Chapter 27 BDOL IC.ppt

(1)

(2)

Unit 1: What is Biology?

Unit 2: Ecology

Unit 3: The Life of a Cell

Unit 4: Genetics

Unit 5: Change Through Time

Unit 6: Viruses, Bacteria, Protists, and Fungi

Unit 7: Plants

Unit 8: Invertebrates

Unit 9: Vertebrates

(3)

Unit 1: What is Biology?

Chapter 1: Biology: The Study of Life

Unit 2: Ecology

Chapter 2: Principles of Ecology

Chapter 3: Communities and Biomes Chapter 4: Population Biology

Chapter 5: Biological Diversity and Conservation

Unit 3: The Life of a Cell

Chapter 6: The Chemistry of Life

Chapter 7: A View of the Cell

(4)

Unit 4: Genetics

Chapter 10: Mendel and Meiosis

Chapter 11: DNA and Genes

Chapter 12: Patterns of Heredity and Human Genetics

Chapter 13: Genetic Technology

Unit 5: Change Through Time

Chapter 14: The History of Life

Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution

(5)

Unit 6: Viruses, Bacteria, Protists, and Fungi

Chapter 18: Viruses and Bacteria Chapter 19: Protists

Chapter 20: Fungi

Unit 7: Plants

Chapter 21: What Is a Plant?

Chapter 22: The Diversity of Plants

(6)

Unit 8: Invertebrates

Chapter 25: What Is an Animal?

Chapter 26: Sponges, Cnidarians, Flatworms, and

Roundworms

Chapter 27: Mollusks and Segmented Worms

Chapter 28: Arthropods

Chapter 29: Echinoderms and Invertebrate Chordates

(7)

Unit 9: Vertebrates

Chapter 30: Fishes and Amphibians Chapter 31: Reptiles and Birds

Chapter 32: Mammals

Chapter 33: Animal Behavior

Unit 10: The Human Body

Chapter 34: Protection, Support, and Locomotion Chapter 35: The Digestive and Endocrine Systems Chapter 36: The Nervous System

Chapter 37: Respiration, Circulation, and Excretion Chapter 38: Reproduction and Development

Chapter 39: Immunity from Disease

(8)

Invertebrates

What Is an animal?

Sponges, Cnidarians, Flatworms, and Roundworms

Mollusks and Segmented Worms

Arthropods

(9)

Chapter 27 Introduction: Mollusks an Segmented Worms

27.1: Mollusks

27.1: Section Check

27.2: Segmented Worms

27.2: Section Check

Chapter 27 Summary

(10)

What You’ll Learn

You will distinguish among the classes

of mollusks and segmented worms.

You will compare and contrast the

(11)

• Identify the characteristics of mollusks.

Section Objectives:

• Compare the adaptations of gastropod,

(12)

• Slugs, snails, squids, and some animals that live in shells in the ocean or on the beach are all mollusks. These organisms belong to the phylum Mollusca.

• Although most

species live in the ocean, others live in freshwater and moist terrestrial habitats.

What is a mollusk?

(13)

• Some mollusks have shells, and others, including slugs and squids, are adapted to life without a hard covering.

What is a mollusk?

(14)

• All mollusks have bilateral symmetry, a

coelom, a digestive tract with two openings, a muscular foot, and a mantle.

What is a mollusk?

Visceral mass

Mantle ShellFoot Tentacle

Arm

Head Reduced internal shell Mantle

Gut

(15)

What is a mollusk?

Visceral mass Mantle

Shell Foot

Head Mantle

Gut Shell

(16)

Radula

• Snails, like many mollusks, use a rasping structure called a radula to obtain food.

How mollusks obtain food

(17)

How mollusks obtain food

• Octopuses and squids are predators that use their radulas to tear up the food that they

capture with their tentacles.

(18)

• Bivalves do not have radulas; they filter food from the water.

How mollusks obtain food

(19)

• Mollusks reproduce sexually and most have separate sexes.

• Many gastropods that live on land, and a few bivalves, are hermaphrodites and produce both eggs and sperm.

Fertilization is internal.

• In most aquatic species, eggs and sperm are released at the same time into the water,

where external fertilization takes place.

Reproduction in mollusks

(20)

• Some marine mollusks

have free swimming larvae that propel themselves.

Reproduction in mollusks

• Most marine snails and bivalves have another

developmental stage called a veliger in which he

(21)

• Molusks have simple nervous systems that coordinate their movement and

behavior.

Nervous control in mollusks

(22)

• Most mollusks have paired eyes that

range from simple cups that detect

light to the complex eyes of octopuses that have irises, pupils, and retinas similar to the eyes of humans.

Nervous control in mollusks

(23)

• Mollusks have a well-developed circulatory system that includes a three-chambered

heart.

Circulation in mollusks

(24)

• In most mollusks, the heart pumps blood through an open circulatory system.

Circulation in mollusks

(25)

• Some mollusks, such as octopuses, move nutrients and oxygen through a closed

circulatory system.

Circulation in mollusks

(26)

• Most mollusks have respiratory structures called gills.

Respiration in mollusks

• Gills are specialized parts of the mantle that consist of a system of filamentous

(27)

• Mollusks are the oldest known animals to have evolved excretory structures called nephridia.

Excretion in mollusks

(28)

• Wastes are discharged into the mantle cavity, and expelled from the body by the pumping of the gills.

Excretion in mollusks

(29)

• Phylum Mollusca is large and diverse.

Diversity of Mollusks

• Three mollusk classes—Gastropoda,

(30)

• The largest class of mollusks is Gastropoda, or the stomach-footed mollusks.

Gastropods: One-shelled mollusks

• The name

comes from the way the

animal’s large foot is

positioned

(31)

• Shelled gastropods include snails, abalones, conches, periwinkles, whelks, limpets,

cowries, and cones.

Gastropods: One-shelled mollusks

• Instead of being protected by a shell, the

(32)

• Colorful sea slugs, also called

nudibranchs, are protected in another

way.

Gastropods: One-shelled mollusks

(33)

• When certain species of sea slugs feed on jellyfishes, they incorporate the poisonous nematocysts of the jellyfish into their own tissues without causing these cells to

discharge.

Gastropods: One-shelled mollusks

(34)

• Two-shelled

mollusks such as clams, oysters, and scallops belong to the class Bivalvia. • Most bivalves are

marine, but a few species live in

freshwater habitats.

Bivalves: Two-shelled mollusks

(35)

• Bivalves have no distinct head or radula. Most use their large, muscular foot for

burrowing in the mud or sand at the bottom of the ocean or a lake.

Bivalves: Two-shelled mollusks

• A ligament, like a hinge, connects their two

shells, called valves;

(36)

• One of the main differences between

gastropods and bivalves is that bivalves are filter feeders that obtain food by filtering

small particles from the surrounding water. • Gill cilia beat to draw water in through an

incurrent siphon.

• As water moves over the gills, food and sediments become trapped in mucus.

Bivalves: Two-shelled mollusks

(37)

• Cilia that line the gills push food particles to the mouth.

• Large particles, sediment, and anything else that is rejected is transported to the mantle where it is expelled through the excurrent siphon, or to the foot, where it is eliminated from the animal’s body.

Bivalves: Two-shelled mollusks

(38)

• This class includes the octopus, squid, cuttlefish, and chambered nautilus.

Cephalopods: Head-footed mollusks

• The only cephalopod with a shell is the

chambered nautilus, but some species, such as the cuttlefish, have a reduced internal

(39)

• In cephalopods, the foot has evolved into tentacles with suckers, hooks, or adhesive structures.

Cephalopods: Head-footed mollusks

• Cephalopods swim or walk over the

ocean floor in

pursuit of their prey, capturing it with

(40)

• Once tentacles have captured prey, it is brought to the mouth and bitten with beaklike jaws.

Cephalopods: Head-footed mollusks

(41)

• Cephalopods have siphons that expel water.

Cephalopods: Head-footed mollusks

• These mollusks can expel water forcefully in any direction, and move quickly by jet

propulsion. Squids can attain speed of 20m per second using this system of movement.

Water in

Water out

(42)

• Squids and octopuses also can release a dark fluid to cloud the water.

Cephalopods: Head-footed mollusks

(43)

Which of the following mollusks does NOT have a radula, and why?

Question 1

D. slug C. clam

B. sea snail A. octopus

The answer is C. Clams are filter feeders that do not need a radula to obtain food.

(44)

Which of the following is NOT a function of the tentacles of a land snail?

Question 2

D. capturing prey C. moving the eyes B. feeling

A. smelling

(45)

Which are the first mollusks you would

expect to be affected by pollution and why?

Question 3

D. squid

C. octopuses B. snails

A. clams

(46)

The answer is A. Clams are filter feeders.

They would be most likely to ingest plankton and become polluted. Later, other mollusks like sea snails that prey on clams might ingest the same pollutant when they eat the clams.

(47)

Nephridia are organs used for _____.

Question 4

D. excretion C. movement B. respiration A. circulation

The answer is D, excretion.

(48)

• Describe the characteristics of segmented

worms and their importance to the survival of these organisms.

Section Objectives:

(49)

• Segmented worms are classified in the

phylum Annelida. They include leeches and bristleworms as well as earthworms.

What is a segmented worm?

(50)

• The basic body plan of segmented worms is a tube within a tube.

What is a segmented worm?

(51)

• Food is taken in by the mouth, an

opening in the

anterior end of the worm, and wastes are released

through the anus, an opening at the posterior end.

What is a segmented worm?

(52)

What is a segmented worm?

• The setae help segmented worms move by providing a way to anchor their bodies in the soil so each segment can move the animal along.

(53)

• The most distinguishing characteristic of

segmented worms is their cylindrical bodies that are divided into ringed segments.

Segmentation supports diversified

functions

Segmentation supports diversified

functions

• In most species, this

segmentation continues internally as each

(54)

• Each segment has its own muscles, allowing shortening and lengthening of the body.

• Segmentation also allows for specialization of body tissues.

• Certain segments have modifications for functions such as sensing and reproduction.

Segmentation supports diversified

functions

(55)

• Segmented worms have simple nervous systems in which organs in anterior

segments have become modified for sensing the environment.

Nervous system

• Some sensory organs are sensitive to light, and eyes with lenses and retinas have

(56)

• In some species there is a brain located in an anterior segment.

Nervous system

• Nerve cords connect the brain to nerve centers called ganglia, located in each segment. Setae Nerve Intestine Gizzard

CropEsophagus_Mouth

(57)

• Segmented worms have a closed circulatory system.

Circulation and respiration

• Blood carrying oxygen to and carbon

dioxide from body cells flow through vessels to reach all parts of the body.

• Segmented worms must live in water or in wet areas on land because they also

(58)

• Segmented worms have a complete internal digestive tract that runs the length of the

body.

Digestion and excretion

(59)

• In the gizzard, a muscular

(60)

• Undigested material and solid wastes pass out the worm’s body through the anus.

Digestion and excretion

• Segmented worms have two nephridia in almost every

segment that collect waste products and transport them through the coelom and out of the body.

(61)

• Earthworms and leeches are hermaphrodites, producing both eggs and sperm.

Reproduction in segmented worms

• During mating, two worms exchange sperm. • Each worm forms a capsule for the eggs and

(62)

• The eggs are fertilized in the capsule, then the capsule slips off the worm and is left behind in the soil.

Reproduction in segmented worms

(63)

• Bristleworms and their relatives have separate sexes and reproduce sexually.

Reproduction in segmented worms

(64)

• Usually eggs and sperm are released into the seawater, where fertilization takes place.

Reproduction in segmented worms

• Bristleworm larvae hatch in the sea and become part of the plankton.

(65)

• The phylum Annelida includes three classes: class Oligochaeta, earthworms; class

Polychaeta, bristleworms and their relatives; and class Hirudinea, leeches.

Diversity of Segmented Worms

(66)

• Earthworms are the most well-known

annelids because they can be seen easily by most people.

Earthworms

(67)

Earthworms

Mouth

Crop

Gizzard

Setae

Nephridia

Circulatory system

(68)

• The class Polychaeta includes bristleworms and their relatives—fanworms, lug worms, plumed worms, and sea mice.

Bristleworms and their relatives

(69)

• Most body segements of a polychaete have many setae, hence the name. Polychaete means “many bristles”.

Bristleworms and their relatives

(70)

• Parapodia also function in gas exchange.

Bristleworms and their relatives

• A polychaete has a head with

(71)

• Leeches are segmented worms with flattened bodies and usually no setae.

Leeches

• Unlike earthworms, many species are

(72)

• Front and rear suckers enable leeches to attach themselves to their hosts.

Leeches

(73)

• The saliva of the leech contains chemicals that act as an anesthetic.

Leeches

• Other chemicals prevent the blood from clotting.

(74)

• Fossil records show that mollusks lived in great numbers as long as 500 million years ago.

• Gastropod, bivalve, and cephalopod fossils have been found in Precambrian deposits.

Origins of Mollusks and Segmented

Worms

(75)

• Annelids probably evolved in the sea,

perhaps from larvae of ancestral flatworms.

Origins of Mollusks and Segmented Worms

(76)

• Tubes constructed by polychaetes are the most common fossils of this phylum.

• Some of these tubes appear in the fossil record as early as 540 million years ago.

Origins of Mollusks and Segmented

Worms

(77)

Why must segmented worms live in a moist environment?

Question 1

Answer

Segmented worms must live in or near water because they exchange gases directly through their moist skin.

(78)

During mating, earthworms exchange _____.

Question 2

D. larvae

C. capsules containing both sperm and eggs B. sperm

A. eggs

(79)

Using this figure,

give the reason why you would

(80)

The anterior portion of an organism would

logically include the brain, as well as the

initial parts of a gut, like the esophagus and crop (the esophagus and crop are necessary to the

(81)

Which organism would likely get the most use from a gizzard, an earthworm or a leech?

Question 4

Answer

A gizzard grinds organic matter into small pieces so the nutrients in the food can be absorbed. Since a leech’s food is liquid

(blood), the earthworm would use a gizzard the most, to grind the food and soil it

ingests.

(82)

Earthworms are considered to be ______.

Question 5

D. grazers

C. filter feeders B. parasites

A. predators

The answer is D, grazers.

(83)

• Mollusks have bilateral symmetry, a coelom, and a digestive tract with two openings. Many also have shells.

Mollusks

(84)

• Bivalve mollusks have paired shells, called valves, and are filter feeders. They have no radula. Clams and scallops are bivalves.

Mollusks

• Cephalopods have tentacles with suckers, beaklike jaws, a mouth with a radula, and a closed circulatory system. Cephalopods

(85)

• The phylum Annelida includes the

earthworms, bristleworms, and their relatives, and leeches. Annelida are bilaterally

symmetrical and have a coelom and two body openings; some have larvae that look like the larvae of mollusks. Their bodies are

cylindrical and segmented.

Segmented Worms

• Earthworms have complex digestive,

(86)

• Bristleworms and their relatives are mostly marine species. They have many setae and parapodia that are used for crawling along.

Segmented Worms

• Leeches are flattened, segmented worms. Most are aquatic parasites.

• Fossil remains of mollusks show that they

first lived over 500 million years ago. Fossil records show that segmented worms first

(87)

Question 1

With the exception of slugs, all mollusks that are slow-moving or sessile have shells. Why?

(88)

Shells provide organisms with a place to hide that is always near them, since they cannot quickly escape a predator.

(89)

Question 2

Why is a closed circulatory system more efficient than an open circulatory system?

(90)

A closed circulatory system is more efficient because blood is transported entirely in closed vessels that can reach deep into the organism’s tissues and provide efficient gas exchange. In an open circulatory system, tissues farthest from the open spaces containing blood are not so likely to be reached for efficient gas exchange.

(91)

Question 3

Why do scientists consider cephalopods to be the most recently evolved of all mollusks?

Answer

Cephalopods possess the most complex structures of all mollusks, such as complex eyes, complex brains, closed circulatory systems and feet that have evolved into complex structures like arms and tentacles.

(92)

Question 4

Why are mollusks considered to be excellent index fossils?

Answer

Mollusks are generally well preserved in the fossil record, abundant, easy to recognize, and widely distributed geographically.

(93)

Question 5

Which of the following is NOT a food source for humans and why?

A. abalones B. octopuses

C. ammonites D. conches

The answer is C. Ammonites are not a food source for any organism, because they are extinct.

(94)

Question 6

How does a leech benefit from the chemicals in its saliva that prevent clots from forming?

Answer

(95)

Question 7

What is the function of parapodia?

Answer

Polychaetes use parapodia for swimming, crawling, and for gas exchange.

(96)

Question 8

Why do annelids have such a limited fossil record?

Answer

The fossil record for segmented worms is limited because segmented worms have almost no hard body parts from which fossils could develop.

(97)

Question 9

What is the function of setae?

Answer

(98)

Question 10

Which of the following features do annelids NOT share with mollusks?

A. coelom

B. bilateral symmetry

C. digestive tract with two openings D. segmented bodies

(99)

Photo Credits

• General Biololgical Inc. • Digital Stock

• Joey Jacques • Corbis

(100)

To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow.

Click on this icon to return to the table of contents

Click on this icon to return to the previous slide

Click on this icon to move to the next slide

(101)