PRELAB: 8 1) Similarities: notochord, dorsal hollow nerve chord, segmented muscles, tentacle head, straight intestine that is not highly modified, pharyngeal gill slits, post anal tail.
Differences: Eye spot only in amocoetes, smocoetes have more complex brain, lamprey has 7 gill slits while amphixious has 50, ammocoetes have a pharynx with muscle and cartligous skeleton support and can pump food into mouth while amphixious relies on action of cilia. 2) Amocoete larva closely resemble cephalochordates look very different from adults. The amocoetes phase is major phase, it is blind and worm like. They hatch from eggs in gravel nests and they are filter feeders. They can lasy 3-4 years but can go up to 10. Adult has eyes, suction mouth and become a smaller version of adult dea lamprey, juveniles are parasitic. 3) Teeth are embedded un flesh, not attached to jaws so are constantly replace through sharks life. They use lower teeth to hold prey and upper teeth to cut into prey. Thin needle like teeth to grip fish and flat teeth adapted for crushing shell fish. Can use electroreception to detect changes in earths geomagnetic field so olfactory organs can sense 1 ppm of blood in seawater. Eyesight well developed. 4) Paedomorphosis led to active mobile cephalochordates and vertebrate. Ancestral chordates was a filter feeder swimming larvae failed to metamorphise into an adult. Sessile tunicate instead developed gonads and continued cephalization. 5) Most salamanders complete development, some don’t so then paedomorphesis occurs. Example is mud puppies in genus nectorus. 6) An external skeleton such as that of a crab gives protection to the animal but as the creature grows it becomes trapped inside its skeleton. The crab (or whatever) must shed the skeleton and then grow swiftly before the new skeleton hardens. During this time it is very vulnerable to attack. 7) Amphibian: a. Dioecious with usually external aquatic fertilization b. Salamanders have internal via spermatophore c. Metamorphesis usually present
Reptile:
a) Evolution of amniotic egg so offspring have 2 stages of development in body and outside b) Shells are leathery or calcareous c) Parental care absent d) Terrestrial so usually no larval stage
Mammal:
a. Fetal membranes using amniotic egg b. Mostly viviparous developing uterus c. Placental attachment for nutrients d. Mammary glands produce milk for nourishment