Lab 7 Chordata Flashcards
List and briefly describe the four characteristics common to all chordates (i.e. the 4 defining characteristics of chordates), and state the function of each trait.
1) Notochord
a flexible rod, located between the digestive tibe and nerve chord that provides support along the length of the animal
2) Dorsal, hollow, nerve chord
a bundle of nerve cells that runs the length of the body. All other animals have solid nerve chords and they are usually ventral
3) Pharyngeal slits
slits in the pharyngeal that open to the outside of the animal, allowing water to enter the mouth and leave the body without passing through the entire digestive tract.
4) muscular, post-anal tail
initially evolved for locomotion in water
Recognize and briefly describe the key characteristics of lancelets (Cephalochordata),
Lancets closely resemble the idealized chordata, with an obvious notochord, dorsal hollow nerve cell, pharyngeal slits and post-anal tail. As larvae they are free swimming and filter feed on plankton suspended in the water. As adults, they bury themselves in sand and filter by drawing water through their pharyngeal gill slits
Recognize and briefly describe the key characteristics of tunicates (Urochordata),
Tunicates reseble other chordates in their larval stage where all four chordata characteristics can be seen. As adults they are sessile and use their pharyngeal gill slits for suspension feeding. Adult tunicates are characterised by their two siphons. One siphon draws water into the organism, from which food is collected in a mucous net and the other expels the filtered water. This can be done quite rapidly, giving the tunicates their more common name of “sea squirts”
Recognize and briefly describe the key characteristics of Hagfish
the hagfish are the first of the chordates to posses a neural crest and a skull and so they belong to the group of chorates known as craniates. the skull is made of cartilage, but there are no jaws and there is no backbone, so hag fish is still technically and invertebrate ( and not a fish ). Most hag fish live on the bottom of the ocean, where they live as deposit feeders, scavenging worms and sick or dead fish
Explain why some organisms that do not exhibit the 4 chordate characteristics as adults are still considered chordates
Because in order to be considered a chordate you must exhibit all 4 chordate characteristics at some point in life but doesnt have to all be at the same time and it is usually in larvae stage
State the oldest living lineage of animals with a vertebral column
lampreys
Describe the major steps (“key innovations”) in the evolution of vertebrates as discussed in lab and as described on pgs. 108-110 of your lab manual; be able to put these steps in the correct order from the first to appear in the evolution of vertebrates to the most recent. Also be able to state or recognize the living lineage that diverged after each innovation.
KEY INNOVATION LIVING LINEAGE Vertebrates i. Vertebral column Petromyzontida (lampreys) ii. Jaws and mineralized skeleton Gnathosomes Chondrichthyes iii. Lungs and/or lung derivatives Osteichthyes Actinopterygii iv. Lobe-fins Actinistia and Dipnoi v. Limbs with digits Tetrapods Amphibia vi. Amniotic egg Amniotes Reptilia vii. Mammary glands Mammalia
What is the significance of: notochord and post anal tail
provides support and propulsion for underwater locomotion
what is the significance of pharyngeal slits
allows suspension feeding and gas exchange
What is the significance of cephalization
better sensory perception and reaction to the surrounding environment
what is the significance of jaws
significantly increases the diversity of food choice
What is the significance if mineralised and jointed skeleton
more flexibility, support and protection
What is the significance of lungs
breathing on land
What is the significance of heart chambers
Fish have a 2 chambered heart, amphibians and reptiles (except birds) a 3 chambered heart and birds and mammalian a 4 chambered heart. Increased heart complexity allows improved circulation (single circulation with 2-chambered heart and double circulation with 3-4 chambered heart) and separation of oxygenated and deoxygentaed blood (4-chambered heart)
limbs
the tetropods have 4 limbs that allow locomotion on land
amniotic egg
a crucial step in terrestrial living, the amniotic egg allows reproduction without water
Differentiate between circulation in a single circuit and circulation in a double circuit, and state the advantage of double circuit circulation over single circuit circulation.
single circuit circulation only goes through capillaries and not lungs, a double circuit goes through lungs. The advantage of double circulation is the capillaries are a slow alternative
Define and distinguish between Gnathostomes, Osteichthyans, Tetrapods, and Amniotes.
Gnathostomes- chondrichthyes (sharks, rays, skates characterised by cartilaginous skeleton but no swim bladder)
osteichthyans- actinopterygii (ray finned fish, characterised by a bony sketleton, a swim bladder ad finns supported by long flexible rays, tuna salmon, trout) , actinistia (coelacanths, characterised by lobed fins), dipnoi (lung fishes, characterised by lobed fins and lungs (as well as gills)
tetrapods- amphibians (frogs salamanders) gas exhange cia lungs and skin, fertilization is external
Amniotes- reptilia (turtles crocodiles, birds and lizards, gas exchange via lungs and skin is dry and scaly, the heart has 3 chambers and shelled eggs are laid. Birds differ becasue they lack teeth, their hearts have 4 chambers plus other modifications for flight and they have feathers) and mammalia (includes the egg laying mammals, characterized by mammalian glands and produce milk their hearts have 4 chambers)
Describe the common traits of amphibians and explain why most amphibians are still tied to aquatic environments.
Common traits of amphibians, they have limbs with digets, lungs, feed on land and lay eggs in the water, for most they perform gas exchange over moist mucus part of their skin
Describe an amniotic egg and explain its significance in the evolution of reptiles and mammals
The amniotic egg is composed of 4 membranes, including a yolk that provides nutrients to the developing embryo. Most amniotic eggs have a shell; however, in mammals, the shell has been lost and the embryo develops within the amnion within the mother instead.
significant because it decreases dehydration of egg in air and allows amniotes to occupy wider range of habitats
Describe at least two reptilian features that are adaptive for life on land.
4 well developed limbs and lungs
List several characteristics that birds share with other reptiles, and features that are found only in birds.
birds share with other reptiles:
vertebral colmn, jaws, limbs, amniotic egg and eyeballs
found only in birds:
egg shell is calcareous and hard (pther reptiles leathery and flexible)
wings, feathers, skeleton of birds have holes to make flight easier
