Bio 2 Ch 33 Smartbook

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

Advantages of a body cavity include:

-cushioning internal organs -providing support and shape to an organism -acting as a rudimentary circulatory system -enabling movement and growth of internal organs independently of the outer body wall

Place the steps of germ layer formation in sequential order. Start with the earliest step on top.

1. Fertilization produces a zygote 2. cleavage 3. Formation of the blastula 4. Gastrulation begins 5. Formation of distinct endoderm, ectoderm, and mesoderm

Animals with radial symmetry have __________ germ layers, and animals with bilateral symmetry have __________ germ layers.

2 3

Hox genes are organized into:

4 clusters of 13 genes

What is a hydrostatic skeleton?

A fluid-filled body cavity surrounded by muscle that provides shape and support to the body.

Which is a blastula?

A hollow sphere of cells produced early in the development of an animal embryo

In the figure of a gastrula, the germ layer represented by A is the __________ , B is the ____________ , and C is the ____________ .

A. endoderm B. ectoderm C. mesoderm

Animals that are bilaterally symmetrical are placed in the group

Bilateria

Animals that have a dorsal and a ventral side, have an anterior and posterior end, and exhibit cephalization belong to the group

Bilateria

Based on the type of symmetry that they display, animals such as grasshoppers, mice, and ostriches are placed in the group _________

Bilateria

What would be regulated by Hox genes?

Changes in body segment specializations

The only phylum that is diploblastic is:

Cnidaria

What happens during gastrulation?

Different cell layers are produced in a developing embryo.

Molecular studies indicate that the protostomes are divided into two clades: the ______ and the ______ .

Ecdysozoa Lophotrochozoa

True or false: Both traditional and molecular methods agree that the presence of a coelom is a useful character to use in the construction of phylogenies.

False

True or false: In protostomes, the blastopore becomes the anus, with the mouth being formed from a secondary opening. The opposite is true for deuterostomes.

False

Which of the following include features traditionally used by biologists to classify animal diversity?

Features of embryonic development Type of body symmetry Number of germ layers

What are Hox genes?

Genes responsible for pattern formation of the body and appendages in early embryos.

The expression of _________ genes results in transitions or changes in body segments.

Hox

Genes involved in pattern formation of the body and appendages in early embryos are _________ _________

Hox genes

Which of the following include functions of the fluid in the body cavity of an animal?

It can act as a circulatory system. It provides shape and support. It plays a role in animal movement.

What are germ layers?

Layers of cells in an embryo that form the organs

With regard to phylogenetic trees based on morphological data and molecular data:

Phylogenies based on molecular data tend to be more accurate

Which animal phyla lack tissue differentiation?

Porifera only

Members of the phylum __________ are not generally thought to possess specialized tissue types or organs, although they may have several distinct types of cells.

Porifera, Sponges, or Parazoa

Which of the following animal characteristics occurs only within the Bilateria?

Presence of a fluid-filled body cavity

Which of the following statements about the number of embryonic germ layers is true?

Radially symmetric organisms have two, while bilaterally symmetric organisms have three

Animals belonging to the pseudocoelomates include:

Rotifers Nematodes

One of the most commonly used nucleotide sequences obtained during molecular phylogenetic analysis is:

SSU rRNA

What morphological features have traditionally been used to classify animals, but are now recognized as being less useful in determining evolutionary relationships than originally thought?

Segmentation Presence/absence of a coelom

Animals that would be placed in the group Bilateria include:

Spider Horse Lobster

Which of the following accurately describes animals with a segmented body plan?

The animal's body is divided into nearly identical units.

What statement about the endoderm and ectoderm is correct?

The ectoderm differentiates into the nervous system and epidermis, while the endoderm lines the digestive tract.

How are presence of a coelom and segmentation used to classify animals?

They are useful in describing body structure, but less useful in understanding evolutionary relationships

Which of the following is true of animals within the group Bilateria?

They have a left and right side that are mirror images of each other.

How do traditional and molecular phylogeneticists view the use of body cavity in animal classification?

Traditional phylogeny used the presence or absence of a body cavity; molecular phylogeny suggests this is not a useful method of classification.

Which of the following statements best describes the difference between triploblastic and diploblastic animals?

Triploblastic animals develop a mesoderm; diploblastic animals do not.

Animals belonging to the group Bilateria exhibit what anatomical characteristics?

a dorsal and a ventral side cephalization (head) an anterior and a posterior end

The mesoderm is:

a layer of cells only found in animals that are bilaterally symmetrical

Animals lacking a body cavity are called ____.

acoelomates

What end of the animal body is towards the front or head?

anterior

Hox genes exist in several clusters. Some of these genes are expressed in ________ segments, while other are expressed in _______ segments.

anterior posterior

In deuterostomes, the blastopore becomes the

anus

The fluid in the body cavity of an animal can:

assist with movement, act as a circulatory system, and provide shape

An animal that can be divided only by a vertical plane along the midline to create two identical halves exhibits __________ symmetry, while an animal that can be divided into two identical halves by any longitudinal plane passing through the central axis exhibits _________

bilateral radial

In the animal kingdom, the majority of species are:

bilaterally symmetric

Which of the following is true of deuterostomes?

blastopore develops into anus

During embryonic development, a hollow sphere of cells called the ___________ forms following rapid mitotic division of the zygote.

blastula

Animals classified as radially symmetric ______, while animals classified as bilaterally symmetric ______.

can be divided into similar halves by any plane along the main axis; when cut in only one plane, the two halves are mirror images of each other

An advantage of ____________ is the ability to detect and respond to food and predators by animals that encounter their environment initially with their head.

cephalization

Which of the following are features associated with animals that are radially symmetric?

circular- or tubular-shaped with a mouth at one end can be divided equally by any longitudinal plane passing through the central axis

Providing support and shape to the body of an organism and cushioning internal organs against injury from external forces are two of the advantages of having a(n) _________

coelom

Within the Bilateria, animals can be divided into three major divisions based on the presence and structure of a body cavity called the ________

coelom

Within the Bilateria, animals can be divided into three major divisions based on the presence and structure of a body cavity called the _________

coelom

In a bilaterally symmetrical animal, a(n) __________ is a fluid-filled body cavity, which develops entirely within the mesoderm.

coelom or true coelom

Animals that undergo embryonic development where the blastopore develops into the animals' anus are called ___________

deuterostomes

____________ refers to animals of the Radiata that have only two germ layers.

diploblastic

The upper surface of an animal, an organ, or a body part is the __________ side

dorsal or superior

The nervous system and the epidermis arise from the embryonic germ layer called the _________

ectoderm

The layer of cells that lines the primitive digestive tract (the archenteron) during gastrulation is called the _________ while the layer of cells differentiating into the nervous system and epidermis is called the ____________

endoderm ectoderm

The three embryonic germ layers are called

endoderm ectoderm mesoderm

The use of molecular data to construct phylogenetic trees is based on the premise that more closely related species exhibit _________ sequence differences than distantly related ones.

fewer, less, rarer, or scarcer

What is a coelom?

fluid filled body cavity

In the developing embryo, invagination of the blastula, known as ___________, is necessary to allow germ layers to form.

gastrulation

A process called ___________ is the inward folding of the blastula, resulting in the development of different cell layers in the growing embryo.

gastrulation or invagination

A process called _____________ is the inward folding of the blastula, resulting in the development of different cell layers in the growing embryo.

gastrulation/invagination

Embryonic cell layers are called

germ layers

Embryonic cell layers are called __________

germ layers

The anterior end of an animal's body is the ______ region of the body.

head

A _______ skeleton is a fluid-filled body cavity surrounded by muscle that provides shape and support to the animal's body.

hydrostatic

What is an advantage of segmentation?

it allows for specialization of body regions

Ventral typically refers to the

lower side of an animal's body.

Only the Bilateria possess a third layer of embryonic cells, called the

mesoderm

The gene that encodes the small subunit of ribosomal RNA is often used for:

molecular phylogenetic analysis

In protostomes, the blastopore becomes the ____________

mouth

Protostomes are animals where the embryonic blastopore becomes the:

mouth

Ectoderm is essential in the formation of the:

nervous system epidermis

The back or rear of the body is called the _________ end

posterior

Animals that undergo embryonic development where the embryonic blastopore develops to become the animal's mouth are ___________

protostomes

Because of the way their body cavity is constructed, rotifers and nematodes belong to the group known as

pseudocoelomates

Because of the way their body cavity is constructed, rotifers and nematodes belong to the group known as __________

pseudocoelomates

Cnidarians (jellyfish) are _________ symmetric animals.

radial

In the figure, the jellyfish (left) is an example of animal that exhibits ___________ symmetry, and the crab (right) is an example of an animal that exhibits ___________ symmetry.

radial or radiata bilateral or bilateria

Animals that are circular or tubular in shape are typically:

radially symmetric

The specialization of body regions is a major advantage of __________ in those animals that possess such a body plan.

segmentation

When an animal's body is divided into a number of nearly identical units or regions, it has a(n) ______ body plan.

segmented

Germ layers develop in all animals except

sponges

Which of the following groups of animals do not develop embryonic germ layers?

sponges

Some of the earliest-diverging animals, such as , __________________ had no plane of symmetry.

sponges or Parazoa

Animals can be divided into categories according to the type of ______ their body displays.

symmetry

Based on recent studies of molecular phylogeny, scientists suggest that:

the Protostomes are divided into two clades, the Ecdysozoa and Lophotrochozoa

Animals of the Bilateria with all three distinct germ layers are referred to as ____________

triploblastic

Most animals have three embryonic germ layers and are therefore called ___________

triploblastic

Morphological and developmental features typically used to classify animals into taxonomic groups include:

type of body symmetry, number of germ layers, and features of embryonic development

Dorsal refers to the

upper side of an animal's body.

The underside or lower surface of the body is called the ____ side.

ventral