Worms and Mollusks - PowerPoint PPT Presentation

1 / 52
About This Presentation
Title:

Worms and Mollusks

Description:

Worms and Mollusks CHAPTER 27 Leeches Class Hirudinea External parasites that suck the blood and body fluids of their host Polychaetes Class Polychaeta Contains ... – PowerPoint PPT presentation

Number of Views:107
Avg rating:3.0/5.0
Slides: 53
Provided by: SAHS5
Category:

less

Transcript and Presenter's Notes

Title: Worms and Mollusks


1
Worms and Mollusks
  • Chapter 27

2
Flatworms
  • Section 27-1

3
What is a flatworm?
  • Phylum Platyhelminthes
  • No more than a few millimeters thick
  • Have tissues and internal organ systems
  • Have bilateral symmetry and cephalization
  • Known as acoelomates (without coelem, which is
    a fluid filled body cavity)

4
Form and Function in Flatworms
  • Feeding
  • Digestive cavity with a single opening through
    which both food and wastes pass
  • Parasitic worms obtain nutrients from foods that
    have already been digested by their hosts

5
Form and Function in Flatworms
  • Respiration, Circulation, and Excretion
  • Rely on diffusion to
  • Transport oxygen and nutrients to internal
    tissues
  • Remove carbon dioxide and other wastes from their
    bodies
  • Have no gills or respiratory organs, heart, blood
    vessels, or blood
  • Some have flame cells remove excess water and
    filter wastes from the body

6
Excretory System
7
Form and Function in Flatworms
  • Response
  • A head encloses several ganglia (groups of nerve
    cells) that control the nervous system
  • Have eyespots that look like eyes, but are groups
    of cells that can detect changes in the amount of
    light in their environment

8
Form and Function in Flatworms
  • Movement
  • Two means of movement
  • Cilia to help glide through water
  • Muscle cells allow them to twist and turn

9
Form and Function in Flatworms
  • Reproduction
  • Most are hermaphrodites that reproduce sexually
  • A hermaphrodite is an individual that has both
    male and female reproductive organs
  • Asexual reproduction takes place by fission, in
    which an organism splits in two

10
Groups of Flatworms
  • Three main groups of Flatworms
  • Turbellarians
  • Flukes
  • Tapeworms
  • Most turbellarians are free-living
  • Most other flatworm species are parasites

11
Turbellarians
  • Free-living flatworms
  • Live in marine or freshwater

12
Flukes
  • Class Trematoda
  • Parasitic flatworms
  • Infect the internal organs of their host

13
Tapeworms
  • Class Cestoda
  • Long, flat, parasitic worms
  • Adapted to life inside the intestines of their
    host
  • No digestive tract
  • Absorb already digested nutrients from host

14
Roundworms
  • Section 2

15
What is a Roundworm?
  • Phylum Nematoda
  • Slender, unsegmented worms with tapering ends
  • Range in size from microscopic to a meter
  • Most are free-living, inhabiting soil and water
  • Others are parasitic

16
What is a Roundworm?
  • Have a pseudocoelom (false coelom)
  • Have a digestive tract with two openings a
    mouth and an anus

17
Form and Function in Roundworms
  • Have specialized tissues and organ systems
  • Body systems of free-living roundworms are more
    complex than parasitic ones

18
Form and Function in Roundworms
  • Feeding
  • Predators that use grasping mouthparts to catch
    and eat small animals
  • Respiration, Circulation, and Excretion
  • Exchange gases and excrete metabolic waste
    through their body walls
  • Depend on diffusion to carry nutrients and waste
    through their bodies

19
Form and Function in Roundworms
  • Response
  • Simple nervous systems
  • Have several types of sense organs
  • Movement
  • Muscles extend the length of their bodies
  • Reproduction
  • Reproduce sexually, and most have separate sexes

20
Roundworms and Human Disease
  • Parasitic roundworms include
  • Trichinosis-causing worms
  • Filarial worms
  • Ascarid worms
  • Hookworms

21
Trichinosis-Causing Worms
  • Trichinosis terrible disease caused by the
    roundworm Trichinella
  • Adult worms live and mate in the intestines of
    their hosts
  • Humans usually get the disease from eating
    undercooked pork

22
Filarial Worms
  • Threadlike worms that live in blood of birds and
    mammals
  • Causes elephantiasis

23
Ascarid Worms
  • Serious parasite of vertebrate animals
  • Causes malnutrition in more than 1 billion people
    worldwide
  • Absorbs digested food from the hosts small
    intestine

24
Hookworms
  • 25 of people in the world are affected with
    hookworms
  • Live in hosts intestines
  • Feed on blood, causing weakness and poor growth

25
Annelids
  • Section 27-3

26
What is an Annelid?
  • Phylum Annelida
  • Worms with segmented bodies
  • Each segment is separated by a septum
  • Have a true coelom

27
Form and Function in Annelids
  • Feeding and Digestion
  • Many get their food using a pharynx
  • Food moves from the pharynx, into the esophagus,
    the crop, the gizzard, and then to the intestine
  • Others obtain food by filter feeding
  • Circulation
  • Closed circulatory system blood is contained
    within a network of blood vessels

28
Form and Function in Annelids
  • Respiration
  • Aquatic annelids often breath through gills
  • Land-dwelling annelids take in oxygen and give
    off carbon dioxide through their moist skin
  • Excretion
  • Digestive wastes pass through the anus at the end
    of the digestive tract
  • Cellular waste is eliminated through nephridia
    (excretory organs)

29
Form and Function in Annelids
30
Form and Function in Annelids
  • Response
  • Well developed nervous system consisting of a
    brain and several nerve cords

31
Form and Function in Annelids
  • Movement
  • Two groups of muscles that work together as part
    of a hydrostatic skeleton
  • Reproduction
  • Most reproduce sexually
  • Some have separate sexes, others are
    hermaphrodites

32
Groups of Annelids
  • Three classes of Annelids
  • Oligochaetes
  • Leeches
  • Polychaetes

33
Oligochaetes
  • Class Oligochaeta
  • Contains earthworms and their relatives
  • Streamlined bodies
  • Relatively few setae
  • Most live in soil or freshwater

34
Leeches
  • Class Hirudinea
  • External parasites that suck the blood and body
    fluids of their host

35
Polychaetes
  • Class Polychaeta
  • Contains sandworms, blood worms, and relatives
  • Marine annelids that have paired, paddlelike
    appendages tipped with setae (brushlike
    structures)

36
Ecology of Annelids
  • Earthworms and many other annelids spend their
    lives burrowing through soil, aerating and mixing
    it
  • Earthworms help plant matter decompose
  • Earthworm castings are rich in nitrogen,
    phosphorus, potassium, micronutrients, and
    beneficial bacteria

37
Mollusks
  • Section 4

38
What is a Mollusk?
  • Soft-bodied animals
  • Usually have an internal or external shell
  • Free-swimming larval stage called a trocophore

39
Form and Function in Mollusks
  • True coeloms
  • Complex, interrelated organ systems

40
Form and Function in Mollusks
  • Body Plan
  • Variation on four main parts
  • Foot takes many forms
  • Mantle layer of tissue that covers the
  • mollusks body
  • Shell made by glands in the mantle
  • Visceral mass consists of internal organs

41
Form and Function in Mollusks
  • Feeding
  • Can be herbivores, carnivores, filter feeders,
    detritivores, or parasites
  • Snails and slugs feed using a tongue-shaped
    structure called a radula

42
Form and Function in Mollusks
  • Feeding
  • Clams, oysters, and scallops use gills
  • Food enters through a siphon tubelike structure
    through which water enters and leaves the body

43
Form and Function in Mollusks
  • Respiration
  • Aquatic mollusks breathe using gills inside their
    mantle cavity
  • Land snails and slugs respire through the moist
    surface of their skin

44
Form and Function in Mollusks
  • Circulation
  • Some have open circulatory systems works well
    for slow-moving mollusks (snails and clams)
  • Others have closed circulatory systems works
    best for fast moving mollusks (octopi and squid)

45
Form and Function in Mollusks
  • Excretion
  • Nephridia remove wastes from the blood and
    release it outside the body

46
Form and Function in Mollusks
  • Response
  • Two-shelled mollusks have simple nervous systems
  • Octopi and relatives have the most highly
    developed nervous systems of all invertebrates
  • Octopus opening a jar

47
Form and Function in Mollusks
  • Movement
  • Move in a variety of ways
  • Snails secrete mucus and move over surfaces using
    the foot
  • Octopi use a form a jet propulsion
  • Reproduction
  • Reproduce in a variety of ways
  • Snails and two-shelled mollusks external
    fertilization (sexually)
  • Tentacled mollusks and some snails internal
    fertilization (sexually)

48
Groups of Mollusks
  • Three major classes
  • Gastropods
  • Bivalves
  • Cephalopods

49
Gastropods
  • Class Gastropoda
  • Shell-less or single-shelled
  • Move using muscular foot on ventral side
  • Includes pond snails, land slugs, sea
    butterflies, sea hares, limpets, and nudibranchs

50
Bivalves
  • Class Bivalvia
  • Have two shells held together by one or two
    powerful muscles
  • Include clams, oysters, mussels, and scallops

51
Cephalopods
  • Class Cephalopoda
  • Soft-bodied
  • Head is attached to a single foot
  • Foot is divided into tentacles or arms
  • Includes octopi, squids, cuttlefishes, and
    nautiluses

52
Ecology of Mollusks
  • Mollusks play many different roles in living
    systems
  • Feed on plants
  • Prey on animals
  • Filter algae out of the water
  • Eat detritus
  • Some mollusks are hosts to symbiotic algae or to
    parasites others are themselves parasites
  • Mollusks are food for many organisms
Write a Comment
User Comments (0)
About PowerShow.com