Chapter 33 connect

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

Approximately how many animal species have been described so far?

1 million

Animals with radial symmetry have _____ germ layers, and animals with bilateral symmetry have ____ germ layer

2,3

An estimated ______ species of animals await discovery and classification.

2-5 million

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

Acoelomate

Animal that lacks a fluid-filled body cavity

Pseudocoelomate

Animal with a body cavity not completely lined with tissue from the mesoderm

Coelomate

Animal with a fluid-filled body cavity lined with tissue from the mesoderm

In the deuterostomes, the blastopore of the animal becomes the

Anus

Place the following steps in the history of animal life on earth in order. Begin with the first event at the top and end with the last event at the bottom.

Appearance of invertebrate animals The Cambrian explosion of animal diversity Appearance of vertebrate animals Colonization of land The post Cretaceous explosion of mammalian diversity

Animals that are bilaterally symmetric are place in the group

Bilateral

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

Which of these animal groups exhibit radial symmetry?

Cnidarians

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

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 and lophotrochozoa

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

Ectoderm is essential in the formation of the:

Epidermis, nervous system

All animals belong to the domain

Eukarya

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

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

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

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

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

Fertilization produces a zygote Cleavage Formation of a blastula Gastrulation begins Formation of distinct ectoderm, endoderm, and 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

What are Hox genes?

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

Embryonic cell layer are called

Germ layers

Embryonic cell layers are called

Germ layers

Which of the following are characteristics found in all animals?

Heterotrophic Characteristic cell junctions Extracellular matrix Multicellularity

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

Hox genes

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

Hydrostatic

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

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

What are germ layers?

Layers of cells in an embryo that form the organs

In what supergroup are animals classified?

Opisthokonta

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

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.

Radially, bilaterally

Animals that can be divided equally by any longitudinal plane passing through the central axis are said to be _____ symmetric, while animals that can be divided along a vertical plane at the midline to create two halves are _____symmetric.

Radially, bilateraly

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

SSU rRNA

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

Segmentation

Animals that would be placed in the group Bilateria include:

Spider Lobster Horse

Germ layers develop in all animals except

Sponges

_____refers to the existence of balanced proportions of the body on either side of a median plane.

Symmetry

____refers to the existence of balanced proportions of the body on either side of a median plane.

Symmetry

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 an anterior and a posterior end

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

Animals lacking a body cavity are called ____.

acoelomates

Advantages of a body cavity include:

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

Cephalization is an advantage in animals because it:

allows for detection and response to predators and other encountered dangers allows animals to better detect and consume prey

Multicellular heterotrophs lacking cell walls are known as

animals

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

anterior

The fluid in the body cavity of an animal can:

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

What is the posterior end of the body?

back or rear

Most animals are _____ symmetric

bilaterally

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

The closest living relatives of animals are the

choanoflagellates

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

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

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

Which of the following is the most likely ancestor from which animals evolved?

colonial flagellated protist

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

deuterostomes

In ______, the blastopore becomes the anus, and the mouth is formed from a secondary opening.

deuterostomes

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

dorsal

What is a coelom?

fluid filled body cavity

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

gastrulation

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

gastrulation

The formation of different cell layers in a growing embryo is called:

gastrulation

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

head

The first animals did not have a backbone. These types of animals are collectively called

invertebrates

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.

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

molecular phylogenetic analysis

Protostomes are animals where the embryonic blastopore becomes the:

mouth

Animals are:

multicellular heterotrophs without cell walls

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

Cnidarians (jellyfish) are ______ symmetric animals.

radially

Animals that are circular or tubular in shape are typically:

radially symmetric

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

segmented

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

sponges

Which of the following groups of animals are asymmetric?

sponges

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

sponges

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 _____, whereas _____ refers to animals of the Radiata that have only two germ layers.

triploblastic, diploblastic

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