finned fish

Jawed Fishes: Chondrichthyans

• Cartilage endoskeleton 

• Electrosensors on their heads 

• Lateral line system helps locate prey 

• Oily liver helps maintain buoyancy (no swim bladder)

• Ex: sharks, rays, skates 

Jawed Fishes: Ray-finned

• Bony endoskeleton 

• Flattened scales covered with mucus 

• Operclum covers gill chamber

• Swim-bladder: air filled sack maintains buoyancy 

• Most diverse group of vertebrates ~27000 species 

• Ex: trout, perch, salmon , seahorse 

Jawed Fishes: Lobe-finned

• Have muscular fins supported by bones 

• Ex: coelacanth, lungfish, mudskippers 

• One group was the ancestor of tetrapods (terrestrial vertebrates with 2 pairs of

 appendages) 

• Amphibians 

• Reptiles including birds 

• Mammals

Tetrapod transition to land

• Ancestral animals transitioning to land faced similar problems as plants: 

• Gravity-water no longer supports body 

• Desiccation-bodies, embryos easily dry out 

Tetrapods: amphibians

• First tetrapods on land: usually have: 

• Most skin that supplements gas exchange 

• poison/mucus glands in skin 

• Return to water to reproduce 

• Moist, jelly-like eggs 

• Metamorphosis 

• Ex: salamanders, frogs, caecilians

Tetrapods: Amniotes

• Have an amniotic egg with 4 membranes: 

• Protects, supports embryo in self contained structure 

• Amnion-fluid filled sac surrounding embryo; protection, moisture 

• Chorion-outermost membrane; protection gas exchange

• Allantois-surrounds waste cavity; disposal of metabolic waste, gas exchange 

• Yolk sac-stores nutrients for developing embryo 

• 2 groups: 

  • Reptiles (non-avian and avian) 

  • Mammals

Tetrapods: non-avian reptiles

• Waterproof skins with scales 

• Ectothermic-absorb heat from environment rather than generating own heat 

• Ex: lizards, snakes, turtles, crocodiles 

Tetrapods: Avian reptiles

• I.e birds 

• Molecular data place birds within the reptiles 

• Bodies modified for flight: 

  • Feathers 

  • Large flight muscles; endothermy (generate own heat) 

  • No teeth; few tail vertebrae 

  • Hollow bones with internal struts 

  • Ex: hawks, hummingbirds, penguins 

Tetrapods: Mammals

• Endothermic amniotes with 

  • Hair-insulation, protection 

  • Mammary glands-produce milk for young 

  • Usually have teeth differentiated for different functions (slicing, chewing, grinding)

mammals: monotremes

• egg laying mammals 

  • Ex: duck billed platypus, echidnas 

• Other mammals have a placenta that nourishes developing embryos

mammals: marsupials

• short gestation, complete development in pouch 

  • Ex: kangaroos opossums

mammals: eutherians

• -longer gestation, more developed young at birth, more complex placenta 

  • Ex: bats, mice, whales, humans 

1. Describe the key traits of the chordates and the chordate subgroups.

• Notochord → support

• Dorsal hollow nerve cord → brain/spinal cord

• Pharyngeal slits → gills/filter

• Post-anal tail → tail

• Endostyle/thyroid → metabolism

Subgroups:

• Cephalochordata: lancelets, retain traits as adults

• Urochordata: tunicates, traits in larvae

• Vertebrata: backbone, complex organs → fish, amphibians, reptiles, birds, mammals

1. Describe the characteristics of and distinguish between each of the following vertebrate groups: hagfishes, lampreys, chondrichthyans, ray-finned fishes, lobe-finned fishes, amphibians, reptiles, birds, and mammals

• Hagfishes: jawless, no vertebrae → hagfish

• Lampreys: jawless, partial vertebrae → sea lamprey

• Chondrichthyans: cartilaginous, jaws → sharks, rays

• Ray-finned fishes: bony, fins with rays → salmon, goldfish

• Lobe-finned fishes: lobed fins, precursor to amphibians → coelacanth, lungfish

• Amphibians: moist skin, metamorphosis → frogs, salamanders

• Reptiles: scaly, cold-blooded, amniotic eggs → snakes, turtles

• Birds: feathers, warm-blooded, hollow bones → eagles, sparrows

• Mammals: hair, milk, warm-blooded → humans, lions

1. Distinguish between monotremes, marsupials, and placental mammals. Provide examples of each.

• Monotremes: Lay eggs, produce milk, no nipples → platypus, echidna

• Marsupials: Short gestation, young develop in pouch → kangaroo, koala

• Placental mammals: Long gestation, young develop inside uterus with placenta → humans, lions, whales