25.+Invertebrates

Animal s are multicelled. In most cases, animal cells form tissues that become arranged as organs and systems which have a diploid chromosome number. Heterotrophs get carbon and energy by ingesting other organisms. Their cells require oxygen for aerobic respiration. Most animals are motile during at least part of the life cycle. Animals reproduce sexually or asexually and their embryos have development stages. Animal tissues help increase their body size and different types of tissue helps increase the different levels of organization. One type of animal tissue is the epithelium which is a tissue with one free surface bathing in a body fluid or exposed to the outside. The epithelium tissue is arranged in a sheetlike array of cells that covers many surfaces. It helps to absorb and secret different materials. It also forms sensory reception which are nerve cells. Nerve cells send out signals to contractile cells that shorten then go back to original length. Epithelial cells help make up the epidermis, which interacts with the outside world (skin) and the gastrodermis which lines the gut.. The rest on thin basement membrane is made up of adhension proteins which are integrins, cadherins and others. The connective tissue is the most abundant type of animal tissue. It is a matrix with living cells and embedded proteins. It is made up of tissue layers (germ layers) such as the ectoderm( first formed, outer primary tissue layer of animal embryos, which gives rise to nervous tissues and outer later of the integument), the endoderm (inner primary tissue layer of animal embryos, source of the inner gut lining and the organs derived from it), and the mesoderm (primary tissue layers give rise to many internal organs and part of the integument; pivotal in the evolution of large, complex animal s). Their body size depends on the surface area to volume ratio. Microvilli help maintian a good ration because of the slender extensions from the free surface of certain cells that increase the absorptive or secretory surface of a cell. In large-bodied animal s, usually use a circulatory system (not diffusion) through the use of a muscular heart which pumps blood throughout the body. The advantages of all of these are the organs, the epithelial layers and the feeding. There are however clues from chanoflagellates. They have flagella and share an ancestor with sponges along witht he signaling molecules and adhesion proteins. Many consider this the concept of “colonial theory.”  Vertebrates contain a backbone while invertebrates do not contain a backbone. Many are symmetrical. They have a polarity which means the body has a frond-to-back axis with an anterior or leading end and a posterior (trailing) end. There are two types of symmetry: radial and bilateral. Radial symmetry is when an animal's body plan with four or more roughly equivalent parts around an anterior-posterior axis. These types of animals live in water. On the other hand, there is bilateral symmetry which means the body plan in which the main axis divides the body into two halves that are mirror images of eachother. Additionally, there is a ventral surface which is the underside of the animal while the dorsal surface is the backside. Gut and Body model has a sac with 1 opening or tube with 2 openings. If there is an incomplete digestive system, it has a sac like gut. In a complete digestive system, it is called a tubular gut which means there are openings at two ends. Here are some examples. Protostomes are a bilateral animals of a lineage characterized in part by events of embryonic development, as when the second indentation to appear on the early embryo's surface becomes the mouth (anus first). Mitotic divisions in the embryo occur parallel and perpindicular to the body axis. The coelem forms from pouches the develop from the sides of the gut. Deuterostomes include echinoderms, a radial invertebrate with some bilateral features and calcified spines or plates on the body wall (ex- sea star) and chordates. They have a unique body cavities. For instanse, the coelom between the gut and body wall which is lined with peritoneum and the peritoneum which is a tissue lining that also encloses organs in the cytoplasm and helps hold them in place. The pseudocoel is a false coelom, a main body cavity incompletely lined with tissue derived from mesode. Furthermore, the repeating units/complexity allows for segmentation of animal body plans, a series of units that may or may not be similar in appearance. This however depends on the types of organisms and the regional specialization. of a branching lineage characterized partly by events in embryonic development, as when the first indetation to form on the early embryo's surface becomes a mouth (and the second becomes an anus) (ex- annelids, mollusks, arthropods). Also, as the embryo is developing, mitotic divisions occur oblique (at an angle) to the body axis. The coelem forms in the midsection around the developing gut. These are flatworms,mollusks, annelids, roundworms, and arthropods. On the other hand, deuterostomes, a bilateral  Sponges are successful yet simple invertebrates which are common in reefs and costal waters. Amost all known species live in salt water, and the others live in fresh water. Sponges have many unique characteristics which include no symmetry(no central axis or an axis down the middle that divides them into identical parts), no epithelial/connective tissue(simply have two linings of flattened cells, between which unspecialized amoeba-like cells live in a gelatinous substance), no organs, shape can be flattened, sprawling, lobed, compact, tubelike, or vaselike. Sponges have skeletal elements such as tough protein fibers which provide support to the sponge body and sharp spicules of calcium carbonate or silica that resemble glass discourage predators from eating the sponge. Sponges can also be homes for many other animal s, presumably providing protection. Sponges are very simple in which they have no tissue or organs.They ingest their food by the use of collar cells which are cells with "collars" that serve as food trapping structures and edible substances get trapped the the flagella and are engulfed. The cells lining the inner chambers of the sponge have fine structures called microvilli, which are interconnected and form a web to catch food. Food must be taken into individual cells by phagocytosis. Thus, sponges are not very thick and have a lot of surface area because they must rely on individual cells digesting food. They can reproduce either sexually or asexually. When they reproduce sexually, they release sperm into the water and retain fertilized eggs and embryos. In the larval stage, the immature stage of many animals which grows into an adult, the larval sponges swim. When sponges produce asexually, they use fragmentation which is when small fragments break away from the parent sponge and grow into new sponges. They also employ gemmules which are clusters of sponge cells which form a hard covering around others and wait until conditions are right to establish a new colony. As a defense system, they use glasslike structural elements that make sponges distasteful. On the other hand, Placozoans are an asymmetric, soft-bodied <span style="color: white; background-color: rgb(80, 204, 197);">animal with two simple tissues around a thin inner matrix. There is only one species: Trichoplax adharens. They are marine animals which have 2 layers of several thousand cells<span style="color: white; background-color: rgb(80, 204, 197);">. In physical appearance, they have an asymmetrical soft body that is shaped like pita bread. They ingeset their food by using gland cells in the lower layer secrete digestive enzymes onto food then individual cells absorb the breakdown products. <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Cnidarians have many distinctive characteristics such as radial symmetry, tentacles, and no organs. They produce nematocysts which are capsules with tubular threads that can be discharged. Cnidarians are anthozoans which are sea anemones and their kin. Their body plans are as follows. They have a sac-like gut which is called the gastrodermis. There are two types: medusa and polyp. The medusa float and look like bells or saucers while the polyp are tubelike have tentacle-ringed mouths. They employ epithelia, which is <span style="color: white; background-color: rgb(80, 204, 197);">animal tissue covering external and internal body surfaces. This favors larger, more complex bodies because the cells start to interact as functional units. Some refer to this as the nerve net: nerve cells and contractile cells. The mesoglea of cnidarians are a gelatinous matrix with scattered cells between the epidermis and the gastrodermis. They function as a buoyant, deformable skeleton. They use a reproduction hydrostatic skeleton which fluid filled cavity or cell mass against which contractile cells can act. Their gonads rupture to release gametes. Later on, they are planulas which are a type of swimming or creeping larva that usually has ciliated epidemal cells. Flatworms are the simplest existing animals with organ systems. There are over 20,000 species of flatworms, and their organs form three primary tissue layers (the ectoderm, endoderm, and mesoderm). They have a branching gut, which is connected to a pharynx that is a muscular tube between the mouth and gut that sucks up food and expels waste - this is the flatworm's digestive system. In addition to this, they have nervous system, a water regulating system, and a reproductiver system (through which they sexually reproduce); however, flatworms are usually hermaphroditic and contain both male and female gonads, in addition to a penis. These animals have no coelom. <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"><span style="font-size: 7pt; color: black; font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal; font-size-adjust: none; font-stretch: normal;"> The majority of flatworms are parasitic flukes, tapeworms, and free-living turbellarians. Parasites feed on tissues of hosts, but do not kill them immediately. In immature stages, they live in intermediate host(s), but they mature sexually in a definite host. Turbellarians manily live in the sea; some live in fresh water, and one of the planarians lives on land. They suck juice from injured or dead animals and ingest tiny ones. The head has light-detecting eyespots, and a ganglia (a cluster of nerve cells that can integrate communication signals). Planarians can reproduce asexually by transverse fission; if a planarian is chopped off (similarly to a worm), parts can then grow back. The protonehpridia is a system of tiny tubes that control water and solute levels, by extending from pores and collecting excess water. Flukes' life cycles require from one to up to four different kinds of hosts, and has both sexual and assexual phases. First, the blood fluke grows and matures in human hosts; the fertilized eggs exit in feces and hatch as swmiming larvae. This larvae burrow into aquatic snails and assexually divide. Swimming larvae develop, and enter into the skin of a human host. Then the cycle restarts. This parasite requires standing water for its larvae as well. Tapeworms' ancestors probablhy had a gut and a mouth, but they no longer have these after evolving in a habitat that is rich of predigested food in vertebrate's intestines. Tapeworms latch onto the intestinal wall with hooks called a scolex; nutrients diffuse across the tapeworms body wall. Larvae initially get into a host because of undercooked/raw beef or fish. Proglottids bud behind these scolexes - these are hermaphrododitic, and produce sperm which transfer between one another, into eggs. Older proglottids, which are generally farther from the scolex, store fertilized eggs. Fertilized egs survive months before reaching an intermediate host. <span style="font-size: 7pt; color: black; font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Roundworms (Nemotoda) are some of the most abundant animals on earth that live in saltwater, freshwater, topsoil, and other animals. They have cylindrical bodies that taper off at both ends. Roundworms came from the bilateral branch of the evolutionary tree and as such, have bilateral features. They have a false coleom packed with reproductive organs and their bodies are covered by a cuticle, a tough, protecive, and flexible body cover. Roundworms are the simplest animals with a complete digestive system. Many are parasitic and live inside the human body as well as the bodies of other animals. Most of these parasites are harmless or even beneficial; however, some can cause painful, sometimes fatal diseases, such as trichonosis.
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Origins of <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Animal ****s**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Basic Body Plans**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Sponges and Placozoans**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Cnidarians**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"><span style="font-size: 7pt; color: black; font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal; font-size-adjust: none; font-stretch: normal;"> ** Flatworms **
 * Roundworms**

Annelids are a group of 12,000 species that include polychates, leeches, and eoligochaetes. Annelids have the most segments of existing animals. All segments havde clusters of chitin-reinforced bristles called chatae or setae (this is not present in leeches). Bristles are used for traction, in order to allow crawling and burrowing. Species show that their environments favored increased size, complexity of internal organs, and specialized tasks for segments. Earthworms have flexible cuticles that are permeable enough for gas exhange - meaning ti cannot conserve body water. There are about 150 coelomic chambers, each having musclse, nerves, blood vessels, and other organs. Through these chambers extends the digestive system; the muscular pharynx squeezes moist soil into the gut. Earthworms eat its own weight in detritus (decaying particles of organic matter) in a single day. Earthworms also aerate the soil. Earthworms have closed circulatory systems with multiple hearts - contraction of the heart and blood vessels keeps blood flowing in one direction. Earthworms also hold a fused pair of ganglia in their heads. Two nerve cords connect to their "brain" which extend through the length of the body for internal communication. This allows for signals from the brain to erach and coordinate bodily activities. An organ system also helps control the composition and volume of coelomic fluids. Units, called nephridia, collect excess fluid in a funnel - this fluid drains into a tube, and then enters a small bladder, delivering it to a pore at the body surface of the next segment in line. These coelomic chambers are a hydrostatic skeleton - they interact with muscle layers and setae (the bristles). Waves of contraction that pass down the body allow for circular muscles to contract and distribute coelomic fluids - this allows the body to shorten and widin, making the setae plunge and tract into the soil. Elongation allows the body to move forward.
 * Annelids and Segmentation**


 * Rotifers**

Rotifers are bilateral, cephalized predators of bacteria and microscopic algae. Rotifers come from the same bilateral ancestry branch of the evolutionary tree as roundworms and flatworms. They have a false coelom,a complete digestive system, and no circulatory or respiratory organs. Near the head, rotifers have crowns of cilia as well as clusters of nerve cells that integrate and control their body activities. The cilial structures help with swimming and feeding and are a feature unique to rotifers. Some have "eyes" that are really clusters of absorptive pigments. Rotifers have two toes that excrete substances which allow them to attach to substrates in order to feed. They are small organisms, most being less and a millimeter long and about ninety-five percent live in fresh water. Many species are entirely female and produce diploid eggs that grow into diploid females. Males form occaisionally when females produce a haploid egg which grows into a haploid male. When a male fertilizes a haploid egg, it grows into a female. The few males that do exist are dwarfed and short-lived. Mollusks are bilateral, soft-bodied animals. They have a compete digestive tract, an open circulatory systems, as well as a reduced coelem,but are most specifically characterized by their mantles. Mantles are skirtlike body extensions that drape over themselves. Many also have shells. Those mollusks that have heads also have eyes and tentacles. Radulas are a toothed organ at the beginning of the digestive systems of mollusks that scrape and cut food. The gills of mullusks have large surface areas and contain thin-walled leaflets. <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Within mollusks are a few distinct groups. Gastropods are a type of mollusks that include many different types of snails. They have a single "foot" which is used for motion. Gastropods are also characterized by the process of torsion. Torsion is the process by which the mantle is rotated 180 degrees in th larval form. This results in the anus being located close the the mouth. Chitons, on the other hand, are slow moving or completely sedentary. They have shells made up of eight overlapping plates. Bivalves, which includes clams and oysters, have two-plated shells. Cephalopods are characterized by their speed and intelligence. They achieve propulsion by pump water through their siphons (extensions of the mantle) at a fast rate. This trait originated when fish, which are better designed for swimming, became competitors with Cephlopods for the same food. Their nervous systems are perhaps the most complex of the invertabrates and their brains are bigger than those of bivalves and gastropods.
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Pliable Mollusks**

The mollusks that have shells use them mostly for defense (to defend their soft bodies from predators). Bivalves can hide themselves form predators by burying themselves under sand and feed by simply raising their pair of siphons, which are extensions of the mantle.

<span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"> The groups arthropod includes many diverse organisms. Arachnids, insects, and crustaceans are all arthropods. Arthropods are characterized by their hardened exoskeleton covering their segmented bodies. Because their bodies are covered by this hard layer of exoskeleton, they must have jointed appendages in order to remain mobile. Thus, they have protection against predators and can still move. However, because their exoskeleton does not grow (an their bodies do) they must molt periodically. This means that an old exoskeleton is shed while a new one is nearly finished being hardened underneath. This process continues throughout the animals life until it reaches full size. In addition, arthropod larvae are usually very different than their adult forms because they undergo a metamorphosis in order to <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">turn into their adult form. Think about caterpillars making cocoons and changing into butterflies. <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Arachnids are eight legged arthropods of which some are harmful such as the brown recluse and the more well known black widow. Spiders and relatives are Chilicerates (1st pair of feeding appendages). Some examples include the Horseshoe crab, Arachnids, Spiders ,Scorpions, Ticks, Chigger mites. They all have 4 pairs of legs (horseshoe crabs have 5). Scorpions, although not spiders, are arachnids and are the only arachnids that bear live young. Spiders and scorpions are efficient predators. They have an open circulatory system with a heart that pumps blood directly into body tissues, with segmented forebody and hindbody,silk gland and spinners for producing a web and egg cases and book lungs which are thin, moist sheets for diffusion. The tiny pests ticks and mites are also included in arthropoda. They attach to a host and can pass on diseases such as lyme disease or can lead to infection. Insects are all arthropods. Some, including mosquitos, are major vecotrs for pathogens in both humans and other animals. Diseases such as malaria, yellow fever, dengue fever, and west nile are contracted through mosquitos.<span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
 * **<span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Arthropod Diversity **
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Unwanted arthropods:

Crustaceans are animals that live mostly in marine habitats and have a hard yet flexible "crust". They must molt and shed this exoskeleton in order to grow larger. Molting is an integral part of a crustacean's life cycle. In the case of a crab, a female carries fertilized eggs until they hatch into larvae. A larva molts five times before it becomes a young crab which must molt many times before growing into a mature crab. Perhaps the most familiar examples of crustaceans are crabs, shrimp, lobsters, and barnacles, with lobsters and crabs being some of the bigger species of crustaceans. They have segmented bodies with many having between sixteen and twenty segments and other with more than sixty segments. Crabs and lobsters have a dorsal cuticle that covers some or all of their segments. Barnacles have a calcified shell which they use for protection. Simple crustaceans resemble their annelid ancestors with similar appendages running along most of their bodies. The more complex structures, such as lobster claws, evolved over time. In this case, claws would be used to feed, intimidate other animals, and burrow. In addition to these structures, crayfish, crabs, lobsters, shrimps, and other related species have five pairs of walking legs, jaw-like appendages, and antennae. Millipedes and centipedes are two other types of segmented organisms. They are famous for their many legs. However, millipedes do not really have a thousand legs as their name suggests (most have about 100 pairs) and centipedes usually have between fifteen and 177 pairs of legs. There are a staggering number of species that are easily diversified. They have an anatomy that consists of a complete digestive system<span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"> that has Malpighian tubules, one of many small tubes that that help insects on land dispose of toxic wastes without losing body water. When they undergo metamorphosis, it is their life cycle which is success of wings vs. no wings. Echinoderms are spiny-skinned with interlocking spines and they have radial with some bilateral features. They have a very complex anatomy with an Echinoderm body wall bears a number of spines, spicules, or plated made rigid with calcium carbonate and a very well developed internal skeleton. They also have a decentralized nervous system and no brain. They also have tube feet which consist of a water vascular system that includes a main canal in each arm. Short side canals extend from them and deliver water to the tube feet. This causes the tube-foot to lengthen. They have predatory behavior such as a sea star which can push stomach out of body to engulf prey.

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 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">//__Glossary__// - List of new chapter terms
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"><span style="color: white; background-color: rgb(80, 204, 197);">**animal** **s**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**any multicelled heterotroph that ingests other organisms or their tissues, develops through a series of embryonic stages, and is motile during at least part of its life (most have epithelial tissues and extracellular matrixes)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**annelids**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**an invertebrate, a segmented worm (ex- oligochaete, leech, or polychaete)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**arthropods**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**bilateral <span style="background-color: rgb(80, 204, 197);">animal s that have a hardened, jointed exoskeleton, specialized appendages, complete gut, reduced coelom, and and open ciruclatory system**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**bilateral symmetry**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a body plan in which the main axis divides the body into two halves that are mirror images of eachother**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**cephalization**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**during evolution of most <span style="color: white; background-color: rgb(80, 204, 197);">animal, the increasing concentration of nerve cells and sensory structures at the anterior end of the body**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**cephalopods**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**soft bodied mollusk with a closed circulatory system, moves by jet propulsion of water from a siphon (ex- squid, octopus, chambered nautilus)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**choanoflagellates**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**single-celled eukaryote with a microvilli collar around a single flagellum at their anterior end (sister taxon of <span style="color: white; background-color: rgb(80, 204, 197);">animal s and fungi)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**cnidarians**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a type or radial invertebrate having ephithelial tissues and a saclike gut, only <span style="color: white; background-color: rgb(80, 204, 197);">animal that makes nematocysts**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**coelom**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**between the gut and body wall, a cavity lined with peritoneum**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**connective tissues**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**most abundant type of <span style="color: white; background-color: rgb(80, 204, 197);">animal tissue**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**detritus**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**decaying particles of organic matter (eaten by some annelids like earthworms)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**deuterostomes**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a bilateral <span style="color: white; background-color: rgb(80, 204, 197);">animal of a lineage characterized in part by events of embryonic development, as when the second indentation to appear on the early embryo's surface becomes the mouth (anus first)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**echinoderm**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**one of the protosomes, a radial invertebrate with some bilateral features and calcified spines or plates on the body wall (ex- sea star)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**ectoderm**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**first formed, outer primary tissue layer of <span style="color: white; background-color: rgb(80, 204, 197);">animal embryos, gives rise to nervous tissues and outer later of the integument**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Ediacarans**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**one of a diverse collection of tiny, multicelluar precambrian species with a highly flattened body, sometimes with many unspecialized sections**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**endoderm**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**inner primary tissue layer of <span style="color: white; background-color: rgb(80, 204, 197);">animal embryos, source of the inner gut lining and the organs derived from it**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**epithelium**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"><span style="color: white; background-color: rgb(80, 204, 197);">**animal** **tissue covering external and internal body surfaces; favors larger, more complex bodies; cells start to interact as functional units**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**exoskeleton**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**an external skeleton (ex- a hardened cuticle)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**flatworms**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**one of the simlest existing <span style="color: white; background-color: rgb(80, 204, 197);">animal s with organ systems that form from three primary tissue layers**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**ganglia**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**distinct cluster of cell bodies of neurons**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**gut**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a sac or tube in which food is digested**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**larva**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**an immature stage between the embryo and the adult in the life cycle of many <span style="color: white; background-color: rgb(80, 204, 197);">animal s**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**malpighian tubule**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**one of many small tubes that that help instecs on land dispose of toxic wastes without losing body water**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**mantle**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a tissue draped over the visceral mass of mollusks**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**mesoderm**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**primary tissue layers give rise to many internal organs and part of the integument; pivotal in the evolution of large, complex <span style="color: white; background-color: rgb(80, 204, 197);">animal s**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**mesoglea**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**of cnidarisans, a gelatinous matrix with scattered cells between the epidermis and the gastrodermis; functions as a buoyant, deformable skeleton**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**metamorphosis**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**major changes in body form of certain <span style="color: white; background-color: rgb(80, 204, 197);">animal s; hormonally controlled growth, tissue reorganization, and remodeling of body parts leads to adult form**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**microvilli**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**slender extensions from the free surface of certain cells; increas the absorptive or secretory surface of a cell**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**mollusks**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**only invertebrate with a mantle draped over a soft, fleshy visceral mass; most have an external or internal shell (ex- gastropods, bivalves, cephalopods)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**molting**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**periodic shedding of worn-out or too-small body structures; permits <span style="color: white; background-color: rgb(80, 204, 197);">animal to grow in size or renew parts**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**nematocysts**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a fluid-filled, jack-in-the-box capsule housed in one of three types of sensory-effector cells in cnidarians; has microreceptor projecting above the cell surface and a dischargable, tubular thread, often with barbs or toxin-drenched**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**nephridia**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**water regulating unit that helps control the composition and volume of fluid tissues in invertebrates**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**organ**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**body structure with definite form and fuction mad of more than one tissue**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**organ system**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a set of organs that are interacting chamically, physically, or both in a comon task**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**parasite**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**oraganism that withdraws nutrients from a living host, which it usually does not kill outright**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**pharynx**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a muscular tube (used by invertebrates for filter-feeding and respiration)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**placozoans**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**an asymmetric, soft-bodied <span style="color: white; background-color: rgb(80, 204, 197);">animal with two simple tissues around a thin inner matrix**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**polarity**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**the body has a frond-to-back axis with an anterior or leading end and a posterior (trailing) end**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**proglottid**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**one of many tapeworm body units that bud behind the scolex**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**protostome**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**bilateral <span style="color: white; background-color: rgb(80, 204, 197);">animal of a branching lineage characterized partly by events in embryonic development, as when the first indetation to form on teh early embryo's surface becomes a mouth (and the second becomes an anus) (ex- annelids, mollusks, arthropods)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**pseudocoel**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**false coelom, a main body cavity incompletely lined with tissue derived from mesoderm**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**radial symmetry**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"><span style="color: white; background-color: rgb(80, 204, 197);">**animal** **body plan with forur or more roughly equivalent parts around an anterior-posterior axis**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**rotifers**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**bilateral, cephalized <span style="color: white; background-color: rgb(80, 204, 197);">animal with a false coelom and a crown of cilia**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**segmentation**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**of <span style="color: white; background-color: rgb(80, 204, 197);">animal body plans, a series of units that may or may not be similar in appearence**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**sponges**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**structurally, the simplest existing <span style="color: white; background-color: rgb(80, 204, 197);">animal ; its asymmetrical body has a spicule-reinforced matrix in two cell laters (not epithelium); its phagocytic collar cells trap food in water flowing through the pores in its wall**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**tentacles**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**long, flexible, prey-capturing extensions of an <span style="color: white; background-color: rgb(80, 204, 197);">animal body (in cnidarians like jellyfish)**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**torsion**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**a drastic twisting of the body, including teh visceral mass, as cerain moluscan embryos develop**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**water-vascular system**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**of echinoderms, a system of tube feet connected to canals, though which contolled water flow can extend the feet in coordinated ways**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Sources:**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**//Biology:// //The Unity and Evolution of Life 11th Edition//, Starr and Taggart**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**//Biology:// //The Unity and Evolution of Life 10th Edition//, Starr and Taggart**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Cliffs AP: AP Biology 3rd Edition, Phillip E. Pack, Ph.D**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**1. Image: Body Plan of a Mollusk - http://static.howstuffworks.com/gif/octopus-mantle.jpg**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Initial Outline Collaborated By:**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Ruchit Rana**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Angie Yu**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Chas Roberts**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Andrea Rahardja**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Expanded Outline Collaborated By:**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Rebecca Matyas**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Alan Sosteck**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Heather Golgart**
 * <span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">**Megan Yociss**
 * **Final Draft Collaborated By:**
 * **Connor Ryan**
 * **Arnav Kejriwal**
 * **Andy Smith**
 * **Jake Golman**