Which Of The Following Best Describes A Characteristic That Distinguishes Animals From Plants?

Characteristics of the Animal Kingdom

The animate being kingdom is very diverse, only animals share many common characteristics, such as methods of development and reproduction.

Learning Objectives

Draw the methods used to classify animals

Key Takeaways

Key Points

• Animals vary in complexity and are classified based on beefcake, morphology, genetic makeup, and evolutionary history.
• All animals are eukaryotic, multicellular organisms, and most animals have complex tissue structure with differentiated and specialized tissue.
• Animals are heterotrophs; they must consume living or dead organisms since they cannot synthesize their own food and can exist carnivores, herbivores, omnivores, or parasites.
• Most animals are motile for at least some stages of their lives, and nigh animals reproduce sexually.

Primal Terms

• body plan: an assemblage of morphological features shared amid many members of a phylum-level group
• heterotroph: an organism that requires an external supply of energy in the class of nutrient, as it cannot synthesize its own
• extant: still in beingness; not extinct

Introduction: Features of the Beast Kingdom

Fauna evolution began in the ocean over 600 meg years ago with tiny creatures that probably practise not resemble any living organism today. Since then, animals have evolved into a highly-various kingdom. Although over one million extant (currently living) species of animals have been identified, scientists are continually discovering more than species equally they explore ecosystems effectually the earth. The number of extant species is estimated to be between iii and 30 meg.

But what is an animal? While we tin easily place dogs, birds, fish, spiders, and worms equally animals, other organisms, such every bit corals and sponges, are non as easy to classify. Animals vary in complexity, from sea sponges to crickets to chimpanzees, and scientists are faced with the difficult job of classifying them inside a unified system. They must identify traits that are common to all animals as well equally traits that can be used to distinguish amidst related groups of animals. The beast classification organization characterizes animals based on their beefcake, morphology, evolutionary history, features of embryological development, and genetic makeup. This classification scheme is constantly developing as new information about species arises. Understanding and classifying the great variety of living species help us meliorate sympathize how to conserve the diversity of life on world.

Even though members of the animal kingdom are incredibly diverse, virtually animals share certain features that distinguish them from organisms in other kingdoms. All animals are eukaryotic, multicellular organisms, and near all animals accept a circuitous tissue structure with differentiated and specialized tissues. Most animals are motile, at least during certain life stages. All animals require a source of nutrient and are, therefore, heterotrophic: ingesting other living or dead organisms. This characteristic distinguishes them from autotrophic organisms, such as nigh plants, which synthesize their own nutrients through photosynthesis. Equally heterotrophs, animals may be carnivores, herbivores, omnivores, or parasites. About animals reproduce sexually with the offspring passing through a series of developmental stages that establish a fixed body plan. The trunk plan refers to the morphology of an animal, determined past developmental cues.

Heterotrophs: All animals are heterotrophs that derive energy from food. 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 mosquitoes and its adult stage infesting the heart of dogs and other mammals.

Complex Tissue Structure

Animals, likewise Parazoa (sponges), are characterized by specialized tissues such as muscle, nervus, connective, and epithelial tissues.

Learning Objectives

Listing the various specialized tissue types found in animals and depict their functions

Key Takeaways

Key Points

• Animal cells don't have jail cell walls; their cells may be embedded in an extracellular matrix and have unique structures for intercellular communication.
• Animals accept nervus and musculus tissues, which provide coordination and motion; these are not nowadays in plants and fungi.
• Complex animal bodies demand connective tissues made up of organic and inorganic materials that provide support and construction.
• Animals are also characterized by epithelial tissues, like the epidermis, which function in secretion and protection.
• The animal kingdom is divided into Parazoa (sponges), which do non incorporate true specialized tissues, and Eumetazoa (all other animals), which practice contain true specialized tissues.

Key Terms

• Parazoa: a taxonomic subkingdom within the kingdom Animalia; the sponges
• Eumetazoa: a taxonomic subkingdom, inside kingdom Animalia; all animals except the sponges
• epithelial tissue: one of the four bones types of animal tissue, which line the cavities and surfaces of structures throughout the trunk, and likewise form many glands

Complex Tissue Structure

As multicellular organisms, animals differ from plants and fungi because their cells don't have jail cell walls; their cells may be embedded in an extracellular matrix (such every bit bone, skin, or connective tissue); and their cells accept unique structures for intercellular advice (such equally gap junctions). In add-on, animals possess unique tissues, absent in fungi and plants, which allow coordination (nervus tissue) and movement (muscle tissue). Animals are too characterized by specialized connective tissues that provide structural support for cells and organs. This connective tissue constitutes the extracellular surround of cells and is fabricated upwardly of organic and inorganic materials. In vertebrates, bone tissue is a type of connective tissue that supports the entire body structure. The complex bodies and activities of vertebrates need such supportive tissues. Epithelial tissues encompass, line, protect, and secrete; these tissues include the epidermis of the integument: the lining of the digestive tract and trachea. They besides make up the ducts of the liver and glands of advanced animals.

The fauna kingdom is divided into Parazoa (sponges) and Eumetazoa (all other animals). As very uncomplicated animals, the organisms in group Parazoa ("beside beast") exercise non contain true specialized tissues. Although they do possess specialized cells that perform different functions, those cells are not organized into tissues. These organisms are considered animals since they lack the ability to make their ain food. Animals with true tissues are in the group Eumetazoa ("true animals"). When we call up of animals, nosotros ordinarily think of Eumetazoans, since nearly animals fall into this category.

Sponges: Sponges, such equally those in the Caribbean Ocean, are classified every bit Parazoans considering they are very simple animals that do non contain true specialized tissues.

The dissimilar types of tissues in true animals are responsible for conveying out specific functions for the organism. This differentiation and specialization of tissues is office of what allows for such incredible animal diversity. For case, the evolution of nerve tissues and muscle tissues has resulted in animals' unique ability to rapidly sense and respond to changes in their environment. This allows animals to survive in environments where they must compete with other species to encounter their nutritional demands.

Brute Reproduction and Development

Most animals undergo sexual reproduction and take similar forms of evolution dictated by Hox genes.

Learning Objectives

Explain the processes of creature reproduction and embryonic development

Key Takeaways

Key Points

• Most animals reproduce through sexual reproduction, simply some animals are capable of asexual reproduction through parthenogenesis, budding, or fragmentation.
• Following fertilization, an embryo is formed, and animal tissues organize into organ systems; some animals may also undergo incomplete or complete metamorphosis.
• Cleavage of the zygote leads to the formation of a blastula, which undergoes further cell division and cellular rearrangement during a process called gastrulation, which leads to the formation of the gastrula.
• During gastrulation, the digestive cavity and germ layers are formed; these will later develop into certain tissue types, organs, and organ systems during a process chosen organogenesis.
• Hox genes are responsible for determining the general body plan, such every bit the number of trunk segments of an animal, the number and placement of appendages, and animal head-tail directionality.
• Hox genes, similar across most animals, tin turn on or off other genes by coding transcription factors that control the expression of numerous other genes.

Cardinal Terms

• metamorphosis: a alter in the form and often habits of an brute after the embryonic stage during normal development
• Hox gene: genes responsible for determining the general body plan, such as the number of body segments of an animal, the number and placement of appendages, and brute head-tail directionality
• blastula: a 6-32-celled hollow structure that is formed after a zygote undergoes jail cell division

Animate being Reproduction and Evolution

Most animals are diploid organisms (their torso, or somatic, cells are diploid) with haploid reproductive ( gamete ) cells produced through meiosis. The majority of animals undergo sexual reproduction. This fact distinguishes animals from fungi, protists, and bacteria where asexual reproduction is common or exclusive. Nevertheless, a few groups, such as cnidarians, flatworms, and roundworms, undergo asexual reproduction, although nearly all of those animals besides accept a sexual phase to their life cycle.

Processes of Animal Reproduction and Embryonic Development

During sexual reproduction, the haploid gametes of the male and female person individuals of a species combine in a process called fertilization. Typically, the small, motile male sperm fertilizes the much larger, sessile female egg. This process produces a diploid fertilized egg chosen a zygote.

Some fauna species (including sea stars and bounding main anemones, as well every bit some insects, reptiles, and fish) are capable of asexual reproduction. The most common forms of asexual reproduction for stationary aquatic animals include budding and fragmentation where part of a parent private can separate and grow into a new individual. In contrast, a grade of asexual reproduction found in certain insects and vertebrates is called parthenogenesis where unfertilized eggs tin can develop into new offspring. This type of parthenogenesis in insects is called haplodiploidy and results in male offspring. These types of asexual reproduction produce genetically identical offspring, which is disadvantageous from the perspective of evolutionary adaptability because of the potential buildup of deleterious mutations. However, for animals that are limited in their capacity to attract mates, asexual reproduction tin ensure genetic propagation.

After fertilization, a serial of developmental stages occur during which primary germ layers are established and reorganize to grade an embryo. During this process, animate being tissues begin to specialize and organize into organs and organ systems, determining their future morphology and physiology. Some animals, such as grasshoppers, undergo incomplete metamorphosis, in which the young resemble the adult. Other animals, such every bit some insects, undergo consummate metamorphosis where individuals enter one or more than larval stages that may differ in structure and function from the adult. In complete metamorphosis, the young and the adult may have different diets, limiting competition for food between them. Regardless of whether a species undergoes complete or incomplete metamorphosis, the series of developmental stages of the embryo remains largely the aforementioned for most members of the animate being kingdom.

Incomplete and complete metamorphosis: (a) The grasshopper undergoes incomplete metamorphosis. (b) The butterfly undergoes complete metamorphosis.

The procedure of animal development begins with the cleavage, or series of mitotic prison cell divisions, of the zygote. Iii cell divisions transform the unmarried-celled zygote into an eight-celled structure. Subsequently farther cell partition and rearrangement of existing cells, a 6–32-celled hollow structure called a blastula is formed. Next, the blastula undergoes further cell division and cellular rearrangement during a process called gastrulation. This leads to the germination of the side by side developmental stage, the gastrula, in which the hereafter digestive cavity is formed. Different prison cell layers (called germ layers) are formed during gastrulation. These germ layers are programed to develop into certain tissue types, organs, and organ systems during a procedure chosen organogenesis.

Embryonic development: During embryonic development, the zygote undergoes a serial of mitotic cell divisions, or cleavages, to form an eight-jail cell phase, then a hollow blastula. During a procedure called gastrulation, the blastula folds inward to form a cavity in the gastrula.

The Role of Homeobox (Hox) Genes in Beast Evolution

Since the early 19^thursday century, scientists take observed that many animals, from the very simple to the circuitous, shared similar embryonic morphology and development. Surprisingly, a man embryo and a frog embryo, at a certain stage of embryonic development, announced remarkably similar. For a long time, scientists did not understand why so many beast species looked similar during embryonic development, simply were very different as adults. Near the stop of the 20^th century, a particular class of genes that dictate developmental management was discovered. These genes that decide animal structure are called "homeotic genes." They contain DNA sequences called homeoboxes, with specific sequences referred to as Hox genes. This family of genes is responsible for determining the full general body plan: the number of body segments of an animal, the number and placement of appendages, and animal head-tail directionality. The outset Hox genes to be sequenced were those from the fruit fly (Drosophila melanogaster). A unmarried Hox mutation in the fruit wing can consequence in an extra pair of wings or even appendages growing from the "incorrect" body role.

There are many genes that play roles in the morphological evolution of an animal, but Hox genes are then powerful considering they tin can plough on or off big numbers of other genes. Hox genes do this by coding transcription factors that control the expression of numerous other genes. Hox genes are homologous in the animal kingdom: the genetic sequences and their positions on chromosomes are remarkably similar across most animals (e.thousand., worms, flies, mice, humans) because of their presence in a common ancestor. Hox genes take undergone at least 2 duplication events during animal evolution: the additional genes allowed more circuitous trunk types to evolve.

Hox genes: Hox genes are highly-conserved genes encoding transcription factors that decide the class of embryonic development in animals. In vertebrates, the genes accept been duplicated into iv clusters: Hox-A, Hox-B, Hox-C, and Hox-D. Genes within these clusters are expressed in certain torso segments at certain stages of evolution. Shown hither is the homology between Hox genes in mice and humans. Notation how Hox gene expression, equally indicated with orangish, pink, blue, and green shading, occurs in the same body segments in both the mouse and the human.

Source: https://courses.lumenlearning.com/boundless-biology/chapter/features-of-the-animal-kingdom/

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