NOTES 12/6- 12/7/2012
Chapter 21 Variety in the World of Invertebrates
Mollusks are the largest group of water animals on earth
They are distinguished by a muscular food used for locomotion, a visceral hump which contains the internal organs and a mantle, a skin-like organ which covers the visceral hump, and in most species produces a calcium carbonate shell for protection
Phylum Mollusca is divided into six classes the most familiar are
Gastropods or univalves include the snail, slug, and whelk.
Bivalves includes the clam, mussel, oyster, and scallop.
Cephalopods includes the squid, octopus, and cuttlefish.
Bivalves: Two-shelled Mollusks
The two shells (valves) of clams scallops, oysters, and mussels give them their name of bivales:
Shells of bivalves have 3 distinct layers: hornlike layer, a crystalline middle layer, and a pearly inner layer
The inner layer some inedible oysters and clams is called mother of pearl. If an irritating substance becomes lodged in the mantle of a bivalve the animal secretes thin sheets of nacre (substance from which the pearly layer is formed around the foreign object) The sheets of nacre build up around the irritant and form a pearl.
2 shells are connected by hinges that held together by adductor muscles (only part of scallops and muscles that are not eaten
A clam uses its food for locomotion
One of the most critical activities for a bivalve is the movement of water into and out of its mantle cavity, the open chamber in which the gills are located
The incurrent siphons takes water into the mantle cavity to the gills where oxygen and carbon dioxide is exchanged
Most of this water then passes out through the excurrent siphon
A bivalve has an open circulatory system and its blood which lacks hemoglobin is blue or colorless
Gastropods: Stomach-footed Mollusks
Shells of Gastropods are often called univalves because most of them have a single shell. Most are spiral or clockwise
Gastropods without shells. Slugs are gastropods which look like snails without shells. Some other gastropods have partial shells. Marine slugs called nudibranches include of the other most beautiful and graceful sea creatures
Economic importance. They can be pests like many land slugs and snails, which carry parasitic diseases affecting man
Body plan. Univalves have a foot, visceral hump, mantle, and usually a shell
Head structure. Some univalves have 2 pairs of tentacles on their heads. One pair is for feeling and the other pair may end in eyes. The mouth contains a radula, a rough file-like organ that scrapes food and carries it to the digestive tract. Most are herbivorous but a few are carnivorous.
Cephalopods: Head-foot Mollusks
Class Cephalopoda consists of creatures such as the octopus, squid, cuttlefish, and chambered nautilus.
Squid is a torpedo-shaped cephalopod noted for its ability to move by jet propulsion by quickly forcing water out of its siphon. When threatened the squid ejects an inky fluid into the water which confuses an attacker and allows it to escape. The giant squid, the largest invertebrate, is found in the Pacific and North Atlantic oceans. Has 10 tentacles with suckers that hold and catch fish.
Octopuses have 8 tentacles which are studded with suction cups for catching prey. The Pacific giant octopus may attain an arm spread more than 20 feet and weigh over 150 pounds. The octopus has the most complex brain of all invertebrates and thought to be the most intelligent.
Nautilus is the only cephalopod with an external shell. Each shell consists of a series of chambers arranged in a spiral. Usually about 10 inches and possesses up to 94 tentacles.
21.2 Echninoderms and Rotifers
Echinoderms: Spiny Skinned Invertebrates
Echinoderms include starfish, sea urchins, sand dollars, sea cucumbers, and brittle stars. All are spiny-skinned marine animals. Only animals with a water-vascular system, a complex system of water filled tubes that extends throughout the body.
Starfish are the best known echinoderms.
Have a body which resembles a five pointed star.
Have 5 arms or rays. At the end of each ray is a small light sensitive eyespot.
Have pincers that has 2 or 3 jaws on each pincer and is attached to the starfish by a ball and socket joint
On the underside of each ray are tube feet which are used for holding things, moving, and opening the shells of clams and oysters.
Rotifers: “Wheel Bearers”
Microscopic multi-cellular animals found in freshwater. Some are sessile while others creep on the bottom or float on the surface of the water. Have a large brain in relation to its body. Reproduce by sexual reproduction. Some of the eggs are parthenogenic (require no fertilization). These eggs are laid in the summer. The eggs laid in the winter require fertilization and have a thick shell for protection
Rotifers are important because they clean up natural wastes and provide food for small crustaceans.
Complete the 21.2 Section Review on page 451 Questions #1-3
21.3 Coelenterates and Porifera
Coelenterates: Hollow-Intestined Invertebrates
Includes jellyfish, sea anemones, corals, and hydras
Phylum is named after the stinging cells called cnidocytes that the organisms possess.
Most live in warms waters of tropical seas, but hydras live in fresh water
Coelenterates have a saclike body with a central digestive cavity having a single opening or mouth at one end through which food enters and wastes are expelled. Have tentacles used for capturing prey. Many stinging cells used to kill or incapacitate prey and draw the prey to the mouth. Body is made up of 2 layers of cells, the ectoderm (outer layer) and the endoderm (inner layer), between the layers is a middle layer called the mesoglea which is composed of protein fibrils and sugars.
Coelenterates are built on a form of radial symmetry and have 2 body forms – the polyp and the medusa. A polyp is a cylindrical body type which is sessile and has a mouth facing upward. A medusa is a free swimming umbrella-shaped body type which has its mouth facing downward.
The hydra is a small (less than ½ inch long) freshwater coelenterate of the polyp form
Body consists of a round base a cylindrical stalk and a central cavity with a single opening surrounded by tentacles.
Have a remarkable ability to regenerate. If cut into several pieces each piece will grow a new complete hydra.
The adult jellyfish is a free-swimming coelenterate with a medusa type of body structure.
Its mouth is located at the center of the “umbrella” and its tentacles hang down around the rim. The tentacles are equipped with cnidocytes with which it paralyzes its prey or defends itself.
Beautiful “flowers” of the ocean
Sea Anemones are comparatively large marine coelenterates which have a polyp type of body; the mouth is located at the top of the organism, surrounded by an array of stinging tentacles.
Some are only a few inches long and about ½ inch in diameter, but other species may measure as much as 2 or 3 feet across
Have grooves which extend from the slit-like mouth to the gastrovascular cavity. Cilia line these grooves and their motion creates currents which wash water down into the body cavity and between the grooves. In this way a constant supply of food and oxygen are brought to the sea anemone, these same currents sweep wastes away from the animals cells and out of its gastrovascular cavity
The coral is a colonial coelenterates.
Corals are like miniature sea anemones, except that the corals produce a lime-stone cup at the base of their bodies. This cup is a shelter in which the coral polyp can retract when disturbed.
Because corals live together in colonies, the limestone cups eventually form vast limestone structures called coral reefs.
There are about 4200 species of sponges which make up the phylum Porifera
Their bodies consists of only two layers, and they always grow attached to an object in the water.
Most live in the sea, only one group lives in fresh water.
Sponges are multicellular but their cells act more or less independently of each other, and there is no coordination of their activities. Sponges are the only multicellular animals which do not have at least a rudimentary nervous system.
A sponge can be described as a hollow saclike animal with a large opening opposite of its base. The mouth opening is called an osculum but does not take in food for the sponge. Waste materials and water flow out of the osculum. An opening of this type through which water leaves an organisms is called an excurrent pore. Water enters the sponge through very small pores called incurrent pores which are located in the sides of the animal. Sponges have an inner layer of cells called the collar cells. Within the mesoglea are special cells which manufacture spicules that support the structure of the sponge.
Sponges regenerate even from a small piece.
Complete Questions #1-4 of the 21.3 (p 455) Section Review
Ch 18 Reptiles and Amphibians
18.1 Reptiles: The Creeping Vertebrates
Coldblooded animals regulate temperature by external factors therefore their body temperature with the temperature of their surroundings
Animals whose body temperatures fluctuate in this manner are referred to as poikilotherms
Similarities among Reptiles
All true reptiles are vertebrates, are coldblooded and have dry tough skins which are covered by a protective layer of scales
Generally, all reptiles except snakes are tetrapods, having two pairs of appendages, each appendage having claws on the toes
Both adult and young reptiles breathe with lungs
Most reptiles are oviparous, reproducing my means of eggs. There are some snakes and lizards who bear live young and re called ovoviviparous.
Lizards: The most numerous reptiles
Lizards are enlongated, four-legged reptiles with a tapered tail
They live mostly in tropical regions and are found in nearly any type of habitat
The majority are less than one foot, but can be as much as 12 feet
Only 2 species of lizards are venomous the Gila monster and the Mexican beaded lizard
Many lizards are able to change their color to blend in with their surroundings
Lizards defense mechanisms
Lizards defend themselves in various ways
Some lizards will detached its tail to escape a predator. In a few weeks the tail will regrow.
Lizards also use venom, great size, speed, camouflage, and some other unusual mechanisms for defense.
A few lizards are vegetarians
Some lizards eat worms and other small animals
The majority are insectivorous and therefore are important for controlling insect populations
In order to catch prey most lizards have a good sense of smell (tongue serves as an olfactory organ) and good eyesight
18.1 Section Review
page 383 Questions # 1-8