Lab 7 Chordata

Question 1

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.

Answer 1

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

Question 2

Recognize and briefly describe the key characteristics of lancelets (Cephalochordata),

Answer 2

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

Question 3

Recognize and briefly describe the key characteristics of tunicates (Urochordata),

Answer 3

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”

Question 4

Recognize and briefly describe the key characteristics of Hagfish

Answer 4

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

Question 5

Explain why some organisms that do not exhibit the 4 chordate characteristics as adults are still considered chordates

Answer 5

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

Question 6

State the oldest living lineage of animals with a vertebral column

Answer 6

lampreys

Question 7

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.

Answer 7

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

Question 8

What is the significance of: notochord and post anal tail

Answer 8

provides support and propulsion for underwater locomotion

Question 9

what is the significance of pharyngeal slits

Answer 9

allows suspension feeding and gas exchange

Question 10

What is the significance of cephalization

Answer 10

better sensory perception and reaction to the surrounding environment

Question 11

what is the significance of jaws

Answer 11

significantly increases the diversity of food choice

Question 12

What is the significance if mineralised and jointed skeleton

Answer 12

more flexibility, support and protection

Question 13

What is the significance of lungs

Answer 13

breathing on land

Question 14

What is the significance of heart chambers

Answer 14

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)

Question 15

limbs

Answer 15

the tetropods have 4 limbs that allow locomotion on land

Question 16

amniotic egg

Answer 16

a crucial step in terrestrial living, the amniotic egg allows reproduction without water

Question 17

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.

Answer 17

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

Question 18

Define and distinguish between Gnathostomes, Osteichthyans, Tetrapods, and Amniotes.

Answer 18

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)

Question 19

Describe the common traits of amphibians and explain why most amphibians are still tied to aquatic environments.

Answer 19

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

Question 20

Describe an amniotic egg and explain its significance in the evolution of reptiles and mammals

Answer 20

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

Question 21

Describe at least two reptilian features that are adaptive for life on land.

Answer 21

4 well developed limbs and lungs

Question 22

List several characteristics that birds share with other reptiles, and features that are found only in birds.

Answer 22

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