Monday, June 20, 2011

More Works Cited

Miller, Kenneth R. and Joseph Levine. Biology. New Jersey: Prentice Hall, 2004. Print

Biology Invertebrates Notes


{ Characteristics }

Echinoderms have spiny skin, an internal skeleton, a water vascular system, and suction-cuplike structures called tube feet. Most adults exhibit five-part radial symmetry. All are marine animals.


Echinoderms have two means of reproducing. They can reproduce asexually or sexually.

Echinoderms can reproduce asexually through regeneration. If a part of the echinoderm has broken off, it can regenerate new parts if it has part of the central disk.

Echinoderms have sex organs in each arm. Since echinoderms are not hermaphroditic, both gametes are released into the water where fertilization occurs.

Examples of Echinoderms

There are about 7000 species of echinoderms.

There are five classes of echinoderms: sea urchins and sand dollars, brittle stars, sea cucumbers, sea stars, and sea lilies and feather stars.


endoskeleton - structural support located inside the body of an animal

water vascular system - system of internal tubes in echinoderms that carries out essential functions such as feeding, respiration, circulation, and movement

madreporite - sievelike structure through which the water vascular system of an echinoderm opens to the outside

tube foot - suction-cuplike structure attached to radial canals of echinoderms’ used to walk and to open shells

Works Cited


{ Characteristics }

Arthropods have a segmented body, tough exeskeleton, and jointed appendages.


Arthropods reproduce sexually.

Terrestrial arthropods have internal fertilization, whereas aquatic arthropods may have internal or external fertilization. There are two different metamorphoses arthropods can undergo. When an egg hatches into a mature adult, no metamorphosis occurs. When an egg develops into a nymph before the adult stage, the arthropod undergoes incomplete metamorphosis. When an egg develops into a larva, pupa, then adult, the arthropod undergoes complete metamorphosis.

Examples of Arthropods

There are three groups of arthropods. The subphylum Crustacea contains crabs, shrimps, lobsters, crayfishes, and barnacles. They are primarily aquatic, have two pairs of antennae, two or three body sections, and chewing mouthparts called mandibles. The subphylum Chelicerata includes horseshoe crabs, spiders, ticks, and scorpions. They have mouthparts called chelicerae and two body sections, and nearly all have four pairs of walking legs. The subphylum Uniramia contains centipedes, millipedes, and insects. They have jaws, one pair of antennae, and unbranched appendages.


exoskeleton - external skeleton; tough external covering that protects and supports the body of many invertebrates

chitin - complex carbohydrate that makes up the external skeletons of arthropods

appendage - structure, such as leg or antenna that extends from the body wall

tracheal tube - one of many branching, air-filled tubes that extend throughout the bodies of many terrestrial arthropods

spiracle - small opening located along the side of the body through which air enters and leaves the body of many terrestrial arthropods

book lung - organ that has layers of respiratory tissue stacked like the pages of a book; used by some terrestrial arthropods for the exchange of gases

Malpighian tubule - saclike organ in most terrestrial arthropods that extracts wastes from the blood, adding them to feces that move through the gut

molting - process in which an arthropod sheds its exoskeleton and manufactures a larger one to take its place

cephalothorax - region of a crustacean formed by the fusion of the head with the thorax

thorax - body part of a crustacean that lies just behind the head and houses most of the internal organs

abdomen - posterior part of an arthropod’s body

carapace - the part of the exoskeleton that covers the cephalothorax

mandible - mouthpart adapted for biting and grinding food

cheliped - on of the first pair of legs of decapods

swimmeret - flipperlike appendages used by decapods for swimming

chelicera - pair of mouthparts in chelicerates that contain fangs and are used to stab and paralyze prey

pendipalp - pair of mouthparts in chelicerates that are usually modified to grab prey

spinneret - organ in spiders that contains silk glands

incomplete metamorphosis - type of insect development characterized by a similar appearance throughout all stages of the life cycle

nymph - immature form that lacks functional sex organs and other adult structures

complete metamorphosis - type of insect development in which the larvae look and act nothing like their parents and also feed in completely different ways

pupa - stage of metamorphosis in which an insect changes from a larva into an adult

pheromone - specific chemical messenger that affects the behavior or development of other individuals of the same species

society - group of closely related animals of the same species that work together for the benefit of the group

caste - group of individual insects specialized to perform particular tasks, or roles

Works Cited


{ Characteristics }

Mollusks are soft-bodied animals that usually have an internal or external shell. All mollusks have a mantle.


Mollusks have one mean of reproducing. They reproduce sexually.

Mollusks can reproduce sexually through internal or external fertilization. Many gastropods and bivalves reproduce using external fertilization. They release enormous numbers of eggs and sperm into open water that fertilize and develop into free-swimming larvae. Cephalopods and certain gastropods reproduce using internal fertilization. Some mollusks are hermaphroditic, but usually fertilize eggs from another.

Examples of Mollusks

There are three major classes of mollusks: Gastropoda, Bivalvia, and Cephalopoda. The class Gastropoda includes pond snails, land slugs, sea butterflies, sea hares, limpets, and nudibranchs. They are shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side. The class Bivalvia include clams, oysters, mussels, and scallops. They have two shells that are held together by one or two powerful muscles. The class Cephalopoda includes octopi, squids, cuttlefishes, and nautiluses. They are typically soft-bodies mollusks in which the dead is attached to a single foot. The foot is divided into tentacles or arms.


trochophore - free-swimming larva stage of an aquatic mollusk

foot - muscular part of a mollusk

mantle - thin layer of tissue that covers most of a mollusks body

shell - structure in mollusks made by glands in the mantle that secrete calcium carbonate

visceral mass - area beneath the mantle of a mollusk that contains the internal organs

radula - tongue-shaped structure used for feeding by snails and slugs

siphon - tubelike structure through which water enters and leaves a mollusk’s body

open circulatory system - system in which blood is not always contained within a network of blood vessels

Works Cited


{ Characteristics }

Annelids have segmented bodies and a true coelom that is line with tissue derived from mesoderm.


Annelids have one mean of reproducing. They reproduce sexually.

Most annelids reproduce sexually, even though they are hermaphroditic. They exchange sperm, and when the eggs are ready for fertilization, a clitellum secretes a mucus ring where the eggs and sperm are released. Fertilization take place in the ring. The ring slips off the worm’s body and forms a protective cocoon where worms hatch from a couple weeks later.

Examples of Annelids

Annelids are divided into 3 classes: Oligochaeta, Hirudinea, and Polychaeta. The class Oligochaeta contain earthworms and their relatives. They are annelids that typically have streamlined bodies and relatively few setae compared to polychaetes. Most live in soil or fresh water. The class Hirudinea contains leeches. Leaches are typically external parasites that suck blood and body fluids of their host. In the Middle Ages, leeches were considered to leech the excess blood from a host to remove a disease. The class Polychaeta are marine annelids that have paired paddlelike appendages tips with setae.


septum - internal body wall between the segments of an annelid’s body

seta - bristle attached to the segments of many annelids

crop - part of the digestive system in which food can be stored

gizzard - part of the digestive system in which food is ground into smaller pieces

closed circulatory system - system in which blood is contained within a network of blood vessels

gill - filamentous organ in aquatic animals specialized for the exchange of gases with water

nerphridium -excretory system of an annelid that filters fluid in the coelom

clitellum - band of thickened, specialized segments in annelids that secretes a mucus ring into which eggs and sperm are released

Works Cited

Nematodes (Roundworms)

{ Characteristics }

Roundworms are unsegmented worms that have pseudocoeloms - a false coelom - and digestive systems with two openings - a mount and an anus.


Roundworms have only one means of reproducing - sexually.

Roundworms reproduce using internal fertilization. Most species are not hermaphroditic, so usually the male inserts sperm inside the females reproductive tract.

Examples of Roundworms

Roundworms are free-living, but hey are better known as parasitic. They include trichinosis-causing worms, filarial worm, ascarid worm, and hookworms. Trichinosis is caused by the Trichinella roundworm. It completes its lifecycle only when an animal eats muscle containing the cysts - inactive larva. Filarial worms cause elephantiasis, a condition where the infected part of the body swells enormously. The filarial worms block the passage of fluids within lymph vessels in the infected area. Acarid worms - such as Ascaris lumbricoides - cause malnutrition in more than 1 billion people worldwide. Hookworms suck their host’s blood, causing weakness and poor growth.


pseudocoelom - false coelom

anus - the posterior end of the digestive tract

Works Cited

Platyhelminthes (Flatworms)

{ Characteristics }

Flatworms are soft, flattened worms that have tissues and internal organ systems. They are the simplest animals to have 3 embryonic germ layers (ectoderm, mesoderm, and endoderm), bilateral symmetry, and cephalization. Although they have 3 embryonic germ layers, they are acoelomates.


Flatworms have two mean of reproducing. They can reproduce asexually or sexually.

Flatworms reproduce asexually through fragmentation or fission.

Since most flatworms are hermaphrodites, they can reproduce sexually through a mutual exchange of sperm. The eggs are laid in clusters and hatch within a couple weeks.

Examples of Flatworms

There are three classes of flatworms: Turbellarians, Trematoda, and Cestoda. Turbellarians are free-living flatworms that mostly live in marine or fresh water. The most familiar are the planarians, the “cross-eyed” freshwater flatworms. Trematoda are known as flukes - parasitic flatworms that infect the internal organs of their host. The Schistosoma fluke causes schistosomiasis, a serious disease in which the eggs clog blood vessels, causing swelling and tissue decay in the lungs, liver, spleen, or intestines. The Cestoda - tapeworms - are long, flat, parasitic flatworms that are adapted to life inside the intestines of their hosts.


acoelomate - without coelom

coelom - a fluid-filled body cavity that is lined with tissue derive from mesoderm

pharynx - muscular tube at the end of the gastrovascular cavity, or throat, that connects the mouth with the rest of the digestive tract and serves as a passageway for air and food

flame cell -specialized cell that filters and removes excess water from the body of a flatworm

ganglion - group of nerve cells

eyespot - group of cells that can detect changes in the amount of light in the environment

hermaphrodite - individual that has both male and female reproductive organs

fission - form of asexual reproduction in which an organism splits in two, and each half grows new parts to become a complete organism

scolex - head of an adult tapeworm; can contain suckers or hooks

proglottid - one of the segments that make up most of a tapeworm’s body

testis - male gonad that produces sperm

Works Cited