Within the Bilateria, animals are divided into three
major divisions based on the presence and structure of a body cavity called a coelom
Animals are multicellular heterotrophs without
cell walls.
History of animal life on earth:
1. Appearance
of invertebrate animals
2. The
Cambrian explosion of animal diversity
3. Appearance
of vertebrate animals
4. Colonization
of land
5. Appearance
of amniotic egg
6. The
post-Cretaceous explosion of mammalian diversity
Animals belonging to the group Bilateria exhibit
what anatomical characteristics?
·
An anterior and a posterior end, Cephalization,
A dorsal and a ventral side
Match each animal group to the morphological or
developmental feature:
·
Parazoa – lack of true tissues
·
Pseudocoelomates – presence of a
fluid-filled body cavity lined on only one side by mesoderm
·
Bilateria – three embryonic germ layers
·
Deuterostomia – indeterminate and radial
cleavage
·
Protostomia – development of the
blastopore into the mouth
·
Radiata – radial symmetry
Which of the following are characteristics found in
all animals? Heterotrophic, Hox genes
that function in patterning the body, Multicellular, Motility, Extracellular
matrix
What are germ layers? Layers of cells in an
embryo that form the organs.
Germ layer formation:
1. Formation
of a zygote
2. Cleavage
3. Formation
of a blastula
4. Gastrulation
begins
5. Formation
of the archenteron
Because of their lack of specialized tissues and
organs, sponges are often considered to be the simplest animals.
The subgroup of animals that have specialized tissue
and different organ types is known as Eumetazoa.
An animal is an organism best described as being: a
multicellular heterotroph that lacks cell walls and is motile at some point
during its life cycle.
Which of the following include features
traditionally used by biologist to classify animal diversity? Type of body
symmetry; Presence/absence of different tissue types; Patterns of embryonic
development
Why are choanoflagellates thought to be the closest living
relatives of animals?
·
They are morphologically similar to
cells found in sponges.
·
Molecular data indicates a close
phylogenetic relationship
Animals can be classified based on the development
of a body cavity:
·
Coelomate – animal with a fluid-filled body
cavity lined with tissue from the mesoderm.
·
Acoelomate – animal that lacks a body
cavity
·
Pseudocoelomate – animal with a body
cavity not completely lined with tissue from the mesoderm.
Features of deuterostome development include: Three
germ layers; Radial cleavage; Indeterminate cleavage
The underside or lower surface of the body is the ventral
side.
The upper surface of an animal, an organ, or a body
part is the dorsal side.
What is a coelom? A fluid-filled body cavity.
Animals that are triploblastic, have a dorsal and a
ventral side, have an anterior and posterior end, and exhibit cephalization
belong to the group bilateria.
Based on the presence or absence of tissue, animals
are divided into the subgroups Parazoa and Eumetazoa.
Characteristic features of protostome development
include: The blastopore becomes the mouth; Spiral cleavage; Determinate
cleavage
The group that is inclusive of all animal species
is: Metazoa.
Match the following animals to the clade to which
they belong:
·
Sponges – parazoa
·
Jellyfish – radiate
·
Flatworms – bilateria
The morphological and developmental features of
animal body plans that have traditionally formed the basis for the
classification of animals include:
·
Segmentation; The fate of the blastopore
during embryonic development; Presence/absence of true tissues and organs; Cleavage
pattern during embryonic development; Presence/absence of a coelom; Number of
germ layers; Symmetry
When an animal’s body is divided into a number of
nearly identical units or regions, it has a segmented body plan.
Animals that undergo embryonic development where the
embryonic blastopore develops to become the animal’s mouth are protostomes.
Animals that are bilaterally symmetrical are placed
in the group bilateria.
Which of the following are common characteristics of
choanoflagellates? Single-celled; Colonial; Single flagellum
The two major groups of animals that are defined
based on their body symmetry are Bilateria and Radiata.
Based on molecular data and their morphological
similarity to a certain type of cell found in sponges, choanoflagellates,
are thought to be the closest living relative of animals.
Anatomical features associated with animals
belonging to the Radiata include:
·
Two germ layers; Circular or tubular
shape with mouth parts at one end; Presence of specialized tissues
Which of the following are true statements about
reproduction and development in animals?
·
Fertilization can occur internally; Some
animals reproduce sexually; Some animals reproduce asexually; Fertilization can
occur externally; Some animals undergo metamorphosis
The phyla that have only the endoderm and ectoderm
are: Cnidarian; Ctenophore
Collectively, all animals are known as Metazoa,
but are divided into two subgroups based on whether or not they have
specialized tissues.
Which of the following are advantages of having a
coelom?
·
A coelom enables the movement of
internal organs
·
A coelom can prevent injury from
external forces
Cephalization is an advantage in animals because it:
·
Allows animals to better detect and
consume prey
·
Allows for detection and response to
predators and other encountered dangers.
During embryonic development, the hollow sphere of
cells formed following rapid mitotic division of the zygote is the blastula.
Advantages of a body cavity include:
·
Providing support and shape to an
organism
·
Enabling movement and growth of internal
organs independently of the outer body wall
·
Acting as a rudimentary circulatory
system
·
Cushioning internal organs
Animals of the Bilateria with all three distinct
germ layers are referred to as triploblastic, whereas diploblastic
refers to animals of the radiate that have only two germ layers.
Which of the following functions of the fluid in the
body cavity of an animal?
·
It plays a role in animal movement; It
can act as a circulatory system; It provides shape and support
A series of rapid cell divisions that produces a
hollow sphere of cells without any significant growth is called cleavage.
A mesoderm is: a layer of cells only found in
animals that are bilaterally symmetrical.
The subgroup of animals that lack specialized tissue
types or organs and consists only of the phylum Porifera is known as Parazoa,
whereas Eumetazoa includes a subgroup of animals with more than one
tissue type.
Which of the following include early animal
adaptations to life on land?
·
Eggs with tough, protective shells; Internal
fertilization; A bony skeleton; Lungs
Animals that would be placed in the group Bilateria
include: Lobster; Horse; Spider
Which animal phyla lack tissue differentiation? Porifera
only.
The animal kingdom is monophyletic because
all the taxa evolved from a single common ancestor.
The ability to coordinate movement and capture prey
has developed because of: The development of specialized sensory structures; The
development of a nervous system
Which of the following animals belong to the group
Radiata? Sea anemone; Jellyfish
What happens during gastrulation? Different cell
layers are produced in a developing embryo.
A hydrostatic skeleton is a fluid-filled body
cavity surrounded by muscle that provides shape and support to the animal’s
body.
The layer of cell forming the primitive digestive
tract during gastrulation is called the endoderm, while the layer of
cells differentiating into the nervous system and epidermis is called the ectoderm.
Based on the type of symmetry that they display,
animals such as grasshoppers, mice, and ostriches are placed in the group Bilateria.
The specialization of body regions is a major
advantage of segmentation in those animals that possess such a body
plan.
Which of the following phyla exhibit tissue
differentiation?
·
Mollusca; Ctenophore; Platyhelminthes; Rotifer;
Cnidarian
The type of cleavage that occurs when developing
cells in a blastula do not align directly over each other, by at an angle is spiral
cleavage.
Animals that exhibit indeterminate cleavage are
called deuterostomes.
Ctenophores an cnidarians (including jellyfish and
related species) belong to the clade Radiata.
Anatomical features associated with animals
belonging to the Radiata include:
·
Circular or tubular shape with mouth
parts at one end
·
Two germ layers; Presence of specialized
tissues
What is cephalization? The localization of
sensory structures near the head of the animal.
Only Bilateral animals possess a third layer of
cells, called the mesoderm.
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