Of All The Phyla Of Animals, Which One Does Not Have Specialized Cells That Form Defined Tissues?

Learning Objectives

By the cease of this section, you volition be able to:

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

Even though members of the animal kingdom are incredibly diverse, animals share mutual features that distinguish them from organisms in other kingdoms. All animals are eukaryotic, multicellular organisms, and almost all animals have specialized tissues. Most 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 dead organic matter. This class of obtaining energy distinguishes them from autotrophic organisms, such every bit almost plants, which brand their own nutrients through photosynthesis and from fungi that digest their food externally. Animals may be carnivores, herbivores, omnivores, or parasites (Figure 15.2). Almost animals reproduce sexually: The offspring pass through a series of developmental stages that establish a determined trunk plan, unlike plants, for case, in which the exact shape of the torso is indeterminate. The body plan refers to the shape of an animal.

Figure xv.2 All animals that derive energy from food are heterotrophs. The (a) black bear 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 phase in mosquitos and its adult stage infesting the hearts of dogs and other mammals, every bit shown here. (credit a: modification of work past USDA Wood Service; credit b: modification of piece 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 collection of similar cells that had a common embryonic origin. There are four main types of animal tissues: nervous, muscle, connective, and epithelial. Nervous tissue contains neurons, or nerve cells, which transmit nerve impulses. Musculus tissue contracts to crusade all types of body movement from locomotion of the organism to movements within the body itself. Animals also accept specialized connective tissues that provide many functions, including transport and structural support. Examples of connective tissues include claret and os. Connective tissue is comprised of cells separated by extracellular material made of organic and inorganic materials, such as the protein and mineral deposits of bone. Epithelial tissue covers the internal and external surfaces of organs inside the animal body and the external surface of the body of the organism.

Link to Learning

Concept in Action

View this video to picket a presentation past biologist E.O. Wilson on the importance of animal diversity.

Animal Reproduction and Development

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

Sexual Reproduction and Embryonic Development

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

Afterwards fertilization, a developmental sequence ensues as cells divide and differentiate. Many of the events in development are shared in groups of related animal species, and these events are i of the chief 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 ane or more than larval stages. For these animals, the immature and the developed accept different diets and sometimes habitats. In other species, a procedure of incomplete metamorphosis occurs in which the young somewhat resemble the adults and become through a series of stages separated by molts (shedding of the skin) until they accomplish the terminal adult class.

Asexual Reproduction

Asexual reproduction, unlike sexual reproduction, produces offspring genetically identical to each other and to the parent. A number of animal species—especially those without backbones, but fifty-fifty some fish, amphibians, and reptiles—are capable of asexual reproduction. Asexual reproduction, except for occasional identical twinning, is absent-minded in birds and mammals. The most mutual forms of asexual reproduction for stationary aquatic animals include budding and fragmentation, in which office of a parent individual can separate and grow into a new private. 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.

Classification Features of Animals

Animals are classified according to morphological and developmental characteristics, such as a body programme. With the exception of sponges, the animal torso plan is symmetrical. This ways that their distribution of body parts is balanced along an axis. Additional characteristics that contribute to animal nomenclature include the number of tissue layers formed during development, the presence or absence of an internal body cavity, and other features of embryological development.

Visual Connection

Visual Connection

Figure 15.3 The phylogenetic tree of animals is based on morphological, fossil, and genetic show.

Which of the following statements is imitation?

1. Eumetazoa have specialized tissues and Parazoa do not.
2. Both acoelomates and pseudocoelomates have a trunk crenel.
3. Chordates are more than closely related to echinoderms than to rotifers according to the figure.
4. Some animals accept radial symmetry, and some animals have bilateral symmetry.

Trunk Symmetry

Animals may be asymmetrical, radial, or bilateral in form (Figure 15.4). Asymmetrical animals are animals with no pattern or symmetry; an instance of an asymmetrical animal is a sponge (Effigy 15.4a). An organism with radial symmetry (Effigy 15.4b) has a longitudinal (up-and-downward) orientation: Whatsoever plane cut along this upwardly–down axis produces roughly mirror-epitome halves. An instance of an organism with radial symmetry is a sea anemone.

Effigy 15.4 Animals exhibit different types of torso symmetry. The (a) sponge is asymmetrical and has no planes of symmetry, the (b) body of water anemone has radial symmetry with multiple planes of symmetry, and the (c) goat has bilateral symmetry with one aeroplane of symmetry.

Bilateral symmetry is illustrated in Figure fifteen.4c using a goat. The caprine animal also has upper and lower sides to it, simply they are not symmetrical. A vertical plane cut from front to back separates the animal into roughly mirror-image right and left sides. Animals with bilateral symmetry besides have a "head" and "tail" (anterior versus posterior) and a back and underside (dorsal versus ventral).

Link to Learning

Concept in Action

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

Layers of Tissues

Nigh animal species undergo a layering of early on tissues during embryonic development. These layers are chosen germ layers. Each layer develops into a specific set of tissues and organs. Animals develop either two or three embryonic germs layers (Figure 15.5). The animals that display radial symmetry develop ii germ layers, an inner layer (endoderm) and an outer layer (ectoderm). These animals are called diploblasts. Animals with bilateral symmetry develop 3 germ layers: an inner layer (endoderm), an outer layer (ectoderm), and a middle layer (mesoderm). Animals with three germ layers are called triploblasts.

Figure 15.5 During embryogenesis, diploblasts develop ii embryonic germ layers: an ectoderm and an endoderm. Triploblasts develop a third layer—the mesoderm—between the endoderm and ectoderm.

Presence or Absenteeism of a Coelom

Triploblasts may develop an internal body cavity derived from mesoderm, called a coelom (pr. see-LŌM). This epithelial-lined cavity is a space, usually filled with fluid, which lies between the digestive system and the body wall. It houses organs such every bit the kidneys and spleen, and contains the circulatory arrangement. Triploblasts that practise not develop a coelom are called acoelomates, and their mesoderm region is completely filled with tissue, although they have a gut cavity. Examples of acoelomates include the flatworms. Animals with a true coelom are called eucoelomates (or coelomates) (Effigy 15.half dozen). A truthful coelom arises entirely within the mesoderm germ layer. Animals such as earthworms, snails, insects, starfish, and vertebrates are all eucoelomates. A tertiary group of triploblasts has a body cavity that is derived partly from mesoderm and partly from endoderm tissue. These animals are chosen pseudocoelomates. Roundworms are examples of pseudocoelomates. New data on the relationships of pseudocoelomates suggest that these phyla are not closely related and so the development of the pseudocoelom must accept occurred more than once (Effigy 15.3). True coelomates can be farther characterized based on features of their early embryological evolution.

Figure fifteen.6 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 similar body crenel, but it is lined with mesoderm and endoderm tissue. (credit a: modification of work by January Derk; credit b: modification of work past NOAA; credit c: modification of work past USDA, ARS)

Protostomes and Deuterostomes

Bilaterally symmetrical, triploblastic eucoelomates can be divided into ii 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 two groups are named from which opening of the digestive crenel develops first: mouth or anus. The word protostome comes from Greek words significant "oral fissure first," and deuterostome originates from words pregnant "mouth 2nd" (in this case, the anus develops commencement). This difference reflects the fate of a structure chosen the blastopore (Figure 15.seven), which becomes the mouth in protostomes and the anus in deuterostomes. Other developmental characteristics differ between protostomes and deuterostomes, including the mode of germination of the coelom and the early on jail cell division of the embryo.

Figure 15.7 Eucoelomates can be divided into two groups, protostomes and deuterostomes, based on their early on embryonic development. Two of these differences include the origin of the mouth opening and the way in which the coelom is formed.

Source: https://openstax.org/books/concepts-biology/pages/15-1-features-of-the-animal-kingdom

Posted by: isondientooltaid.blogspot.com

Share this post