32 Flashcards
what are animals?
Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers
Bodies are held together by structural proteins such as
collagen
what is their nutritional mode
Chemoheterotrophs
This ancestor may have resembled modern ______ , protists that are the closest living relatives of animals
choanoflagellates
At the beginning of the ______ animals underwent a rapid diversification.
Cambrian period (535 to 525 million years ago)
bilaterians
organisms that have the following traits:
– Bilaterally symmetric form
– Complete digestive tract
– One-way digestive system
Kingdom Animalia is
Monophyletic and very diverse
body plan
set of morphological and developmental traits, integrated into a functional whole
– Symmetry: absent, present (radial or bilateral)
– Tissues: collections of specialized cells
– Germ layers: diploblasts or triploblasts
– Body cavities
radial symmetry
Parts radiate from the center, so any slice through the central axis divides into mirror images.
Bilateral symmetry
Only one slice can divide left and right sides into mirror-image halves
Bilaterally symmetrical animals have:
- Dorsal (top side)
- Ventral (bottom side)
- Anterior (head/front)
- Posterior (tail/back)
- Cephalization (development of a head)
tissues
Tissues are collections of specialized cells isolated from other tissues by membranous layers
During development, ______ give rise to the tissues and organs of the animal embryo
three germ layers
ectoderm
is the germ layer covering the embryo’s surface, that forms the nervous system and the skin
Endoderm
is the innermost germ layer and lines the developing digestive tube, called the archenteron
Mesoderm
is the middle layer that forms the heart, kidneys, and muscles.
_____animals have ectoderm and endoderm
Diploblastic
_______ animals also have an intervening mesoderm layer; these include all bilaterians
triploblastic
Most triploblastic animals possess a
body cavity
A true body cavity is called a ______ and is
derived from mesoderm
coelom
_____ are animals that possess a true coelom
Coelomates
Advantages of a coelom:
- Creates a medium for circulation
- Makes space for internal organs
- A hydrostatic skeleton • fluid-filled chamber
- allows movement
pseudocoelomates
animals that have one
have a body cavity lined by tissue from mesoderm and by tissue derived from endoderm
acoelomate
lack a body cavity between the digestive cavity and outer body wall
protostome development
(examples: molluscs, annelids)
eight-cell stage, spiral and determinate
mouth develops from blastopore
Deuterostome development
(examples: echinoderm, chordates)
radial and indeterminate
anus develops from blastopore
indeterminate
embryo cells retain the capacity to develop into a complete embryo
In gastrulation, the developing digestive tube of an embryo initially forms as a blind pouch, the
archenteron
Five key points about Animal Phylogenetic Tree:
- All animals share a common ancestor
- Sponges are basal animals
- Eumetazoa (“true animals”) is a clade of animals with
true tissues - Most animal phyla belong to the clade Bilateria
- There are three major clades of bilaterian animals, all of which are invertebrates, animals that lack a backbone, except Chordata, which are classified as vertebrates because they have a backbone
Ecdysozoa
bilateral invertebrates
characteristics shared by nematodes, arthoprods
secrete exoskeletons
Lophotrochozoa
2 different features observed- lophophore and trochophore
lophohpore
a crown of ciliated tentacles that function in feeding
trochophore larva
includes molluscs and annelids
one of the characteristics unique to animals is
gastrulation
the distinction between sponges and other animal phyla is based mainly on the absence vs presence of
tissues
which of the following was probably the least important factor in bringing about the cambrian explosion
the movement of animals onto land
based on the tree in figure 32.11 which statement in false?
coelomate flatworms are more closely related to the echinoderms than to annelids
Animals probably evolved from colonial protists. How do animals differ from these protist ancestors?
Animals have more specialized cells.
The animal phylum most like the protists that gave rise to the animals is _____.
Porifera
A graduate student finds an organism in a pond and thinks it is a freshwater sponge. A postdoctoral student thinks it looks more like an aquatic fungus. How can they decide whether it is an animal or a fungus?
look for cell walls under a microscope
Unlike other animals, sponges _____.
lack true tissues
Symmetry is one of the most basic characteristics of animals. The phylum that has a different symmetry from the other three phyla listed is the ____________.
Porifera
Which of the following is associated with bilateral symmetry?
cephalization
“Cephalization” refers to having _____.
a head end
cephalization
the concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain, both during evolution and in the course of an embryo’s development.
How do cnidarians and ctenophores differ from all other eumetazoans?
Cnidarians and ctenophores are radially symmetrical.
All animals with bilateral symmetry have _______ germ tissue layer(s).
three
Ectoderm can give rise to _______; mesoderm can give rise to ______; endoderm can give rise to _________.
the central nervous system … muscle … the lining of the digestive tube
Which of the following is NOT a characteristic of cnidarians?
mesoderm
The difference between pseudocoelomates and coelomates is that pseudocoelomates _________, whereas coelomates _________.
have a body cavity partially lined with tissue derived from mesoderm … have a body cavity completely lined with tissue derived from mesoderm
A true coelom is ____________.
a body cavity lined with mesoderm
One of the primary developmental/anatomical characteristics distinguishing the major animal phyla is the condition of the body cavity. A pseudocoelomate animal is one in which the body cavity is _____.
bounded partly by mesoderm
The presence of a coelom is advantageous because _____.
it allows room for the development and movement of internal organs
Coelomates gave rise to _____
protostomes and deuterostomes
Coeloms _____.
evolved independently more than once
Zoologists place chordates and echinoderms on one major branch of the animal phylogenetic tree, and mollusks, annelids, and arthropods on another major branch. Which of the following is a basis for this separation?
how the body cavity is formed
The zygotes of many protostomes undergo ______ and ______ cleavage.
spiral … determinate
Which of the following is NOT a difference between protostomes and deuterostomes?
the presence of a body cavity
All of the following are deuterostomes EXCEPT ____________.
mollusks
An animal with a true coelom that has ____________ cleavage must be a____________.
indeterminate, radial … deuterostome
Protostomous animals are those in which the _____.
blastopore forms the mouth
The phrase “Cambrian explosion” refers to _____.
the rapid adaptive radiation that gave rise to most extant animal phyla
Why are echinoderms a model species for studying embryonic development?
- Has a more rapid development and life history.
- External fertilization
- deuterostome development
The sea urchin embryo has long been used as a model organism to address many questions in developmental biology. The straightforward artificial spawning, fertilization and rearing, and embryo optical transparency make this organism a great resource. Also, the simple organization. Sea urchins undergo radial, reductive cleavage.
