Important words and concepts
from Chapter 33, Campbell & Reece, 2002 (5/12/2003):
by Stephen T. Abedon (abedon.1@osu.edu)
for Biology 113 at the Ohio State University
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(1)
Chapter title: Invertebrates
(a)
[invertebrates (Google Search)]
[index]
(a)
This chapter surveys the invertebrate animals
(b)
Most animal phyla are invertebrates (in fact, all animal phyla but one
contain nothing but invertebrates)
(c)
Extant animals are grouped into approximately 35 phyla
(d)
In our survey of the invertebrates we will consider only 10 of these
(those not considered here but considered by your text are in parentheses and
are linked to a Google Search)
(i)
Porifera
(ii)
Cnidaria
(iii)
(Ctenophora)
(iv)
Platyhelminthes
(v)
Rotifera
(vi)
Nematoda
(vii)
(Nemertea)
(viii)
(Bryozoa)
(ix)
(Phoronida)
(x)
(Brachiopoda)
(xi)
Mollusca
(xii)
Annelida
(xiii)
Arthropoda (actually perhaps better classified
as a “superphylum” containing at least four phyla)
(xiv)
Echinodermata
(xv)
Chordata
(e)
See Figure 32.4, A
traditional view of animal diversity based on body-plan grades (for an overview of
invertebrate relationships and characteristics)
(f)
As discussed in the previous chapter, these phyla may be grouped
according to their adult and embryological forms into
(iii)
Diploblastic vs. Triploblastic
(iv)
Acoelomates vs. Pseudocoelomates vs. Coelomates
(v)
Protostomes vs. Deuterostomes
(g)
See Table 33.7, Animal phyla
(h)
Note that while common names are important, when one formally asks for
a taxon (e.g., phylum, order, class, etc. as an exam question) one
expects a formal taxon as a reply (e.g., phylum Cnidaria rather than jellyfish)
(i)
[invertebrates (Google Search)]
[index]
PHYLYM PORIFERA (SPONGES)
(3)
Phylum Porifera (sponges, amoebocyte, choanocyte)
(a)
Poriferans are considered to be the only members of the Parazoa (versus eumetazoa) split
Phylum Porifera includes the sponges
Sponges…
Lack true tissues
Are the simplest of Animals
Have no nerves or muscles (though they are capable of responding, as individual cells, to their environments)
Possess choanocytes (collar cells) which are “unique flagellated cells that ingest bacteria and tiny food particles” (p. 675, Campbell & Reece, 2002)choanocytes look a lot like choanoflagellates)
Possess amoebocytes, a type of cell that transfers food to rest of the sponge cells
Are sessile as adults but are non-sessile as larvae (juvenile form)
(vii)
Sponge “cells tend to be totipotent
(retain zygote’s ability to form the whole animal)” (p. 675, Campbell &
Reece, 2002)
(d)
"Sponges are among the least complex of all animals. They lack
organs, and the cell layers are loose federations of cells, not really tissues
because the cells are relatively unspecialized. Sponges have no nerves or
muscles, but the individual cells can sense and react to changes in the
environment."
(e)
“The body of a simple sponge resembles a sac perforated with holes (Porifera
means pore bearer). Water is drawn through the pores into a central cavity…,
then flows out of the sponge through a larger opening… Under certain conditions
the cells around the pores [and larger opening] contract, closing the
openings.” (p. 648, Campbell & Reece, 2002)
(f)
“Nearly all sponges are suspension-feeders (also known as filter
feeders), which are animals that collect food particles from water passed
through some type of food-trapping equipment.”
(p. 649, Campbell & Reece, 2002)
(i)
(note, however, that there are some sponges that are, in fact,
carnivorous, trapping and then consuming animals such as crustaceans)
(g)
Sponges feed by using flagellated cells
(choanocytes) to move water through their bodies
(h)
Food particles are trapped by collared and flagellated cells (also the
choanocytes) and are then phagocytized
(i)
These food particles are transferred to cells with mobile, amoeboid
morphology called amoebocytes, which digest food and then make the digestive
products available to the rest of the sponge cells
(j)
Though sessile (i.e., anchored in place to the sea bottom), sponges
produce non-sessile larvae that allow the sponges to disseminate to new locals
(k)
See Figure 33.2, A sponge
(l)
See Figure 33.3, Anatomy of a sponge
(m)
[phylum Porifera, sponges, amoebocyte, choanocyte, amoebocyte and sponges
(Google Search)]
[index]
PHYLYM CNIDARIA (JELLIS, CORALS, ETC.)
(4)
Phylum Cnidaria (medusa,
polyp, cnidocytes, coral polyps, hydra, jellyfish, sea
anemone)
(a)
Phylum Cnidaria includes the hydra, jellyfish, sea anemones, and coral
polyps
(b)
See Figure 33.6,
Representatives of the cnidarian classes
(c)
Cnidarians are Radiata Eumetazoans
(d)
Cnidarians have only a single opening to their digestive cavity; i.e.,
they don’t have a gut
(e)
See Figure 33.4, Polyp and
medusa forms of cnidarians
(f)
They are carnivores, i.e., they eat other, living
animals, employing cells called cnidocyotes to sting and grasp their prey
(g)
See Figure 33.5, A cnidocyte
of a hydra
(h)
Cnidarians possess simple nervous systems as well as muscles (though
the latter are not considered true
muscles since true muscles are
derived from mesodermal tissue and Cnidarians lack
mesodermal tissue, i.e., they are diploblastic)
(i)
Cnidarians exist as either sessile polyps or as floating medusa; some
Cnidarians switch back and forth between the two body plans while others exist
as either one body plan or the other
(j)
See Figure 33.7, The life
cycle of the hydrozoan Obelia
(k)
Polyps are cylindrical, adhere to substratum and expose their
mouth/anus to the water where their tentacles serve to snare food, e.g., hydra
and sea anemones
(m)
Medusa are flattened (pancake-like) and have their mouth hanging
beneath their bodies, also employing their tentacles to snare food, e.g.,
jellyfish
(o)
See Figure 33.4, Polyp and
medusa forms of cnidarians
(p)
[phylum Cnidaria, cnidarians, medusa and cnidaria,
polyp and cnidaria,
class Anthozoa, coral polyp, sea anemone, class Hydrozoa, hydra and cnidaria,
class Scyphozoa, jellyfish (Google Search)]
[index]
PHYLYM PLATYHELMINTHES
(FLATWORMS)
(5)
(a)
Phylum Platyhelminthes includes the flatworms (which, as parasitic
flatworms, are known as flukes and tapeworms)
(b)
Platyhelminthes live in water or damp environments
(c)
See Figure 33.9, A flatworm
(d)
See Figure 33.10, Anatomy of a planarian
(e)
Platyhelminthes are bilaterally symmetrical
acoelomates
(f)
The digestive cavity of flatworms possesses only a single opening
(g)
Platyhelminthes lack a circulatory system
(h)
They are able to diffuse oxygen and wastes to their body cells; this is
possible because of the short distances within their bodies afforded by their
very flat shape and the branching nature of their digestive cavity
(i)
"The flat shape of the body (of the flatworm) places all cells
close to the surrounding water, and fine branching of the gastrovascular cavity
(i.e., serving as both digestive cavity and circulatory system) distributes
food throughout the animal."
(j)
Flatworms move by employing cilia found on
their ventral (bottom) surface
(k)
"A planarian has a head (is cephalized) with a pair of eyespots
that detect light and lateral flaps that function mainly for smell. The
planarian nervous system is more complex and centralized than the nerve nets of
cnidarians. Planarians can learn to modify their responses to stimuli."
(l)
The flukes and tapeworms are parasitic Platyhelminthes
(m)
See Figure 33.12, Anatomy of a tapeworm
(n)
[phylum Platyhelminthes,
platyhelminths, class Cestoidea, tapeworms, class Monogenea, class Trematoda, flukes, flukes and platyhelminthes,
class Turbellaria, flatworms (Google Search)]
[index]
PHYLYM ROTIFERA
(a)
Phylum Rotifera includes the rotifers
(b)
Rotifers are extremely small animals and possess a pseudocoelom
(c)
Rotifers possess a gut, a digestive system possessing both a
mouth and an anus
(d)
Rotifers fill a niche somewhat similar to that of a large, engulfing protozoa
(e)
"Internal organs lie within the pseudocoelom. The fluid that fills
the pseudocoelom serves as a hydrostatic skeleton and as a medium for the
internal transport of nutrients and wastes."
(g)
See Figure 33.13, A rotifer
(h)
[Rotifera, rotifers (Google Search)]
[index]
PHYLYM NEMATODA
(7)
Phylum Nematoda (roundworms)
(a)
Phylum Nematoda are the round worms
(b)
"Roundworms are among the most numerous of all animals in both
species and individuals."
(c)
Roundworms can be found in most moist habitats, both free living and as
symbionts (including parasitic
symbionts)
(d)
Parasitic roundworms include the pinworms and hookworms
(e)
"They have a complete digestive tract, and the pseudocoelom with
its fluid serves as a blood vascular system that transports nutrients
throughout the body."
(f)
“Though the ecdysozoans are considered a clade based mainly on the data
of molecular systematics, this branch of protosomes is named for a characteristic
life history: ecdysis, the shedding of an exoskeleton outgrown by the animal.
Of the several ecdysozoan phyla, we will examine only the nematodes and the
arthropods… [speaking of the former…] A tough exoskeleton called cuticle covers
the body; as the worm grows, it periodically sheds its old cuticle (molting, or
ecdysis) and secretes a new, larger one.” (p. 661, Campbell & Reece, 2002)
(g)
See Figure 33.25, Nematodes
(h)
[phylum Nematoda, nematodes, roundworms, pinworms, hookworms (Google Search)]
[index]
PHYLYM MOLLUSCA
(8)
Phylum Mollusca (mollusks,
foot, mantle, visceral
mass)
(a)
Phylum Mollusca
includes the mollusks
(b)
Mollusks are Protostomes
(c)
Mollusks lack segmentation
(d)
Most mollusks possess a calcium carbonate shell, though such things as
squids, octopuses, and slugs partially or completely lack a shell (for a
mollusk a lack of a shell is a derived character)
(e)
The circulatory system of most mollusks is an open one; that is,
the heart pumps vascular fluid (hemolymph) to the tissues through vessels,
but there are no vessels in which the hemolymph returns to the heart; instead
the blood returns by moving through the space between cells
(f)
"Despite their apparent differences, all mollusks have a similar
body plan. The body has three main parts:
(i)
a muscular foot, usually
used for movement;
(ii)
a visceral mass, containing
most of the internal organs; and
(iii)
a mantle, a heavy fold of
tissue that drapes over the visceral mass and may secrete a shell."
(g)
See Figure 33.16, The basic
body plan of mollusks
(h)
[phylum Mollusca, mollusks, visceral mass, class polyplacotora [check spelling] (Google Search)]
[images: mollusks (Australian Museum Online)] [images: mollusks (Molluscan Pictures)] [glossary of molluscan
terminology] [mollusk larva home page]
[phylum mollusca] [index]
(9)
Class Gastropoda (snails,
slugs, sea slugs)
(a)
These are the snails, slugs, and sea slugs
(b)
Gastropoda is the largest class of phylum Mollusca
(c)
Most gastropods are herbivores (i.e.,
they eat producers, e.g., algae)
(d)
See Figure 33.19, Gastropods
(e)
[class Gastropoda, gastropods, snails, slugs, sea slugs, slugs and gastropods
(Google Search)]
[index]
(10)
Class Bivalvia (clams, muscles, scallops)
(a)
These are the clams, muscles, scallops, i.e., the mollusks possessing hinged
shells that divided into two halves
(b)
See Figure 33.21, Anatomy of
a clam
(c)
Most bivalves are suspension feeders
(d)
See Figure 33.20, A bivalve
(e)
[class Bivalvia, bivalves, clams, scallops (Google Search)]
[index]
(11)
Class Cephalopoda (octopuses,
squids, chambered nautilus)
(a)
Cephalopods are carnivorous mollusks
(b)
Included in class Cephalopoda are the octopuses, the squids, and the
chambered nautilus
(c)
See Figure 33.22,
Cephalopods
(d)
All but the chambered nautilus possess either reduced shells (e.g., squids) or no shell
at all (octopuses)
(e)
Cepholods include the largest invertebrates, as well as the brightest
(i.e., smartest), and also possess a closed circulatory systems
(f)
[Cephalopoda, cephalopods, octopuses, squids, chambered nautilus,
cuttlefish, ammonites (extinct
shelled cephalopods) (Google Search)] [index]
(12)
Closed circulatory system
(a)
A closed circulatory system is one in which blood flows throughout an
animal entirely within a series of tubes
(b)
In particular, there are tubes that carry the blood back to the heart
as well as the typically found tubes that carry blood away from the heart
(c)
Contrast with open circulatory system
(d)
We have a closed circulatory system
(e)
[closed circulatory system
(Google Search)]
[index]
PHYLYM ANNELIDA (SEGMENTED
(13)
Phylum Annelida (segmented
worms)
(a)
Phylum Annelida includes the segmented worms
(b)
The segmented worms live in moist and wet environments
(c)
The segmented worms are Protostomes
(d)
These worms, of course, are also segmented
(e)
In addition, they possess a closed circulatory system
(f)
Various classes make up the annelids including (no need to memorize
formal names of these taxa): (supplemental discussion)
(i)
Oligochaeta (earthworms)
(ii)
Polychaeta (marine worms)
(g)
See Figure 33.23, Anatomy of
an earthworm
(h)
[Annelida, annelids, segmented worms (Google Search)]
[index]