Chordate notes 2012.notebook
Phylum: Chordata
All Chordates have: May 20, 2013
Subphyla of Chordates
1) a notochord 2) pharyngeal slits *gill pouches (gills never break to outside) *earliest chordates used them for filter feeding *some (fishes) have developed gills in pharyngeal pouches for gas exchange
*gill slits of higher vertebrates are mainly embryonic 3) a postanal tail *present in humans as coccyx; in most other mammals as wagging tail.
4) a hollow dorsal nerve chord *Nervous system
In the subphylum Vertebrata, all members possess the four chordate characteristics at some time in development, but often these structures are altered significantly in adult animals. May 27­10:02 AM
• The Phylum Chordata includes all of the vertebrates, as well as two groups of marine
animals that lack backbones and are called invertebrate chordates
• Subphylum Cephalochordata contains lancelates that retain the notochord, dorsal nerve
chord, pharyngeal pouches, and postanal tail throughout their life • Subphylum Urochordata contains tunicates because their bodies are covered by a tough
covering, or tunic and sea squirts because they shoot out a stream of water when touched
• *Adults do not have a notochord, dorsal nerve cord, or postanal tail • Subphylum Vertebrata is the largest subphylum in which the notochord is replaced with
vertebrae
• * Skeletons consist of bone &/or cartilage
• * Brain is protected by a cranium
• * Well developed chambered heart with a closed circulatory system
• * Includes fish, amphibians, reptiles, aves & mammals May 25­9:52 AM
Fish
1. Fish are ectothermic, aquatic vertebrates.
2. Their skin is generally covered with scales.
3. Their limbs are modified into fins for swimming.
4. They breathe with gills.
5. They lay eggs that must be in water. You probably knew most of this already, didn't you? The term "ectothermic" may be new to you. It means "external temperature" in Latin. The simpler term is "cold­blooded", that is, it has a body temperature equal to the surrounding environment. You know that fish are cold­blooded if you ever picked one up: they are as cold as the water they were swimming in. Even if you go swimming and are shivering with cold, you are always warmer than the water. "Aquatic" means that they spend their lives in the water.
May 25­10:04 AM
May 27­10:07 AM
Reptile
Amphibian
1. Amphibians are ectothermic vertebrates.
2. Their skin lacks scales, hair, and feathers, and is either smooth (like a frog) or rough (like a toad). They are must remain moist to aid in breathing
dependent upon moisture and subject to desiccation; their skin .
tadpole or larva) that usually breathes 3. They lay eggs in water, which hatch into an intermediate life form (
with gills, and change into the adult form that breathes air and can live outside water
. 4. They have three­chambered hearts.
5. They lack claws on their toes. May 27­10:08 AM
1. Reptiles are ectothermic vertebrates.
2. Their skin has scales, but no hair or feathers .
3. They have three­chambered hearts (except for alligators and crocodiles, which have four­
chambered hearts).
4. They have claws on their toes (except those which do not have legs, such as legless lizards).
5. They are the first animals, in evolution, to develop the amniotic egg. This allows reptiles to lay eggs on land. May 27­10:11 AM
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Chordate notes 2012.notebook
May 20, 2013
Aves = Birds
Mammal
1. Birds are endothermic vertebrates.
2. Their skin is covered with feathers.
3. They have four­chambered hearts.
4. Their bones are lightweight and usually hollow.
5. Their forelimbs are modified as wings.
6. They lay amniotic hard eggs. May 27­10:14 AM
Animal One
You come to a strange island and the islanders tell you about a strange creature that has a backbone. They say it flies around with two wings. What is your first guess? You would probably say a bird. But they tell you it does not lay eggs. Could not possibly be a bird. It has fur. Can you now guess?
May 27­10:17 AM
Animal Two
You are also told about an animal with a backbone that is now extinct, but the elders remember that it ran around on the ground and couldn't fly like a bird. But it laid eggs. What is your first guess? You would probably say a reptile, like a lizard. But they tell you it did not have scales, but feathers. Can you guess what it must be?
May 27­10:18 AM
1. Mammals are endothermic vertebrates.
2. They have hair, which varies greatly among species.
3. Most have sudoriferus (sweat) glands.
4. They have mammary (milk­secreting) glands.
5. They have sebaceous (fat­secreting) glands.
6. They have heterodont dentition (different types of teeth).
May 27­10:15 AM
A Pallid bat, common in California. It is a member of the class Mammalia. Despite the fact that it has wings, you can tell it is not a bird because it does not have feathers or lay eggs. It must be a mammal because it has fur (fish have scales, amphibians have moist skins with fur, reptiles have scales). This also tells you that it bears live young that it feeds with milk and that it is warm­
blooded.
May 27­10:17 AM
A Dodo bird. Although it cannot fly like most birds, it would have to be a bird because of the feathers. The fact that it has wings also makes it a bird. Although it lays eggs, so do fish, amphibians, and reptiles. Running around on the ground rules out fish. Even if you never saw one alive, you would know it was a bird. What else would it tell you, that you could not find out from if you examined one in a museum? You would know it was warm­blooded.
May 27­10:19 AM
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Chordate notes 2012.notebook
Animal Three
You are also told about an animal with a backbone with no legs that lays eggs, but is definitely not a snake. What is your first guess? You would probably say a fish. However, this strange creature lives on land, has scales, and lays eggs on the dry land.
May 27­10:19 AM
Animal Four
The islanders also tell you about an animal that lives its whole life in the water and has gills. What is your first guess? You are wrong! It is not a fish! They tell you that it lays eggs in the water, does not have a larval stage but is born as a small version of an adult of the species. Guess again? It can't be an amphibian, as it does not have a larval stage. Reptile? No, it has gills. Reptiles breathe with lungs. Mystified? May 27­10:22 AM
Animal Five
The final animal that you are told about is rather strange, indeed. It has a backbone, swims in the water and lays eggs. What is your first guess? You might think that it is a fish or an amphibian, or even a reptile or bird. They all lay eggs and some of each group swims. You really can't guess yet. They tell you it has claws and a bill like a duck. You might think it is a bird. Then they tell you it has no feathers. That rules out a bird. What's left? A fish, an amphibian, or a reptile, but this is strange. A fish with a bill like a duck? Then they tell you it breathes air, and its eggs are laid on the ground. That rules out what? A fish. Reptile? But they tell you it is warm blooded, and nurses its young with milk. Boy, you are in a quandary now! What class would a vertebrate be in?
May 27­10:24 AM
May 20, 2013
A legless lizard. A first glance you might think it is a snake, but its anatomy reveals that it is a lizard. The skull and internal organs are that of a lizard.
You might at first think, from the description, that it was a fish, because it lays eggs. But when you hear it has scales, only a reptile has scales over its entire body.
May 27­10:21 AM
I tricked you: all the other creatures in this quiz had a backbone, but I did not mention that for this creature. You need to be careful: we are studying vertebrates. If the creature does not have a backbone, the criteria for the classes of vertebrates do not apply. There are a lot of creatures that are not vertebrates, but share some vertebrate characteristics. Insects have wings and can fly like birds. Many creatures lay eggs, such as insects. Many have larval stages, like clams and insects.
May 27­10:23 AM
A duck­billed platypus. If you were mystified at first, you are in good company: the scientists were mystified, too. However, this is how they solved the puzzle: the animal has fur and feeds its young on milk. This makes it a mammal, but a rather unusual one. It forced the creation of a subset of mammals called monotremes.
It could not be a fish, amphibian, reptile, or bird, because it has fur. It has a backbone, so it could only be a mammal. Other characteristics of anatomy, such as arms and legs, pelvis, kidney structure, heart chambers, and other features are also shared only with mammals.
May 27­10:24 AM
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Chordate notes 2012.notebook
May 20, 2013
http://www.youtube.com/watch?v=ZXEC1Qx4cJg
A baby echidna is called a puggle. Puggles are born blind and hairless.
Puggles drink milk. Echidna milk is pink because of the high iron content.
http://www.abc.net.au/local/videos/2009/12/30/2780207.htm
http://www.arkive.org/short­beaked­echidna/tachyglossus­aculeatus/video­09a.html
May 31­10:41 AM
May 25­11:45 AM
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