How Are All Animals Alike As Heterotrophs

Characteristics of the Animal Kingdom

The animal kingdom is very diverse, but animals share many mutual characteristics, such as methods of evolution and reproduction.

Learning Objectives

Draw the methods used to classify animals

Key Takeaways

Key Points

• Animals vary in complexity and are classified based on anatomy, morphology, genetic makeup, and evolutionary history.
• All animals are eukaryotic, multicellular organisms, and near 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 tin can be carnivores, herbivores, omnivores, or parasites.
• Most animals are motile for at least some stages of their lives, and virtually animals reproduce sexually.

Central Terms

• body plan: an aggregation of morphological features shared among many members of a phylum-level group
• heterotroph: an organism that requires an external supply of energy in the grade of food, as it cannot synthesize its own
• extant: still in existence; not extinct

Introduction: Features of the Animal Kingdom

Animal development began in the ocean over 600 million years agone with tiny creatures that probably practise non resemble whatsoever living organism today. Since and so, animals take evolved into a highly-diverse kingdom. Although over ane million extant (currently living) species of animals have been identified, scientists are continually discovering more species every bit they explore ecosystems around the world. The number of extant species is estimated to be between 3 and 30 1000000.

Just what is an beast? While we can easily identify dogs, birds, fish, spiders, and worms as animals, other organisms, such every bit corals and sponges, are non every bit easy to allocate. Animals vary in complexity, from sea sponges to crickets to chimpanzees, and scientists are faced with the difficult task of classifying them within a unified arrangement. They must identify traits that are common to all animals as well as traits that can be used to distinguish amid related groups of animals. The brute classification organisation characterizes animals based on their anatomy, morphology, evolutionary history, features of embryological evolution, and genetic makeup. This classification scheme is constantly developing as new data about species arises. Understanding and classifying the great variety of living species help u.s. better empathize how to conserve the variety of life on earth.

Even though members of the animal kingdom are incredibly various, most animals share sure features that distinguish them from organisms in other kingdoms. All animals are eukaryotic, multicellular organisms, and virtually all animals have a complex tissue structure with differentiated and specialized tissues. Most animals are motile, at least during certain life stages. All animals crave a source of nutrient and are, therefore, heterotrophic: ingesting other living or dead organisms. This feature distinguishes them from autotrophic organisms, such as most plants, which synthesize their own nutrients through photosynthesis. Every bit heterotrophs, animals may be carnivores, herbivores, omnivores, or parasites. Virtually animals reproduce sexually with the offspring passing through a series of developmental stages that establish a stock-still body programme. The trunk programme refers to the morphology of an animal, determined by developmental cues.

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

Circuitous Tissue Structure

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

Learning Objectives

List the various specialized tissue types constitute in animals and draw their functions

Key Takeaways

Fundamental Points

• Animal cells don't take prison cell walls; their cells may exist embedded in an extracellular matrix and have unique structures for intercellular communication.
• Animals have nerve and musculus tissues, which provide coordination and movement; these are not present in plants and fungi.
• Complex beast bodies demand connective tissues made up of organic and inorganic materials that provide support and structure.
• Animals are likewise characterized by epithelial tissues, similar the epidermis, which function in secretion and protection.
• The animate being kingdom is divided into Parazoa (sponges), which practice not contain true specialized tissues, and Eumetazoa (all other animals), which do comprise true specialized tissues.

Key Terms

• Parazoa: a taxonomic subkingdom inside the kingdom Animalia; the sponges
• Eumetazoa: a taxonomic subkingdom, within kingdom Animalia; all animals except the sponges
• epithelial tissue: one of the iv basic types of fauna tissue, which line the cavities and surfaces of structures throughout the body, and also grade many glands

Complex Tissue Structure

Every bit multicellular organisms, animals differ from plants and fungi because their cells don't have cell walls; their cells may be embedded in an extracellular matrix (such as bone, peel, or connective tissue); and their cells have unique structures for intercellular communication (such every bit gap junctions). In addition, animals possess unique tissues, absent in fungi and plants, which allow coordination (nervus tissue) and motility (muscle tissue). Animals are as well characterized by specialized connective tissues that provide structural support 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 comprehend, line, protect, and secrete; these tissues include the epidermis of the integument: the lining of the digestive tract and trachea. They also make up the ducts of the liver and glands of advanced animals.

The animal kingdom is divided into Parazoa (sponges) and Eumetazoa (all other animals). As very simple animals, the organisms in group Parazoa ("abreast animal") exercise not contain true specialized tissues. Although they practise 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 truthful tissues are in the grouping Eumetazoa ("true animals"). When we think of animals, we usually think of Eumetazoans, since near animals fall into this category.

Sponges: Sponges, such as those in the Caribbean Body of water, are classified equally Parazoans considering they are very unproblematic animals that do not contain true specialized tissues.

The different types of tissues in true animals are responsible for carrying out specific functions for the organism. This differentiation and specialization of tissues is part of what allows for such incredible fauna diversity. For example, the evolution of nerve tissues and muscle tissues has resulted in animals' unique power to quickly 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.

Animal Reproduction and Development

Most animals undergo sexual reproduction and have like forms of development dictated by Hox genes.

Learning Objectives

Explain the processes of animal reproduction and embryonic evolution

Key Takeaways

Key Points

• Most animals reproduce through sexual reproduction, merely some animals are capable of asexual reproduction through parthenogenesis, budding, or fragmentation.
• Following fertilization, an embryo is formed, and brute tissues organize into organ systems; some animals may likewise undergo incomplete or complete metamorphosis.
• Cleavage of the zygote leads to the formation of a blastula, which undergoes further cell partition 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 subsequently develop into sure tissue types, organs, and organ systems during a process called organogenesis.
• Hox genes are responsible for determining the full general body plan, such every bit the number of trunk segments of an animal, the number and placement of appendages, and animate being caput-tail directionality.
• Hox genes, similar beyond most animals, tin can plow on or off other genes by coding transcription factors that control the expression of numerous other genes.

Key Terms

• metamorphosis: a change in the form and ofttimes habits of an animal after the embryonic stage during normal development
• Hox cistron: 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 fauna head-tail directionality
• blastula: a half-dozen-32-celled hollow structure that is formed afterward a zygote undergoes cell division

Animal Reproduction and Development

Most animals are diploid organisms (their body, 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. Notwithstanding, a few groups, such as cnidarians, flatworms, 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 individuals of a species combine in a procedure called fertilization. Typically, the small, motile male sperm fertilizes the much larger, sessile female person egg. This process produces a diploid fertilized egg chosen a zygote.

Some creature species (including bounding main stars and ocean anemones, equally well every bit some insects, reptiles, and fish) are capable of asexual reproduction. The nigh mutual forms of asexual reproduction for stationary aquatic animals include budding and fragmentation where part of a parent individual can split up and abound into a new individual. In contrast, a form of asexual reproduction plant in certain insects and vertebrates is called parthenogenesis where unfertilized eggs can develop into new offspring. This blazon 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 considering of the potential buildup of deleterious mutations. However, for animals that are limited in their capacity to concenter mates, asexual reproduction can ensure genetic propagation.

Later on fertilization, a serial of developmental stages occur during which primary germ layers are established and reorganize to course 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 equally some insects, undergo complete metamorphosis where individuals enter one or more than larval stages that may differ in construction and part from the developed. 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 same 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 evolution begins with the cleavage, or serial of mitotic cell divisions, of the zygote. Three cell divisions transform the single-celled zygote into an eight-celled structure. After farther cell partition and rearrangement of existing cells, a vi–32-celled hollow structure called a blastula is formed. Side by side, the blastula undergoes further cell division and cellular rearrangement during a procedure called gastrulation. This leads to the germination of the adjacent developmental stage, the gastrula, in which the time to come digestive cavity is formed. Different cell layers (called germ layers) are formed during gastrulation. These germ layers are programed to develop into sure tissue types, organs, and organ systems during a process called organogenesis.

Embryonic evolution: During embryonic evolution, the zygote undergoes a series of mitotic cell divisions, or cleavages, to form an eight-prison cell stage, and so a hollow blastula. During a process called gastrulation, the blastula folds in to grade a cavity in the gastrula.

The Role of Homeobox (Hox) Genes in Beast Evolution

Since the early on nineteen^th century, scientists take observed that many animals, from the very simple to the complex, shared similar embryonic morphology and development. Surprisingly, a human embryo and a frog embryo, at a sure phase of embryonic development, appear remarkably similar. For a long fourth dimension, scientists did not understand why so many brute species looked like during embryonic development, but were very different every bit adults. Near the end of the 20^th century, a particular class of genes that dictate developmental direction was discovered. These genes that determine brute structure are chosen "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 general body programme: the number of body segments of an animal, the number and placement of appendages, and brute head-tail directionality. The first Hox genes to be sequenced were those from the fruit fly (Drosophila melanogaster). A single Hox mutation in the fruit fly can result in an extra pair of wings or even appendages growing from the "wrong" body part.

There are many genes that play roles in the morphological evolution of an animal, but Hox genes are and then powerful because they can turn 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 brute kingdom: the genetic sequences and their positions on chromosomes are remarkably similar across nearly animals (e.g., worms, flies, mice, humans) because of their presence in a mutual antecedent. Hox genes take undergone at least two duplication events during animal evolution: the additional genes allowed more complex body types to evolve.

Hox genes: Hox genes are highly-conserved genes encoding transcription factors that make up one's mind the course of embryonic development in animals. In vertebrates, the genes have been duplicated into four clusters: Hox-A, Hox-B, Hox-C, and Hox-D. Genes inside these clusters are expressed in sure body segments at certain stages of development. Shown here is the homology between Hox genes in mice and humans. Annotation how Hox gene expression, as indicated with orange, 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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