How Are Animals Different From Other Life Forms
Learning Objectives
- List the features that distinguish the brute kingdom from other kingdoms
- Explain the processes of animal reproduction and embryonic development
- Describe the bureaucracy of basic creature nomenclature
- Compare and contrast the embryonic development of protostomes and deuterostomes
Even though members of the animate being kingdom are incredibly diverse, animals share common features that distinguish them from organisms in other kingdoms. All animals are eukaryotic, multicellular organisms, and about all animals have specialized tissues. Nearly animals are motile, at to the lowest degree during certain life stages. Animals require a source of nutrient to grow and develop. All animals are heterotrophic, ingesting living or dead organic matter. This form of obtaining energy distinguishes them from autotrophic organisms, such as most 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 xv.2). Most animals reproduce sexually: The offspring laissez passer through a series of developmental stages that establish a determined body plan, unlike plants, for example, in which the exact shape of the trunk is indeterminate. The body program refers to the shape of an animal.
Figure 15.2 All animals that derive free 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 stage in mosquitos and its adult stage infesting the hearts of dogs and other mammals, as shown here. (credit a: modification of work past USDA Forest Service; credit b: modification of work past Clyde Robinson)
Complex Tissue Structure
A hallmark trait of animals is specialized structures that are differentiated to perform unique functions. Every bit 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 mutual embryonic origin. In that location are 4 main types of animal tissues: nervous, muscle, connective, and epithelial. Nervous tissue contains neurons, or nerve cells, which transmit nerve impulses. Muscle tissue contracts to cause all types of body movement from locomotion of the organism to movements within the body itself. Animals also have specialized connective tissues that provide many functions, including ship and structural back up. Examples of connective tissues include blood and bone. 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 within the beast torso and the external surface of the body of the organism.
Link to Learning
Concept in Action
View this video to watch a presentation by biologist Eastward.O. Wilson on the importance of animal diversity.
Animal Reproduction and Development
Most animals take diploid torso (somatic) cells and a small number of haploid reproductive (gamete) cells produced through meiosis. Some exceptions exist: For instance, in bees, wasps, and ants, the male person is haploid considering it develops from an unfertilized egg. Most animals undergo sexual reproduction, while many also have mechanisms of asexual reproduction.
Sexual Reproduction and Embryonic Development
Almost all creature 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 sectional. During sexual reproduction, the male and female gametes of a species combine in a process chosen fertilization. Typically, the modest, motile male person sperm travels to the much larger, sessile female person egg. Sperm course 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 exist internal, especially in land animals, or external, equally is common in many aquatic species.
Later on fertilization, a developmental sequence ensues equally cells split up and differentiate. Many of the events in evolution are shared in groups of related animate being species, and these events are i of the main ways scientists classify high-level groups of animals. During evolution, animal cells specialize and form tissues, determining their futurity morphology and physiology. In many animals, such as mammals, the young resemble the developed. Other animals, such as some insects and amphibians, undergo complete metamorphosis in which individuals enter i or more larval stages. For these animals, the young and the adult have different diets and sometimes habitats. In other species, a procedure of incomplete metamorphosis occurs in which the immature somewhat resemble the adults and go through a series of stages separated by molts (shedding of the pare) until they achieve the final developed form.
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 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 individual tin separate and grow into a new individual. In dissimilarity, a grade of asexual reproduction found in sure invertebrates and rare vertebrates is called parthenogenesis (or "virgin outset"), 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 program. With the exception of sponges, the animal trunk program is symmetrical. This ways that their distribution of body parts is balanced forth an axis. Additional characteristics that contribute to animate being classification 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
Effigy 15.three The phylogenetic tree of animals is based on morphological, fossil, and genetic prove.
Which of the following statements is false?
- Eumetazoa have specialized tissues and Parazoa exercise non.
- Both acoelomates and pseudocoelomates have a trunk cavity.
- Chordates are more closely related to echinoderms than to rotifers according to the figure.
- Some animals have radial symmetry, and some animals have bilateral symmetry.
Trunk Symmetry
Animals may exist asymmetrical, radial, or bilateral in form (Figure fifteen.4). Asymmetrical animals are animals with no pattern or symmetry; an instance of an asymmetrical animate being is a sponge (Figure 15.iva). An organism with radial symmetry (Figure 15.fourb) has a longitudinal (upward-and-downwardly) orientation: Any plane cutting forth this up–down centrality produces roughly mirror-image halves. An example of an organism with radial symmetry is a sea anemone.
Figure 15.4 Animals exhibit dissimilar types of torso 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 15.4c using a goat. The goat likewise has upper and lower sides to it, but they are not symmetrical. A vertical plane cut from forepart to dorsum separates the animal into roughly mirror-image right and left sides. Animals with bilateral symmetry also take a "caput" and "tail" (anterior versus posterior) and a back and underside (dorsal versus ventral).
Link to Learning
Concept in Action
Watch this video to see a quick sketch of the unlike types of trunk symmetry.
Layers of Tissues
About animal species undergo a layering of early on tissues during embryonic evolution. 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.v). The animals that display radial symmetry develop two germ layers, an inner layer (endoderm) and an outer layer (ectoderm). These animals are called diploblasts. Animals with bilateral symmetry develop three germ layers: an inner layer (endoderm), an outer layer (ectoderm), and a center layer (mesoderm). Animals with iii germ layers are chosen triploblasts.
Figure 15.v During embryogenesis, diploblasts develop two embryonic germ layers: an ectoderm and an endoderm. Triploblasts develop a tertiary layer—the mesoderm—betwixt 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 system and the torso wall. Information technology houses organs such as the kidneys and spleen, and contains the circulatory organisation. Triploblasts that do 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 truthful coelom are called eucoelomates (or coelomates) (Effigy 15.6). A true coelom arises entirely within the mesoderm germ layer. Animals such equally earthworms, snails, insects, starfish, and vertebrates are all eucoelomates. A tertiary grouping of triploblasts has a body cavity that is derived partly from mesoderm and partly from endoderm tissue. These animals are called pseudocoelomates. Roundworms are examples of pseudocoelomates. New data on the relationships of pseudocoelomates propose that these phyla are not closely related and so the evolution of the pseudocoelom must have occurred more than once (Effigy 15.3). True coelomates can be further characterized based on features of their early embryological evolution.
Figure 15.6 Triploblasts may be acoelomates, eucoelomates, or pseudocoelomates. Eucoelomates have a body cavity within the mesoderm, called a coelom, which is lined with mesoderm tissue. Pseudocoelomates have a similar body cavity, simply information technology is lined with mesoderm and endoderm tissue. (credit a: modification of work by Jan Derk; credit b: modification of work by NOAA; credit c: modification of work by USDA, ARS)
Protostomes and Deuterostomes
Bilaterally symmetrical, triploblastic eucoelomates can be divided into two groups based on differences in their early on embryonic evolution. Protostomes include phyla such as arthropods, mollusks, and annelids. Deuterostomes include the chordates and echinoderms. These ii groups are named from which opening of the digestive cavity develops first: oral fissure or anus. The give-and-take protostome comes from Greek words meaning "mouth offset," and deuterostome originates from words meaning "oral fissure 2nd" (in this case, the anus develops first). This departure reflects the fate of a structure called the blastopore (Effigy 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 formation of the coelom and the early on jail cell division of the embryo.
Effigy 15.7 Eucoelomates can be divided into two groups, protostomes and deuterostomes, based on their early embryonic evolution. 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
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