Animals (Chapter 32)

Question 1

Describe the general characteristics that define animals as a lineage on the tree of life (including two unique cell types).

Answer 1

• Multicellularity.
• Heterotrophy—they ingest their food.
• They move under their own power at some point in their life cycle.
• All animals except sponges also have: Nerve cells called neurons that transmit electrical signals to other cells.
• Muscle cells that can change the shape of the body by contracting.

Question 2

Animals have evolved differences in four fundamental aspects of the body plan:

Answer 2

1. Presence of tissues, especially the tissues found in embryos
2. Nervous system and head region
3. A fluid-filled body cavity
4. The nature of embryonic development

Question 3

Which two animal groups are considered to be diploblastic?

Answer 3

1. cnidarians (which include the jellyfish, corals, sea anemones, and more)
2. all ctenophores (comb jellies) are diploblastic.

Question 4

As animals diversified, how did nervous systems, body plan and cephalization change?

Answer 4

Bilateral symmetry allowed cephalization, the development of a head region where structures for feeding, sensing the environment, and processing information are concentrated

Question 5

Differentiate between acoelomates, pseudocoelomates and coelomates.

Answer 5

1

Question 6

Why was the evolution of a body cavity significant?

Answer 6

• The coelom creates a container for circulation of oxygen and nutrients, and acts as an efficient hydrostatic skeleton that allows soft-bodied animals to move even without fins or limbs.
• The evolution of the coelom and the resulting hydrostatic skeleton gave bilaterally symmetric organisms the ability to move efficiently in search of food.

Question 7

Protostomes and deuterostomes together make up Bilateria, a monophyletic lineage of animals that are bilaterally symmetrical at some point in their life cycle, have three embryonic germ layers, and have a coelom. What are the protostome and deuterostome patterns of development?

Answer 7

1. Protostomes, the mouth develops before the anus, and blocks of mesoderm hollow out to form the coelom. Includes arthropods, mollusks, and segmented worms.
2. Deuterostomes, the anus develops before the mouth, and pockets of mesoderm pinch off to form the coelom. Includes chordates and echinoderms.

Question 8

Choanoflagellata are sessile, single-celled or colonial protists that share key characteristics with animals. What is the difference between a choanoflagellate colony and a sponge?

Answer 8

1

Question 9

Choanoflagellata are sessile, single-celled or colonial protists that share key characteristics with animals. Why is the sponge considered an animal, but the choanoflagellate colony is not?

Answer 9

multicellular

Question 10

Within the context of Bilateria, what is meant by the phrase ‘tube-within-a-tube’?

Answer 10

The basic animal body plan is a tube-within-a-tube design in which the outer tube forms the body wall and the inner tube forms the gut.

Question 11

Identify and characterize the two protostome lineages.

Answer 11

1. Lophotrochozoa grow by extending the size of their skeletons and includes the mollusks and the annelids.
2. The Ecdysozoa grow by shedding their external skeletons or outer coverings and expanding their bodies and includes the arthropods and the nematodes.

Question 12

Which Lophotrochozoan lineage lost the coelom in their evolutionary history?

Answer 12

coelom was lost during flatworm (Platyhelminthes) development.

Question 13

Identify the three animal lineages in which segmentation evolved independently.

Answer 13

1

Question 14

Refer to Figure 32.9. Are the Mollusca more closely related to the Nematoda or the Rotifera. Explain.

Answer 14

1

Question 15

Refer to Figure 32.9. What synapomorphies are shared by Annelida and Chordata? Is segmentation a synapomorphy for these two groups?

Answer 15

1

Question 16

In addition to the common senses of touch, balance, smell, taste, and hearing, name three more specialized senses and examples of animals that have them.

Answer 16

1. Magnetism—some animals can detect magnetic fields and use them as a navigation aid.
2. Electric fields—some aquatic predators can detect electrical activity in the muscles of passing prey.
3. Barometric pressure—some birds can avoid storms by sensing changes in air pressure.

Question 17

Describe the four general tactics of animal feeding and examples of each.

Answer 17

1. Suspension feeders.
2. Deposit feeders.
3. Fluid feeders.
4. Mass feeders.

Question 18

How can animals be classified by the source of their food? Provide examples of each.

Answer 18

1. Animals that feed on plants or algae are classed as herbivores.
2. Animals that feed on other animals are carnivores.
3. Animals that feed on dead organic matter are detritivores.
4. Omnivores, such as humans, eat both plants and animals

Question 19

Answer the question, “Are all animal appendages homologous?” using a discussion of research into the Dll gene.

Answer 19

Research suggests that the Dll gene is involved in limb formation in diverse species. The conclusion is that the protein product of the same gene marks the initial site of appendage growth in most if not all animals.

Question 20

List some animal taxa that use asexual reproduction at least some of the time.

Answer 20

least some species in most animal phyla can reproduce asexually (via mitosis), as well as sexually (via meiosis).

Question 21

External fertization is extremely common in aquatic animal species. When internal fertilization takes place in animals, the male typically inserts a sperm-transfer organ into the body of the females. How does this pattern differ in sea horses?

Answer 21

1

Question 22

Turn to the internet and research how sharks and bedbugs transfer sperm from the male to the female.

Answer 22

1

Question 23

Describe the three stages in the typical animal life cycle.

Answer 23

1. Larvae look radically different from adults, live in different habitats, eat different foods, and are sexually immature.
2. Juveniles look and behave like adults, but are sexually immature.
3. Adults are the reproductive stage in the life cycle.

Question 24

What is metamorphosis?

Answer 24

Perhaps the most spectacular innovation in animal life cycles involves the phenomenon known as metamorphosis—a change from an immature body type to an adult body type.

Question 25

What is the adaptive significance of metamorphosis?

Answer 25

1

Question 26

What are the four aspects of the findamental architecture or body plan of animals - original and early evolution

Answer 26

1. the origin and elaboration of tissues—especially the tissues found in embryos;
2. the origin and elaboration of the nervous system and the subsequent evolution of a cephalized body—one with a distinctive head region;
3. the evolution of a fluid-filled body cavity;
4. variation in the events of early embryonic development

Question 27

All animals have _________ —tightly integrated structural and functional units of cells.

Answer 27

tissues

Question 28

With the exception of most of the sponges, all animals have _________-_, a layer of tightly joined cells that covers the body surface.

Answer 28

epithelium

Question 29

Diploblasts are animals whose embryos have two types of tissues, or germ layers: Define

Answer 29

1. The ectoderm (“outside skin”).
2. The endoderm (“inside skin”).

Question 30

Triploblasts are animals whose embryos have three germ layers: name them

Answer 30

1. The ectoderm.
2. The endoderm.
3. The mesoderm (“middle skin”).

Question 31

In a triploblast: _________ gives rise to skin and the nervous system. ________ gives rise to the lining of the digestive tract. __________ gives rise to the circulatory system, muscle, and internal structures such as bone and most organs.

Answer 31

Ectoderm

Endoderm

Mesoderm

Question 32

Animals may or may not have an enclosed, fluid-filled body cavity called a __________

Answer 32

coelom

Question 33

Triploblasts that do not have a coelom are called ___________; those that possess a coelom are ____________.

Answer 33

acoelomates

coelomates

Question 34

___________ species retain the eggs or embryos in the female’s body during development.

Answer 34

Viviparous

Question 35

In _________ species eggs are laid outside to develop independently of the mother. The vast majority of animal species are oviparous.

Answer 35

oviparous

Question 36

In ____________ species, the female retains eggs inside her body during early development, but the growing embryos are nourished by yolk inside the egg and not by nutrients transferred directly from the mother.

Answer 36

ovoviviparous

Question 37

Some cnidarians have three distinct body types during their life cycle: name them

Answer 37

1. A largely sessile form called a polyp, which reproduces asexually.
2. A sexually reproducing, free-floating stage called a medusa.
3. A larval stage.

Question 38

Polyps may reproduce asexually by:

Answer 38

1. Budding.
2. Fission.
3. Fragmentation.

Question 39

Animals are ____________, ___________ eukaryotes that lack cell walls and ingest their prey.

Answer 39

multicellular

heterotrophic

Question 40

Recent phylogenetic analyses have shown that there are four major groups of animals: list them

Answer 40

• non-bilaterian lineages,
• two protostome groups (Lophotrochozoa and Ecdysozoa),
• the deuterostomes.

Question 41

Within major groups of animals, evolutionary diversification was based on innovative ways of…. What

Answer 41

sensing the environment, feeding, and moving.

Question 42

Animals are the only multicellular heterotrophs on the tree of life that______________

Answer 42

ingest their food.