What Percent Of The Animal Kingdom Do Vertebrates Makeup Annelida

In this explainer, we will acquire how to recall the characteristics of dissimilar invertebrates within the animal kingdom.

Nosotros will commencement take a look at some of the organisms that are considered invertebrates. This group is hugely various and incredibly large. Electric current estimates propose that around 1.25 million different invertebrate species have been identified, but there could be equally many as thirty 1000000 species in total. Invertebrates make up around of the animal species on Earth, and they can be found everywhere, from deserts to oceans to even your back garden.

When studying living organisms, scientists often classify them into singled-out groups, in a process known as taxonomy. Organisms within the same grouping share some central characteristics.

Definition: Taxonomy

Taxonomy is the scientific written report of biological nomenclature.

An case of a taxonomic group is a kingdom, which is a large grouping consisting of many different organisms that all share some key characteristics. An outline of the traditional five-kingdom organization of classification is shown in Effigy i.

Near all the organisms belonging to kingdom Animalia share some key characteristics. They are usually mobile and can freely move around. Animals are multicellular, eukaryotic organisms, which means their cells contain a membrane-spring nucleus. They are besides heterotrophic, which means they need to consume other organisms to obtain their nutrition.

Definition: Heterotroph

A heterotroph is an organism that obtains its diet by consuming other organisms or organic matter.

If nosotros take a closer look at kingdom Animalia, we can see that biologists have classified this kingdom into two different groups: vertebrates and invertebrates. The basic outline of this grouping, along with some primal characteristics of each group, is shown in Figure two.

As shown in Figure 2, organisms classified as invertebrates do not possess a vertebral column, or courage. This is a characteristic that all invertebrates, no matter how complex or different they are, share.

In the taxonomic system, each kingdom is made up of many smaller groups called phyla. Organisms within the same phylum share even more key characteristics. Allow's accept a closer look at some of the phyla that are classified as invertebrates in the animal kingdom.

Key Term: Kingdom

A kingdom is a taxonomic rank that is below domain and contains multiple unlike phyla.

Primal Term: Phylum

A phylum is a taxonomic group that is below kingdom and contains multiple different classes.

Phylum Porifera comprises organisms that more commonly known as sponges. A pic of a sponge is shown below.

Figure 3

Sponges are constitute in aquatic environments. They consume other organisms for their nutrition and are made up of multiple different cells. Their construction is very simple; their cells do not take a cell wall, and they do non have true tissues or organs like other animals do. This means that they have no digestive, respiratory, or circulatory systems, and instead their biological processes are carried out past specialized cells. Dissimilar most other invertebrates, sponges lack an exoskeleton just instead have spicules (or spikes) that provide structural support. They are unremarkably hermaphroditic (which means they have both male person and female reproductive cells or organs) and can reproduce either sexually using gametes or asexually via a procedure chosen budding.

Definition: Hermaphrodite

A hermaphrodite is an organism that contains both male and female reproductive cells or organs.

However, you might think that it is slightly odd that we have placed this phylum into kingdom Animalia, as different many other fauna species sponges are not mobile. Really, the young and larval stages of sponges are mobile, and they swim in search for a suitable place to settle and develop into an adult. Although adult sponges are immobile, their other characteristics (e.1000., being multicellular heterotrophs) imply that they are all-time classified every bit animals. Sometimes, organisms are not a perfect fit for the grouping they are placed in, only they are close enough.

Instance 1: Recalling the Characteristics of Sponges Placing Them into Kingdom Animalia

The picture provided shows a member of phylum Porifera, more usually known as sponges. Sponges are immobile merely are yet classified into kingdom Animalia. Which characteristics do they share with the residual of the animal kingdom?

1. They are unicellular and reproduce sexually.
2. They are eukaryotic and reproduce asexually.
3. They are multicellular and autotrophic.
4. They are multicellular and heterotrophic.

Answer

Adult sponges, like the one shown here, are immobile invertebrates that are often found in marine environments, such every bit oceans. Surprisingly, they are classified as animals. Permit's recap the main features of the organisms belonging to the animal kingdom to help us reply this question.

Starting time, all organisms belonging to the animate being kingdom are multicellular. This ways that their bodies are made up of more than one cell.

2d, animals are eukaryotic. This ways that their cells comprise a nucleus, which contains the genetic material of the organism.

3rd, all organisms belonging to kingdom Animalia are heterotrophs. This means that they cannot synthesize their own food, unlike plants, which produce their ain sugars. Animals, however, must consume other organic material to obtain their nutrition. Every bit developed sponges cannot movement, they obtain their nutrition by filtering water through their bodies and extracting tiny organic particles and very pocket-sized organisms similar plankton.

Using our noesis of the animal kingdom and looking back at our answer options, we can see that the simply correct option is selection D. Sponges are multicellular and heterotrophic.

Phylum Cnidaria is a group that is largely composed of aquatic animals, such as hydras, anemones, and jellies, which tin live individually or in groups called colonies. A picture of a hydra is shown beneath.

Figure four

These organisms do not possess a head but practise have appendages, called tentacles, that surround an opening that functions every bit both a mouth and an anus. The body of a cnidarian is formed of ii layers, with the external layer possessing cnidocytes. Cnidocytes are commonly called stinging cells and are important in capturing prey and in helping the organism to defend itself confronting predators.

Organisms belonging to phylum Platyhelminthes are commonly called flatworms. All flatworms, as the name indicates, have a very flat body. The anterior (top) and posterior (bottom) areas of their bodies can be identified. Their bodies are bilaterally symmetrical, which means that if they are split lengthways downward the middle, each side volition be the same. Their bodies are made up of three layers, so they are referred to as triploblastic. The prefix triplo- in this term ways "three times." While flatworms practice have a central nervous organisation, they practise not have a specialized circulatory system. Most flatworms rely on a single opening that acts as a mouth to have in food and as an anus to remove waste. Some flatworms are free living, and some are parasitic and rely on obtaining nutrients from other organisms to survive. The majority are hermaphroditic, so they contain both male and female person reproductive cells.

An example of flatworms is tapeworms. Tapeworms are especially interesting every bit adult worms live within vertebrate organisms and attach, using suckers and hooks, to the host organism's intestines. This allows them to feed off of the nutrient that is being digested by the host. The photo below shows an enlarged image of a tapeworm.

Figure 5

The organisms belonging to phylum Nematoda are unremarkably referred to every bit roundworms. These worms take unsegmented, bilaterally symmetrical bodies fabricated upwardly of three layers. Unlike flatworms, they have two distinct openings for the oral fissure and the anus connected by an gastrointestinal tract. As well dissimilar flatworms, they are unisexual, so each private organism has either male or female sex cells. They are widely distributed and constitute in many dissimilar environments. Examples of roundworms include Ascaris lumbricoides, which is the most mutual parasitic worm in humans, and filarial worms, which can cause a serious affliction of the lymphatic arrangement called lymphatic filariasis (unremarkably referred to as elephantiasis).

The organisms belonging to phylum Annelida are known every bit ringworms, or segmented worms. As the name suggests, their bodies are segmented. A common example of an annelid is the earthworm, which has a distinctly segmented torso. These worms thrive in high-moisture environments, so they are almost usually constitute in the sea, fresh water, and dingy soils. These worms can be unisexual (either male or female) or hermaphroditic. Some of them are besides parasites, such every bit leeches, like the i shown below.

Figure 6

Effigy vii compares and contrasts the characteristics of the three phyla of worms that we have discussed so far.

Example two: Classifying Organisms into Phyla co-ordinate to a Given Description

An unknown species of worm has been discovered. The torso is cylindrical and bilaterally symmetrical. The organism found is adamant to exist a male. What phylum (Platyhelminthes, Nematoda, or Annelida) is this worm most likely to belong to?

Answer

To answer this question, nosotros need to recall the features shared by the organisms belonging to the phyla given in the question and and so determine which phylum the organism in the question would best fit into. Organisms belonging to phyla Platyhelminthes, Nematoda, and Annelida are all types of worms, and then they are invertebrates with bilaterally symmetrical bodies. Phylum Platyhelminthes includes flatworms, which are organisms with a flattened body. They are also hermaphroditic, meaning that they contain both male person and female sexual practice cells. Phylum Nematoda includes roundworms, which are organisms with a cylindrical body and a separate mouth and anus. They are as well unisexual, meaning that they are either a male person or a female. Phylum Annelida includes segmented worms, which are characterized by distinct rings along their bodies. These worms can be either hermaphroditic or unisexual. The organism mentioned in the question has a cylindrical torso and is a male, and so it is unisexual.

Therefore, the species of worm that has been discovered is nigh probable to vest to phylum Nematoda.

Phylum Arthropoda contains all the invertebrates that nosotros commonly refer to every bit insects. This phylum can be farther divided into three classes—Crustacea, Arachnida, and Insecta—and the subphylum Myriapoda. All of these classes share the characteristics of having a bilaterally symmetrical body covered by a hard exoskeleton and divided into segments with pairs of appendages (e.g., claws). They are all unisexual and reproduce sexually. Still, there are some differences betwixt the classes, which are outlined in Tabular array 1.

Table ane: Comparison of the central characteristics of the classes belonging to phylum Arthropoda.

Form/Subphylum	Trunk Structure	Appendages	Type of Optics	Animate Arrangement	Example Organisms
Crustacea	Divided into two regions, a cephalothorax and an abdomen and covered past a chitinous cuticle	Many jointed appendages (e.k., claws, tail)	Chemical compound	Gills	Lobsters, crabs, and prawns
Arachnida	Divided into 2 regions: a cephalothorax and an abdomen	Iv pairs of legs	Simple	Tracheoles or book lungs	Spiders, scorpions
Insecta	Divided into three regions: a caput, a thorax, and an abdomen	One pair of antennae and iii pairs of walking legs, with some having one or two pairs of wings	Chemical compound	Tracheoles	Flies, ants, bees, and locusts
Myriapoda	Divided into two regions, a caput and a trunk, with the trunk segmented	Many pairs of legs	Mostly uncomplicated	Trachea	Millipedes, centipedes

Example iii: Recalling the Defining Characteristics of Phylum Arthropoda

Which of the following is not a characteristic of an organism that belongs to the Arthropoda phylum?

1. Existence immobile
2. Having a trunk divided into segments
3. Being covered past an exoskeleton
4. Having a bilaterally symmetrical trunk

Answer

Arthropods are an incredibly diverse range of organisms. However, they all accept some characteristics in common. All arthropods have bilaterally symmetrical bodies covered past a hard exoskeleton. Their bodies are divided into segments, unremarkably two regions and sometimes fifty-fifty 3, and these segments accept various specialized appendages fastened to them. Examples of arthropods include lobsters, spiders, scorpions, ants, bees, and centipedes.

Therefore, the only characteristic listed that is not a characteristic of phylum Arthropoda is being immobile.

The organisms belonging to phylum Mollusca, known as mollusks, are generally found in salt water, with a few species living in fresh water or on country. All mollusks share a similar bones torso program, with the 3 main divisions existence a muscular foot for movement, a soft mass containing virtually of the internal organs, and a fold of tissue that covers this mass, called a mantle, which may secrete a calcareous crush. A large proportion of mollusks are unisexual, and a few species are hermaphroditic. Organisms belonging to this grouping that you may recognize are snails and octopuses. The heads of these snails and octopuses are well developed compared to other invertebrate species, and they even contain sense organs, like the specialized antennae on a snail's head.

Example iv: Using Our Knowledge of Invertebrates to Distinguish between Phyla

Which of the following characteristics would help distinguish an arthropod from a clam?

1. A torso divided into distinct segments
2. The absence of a courage
3. Having a unmarried opening acting as both the mouth and the anus
4. Possessing extensions from the trunk or appendages
5. The absenteeism of a complex nervous organization

Answer

Both arthropods and mollusks are organisms in phyla that belong to the invertebrate group of the beast kingdom. This ways that they accept some characteristics in mutual, namely, that they practise non possess a backbone (vertebral cavalcade). As more than circuitous invertebrates, both of these phyla accept extensions or appendages attached to their body, and dissimilar simpler forms, they have separate openings for their mouth and anus.

Yet, there are some key differences between the two. Mollusks, common examples of which are snails, oysters, and octopuses, take a large, fleshy body. They are all composed of a muscular human foot for movement, a soft mass for their internal organs, and a fold of tissue, chosen the mantle, that may or may not secrete a calcareous beat out (due east.1000., a snail's beat out). Some mollusks have complex nervous systems, such as that of an octopus, and some have far simpler nervous systems. Arthropods, such as lobsters, spiders, and scorpions, are characterized by having a hard exoskeleton and bodies that are divided into singled-out segments. For instance, they may have a distinct head, thorax, and abdomen, from which their appendages extend.

Therefore, we can see that, of the given options, the characteristic that best distinguishes between an arthropod and a mollusk is having a torso divided into distinct segments.

Phylum Echinodermata contains organisms that accept an unsegmented body and a hard endoskeleton covered by epidermis. This endoskeleton may possess bumps and spines, which brand them appear prickly. Echinoderms are largely found in marine environments. Examples of echinoderms include sea stars (shown below), ocean urchins, and bounding main cucumbers.

Some echinoderms, such as the ocean star shown, display radial symmetry; dissimilar other phyla of invertebrates, this means that their bodies are not symmetrical if they are carve up down the center. Instead, their extensions symmetrically extend from a central point, or axis. These organisms are unisexual and tin reproduce sexually. They also demonstrate regeneration, that is, the division of cells by asexual methods. This ways that if an organism like a sea star is damaged and lost an arm, it tin can regrow this arm from the central part of its body. The bodies of echinoderms develop extensions chosen tube feet, which assistance them movement. In dissimilarity to invertebrates like roundworms and segmented worms, echinoderms practise not have a front end and back end. Instead, they have two surfaces: an oral surface, where the organism's mouth is located, and an aboral surface, located on the opposite side to the oral surface. Equally these organisms are more often than not bottom-feeders, the oral surface is what we would picture the bottom of the organism to be.

Let's review some of the key points that nosotros take learned and so far.

Key Points

• Kingdom Animalia is divided into two singled-out groups: vertebrates and invertebrates.
• Invertebrates are organisms that do non possess a vertebral cavalcade, or backbone.
• Invertebrate phyla include Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, and Echinodermata.
• Organisms tin be classified into these phyla according to the key characteristics that they share.

Source: https://www.nagwa.com/en/explainers/413191401075/

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