Download Chapter # 13 Notes

Chapter # 13 Notes
Mollusks, Worms, Arthropods, and Echinoderms
Sec. # 13-1
What are Mollusks?
Mollusks – are soft bodied invertebrates with bilateral symmetry and usually one or two shells.
Bilateral Symmetry – body parts arranged in a similar way on both sides of the body, with each side
being nearly a mirror image of the other half.
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Mollusk comes from the Latin word meaning “soft”
There are about 110,000 species of mollusks. (ex. Snails, clams, octopuses, squids, slugs,
oysters, etc.)
Characteristics of Mollusks:
 All Mollusks have a mantle that secretes a shell and/or protects the body
 Most Mollusks have an open circulatory system.
 Some Mollusks, such as snails, use a muscular foot to move.
 Tentacles can be found on some Mollusks.
 Mollusks have a mantle, visceral mass, foot, and usually a shell
 Some Mollusks have gills
 The underside of a Mollusk is called the muscular foot, which is used for movement.
 Glands in the Mollusks foot secrete a layer of mucus on which they slide.
Mantle – A thin layer of tissue that covers a Mollusks body organs. It secretes the shell or protects the
body without a shell.
Visceral mass – were the organs are located in a Mollusks
Gills – Organs that exchange carbon dioxide for oxygen in the water.
Open Circulatory System – Blood circulation system in which blood moves through vessels and into
open spaces around body organs.
Classification of Mollusks:
 The three common groups of Mollusks are Gastropods, bivalves, and cephalopods.
1) Gastropods Largest group of mollusks
 Only group to use a radula
Radula – a tongue-like organ with rows of teeth used to scrape and tear food.
 This group includes snails, conchs, sea slugs, garden slugs, and abalones
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Bivalvesmollusks that have a hinge, two-part shell joined by strong muscles
includes clams, oysters and scallops
often eaten as sea food
to close their shell they contract powerful muscles and to open the shell they relax these muscles
for protection they burrow deep into the sand
3) Cephalopods most specialized and complex mollusks
 most intelligent invertebrates
 include squids, octopuses, cuttlefish, and chambered nautiluses
 Means “head-footed”
 Feed on fish, crustaceans, worms and other mollusks
 Have a well developed nervous system
 have a closed circulatory system
Closed Circulatory System – blood circulation in which blood moves through the body in a closed
loop or vessels.
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some squid can jump out of the water over 5 meters above the ocean surface
Mollusk fossils date back more than 500 million years ago
Many species became extinct about 65 million years ago
Mollusks have many uses such as food for fish, sea stars, birds and human, their shells are homes
to other animals, make beautiful pearls, and provide information about ecosystems.
Sec. 13-2 Segmented Worms
Segmented worms – the things crawling down the street and on the end of your fishing pole. Also
called annelid worms.
Annelid –means “little rings” or segments.
Setae – Bristle-like structures on the outside of each body segment that helps segmented worms move.
 Each of their body segments except the first and last have four pairs of setae
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can be found in fresh water, salt water or moist soil
bilateral symmetry
Earthworms have more than 100 segments
Crop – a sac (organ) used for storage
Gizzard – A muscular organ behind the crop, that grinds the soil and the bits of organic matter.
Earthworm body Systems:
 Earthworms have a closed circulatory system
 Earthworms get oxygen through their skin they do not have gills or lungs
 Earthworms are hermaphrodites and produce eggs and sperm in the same body
 Earthworm casting’s help fertilize the soil.
 Respond to light, temperature and moisture
 They are very simple animals that have a brain about the size of the hole in a small needle
Marine Worms:
 there are more than 8000 species of marine worms (polychaetes)
 live in water
 polychaete means “many bristles”
 include ice worms, Christmas tree worms and bristle worms
 Have parapodia
Parapodia – fleshy outgrowths on each segment, which aid in feeding and locomotion
Leeches:
 Leeches do not have setae
 Produce many chemicals including an anesthetic that numbs the wound
 Produce chemicals that prevent the blood from coagulating
Value of Segmented Worms:
 speed up the return of nitrogen and other nutrients to the soil for use by plants
 Leech saliva prevents blood clots
 Marine worms and their larvae are food for mammals
Origin of Segmented Worms:
 fossils date back to about 620 million years ago
 have a one way digestive system with a separate mouth and anus
 first evolved in the sea
 first animals to have space for body organs to develop and function
Sec. 13-3 Arthropods
 arthropod means “jointed foot”
 Largest group of animals with more than a million different species
Major Characteristics1) Bilateral Symmetry
2) Exoskeleton
3) Segmented Bodies
4) Nervous System
5) Digestive System with two openings
6) Body Cavity (Coelum)
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Some can be found with a waxy layer over the exoskeleton that keeps moisture inside.
Appendages – jointed structures of arthropods, such as legs, wings, antennae, claws and pinchers
Exoskeleton – A hard outer covering (an external skeleton)
Molting – Shedding and replacing of an arthropods exoskeleton
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Reproduce Sexually
Arthropods include over 700,000 species of insects
Insects: (grasshoppers, butterflies, flies, beetles, stick bugs, etc.)
 Have 3 main body parts1) Head - have a pair of antennae, eyes and mouth
Antennae = touch and smell
Eyes = simple and/or compound
2) Thorax – have three pairs (6 total) of legs, one or two pairs of wings if present are
attached to the thorax
3) Abdomen – reproductive structures and spiracles are found here
Spiracles – Openings on the abdomen and thorax through which air enters and waste
gases leave the body.
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Many insects go through metamorphosis
Metamorphosis – A process in which many insect species change their body form to become adults;
can be complete or incomplete.
Two types of Metamorphosis:
1) Incomplete – Stages include egg, nymph and adult
2) Complete – Stages include egg, larva, pupa, and adult.
Arachnids: (spiders, scorpions, mites and ticks)
 have 2 main body regions - the cephalothorax and the abdomen
Cephalothorax – the head-chest region
 have 4 pairs (8 total) legs
 some are parasites
 kill prey with venomous glands, stingers or fangs
Centipedes and Millipedes:
 have many segments and legs
 centipedes have one pair of legs per segment
 millipedes have 2 pairs of legs per segment
 found in damp environments
 reproduce sexually
 centipedes prey includes snails, slugs, worms and have a pair of venomous claws that inject
venom
 Millipedes feed on decaying material
Crustaceans: (crabs, lobsters, crayfish, shrimp, barnacles, pill bugs)
 have one or two pairs of antennae and mandibles
 most crustaceans live in the water
 if a crustacean loses an appendage it will regenerate or grow back
 5 pairs of legs. The first pair of legs are claws the other 4 pairs are walking legs
 They also have 5 pairs of appendages on the abdomen called swimmerets.
Value of Arthropods:
 source of food for many animals
 pollinate crops for agriculture
 some help in the medical field
 if you remove all the insects from the world it would do more harm than good
Arthropods date back 500 million years.
Sec. 13-4 Echinoderms ( sea urchins, sea stars, brittle stars, sea cucumbers)
 found in oceans all around the world
 live on the sea floor
 radial symmetry
 Echinoderm means “spiny skin”
 Have a mouth, stomach and intestines
 Have no head or brain
 Have tube feet
Tube feet – Hollow thin walled tubes that end in suction cups and enable echinoderms to move.
 Nerve ring surrounds the mouth
 Have a water vascular system
Water Vascular System – network of water filled canals that allows echinoderms to move, capture
food, give off wastes, and exchange carbon dioxide and oxygen.
 there are over 6000 species
 one third of all echinoderms are sea stars
Sea Stars & Brittle Stars:
 at least 5 arms around a central point
 thousands of tube feet
 can push its stomach through its mouth and into its prey
 reproduce sexually
 can regenerate an arm if one is lost
 feed on some mollusks
 live on the ocean floor
Sea urchins and Sand Dollars:
 do not have arms
 covered with stiff, hair-like spines, in which the ends are filled with toxic fluid that it injects into
prey
Sea Cucumbers:
 soft bodied with a leathery covering which makes them different from all other echinoderms
 have tentacles around their mouth
 rows of tube feet on their upper and lower surfaces
 when threatened they can expel their internal organs which regenerate in a few weeks
Value of Echinoderms:
 feed on dead organisms
 recycle materials
 control the growth of algae
 used for food
Around 400 million years old. They more closely resemble animals with a backbone than any other
group of invertebrates. Even have an endoskeleton like vertebrates.
Chapter # 13 Vocabulary
Sec. 13-1
Mollusks – are soft bodied invertebrates with bilateral symmetry and usually one or two shells.
Mantle – A thin layer of tissue that covers a Mollusks body organs. It secretes the shell or protects the body without a shell.
Visceral mass – were the organs are located in a Mollusks
Gills – Organs that exchange carbon dioxide for oxygen in the water.
Open Circulatory System – Blood circulation system in which blood moves through vessels and into open spaces around
body organs.
Radula – a tongue-like organ with rows of teeth used to scrape and tear food.
Closed Circulatory System – blood circulation in which blood moves through the body in a closed loop or vessels.
Sec. 13-2
Annelid –means “ little rings” or segments.
Setae – Bristle-like structures on the outside of each body segment that helps segmented worms move.
Crop – a sac (organ) used for storage
Gizzard – A muscular organ behind the crop that grinds the soil and the bits of organic matter.
Sec. 13-3
Appendages – jointed structures of arthropods, such as legs, wings, antennae, claws and pinchers
Exoskeleton – A hard outer covering (an external skeleton)
Molting – Shedding and replacing of an arthropods exoskeleton
Spiracles – Openings on the abdomen and thorax through which air enters and waste
gases leave the body.
Metamorphosis – A process in which many insect species change their body form to become adults; can be complete or
incomplete
Cephalothorax – the head-chest region
Sec. 13-4
Tube feet – Hollow thin walled tubes that end in suction cups and enable echinoderms to move.
Water Vascular System – network of water filled canals that allows echinoderms to move, capture food, give off wastes,
and exchange carbon dioxide and oxygen.