Study Guide Chapter 19

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Study Guide Chapter 19 Animal Diversity
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19.1- What is an animal? Your text defines an
animal as a eukaryotic, multicellular,
heterotroph, that lacks a cell wall.
Eukaryotic- separates animals from bacteria
and blue-green algae (cyanobacteria) Multicellul
ar- separates animals from any
protists heterotroph- separates animals from
plants and some protists lacks a cell wall-
separates animals from plants.
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Other distinguishing features- Life cycles.
Most adult stages are diploid which form gametes
by meiosis. Gametes (egg and sperm) fuse to form
a new individual which begins as a diploid
zygote. The zygote divides by mitosis to an
early stage refered to as a blastula, a single
layer of cells surrounding a hollow cavity.
Further development results in a gastrula which
looks like an indented blastula. The gastrula
develops into a saclike embryo. Eventually three
layers of cells form from which the epidermis and
nervous system, the digestive tract, and other
organs develop. Some animals develop through
several morphological forms. The most immature
form is the larvae which eventually develops into
an adult through these stages. Development of
this type is called metamorphosis.
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March through the phyla of the kingdom
Animalia 19.3- Porifera. These are the sponges.
There are about 5000 species. Most are marine
but some (150) are freshwater aquatic organisms.
Most feed on bacteria that flow through their
porous bodies.
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19.4- Cnidaria. Radial symmetry, seen is some
sponges, is a hallmark of Cnidarians. These
include Hydra which have a polyp body form and
jellyfish which have a medusa body form. The two
traits that mark an animal as a cnidarian is
radial symmetry and the presence of cnidocytes
(stinging cells) used to capture prey and defend
the animal. These animals have a digestive
cavity and a gastrula stage which are not seen in
sponges. However, these animals are considered
to be "tissue animals" which means the functions
are achieved by tissue rather than organs, which
are organized layers of tissues (different
tissues) that perform a function or functions.
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19.6- Platyhelminthes. The flatworms. These
animals show bilateral symmetry or left and right
are symmetrical. They do have a dorsal (back or
top) that is different from the ventral (front or
bottom). These animals include the planaria that
you played with in high school biology, flukes,
and tapeworms. Many are parasitic. These
organisms do not have a body cavity except for
the digestive tract itself. The body cavity on
higher organisms is called a coelom and it is
lined by a layer of tissue from the middle in
development. It was the evolution of the coelom
that allowed for the development of organs.
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19.8- Nematoda. The roundworms. These are the
first organisms covered by a nonliving layer of
tissue called the cuticle, that protects the
organisms from drying and being crushed. It is
a "skin". This allows these to live in the soil
rather that wet environments. They have a
pseudocoelom. An animal with a pseudocoelom has
a cavity lined with tissue, but the tissue is
only in contact with the outer wall and doesn't
surrond the digestive tract as it does with the
coelom (see figure 19.7 a,b,c). Many of the
nematodes are parasitic.
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19.9- Mollusca. The mollusks. This a very
morphologically diverse group and yet they share
a basic body plan (shown in figure 19.9A.) The
four points to look for is the presence of a foot
for locomotion, a radula used to scrape up food,
a mantle covering the body, and the presence of a
coelom. These animals also have a primitive
heart and circulatory system. The phylum is
divided further into the gastropods (snails and
slugs), the bivalves (clams, oysters, mussels,
and scallops), and the cephalopods (squids and
octopus).
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19.11- Annelida. The segmented worms.
Earthworms, polychaetes, and leeches are members
of this phylum. This group is distinguished by
having a ringlike body that is repeated in many
segments. Only the head is distinguished from
the other segments externally.
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19.12- Arthropoda. The arthropods. They are
distinguished by the presence of an exoskeleton
made of chitin, and jointed appendages used for
walking, swimming, capturing prey or defending
against predators. They grow in size by shedding
the exoskeleton through a process called molting.
The four groups of arthropods are the horseshoe
crabs, the crustaceans (lobsters, barnacles,
crayfish), arachids (spiders, scorpions, mites),
and the wormlike arthropods (millipedes and
centipeds).
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19.13- Insecta. The insects. There are more
species of insects than all other species
combined. They are similar to arthropods in that
they have an exoskeleton of chitin but are
distinguished in that they have three body
segments, the head, thorax, and abdomen. Most
have wings that allow for flight.
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19.14- Echinodermata. The echinoderms. These
animals have a spiny skin, and endoskeleton, and
a water vascular system for movement. This group
includes starfish, sea urchin, and sea stars.
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19.15- Chordata. The chordates. We are
chordates. Our phylum is distinguished by (1) a
dorsal hollow nerve chord (2) a notochord, a
flexible, longitudinal rod located between the
digestive tract and the nerv cord (3) gill
structures behind the mouth and (4) and post anal
tail. Doesn't sound much like you does it. You
have all four of these during embryonic
development and except for the gills, you have
remnants as adults. The chordates are first
divided into two groups, the invertebrates and
the vertebrates. The invertebrates include the
tunicates and the lanclets. The vertebrates have
an endoskeleton that includes a skull and a
backbone segmented into vertebrae. Most have a
hinged jaw (section 19.17). The vertebrates
include fish, amphibians, reptiles, birds, and
mammals.
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19.18- The fish are divided into the
cartilaginous fish called the Chondrichthyes, and
the bony fish called the Osteichthyes. The
cartilaginous fishe include the shark. The bony
fish have a protective flap over the gills which
can be moved. This allows the fish to move water
across the gills without moving.
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19.19- Amphibians have two stages in life. An
embryonic stage in which they have gills and swim
in water and an adult stage in which they breath
air and usually spend at least some time on the
dry land. They must return to the water to lay
they eggs so that the next generation can again
start in the water.
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19.20- Reptiles include snakes, lizards,
turtles, etc. Unlike amphibians they do not have
a stage where they live and breath water. They
have an amniotic egg which is filled with fluid
and covered in a shell that allows the egg to be
layed on land rather than in water. The
chordates up to this point are all ecotherms
which means they do not regulate their own
temperature. Their bodies get heat from the
environment. Birds and mammals are endotherms.
They generate their own body heat through
metabolism.
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19.21- Birds are in the class Aves. They are
covered in feathers and most are capable of
flight. 19.22- Mammals are distinguished by
the presence of mammary glands that produce milk
to nourish their young and by the presence of
hair. We divide these into three groups. The
montremes are the egg laying mammals (the
kuck-billed platypus). The marsupials are the
pouched mammals that carry embryo in a marsupium
on the mothers abdomen where it is attached to a
nipple. The placentals carry their embryo
internally in a placenta and nourish them by
transfering nutrients from mothers blood to the
embryo's blood system within the placenta tissue.
The placenta is derived from tissue from both
mother and embryo.
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19.23- This section shows a phylogenetic tree
which shows the evolutionary relationships
between these organisms. You might be surprised
to not that the echinoderms are the most near the
chordates. This is because of the internal
skeleton. Notice that we begin with protists and
develop tissue. The next division is based on
symmetry, then the presence of a pseudocoelom or
coelom. The next division we really didn't
discuss but is based on whether the coelom comes
from cell masses or from a digestive tube. These
are the protostomes or deuterostomes
respectively. Of the deuterostomes include only
the echinoderms and the chordates.
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