Characteristics Of The Animal Kingdom

Introduction to Brute Variety

Features of the Animate being Kingdom

OpenStaxCollege

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Learning Objectives

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

Listing the features that distinguish the kingdom Animalia from other kingdoms
Explain the processes of beast reproduction and embryonic evolution
Describe the roles that Hox genes play in development

Fifty-fifty though members of the beast kingdom are incredibly diverse, almost animals share sure features that distinguish them from organisms in other kingdoms. All animals are eukaryotic, multicellular organisms, and almost all animals accept a complex tissue structure with differentiated and specialized tissues. Virtually animals are motile, at least during certain life stages. All animals require a source of food and are therefore heterotrophic, ingesting other living or dead organisms; this feature distinguishes them from autotrophic organisms, such every bit nearly plants, which synthesize their own nutrients through photosynthesis. Every bit heterotrophs, animals may be carnivores, herbivores, omnivores, or parasites ([link]ab). Most animals reproduce sexually, and the offspring pass through a series of developmental stages that establish a determined and fixed body program. The body plan refers to the morphology of an animal, determined by developmental cues.

All animals are heterotrophs that derive energy from food. The (a) black conduct 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 mosquitoes and its adult stage infesting the heart of dogs and other mammals, equally shown here. (credit a: modification of work past USDA Forest Service; credit b: modification of work by Clyde Robinson)

Part a shows a bear with a large fish in its mouth. Part b shows a heart in a jar. Long, threadlike worms extend from the heart.

Complex Tissue Construction

As multicellular organisms, animals differ from plants and fungi because their cells don't accept cell walls, their cells may be embedded in an extracellular matrix (such every bit bone, skin, or connective tissue), and their cells have unique structures for intercellular advice (such every bit gap junctions). In addition, animals possess unique tissues, absent in fungi and plants, which allow coordination (nerve tissue) of motility (musculus tissue). Animals are also characterized by specialized connective tissues that provide structural back up for cells and organs. This connective tissue constitutes the extracellular surroundings of cells and is made up of organic and inorganic materials. In vertebrates, bone tissue is a type of connective tissue that supports the unabridged body structure. The complex bodies and activities of vertebrates demand such supportive tissues. Epithelial tissues cover, line, protect, and secrete. Epithelial tissues include the epidermis of the integument, the lining of the digestive tract and trachea, and make up the ducts of the liver and glands of avant-garde animals.

The animate being kingdom is divided into Parazoa (sponges) and Eumetazoa (all other animals). Equally very unproblematic animals, the organisms in group Parazoa ("beside brute") do not incorporate true specialized tissues; although they do possess specialized cells that perform dissimilar functions, those cells are non organized into tissues. These organisms are considered animals since they lack the ability to make their own food. Animals with true tissues are in the group Eumetazoa ("true animals"). When we recollect of animals, we normally retrieve of Eumetazoans, since virtually animals fall into this category.

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

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Spotter a presentation past biologist E.O. Wilson on the importance of diversity.

Fauna Reproduction and Development

Most animals are diploid organisms, meaning that their torso (somatic) cells are diploid and haploid reproductive (gamete) cells are produced through meiosis. Some exceptions exist: For example, in bees, wasps, and ants, the male is haploid because it develops from unfertilized eggs. Near animals undergo sexual reproduction: This fact distinguishes animals from fungi, protists, and bacteria, where asexual reproduction is common or exclusive. Yet, a few groups, such as cnidarians, flatworm, and roundworms, undergo asexual reproduction, although nearly all of those animals also have a sexual stage to their life cycle.

Processes of Creature 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-scale, motile male person sperm fertilizes the much larger, sessile female egg. This process produces a diploid fertilized egg called a zygote.

Some beast species—including bounding main stars and ocean anemones, as well equally 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 individual can separate and abound into a new individual. In contrast, a course of asexual reproduction found in certain insects and vertebrates is called parthenogenesis (or "virgin beginning"), where unfertilized eggs can develop into new male offspring. This blazon of parthenogenesis is chosen haplodiploidy. 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 can ensure genetic propagation.

After fertilization, a serial of developmental stages occur during which master germ layers are established and reorganize to class an embryo. During this process, animal 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 as some insects, undergo complete metamorphosis where individuals enter one or more larval stages that may in differ in construction and office from the developed ([link]). For the latter, the young and the adult may have different diets, limiting competition for food betwixt them. Regardless of whether a species undergoes complete or incomplete metamorphosis, the series of developmental stages of the embryo remains largely the same for well-nigh members of the animal kingdom.

(a) The grasshopper undergoes incomplete metamorphosis. (b) The butterfly undergoes consummate metamorphosis. (credit: S.E. Snodgrass, USDA)

Illustration A shows the egg, nymph and adult stages of a grasshopper. The nymph stages are similar in appearance to the adult stage, but smaller. Illustration B shows the egg, larvae, pupa and adult stages of a butterfly. The pupa is a cocoon the butterfly makes when transforming from the larval to adult stages. The winged adult butterfly looks nothing like the caterpillar larva.

The process of beast evolution begins with the cleavage, or series of mitotic cell divisions, of the zygote ([link]). Three cell divisions transform the single-celled zygote into an 8-celled structure. Afterwards further cell division and rearrangement of existing cells, a half dozen–32-celled hollow structure called a blastula is formed. Side by side, the blastula undergoes further cell sectionalization and cellular rearrangement during a process called gastrulation. This leads to the formation of the next developmental stage, the gastrula, in which the hereafter digestive cavity is formed. Different cell layers (chosen germ layers) are formed during gastrulation. These germ layers are programmed to develop into certain tissue types, organs, and organ systems during a process chosen organogenesis.

During embryonic evolution, the zygote undergoes a series of mitotic cell divisions, or cleavages, to form an 8-cell stage, and then a hollow blastula. During a process chosen gastrulation, the blastula folds in to course a cavity in the gastrula.

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Watch the following video to run across how homo embryonic evolution (afterward the blastula and gastrula stages of development) reflects development.

The Role of Homeobox (Hox) Genes in Beast Development

Since the early on 19^th century, scientists have observed that many animals, from the very simple to the circuitous, shared like embryonic morphology and development. Surprisingly, a human being embryo and a frog embryo, at a certain stage of embryonic development, wait remarkably alike. For a long time, scientists did not understand why so many animal species looked similar during embryonic evolution just were very different as adults. They wondered what dictated the developmental direction that a fly, mouse, frog, or human embryo would accept. Well-nigh the finish of the 20^thursday century, a particular class of genes was discovered that had this very chore. These genes that determine animate being construction are called "homeotic genes," and they incorporate DNA sequences called homeoboxes. The animal genes containing homeobox sequences are specifically referred to as Hox genes. This family unit of genes is responsible for determining the general body plan, such every bit the number of body segments of an fauna, the number and placement of appendages, and animal caput-tail directionality. The showtime Hox genes to be sequenced were those from the fruit fly (Drosophila melanogaster). A single Hox mutation in the fruit fly can event in an extra pair of wings or even appendages growing from the "wrong" body part.

While there are a great many genes that play roles in the morphological evolution of an creature, what makes Hox genes so powerful is that they serve as master control genes that can plow on or off large 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 beast kingdom, that is, the genetic sequences of Hox genes and their positions on chromosomes are remarkably similar across nearly animals because of their presence in a common antecedent, from worms to flies, mice, and humans ([link]). One of the contributions to increased animate being torso complexity is that Hox genes have undergone at least two duplication events during animal evolution, with the boosted genes allowing for more complex body types to evolve.

Art Connexion

Hox genes are highly conserved genes encoding transcription factors that determine the course of embryonic development in animals. In vertebrates, the genes have been duplicated into iv clusters: Hox-A, Hox-B, Hox-C, and Hox-D. Genes within these clusters are expressed in certain trunk segments at certain stages of evolution. Shown here is the homology between Hox genes in mice and humans. Note how Hox gene expression, as indicated with orange, pink, blueish and greenish shading, occurs in the same body segments in both the mouse and the human.

If a Hox 13 factor in a mouse was replaced with a Hox 1 gene, how might this alter brute evolution?

<!–<para>The animal might develop two heads and no tail.–>

Department Summary

Animals constitute an incredibly diverse kingdom of organisms. Although animals range in complication from elementary sea sponges to human beings, near members of the animal kingdom share certain features. Animals are eukaryotic, multicellular, heterotrophic organisms that ingest their food and usually develop into motile creatures with a fixed torso plan. A major feature unique to the animate being kingdom is the presence of differentiated tissues, such as nerve, muscle, and connective tissues, which are specialized to perform specific functions. Most animals undergo sexual reproduction, leading to a series of developmental embryonic stages that are relatively like across the animal kingdom. A grade of transcriptional control genes called Hox genes directs the arrangement of the major beast body plans, and these genes are strongly homologous across the animal kingdom.

Art Connections

[link] If a Hox 13 gene in a mouse was replaced with a Hox 1 factor, how might this alter animal development?

[link] The fauna might develop two heads and no tail.

Review Questions

Which of the following is non a characteristic mutual to most animals?

development into a fixed body program
asexual reproduction
specialized tissues
heterotrophic nutrient sourcing

During embryonic development, unique cell layers develop and distinguish during a stage called ________.

the blastula stage
the germ layer phase
the gastrula phase
the organogenesis stage

Which of the following phenotypes would most likely exist the upshot of a Hox gene mutation?

abnormal body length or height
two different heart colors
the contraction of a genetic illness
2 fewer appendages than normal

Complimentary Response

Why might the development of specialized tissues exist important for animal office and complication?

The development of specialized tissues affords more complex fauna anatomy and physiology because differentiated tissue types can perform unique functions and work together in tandem to permit the animal to perform more functions. For example, specialized muscle tissue allows directed and efficient move, and specialized nervous tissue allows for multiple sensory modalities equally well as the ability to respond to various sensory information; these functions are not necessarily available to other not-animate being organisms.

Describe and requite examples of how humans display all of the features common to the animal kingdom.

Humans are multicellular organisms. They also contain differentiated tissues, such as epithelial, muscle, and nervous tissue, likewise as specialized organs and organ systems. Every bit heterotrophs, humans cannot produce their ain nutrients and must obtain them by ingesting other organisms, such as plants, fungi, and animals. Humans undergo sexual reproduction, as well as the aforementioned embryonic developmental stages equally other animals, which eventually atomic number 82 to a stock-still and motile body plan controlled in large part by Hox genes.

How have Hox genes contributed to the diversity of animal body plans?

Altered expression of homeotic genes can atomic number 82 to major changes in the morphology of the private. Hox genes can affect the spatial arrangements of organs and trunk parts. If a Hox gene was mutated or duplicated, it could affect where a leg might be on a fruit fly or how far apart a person's fingers are.

Glossary

blastula: sixteen–32 jail cell stage of evolution of an animal embryo

body plan: morphology or constant shape of an organism

cleavage: cell division of a fertilized egg (zygote) to form a multicellular embryo

gastrula: stage of animal development characterized past the formation of the digestive cavity

germ layer: collection of cells formed during embryogenesis that will give rising to future torso tissues, more than pronounced in vertebrate embryogenesis