Which Statement Is True About All Animals?

Affiliate xv: Diversity of Animals

Features of the Creature Kingdom

Learning Objectives

Past the end of this section, y'all volition be able to:

• List the features that distinguish the animal kingdom from other kingdoms
• Explain the processes of animal reproduction and embryonic development
• Describe the hierarchy of basic animal nomenclature
• Compare and contrast the embryonic development of protostomes and deuterostomes

Even though members of the animal kingdom are incredibly diverse, animals share common features that distinguish them from organisms in other kingdoms. All animals are eukaryotic, multicellular organisms, and almost all animals have specialized tissues. Nearly animals are motile, at least during certain life stages. Animals crave a source of food to abound and develop. All animals are heterotrophic, ingesting living or expressionless organic matter. This grade of obtaining energy distinguishes them from autotrophic organisms, such every bit about plants, which make their ain nutrients through photosynthesis and from fungi that digest their food externally. Animals may exist carnivores, herbivores, omnivores, or parasites ([Figure 1]). Nigh animals reproduce sexually: The offspring pass through a series of developmental stages that found a determined body plan, unlike plants, for example, in which the verbal shape of the body is indeterminate. The trunk program refers to the shape of an animate being.

Effigy 1: All animals that derive energy from food are heterotrophs. The (a) blackness behave is an omnivore, eating both plants and animals. The (b) heartworm Dirofilaria immitis is a parasite that derives energy from its hosts. It spends its larval stage in mosquitos and its adult stage infesting the hearts of dogs and other mammals, equally shown here. (credit a: modification of work by USDA Woods Service; credit b: modification of work by Clyde Robinson)

Complex Tissue Structure

A hallmark trait of animals is specialized structures that are differentiated to perform unique functions. As multicellular organisms, most animals develop specialized cells that group together into tissues with specialized functions. A tissue is a drove of similar cells that had a mutual embryonic origin. There are four master types of animal tissues: nervous, musculus, connective, and epithelial. Nervous tissue contains neurons, or nerve cells, which transmit nerve impulses. Muscle tissue contracts to cause all types of torso movement from locomotion of the organism to movements within the torso itself. Animals also have specialized connective tissues that provide many functions, including send and structural support. Examples of connective tissues include blood and bone. Connective tissue is comprised of cells separated past extracellular material made of organic and inorganic materials, such equally the protein and mineral deposits of bone. Epithelial tissue covers the internal and external surfaces of organs within the fauna trunk and the external surface of the trunk of the organism.

View this video to watch a presentation by biologist E.O. Wilson on the importance of beast diversity.

Animal Reproduction and Development

Most animals have diploid body (somatic) cells and a small number of haploid reproductive (gamete) cells produced through meiosis. Some exceptions be: For case, in bees, wasps, and ants, the male person is haploid because it develops from an unfertilized egg. Well-nigh animals undergo sexual reproduction, while many also take mechanisms of asexual reproduction.

Sexual Reproduction and Embryonic Evolution

Nearly all animal species are capable of reproducing sexually; for many, this is the simply mode of reproduction possible. This distinguishes animals from fungi, protists, and leaner, where asexual reproduction is common or sectional. During sexual reproduction, the male and female person gametes of a species combine in a procedure called fertilization. Typically, the small, motile male person sperm travels to the much larger, sessile female person egg. Sperm form is diverse and includes cells with flagella or amoeboid cells to facilitate move. Fertilization and fusion of the gamete nuclei produce a zygote. Fertilization may be internal, especially in land animals, or external, as is common in many aquatic species.

Later fertilization, a developmental sequence ensues every bit cells divide and differentiate. Many of the events in development are shared in groups of related beast species, and these events are ane of the principal ways scientists classify high-level groups of animals. During development, animal cells specialize and form tissues, determining their future morphology and physiology. In many animals, such as mammals, the young resemble the adult. Other animals, such as some insects and amphibians, undergo complete metamorphosis in which individuals enter 1 or more larval stages. For these animals, the young and the developed have different diets and sometimes habitats. In other species, a process of incomplete metamorphosis occurs in which the immature somewhat resemble the adults and become through a serial of stages separated by molts (shedding of the skin) until they achieve the final adult class.

Asexual Reproduction

Asexual reproduction, different sexual reproduction, produces offspring genetically identical to each other and to the parent. A number of creature species—especially those without backbones, but even some fish, amphibians, and reptiles—are capable of asexual reproduction. Asexual reproduction, except for occasional identical twinning, is absent in birds and mammals. The most common forms of asexual reproduction for stationary aquatic animals include budding and fragmentation, in which part of a parent private tin can separate and grow into a new individual. In contrast, a form of asexual reproduction found in certain invertebrates and rare vertebrates is called parthenogenesis (or "virgin beginning"), in which unfertilized eggs develop into new offspring.

Nomenclature Features of Animals

Animals are classified according to morphological and developmental characteristics, such equally a trunk plan. With the exception of sponges, the animal torso program is symmetrical. This means that their distribution of body parts is counterbalanced along an axis. Additional characteristics that contribute to animate being nomenclature include the number of tissue layers formed during development, the presence or absenteeism of an internal torso cavity, and other features of embryological evolution.

Art Connection

Figure 2: The phylogenetic tree of animals is based on morphological, fossil, and genetic evidence.

Which of the following statements is false?

1. Eumetazoa have specialized tissues and Parazoa do not.
2. Both acoelomates and pseudocoelomates have a torso cavity.
3. Chordates are more closely related to echinoderms than to rotifers according to the effigy.
4. Some animals have radial symmetry, and some animals have bilateral symmetry.
   [reveal-answer q="124725″]Show Reply[/reveal-answer]
   [hidden-answer a="124725″]2[/subconscious-answer]

Body Symmetry

Animals may be asymmetrical, radial, or bilateral in course ([Effigy 3]). Asymmetrical animals are animals with no pattern or symmetry; an example of an asymmetrical animal is a sponge ([Figure 3]a). An organism with radial symmetry ([Figure iii]b) has a longitudinal (upward-and-downward) orientation: Any plane cut forth this up–downwardly axis produces roughly mirror-image halves. An example of an organism with radial symmetry is a sea anemone.

Figure iii: Animals exhibit different types of body symmetry. The (a) sponge is asymmetrical and has no planes of symmetry, the (b) sea anemone has radial symmetry with multiple planes of symmetry, and the (c) caprine animal has bilateral symmetry with one plane of symmetry.

Bilateral symmetry is illustrated in [Figure 3]c using a goat. The caprine animal likewise has upper and lower sides to information technology, but they are non symmetrical. A vertical plane cutting from front to dorsum separates the animal into roughly mirror-image right and left sides. Animals with bilateral symmetry too have a "head" and "tail" (anterior versus posterior) and a back and underside (dorsal versus ventral).

Watch this video to see a quick sketch of the different types of torso symmetry.

Layers of Tissues

Most animate being species undergo a layering of early tissues during embryonic development. These layers are called germ layers. Each layer develops into a specific set of tissues and organs. Animals develop either 2 or 3 embryonic germs layers ([Figure 4]). The animals that display radial symmetry develop two germ layers, an inner layer (endoderm) and an outer layer (ectoderm). These animals are chosen diploblasts. Animals with bilateral symmetry develop iii germ layers: an inner layer (endoderm), an outer layer (ectoderm), and a heart layer (mesoderm). Animals with three germ layers are called triploblasts.

Effigy 4: During embryogenesis, diploblasts develop two embryonic germ layers: an ectoderm and an endoderm. Triploblasts develop a third layer—the mesoderm—between the endoderm and ectoderm.

Presence or Absence of a Coelom

Triploblasts may develop an internal body cavity derived from mesoderm, chosen a coelom (pr. see-LŌM). This epithelial-lined cavity is a space, usually filled with fluid, which lies between the digestive organization and the body wall. It houses organs such as the kidneys and spleen, and contains the circulatory organization. Triploblasts that do not develop a coelom are chosen acoelomates, and their mesoderm region is completely filled with tissue, although they have a gut crenel. Examples of acoelomates include the flatworms. Animals with a true coelom are called eucoelomates (or coelomates) ([Effigy 5]). A true coelom arises entirely within the mesoderm germ layer. Animals such as earthworms, snails, insects, starfish, and vertebrates are all eucoelomates. A third group of triploblasts has a trunk cavity that is derived partly from mesoderm and partly from endoderm tissue. These animals are called pseudocoelomates. Roundworms are examples of pseudocoelomates. New information on the relationships of pseudocoelomates suggest that these phyla are not closely related and then the evolution of the pseudocoelom must have occurred more than once ([Effigy 2]). True coelomates can be further characterized based on features of their early on embryological evolution.

Figure five: Triploblasts may be acoelomates, eucoelomates, or pseudocoelomates. Eucoelomates accept a body cavity within the mesoderm, called a coelom, which is lined with mesoderm tissue. Pseudocoelomates have a like torso cavity, only it is lined with mesoderm and endoderm tissue. (credit a: modification of work by January Derk; credit b: modification of work by NOAA; credit c: modification of work past USDA, ARS

Protostomes and Deuterostomes

Bilaterally symmetrical, triploblastic eucoelomates can be divided into two groups based on differences in their early embryonic development. Protostomes include phyla such as arthropods, mollusks, and annelids. Deuterostomes include the chordates and echinoderms. These 2 groups are named from which opening of the digestive crenel develops start: mouth or anus. The give-and-take protostome comes from Greek words meaning "mouth beginning," and deuterostome originates from words meaning "mouth second" (in this case, the anus develops first). This departure reflects the fate of a construction called the blastopore ([Effigy 6]), which becomes the mouth in protostomes and the anus in deuterostomes. Other developmental characteristics differ between protostomes and deuterostomes, including the manner of formation of the coelom and the early on jail cell division of the embryo.

Figure half-dozen: Eucoelomates can be divided into ii groups, protostomes and deuterostomes, based on their early on embryonic evolution. Two of these differences include the origin of the rima oris opening and the style in which the coelom is formed.

Section Summary

Animals constitute a diverse kingdom of organisms. Although animals range in complexity from simple body of water sponges to man beings, most members share sure features. Animals are eukaryotic, multicellular, heterotrophic organisms that ingest their food and usually develop into motile creatures with a fixed body plan. Most members of the creature kingdom have differentiated tissues of four main classes—nervous, muscular, connective, and epithelial—that are specialized to perform unlike functions. Most animals reproduce sexually, leading to a developmental sequence that is relatively similar across the animal kingdom.

Organisms in the animal kingdom are classified based on their body morphology and evolution. True animals are divided into those with radial versus bilateral symmetry. Animals with three germ layers, called triploblasts, are further characterized past the presence or absence of an internal body crenel chosen a coelom. Animals with a body cavity may be either coelomates or pseudocoelomates, depending on which tissue gives rise to the coelom. Coelomates are farther divided into two groups called protostomes and deuterostomes, based on a number of developmental characteristics.

Review Questions

Which of the following is not a feature mutual to most animals?

1. evolution into a fixed body plan
2. asexual reproduction
3. specialized tissues
4. heterotrophic nutrient sourcing

[reveal-respond q="796334″]Evidence Answer[/reveal-answer]
[hidden-respond a="796334″]2[/subconscious-respond]

Which of the post-obit does not occur?

1. radially symmetrical diploblast
2. diploblastic eucoelomate
3. protostomic coelomate
4. bilaterally symmetrical deuterostome

[reveal-answer q="741875″]Prove Answer[/reveal-answer]
[hidden-reply a="741875″]ii[/hidden-reply]

Gratuitous Response

How are specialized tissues important for creature function and complication?

Specialized tissues allow more efficient functioning considering differentiated tissue types can perform unique functions and piece of work together in tandem to let the animal to perform more functions. For example, specialized musculus tissue allows directed and efficient move, and specialized nervous tissue allows for multiple sensory modalities as well equally the ability to reply to various sensory information; these functions are non necessarily available to other non-fauna organisms.

Using the following terms, explain what classifications and groups humans fall into, from the nigh general to the nigh specific: symmetry, germ layers, coelom, embryological development.

Humans have trunk plans that are bilaterally symmetrical and are characterized by the development of 3 germ layers, making them triploblasts. Humans have truthful coeloms, and are thus eucoelomates. Humans are deuterostomes.

Glossary

acoelomate

without a body cavity

asymmetrical

having no aeroplane of symmetry

bilateral symmetry

a blazon of symmetry in which there is merely one plane of symmetry that creates two mirror-epitome sides

body program

the shape and symmetry of an organism

coelom

a lined trunk crenel derived from mesodermal embryonic tissue

deuterostome

describing an animal in which the blastopore develops into the anus, with the second opening developing into the mouth

diploblast

an animal that develops from ii embryonic germ layers

eucoelomate

describing animals with a body crenel completely lined with mesodermal tissue

germ layer

a collection of cells formed during embryogenesis that volition give rise to future trunk tissues

protostome

describing an fauna in which the rima oris develops first during embryogenesis and a second opening developing into the anus

pseudocoelomate

an fauna with a coelom that is not completely lined with tissues derived from the mesoderm as in eucoelomate animals

radial symmetry

a blazon of symmetry with multiple planes of symmetry all cross at an axis through the center of the organism

triploblast

an animal that develops from three germ layers

Source: https://opentextbc.ca/conceptsofbiologyopenstax/chapter/features-of-the-animal-kingdom/

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