Mr. Bouyer

Day 1 | Day 2 | Day 3 | Lab | Reading Assignment

Describe the characteristics of the Phylum Chordata. Describe the characteristics of the Subphylum Vertebrata. Describe the stages of vertebrate development from zygote to fetus. Compare viscreal and somatic body parts. Compare the lives of homeothermic vertebrates with those vertebrates that are not homeothermic. Use a dichotomous key to identify the six Classes of Texas vertebrates.

Animal Identification Assignment.

What do chordate gill slits become in terrestrial vertebrates?

Chordate characteristics:

Notochord - an endoskeletal rod providing longitudinal support.
Dorsal tubular nerve cord - the brain and spinal cord.
Gill slits - located in the pharynx, for filter feeding, gas exchange, or other internal functions.
Postanal tail - extensions of the notochord and nerve cord.

The Phylum Chordata is divided into three subphyla:

• Subphylum Cephalochordata, invertebrate lancelates, and Subphylum Urochordata, invertebrate tunicates, are small marine animals that are not found in Texas.
• Subphylum Vertebrata - the vertebrates:
  • have a spinal column of composed of metameric, repetition of body parts along the longitudinal axis, vertebrae.
  • have a skull protecting the brain.
  • have a closed circulatory system.

Key to the Classes of U.S. Vertebrates
(This key does not include the saltwater Chondrichthyes)
Class names in this key are linked to other zoology class keys.

1	a. Fins present b. Fins absent	2 3
2	a. Jawless; several gill openings behind head b. Bony jaws present; usually a single gill opening behind head covered by an operculum	Agnatha Osteichthyes
3	a. Skin naked, with no protective coverings b. Skin with scales or other protective coverings	Amphibia 4
4	a. Skin with scales; feathers or hair not present b. Skin without scales; either feathers or hair present	Reptilia 5
5	a. At least some part of body with feathers b. At least some part of body with hair	Aves Mammalia

Vertebrate reproduction:

All vertebrates reproduce sexually. The vertebrate body is much more complex than the invertebrate. There is a longer period of development until vertebrates reach sexual maturity. Amphibians are the only vertebrates that go through any type of metamorphosis after being born. Under certain conditions amphibian reproduction by a larvalike adult occurs, neoteny, but this is a very rare exception.

Zygote or Fetus:

• Sperm and egg come together to form the zygote. The fertilized egg has a complete set of chromosomes and begins to go through rapid cell division, clevage. This developing mass of cells reaches a critical size and must make a transformation.
• In order for all the cells to remain in contact, they must form a blastula, a hollow sphere of cells. The blastula continues to increase in size, but the surface remains only a few cell layers thick. At a critical size, the sphere begins to fold inward. The point where this folding begins is called the blastopore. (# 5 on the chart)
• The embryo now begins the gastrulation stage of development. Cells become specialized, forming the three germ layers found in all vertebrates.
• For a period of time, embryos of all vertebrates look quite similar. The head and vertebrae are seen first. Then the internal organs, with the heart forming next. It is usually after the limbs begin to form that it is obvious what the vertebrate will become. The embryo has now become a fetus, because its final shape can be identified.

In-Class Assignment 101:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

1. Paste the diagram of an invertebrate lancelate onto a Word page. Use red "arial" font to label the four chordate characteristics.
2. Use the vertebrate key above to answer the following questions on the page. Type the answers as complete statements.
   1. Given a vertebrate with fins and several gill openings - what class does it belong to?
   2. Given a vertebrate with no fins, but with scales - what class does it belong to?
3. Find a website that gives a good explaination of osmoregulation. Summarize the information on the website with a paragraph of your own on the page.
4. Which number on this study chart best shows the three germ layers of the embryo?
5. Show the completed page to your science facilitator.

Day 2

Are humans tetrapods?

Two types of body components:

• Visceral body components are derived from or associated with the gut or coelom. These include the digestive tract and other organs of the body cavity, as well as muscles, nerves, and skeletal parts.
• Somatic body components are elements of the outer body; the integument, body wall, and their derivatives. The Cuticle is the outermost layer of the epidermis, composed of sloughed dead cells and cell secretions that cover the living cells of the epidermis.

Bone development:

Ossification is the gradual transition from a soft template to bone.

• Endochondral bone - is dense and has a system of Haversian canals through which blood vessels can pass. These three stages are the way most bones in the body are formed:
  • Fibrous connective tissue develops first.
  • Cartilage forms from the fibrous tissue.
  • Finally, a bone matryx replaces the cartilage.

• Intermembranous bone - develops between two layers of fibrous connective tissue without the cartilage stage. The flat bones that form this way are not dense and do not have a system of Haversian canals.

In-Class Assignment 102:
This assignment must be completed by the end of class today to receive credit.
Scoring criteria

1. Use the Internet to find a diagram clearly showing the five regions of the vertebral column of a mammal. Paste this diagram onto the top half of a Word page and label the five regions.
2. Use the Internet to find a diagram of a complete vertebrate skeleton. Paste this diagram onto the botom of the same page and label the following parts:
   • skull
   • pectoral girdle
   • pelvic girdle
   • humerus
   • radius
   • ulna
3. Save the page on your computer and show it to your facilitator.

Day 3

What vertebrate in Texas has a skeleton made of cartilage?

Vertebrate classification:

Superclass Agnatha - "jawless" vertebrates
• Class Agnatha - the only Texas example is the lamprey.
  • do not have paired appendages.
  • have a notochord as adults.
  • have a cartilaginous endoskeleton.

Superclass Gnathostomata - "jawed mouth" vertebrates

• Class Chondrichthyes - Cartilaginous fish - Texas has no examples.

• Class Osteichthyes - The bony fish - All other Texas fish.
  • Two-chambered heart

  The Tetrapods - All the animals below have four limbs, or are descended from 4-legged ancestors.

• Class Amphibia - The amphibians - Frogs, toads, and salamanders.
  • The "tadpole" stage has a two-chambered heart.
  • The adult has a three-chambered heart.

  The Amniotes - All the animals below have special membranes that surround and protect the developing embryo.

• Class Reptilia - The Reptiles - Turtles, lizards, and snakes.
  • Three-chambered heart with an incomplete interventricular septum.
  • The amniotic membranes are formed inside an egg whose shell is not high in calcium.

• Class Aves - The Birds
  • Four-chambered heart.
  • The amniotic membranes are formed inside an egg whose shell is high in calcium.
  • Homeothermic - Maintain a warm, constant body temperature.

• Class Mammalia - The Mammals
  • Four-chambered heart.
  • The amniotic membranes are formed inside the body of the female.
  • Homeothermic

In-class Assignment 103:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

1. Describe how the shells of reptile eggs and bird eggs differ.
2. Which classes of vertebrates are homeothermic?
3. How many species of fish in Texas are not bony fish?
4. List two ways in which members of the class Agnatha are structurally different from members of the class Chondrichthyes.
5. What is a tetrapod?
6. What group of tetrapods are not amniotes?
7. Where are the amniotic membranes found in mammals?
8. In which class of vertebretes do the adults have a notochord?
9. Describe the chambers of the heart of an adult reptile.

Research Links:

• Early Human Carnegie Stages - University of New South Wales - Sydney, Australia
• Carnegie Stage Comparison - University of New South Wales - Sydney, Australia
• Embryology Notes - University of New South Wales - Sydney, Australia
• Zygote - Developmental Biology Textbook

Zoology Class

Chordate gill slits become jaws, inner ear, tonsils, or vocal organs in terrestrial chordates.

While humans are not related to a four-legged ancestor, the bone structure of their limbs makes them tetrapods.

The only vertebrate in Texas with a skeleton made of cartilage is the lamprey.