Transcript Introduction to Invertebrates

IntroductionChapter
to
29
Invertebrates
Introduction to
Invertebrates
Animals
Introduction to
Invertebrates
What makes an animal?
How can you tell if something is an animal or
not?
What are some examples of animals?
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Evolution of Animals (intro)
Introduction to
Invertebrates
All animals are multicellular heterotrophic
organisms that must take in preformed food.
mulitcellular: made of more than one cell
heterotrophic: take in preformed food from other
organisms
food: complex organic molecules; often glucose
related compounds
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Outline
Introduction to
Invertebrates
Criteria for the Evolution of Animals
1. Multicellularity
2. True Tissues
3. Bilateral Symmetry
4. Body Cavities
5. The Coelom
6. Segmentation
7. Development
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Evolution of Animals (intro)
Introduction to
Invertebrates
All animals are multicellular heterotrophic
organisms that must take in preformed food
Classification Criteria
Level of organization
- Cellular, tissue, organ
Body Plan
- Sac, tube-within-a-tube
Segmentation
- Segmentation leads to specialization
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Evolution of Animals (intro)
Introduction to
Invertebrates
6
Classification Criteria, cont
Symmetry
- Radial - Two identical halves
- Bilateral - Definite right and left halves
Type of Coelom
- Acoelomate
- Pseudocoelom
- Coelom
Early Developmental Pattern
- Protostome - First embryonic opening becomes the
mouth
- Dueterostome - Second embryonic opening
becomes the mouth
Animals:
How does this picture demonstrate that
an animal is involved?
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Traditional
Phylogenetic
Tree of
Animals
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Animal?
In order to be considered
an animal, what must be
true about this organism?
Introduction to
Invertebrates
9
Multicellularity
Sponges
Introduction to
Invertebrates
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Only level of animal to have cellular organization
Saclike bodies perforated by many pores
Beating of flagella produces water currents that
flow through pores into central cavity and out
osculum
Sessile filter feeders
Asexual reproduction by fragmentation or
budding
Simple Sponge Anatomy
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Introduction to
Invertebrates
Porifera in the Animal Cladogram
Sponges
sitting at the bottom of
the animal phylogeny
simplest of the existing
animals and possibly
one of the simplest of
all time
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Introduction to
Invertebrates
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True Tissue Layers – Ctenophora & Cnidarians
Many animals have a total of three possible germ
layers
 Ectoderm – outside layer; skin or outer covering , brain and peripheral nerves
 Endoderm – inside layer; gut track and some digestive tissues
 Mesoderm – inner layer; muscles
phlya Ctenophora and Cnidaria develop only
ectoderm and endoderm
Diploblasts – animals derived from only 2
embryonic layers
Radially symmetrical
True Tissue Layers
Introduction to
Invertebrates
phlya Ctenophora and Cnidaria develop only
ectoderm and endoderm
So what is in the middle if these organisms (the
first with true tissue layers) ?
What are Ctenophora called again?
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Types of Symmetry
Introduction to
Invertebrates
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Comb Jellies - Ctenophora
Introduction to
Invertebrates
Characteristics:
• Small, transparent, and often luminescent
• Most of body composed of mesoglea
• Largest animals propelled by beating of cilia
• Capture prey with tentacles
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Comb Jelly Compared to Cnidarian
Cnidarians
Introduction to
Invertebrates
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Tubular animals that most often reside in shallow
marine waters
Polyp and medusa body forms
Specialized stinging cells (cnidocytes)
- Fluid-filled capsule, nematocyst
Two-layered body sac
- Outer layer - Protective epidermis
- Inner layer - Gastrovascular cavity
Nerve net found throughout body
Cnidarian Diversity
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Hydra
Introduction to
Invertebrates
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Freshwater cnidarian
Small tubular poly body about one-quarter inch in
length
- Gastrovascular cavity is central cavity
Tentacles can respond to stimuli
Can reproduce sexually and asexually
Anatomy of Hydra
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Obelia
Introduction to
Invertebrates
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A colony of polyps enclosed by a hard, chitinous
covering. Chitin?
Feeding polyps
- Extend beyond covering
- Have nematocyst-bearing tentacles
Reproductive polyps
- Budding of new polyps
Also has sexual reproduction (medusae) stage
Obelia Life Cycle
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Ctenophora and Cnidarians
Where are we now?
How are cnidarians and
ctenophora different
from sponges?
What new “feature” do
they posses that
sponges did not have?
http://www.youtube.com
/watch?v=bcmLxsJ5SA
g&feature=related
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Bilateral Symmetry
New Characteristics
Introduction to
Invertebrates
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Bilateral Symmetry
animals have a “left and right”
one plane of symmetry
Cephalization
identifiable or obvious “head” end of the animal
having mouth and/or sensory organs at one end
Bilateral Symmetry
Introduction to
Invertebrates
Pseudocoelomates
Both phyla today will be considered
pseudocoelomates
What is the difference between acoelomates,
pseudocoelomates and coelomates (or
eucoelomates?)
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Bilateral Symmetry
Introduction to
Invertebrates
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Coelomates (also known as eucoelomates — "true coelom")
have a fluid filled body cavity called a coelom with a complete
lining called peritoneum derived from mesoderm (one of the
three primary tissue layers).
Pseudocoelomate
have a pseudocoel (literally “false
cavity”), which is a fully functional body cavity. Tissue derived
from mesoderm only partly lines the fluid filled body cavity of
these animals. Thus, although organs are held in place loosely,
they are not as well organized as in a coelomate.
Acoelomate animals, like flatworms, have no body cavity at
all. Organs have direct contact with the epithelium. Semi-solid
mesodermal tissues between the gut and body wall hold their
organs in place.
Bilateral Symmetry
Introduction to
Invertebrates
Flatworms (phylum Platyhelminthes)
 Majority are parasitic
 Organ-level organization
- No specialized circulatory or respiratory structures
 Have undergone cephalization
 Ladder-type nervous system
Ribbon worms (phylum Nemertea)
 Have distinctive proboscis
 Have a complete gut track
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Flatworms
Belong to the phylum platyhelminthes.
(Plat = flat)
There are three classes:
Turbellaria
Trematoda
Cestoda
Characteristics of Flatworms
They are acoelomates (they don’t have
body cavities)
They have bilateral symmetry
Show cephalization
Respiration through skin
Single opening to digestive tract (pharynx)
Free-living Flatworms
Planarians (genus Dugesia)
Live in freshwater habitats
Head is bluntly arrow shaped
- Auricles function as sense organs
- Two light-sensitive eye spots
Three kinds of muscle layers:
- Outer circular layer
- Inner longitudinal layer
- Diagonal layer
Introduction to
Invertebrates
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Planarian Anatomy
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Planarians
Introduction to
Invertebrates
Planarians, cont.
Excretory organ functions in osmotic regulation
and water excretion
Can reproduce asexually
Hermaphroditic
- Practice cross-fertilization
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Parasitic Flatworms
Introduction to
Invertebrates
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Parasitic flatworms are flukes (trematodes) and
tapeworms (cestodes)
Well-developed nerves and gastrovascular cavity
are unnecessary
Flukes
Reproductive system well developed
Usually hermaphroditic
Life Cycle of Schistosomiasis
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Parasitic Flatworms
Introduction to
Invertebrates
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Tapeworms
Have anterior region with modifications for
attachment to intestinal wall of host
Behind head region, scolex, a long series of
proglottids are found
Segments each containing a full set of both male
and female sex organs
Complicated life cycles
Life Cycle of a Tapeworm, Taenia
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Class Trematoda
Are parasitic flukes
Have suckers on
both ends of the
body
Can live inside or
outside of host
Not much
cephalization
Class Trematoda
Nervous and excretory
systems like
turbellarians
Hermaphrodites
Have complex life
cycles
Class Cestoda
Parasitic
Tapeworms
Long, ribbon-like
bodies
Absorbs nutrients
from host
Hermaphrodites
Tapeworm Anatomy
Ribbon Worm, Lineus
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Phylum Nemertea
(Rhynchocoela) Ribbonworms
The nemerteans (ribbon worms) are
long, marine predatory worms and there
are about 1000 species known.
Unlike members of the Platyhelminthes
nemerteans have a complete gut with a
mouth and anus and a true circulatory
system
Phylum Nemertea
(Rhynchocoela) Ribbonworms
Prey is captured using a long muscular proboscis
armed with a barb called a stylet..
The proboscis lies in an interior cavity called the
rhynchocoel and muscular pressure on fluid in the
rhynchocoel causes the proboscis to be quickly
everted.
The prey is wrapped in the sticky, slime-covered,
proboscis and stabbed repeatedly with the stylet.
Neurotoxins in the slime incapacitate the prey.
Figure 14.24a
Internal structure of
female ribbon worm
(left).
Nemertean with proboscis
extended (below)
Figure 14.24b
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Figure 14.25
8.19
Baseodiscus mexicanus a nemertean from
the Galapagos Islands
Pseudocoelom
What is different about the
animals we discussed
today?
How are flatworms
(Platyhelminthes)
different from
cnidarians?
How are nemertea (ribbon
worms) different from
flatworms?
Introduction to
Invertebrates
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Pseudocoelom
Introduction to
Invertebrates
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Pseudocoelom:
A “false” body cavity that is incompletely lined by
mesoderm
Provides a space for internal organs and can
serve as hydrostatic skeleton
Both phyla today are animals with a complete
body gut track and pseudo coelom
- phylum Nematoda and Rotifera
Types of Body Cavities
3 types of body cavities
Introduction to
Invertebrates
Types of Body Cavities
acoelomate
Introduction to
Invertebrates
Types of Body Cavities
pseudocoelomate
Introduction to
Invertebrates
Types of Body Cavities
Coelomates – not
there yet
Introduction to
Invertebrates
Pseudocoelom
Introduction to
Invertebrates
Roundworms (phylum Nematoda)
Non-segmented, generally colorless worms
Several parasitic roundworms infect humans
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Roundworm Anatomy
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Parasitic Roundworms
Ascaris – Intestinal roundworm
Trachinella - Trichinosis
Dirofilaria - Heartworms
Wuchereria - Elephantiasis
Introduction to
Invertebrates
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Filarial Worm
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Rotifers
Introduction to
Invertebrates
Rotifers (phylum Rotifera)
Named for crown of cilia resembling a rotating
wheel
Serves as both as an organ of locomotion and
aids direction of food to mouth
Important base of many ecosystems
- Planktonic
Transparent organisms
Can survive dessication
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Rotifer
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Rotifers on youtube.com
25X
Magnification
Pseudocoelomates
How are nematoda
and rotifera
different from
platyhelminthes
and nemertea
(flatworms and
ribbon worms?)
Introduction to
Invertebrates