KINGDOM ANIAMLIA

Introduction to the animal kingdom:

The animal kingdom is the most diverse in appearance; it includes an incredible diversity of forms and lifestyles. Animals are multicellular, eukaryotic heterotrophs, whose cells lack cell walls. Only 5% of animals have a backbone, meaning that they are vertebrates and the other 95% are invertebrates. In order to survive, all the animals, according to their body plans, have evolved different ways to carry out essential functions:

· Feeding: herbivores eat plants, carnivores feed on other animals, filter feeders are aquatic and strain tiny floating animals and plants from the water around them. Some are detritivores and feed on pieces of decaying plant and animal material called detritus. Others, as parasites and form symbiotic relations.

· Respiration: this means to take in oxygen and give off carbon dioxide. Some animals rely on the diffusion of these substances through their skin, but most of them have evolved complex tissues and organ systems to respire.

· Circulation: animals that are only a few cell layers thick rely solely on diffusion. Larger animals have circulatory systems to move material around their bodies

· Excretion: excretory systems are needed to eliminate ammonia or convert it into a less toxic substance that is removed from the body.

· Response: animals respond to stimuli using nerve cells that in some animals, hook up and form a nervous system. The arrangement of these cells in the body varies from phylum to phylum.

· Movement: Most animals are motile (they can move). Muscles and skeletons enable animals to move around; however some animals live their adult lives attached to a single spot.

· Reproduction: Most animals reproduce sexually by producing haploid gametes, this contributes to genetic diversity and evolution. Other animals, especially invertebrates, reproduce asexually. This kind of reproduction allows animals to increase their numbers rapidly.

 

 This picture shows evolutionary traits and relationships among kingdom animalia's phyla. During the course of evolution that produced these different groups, important traits evolved.

Complex animals tend to have high levels of cell specialization and internal body organization, bilateral body symmetry, a front end or head with sense of organs (cephalization), and a body cavity (development of a coelom)!

 

Phylum Porifera

 

Porifera are divided into 3 classes: Calcarea, Glass Sponges, and Demosponges.  Sponges are multicellular, heterotrophic, have no cell walls and contain few  specialized cells. The movement of water through a sponge provides a simple mechanism for feeding, respiration, circulation and excretion.

Sponges are asymmetrical and its body forms a wall around a large central cavity through which water is circulated continually. Choanocytes are specialized cells that use flagella to move a steady current of water through the sponge, this water enters through pores located in the body wall. Water then leaves thorugh the osculum, a large hole at the top of the sponge. They have a simple skeleton. In harder sponges, the skeleton is made of spiny spicules, which is a spike-shaped structure made of chalklike calcium carbonate or glasslike silica. Spicules are made by archaeocytes, which are specialized cells that move around within the walls of the sponge. Softer sponges have an internal skeleton made of spongin, a network of flexible protein fibers. There are the sponges that are harvested and used as natural bath sponges.
 

Reproduction in porifera

Sponges can reproduce either sexually or asexually. In most sponge species, a single sponge forms both eggs and sperm at different times. In sponges eggs are fertilized inside the sponge’s body, a process called internal fertilization. Sperm is released from one sponge and are carried by water. Archaeocytes carry the sperm to an egg, which is located in the wall of the sponge. After fertilization, the zygote develops into a larva. A larva is an immature stage of an organism. That looks different from the adult form. The larvae of sponges are motile and are usually carried by currents before they settle to the sea floor.Sponges can reproduce asexually by budding or by producing gemmules. In budding, part of a sponge breaks off of the parent sponge, settles to the sea floor, and grows into a new sponge. When faces with difficult environmental conditions, some sponges poduce gemmules which are groups of archaeocyte surrounded by a tough layer of spicules. Gemmules can survive freezing temperatures and drought conditions that would kill adult sponges. When conditions become favorable, a gemmule grows into a new sponge.




Respiration in porifera


Sponges rely on the movement of water though their bodies to carry out body functions. As water moves through the body cavity oxygen dissolved in the water diffuses into the surrounding cells. At the same time, carbon dioxide and other wastes such as ammonia, diffuse into the water and are carried away.

Phylum Cnidaria

They are soft-bodied, carnivorous animals that have stinging tentacles arragend in circles around their mouth. They are the simplest animals to have body symmetry and specialized tissues. Their life cycle typically includes two different- looking stages, a polyp and a medusa.

Cnidarians include jelly fish, sea anemones and corals.

Cnidarian polyps and medusas each have a body wall that surrounds an internal space called a gastrovascular cavity. The gastroderm is the inner lining of the gastrovascular cavity, where digestion takes place. The epidermis is the outer layer of cells. The mesoglea is a layer that lies between these two tissues. It varies from a thin, noncellular membrane to a thick, jellylike material that contains cells

 

 

Reproduction in cnidarians

 

 

Most cnidarians reproduce both sexually and asexually. Polyps can reproduce asexually by budding. The new animal is genetically identical to the parent animal. One type of budding begins with a swelling on the side of an existing polyp. This swelling grows into a new polyp. In another type of budding, polyps produce tiny medusas that separate and become new individuals. In most cnidarians, sexual reproduction takes place with external fertilization in water. External fertilization takes place outside the female’s body. The sexes are usually separate.

 

Respiration in cnidarians

Following digestion, nutrients are usually transported throughout the body by diffusion. Cnidarians respire and eliminate the wastes of cellular metabolism by diffusion through their body walls.

Phylum Platyhelmithes

Flatworms are soft, flattened worms that have tissues and internal organ systems. They are the simplest animals to have three  embryonic germ layers, bilateral symmetry and cephalization.

Tubellarians are free-living marine or freshwater flatworms.

Flukes are parasitic  flatworms  that usually infect the internal organs of their hosts

Tapeworms are long, flat parasitic worms that are adapted to life inside the intestine of their hosts.

 

 

Reproduction in Platyhelminthes:

Most free-living flatworms are hermaphrodite that reproduce sexually. A hermaphrodite is an individual that has both male and female reproductive organs. During sexual reproduction, two worms join in a pair. The worms in the pair deliver sperm to each other. The eggs are laid in clusters and hatch within a few weeks.   Asexual reproduction is common in free-living flatworms. It takes place by fission, in which and each half grows new parts to become a complete organism. In some species, a worm simply “falls to pieces”, and each pieces grows into a new worm. Parasitic flatworms often have complex life cycles that involve both sexual and asexual reproduction.

 

Respiration in Platyhelminthes:

 Because their bodies are so flat and thin, many flatworms do not need a circulatory system to transport materials. Instead, flatworms rely on diffusion to transport oxygen and nutrients to their internal tissues, and to remove carbon dioxide and other wastes from their bodies. Flatworms have no gills or other respiratory organs, and no heart, blood vessels, or blood.

Phylum Nematoda

Roundworms are unsegmented worms that have pseudocoeloms and digestive systems with two openings: a mouth and an anus.

Parasitic roundworms include trichinosis- causing worms, filarial worms, ascarid worms, and hookworms

Reproduction in nematode:

Roundworms reproduce sexually, and most species of roundworms have separate males and females . Roundworms reproduce using internal fertilization. Usually, the male deposits sperm inside the female’s reproductive tract. Parasitic roundworms, such as hookworms or ascarid worms, often have complex life cycles that involve two or three different hosts or several organs within a single host.

Respiration in nematode:

 Like flatworms, roundworms exchange gases and excrete metabolic waste through their body walls. They have no internal transport system. Therefore, they depend on diffusion to carry nutrients and waste through their bodies.

Phylum Annelida

Annelids are worms with segmented bodies, they have a true coelom that is completely lined with mesoderm.

Oligochaetes are annelids that typically have streamlines bodies and relatively few setae compared to polychaetes. Most oligochaetes live in soil or fresh water. Leeches are typically external parasites that suck the blood and body fluids of their hosts.

Polychaetes are marine annelids that have paired, paddle like appendages tipped with setae.

 

 

Reproduction in annelids

Most annelids reproduce sexually. Some species use external fertilization and have separate sexes ( either male or female). Other annelids, such as earthworms and leeches are hermaphrodites, each worm produces both sperm and eggs. Individuals rarely fertilize their own eggs, instead two worms attach to each other and exchange sperm, then store it in special sacs. When eggs are ready for fertilization, a clitellum or band of thickened, specialized segments, secretes a mucus ring into which eggs and sperm are released. fertilization takes place within this ring, which then splins off the worms body and forms a protective cocoon. Young worms hatch weeks later.


Respiration in annelids

Aquatic annelids often breathe through gills. A gill is a filamentous organ specialized for the exchange of gases underwater. Land-dwelling annelids take in oxygen and give off carbon dioxide through their moist skin. These annelids secrete a thin protective cooating of mucus, which keeps their skin moist.

Phylum Mollusca

They are soft bodied animals thata usually have an external or internal shell. The typical mollusk body plan has four parts: foot, mantle, shell and visceral mass.

Gastropods are shell-less or single-shell mollusks that move by using a muscular foot located on the ventral side.

Bivalves have 2 shells that are held together by one or two powerful muscles.

Cephalopods are typically soft- bodied mollusks in which thehead is attached to a single foot, and this is divided into tentacles or arms.

 

 

Like the annelids, mollusks have true coeloms surrounded by mesoderm tissue. They also have complex organ systems that carry out processes such as respiration and excretion.

The body plan of most mollusks has four parts: foot, mantle, shell, and visceral mass. The muscular foot takes many forms, including flat structures for crawling, spade-shaped structures for burrowing, and tentacles for capturing prey. The mantle is a thin layer of tissue that covers most of the mollusk’s body, much like a cloak. The shell is made by glands in the mantle that secrete calcium carbonate. The shell has been reduced or lost in slugs and some other mollusk groups. Just beneath the mantle is the visceral mass, which consists of the internal organs

Reproduction in mollusca

Mollusks reproduce in a variety of ways. Many snails and two-shelled mollusks reproduce sexually by external fertilization. They release enormous number of eggs and sperm into the open water. The eggs are fertilized in the water and then develop into free-swimming larvae. In tentacle mollusks and certain snails, fertilization takes place inside the body of the female. Some mollusks are hermaphrodites, having both male and female reproductive organs. Individuals of these species usually fertilize eggs from another individual.

Respiration in mollusca

 

Aquatic mollusks such as snails, clams, and octopi typically breathe using gills inside their mantle cavity. As water passes through the mantle cavity, oxygen and carbon dioxide diffuse over the surface of the animal’s gills. Land snails and slugs do not have gills. Instead, they respire using a mantle cavity that has a large surface area lined with blood vessels. Because this lining must be kept moist so that oxygen can diffuse across its surface, land snails and slugs typically live only in moist places.

 

 

 Phylum Arthropoda

 

Arthropods have a segmented body, a tough exoskeleton, and jointed appendages.

In many groups of arthropods, continuing evolution has led to fewer body segments and highly specialized appendages for feeding, movement and other functions.

When they outrgrow their exoskeletons, arthropods undergo periods of molting.

Arthropods are classified based on the number and structure of their body segments and appendages, particularly their mouthparts:

Crustaceans typically have two pairs of branched antennae, two or three body sections and chewing moutharts called mandibles.

Chelicerates have mouthparts called chelicerae and two body sections, and most have four pairs of walking legs.

Uniramians have jaws, one pair of antennae, and unbranched appendages.

Insects:

They have a body divided into three parts: head, torax and abdomen. Three pair of legs are attached to the torax.

The growth and development of insects usually involve metamorphosis, which is a process of changing shape and form.

Ants, bees, termites and other relatives form complex associations called societies.

The evolution of arthropods has led to fewer body segments and highly specialized appendages for feeding movement, and other functions.

A typical primitive arthropod was composed of many identical segments, each varying a pair of appendages. Its body probably closely resembled that of a trilobite. This early body plan was modified gradually. Body segments were lost or fused over time. Most living arthropods, such as spiders and insects, have only two or three body segments. Arthropod appendages also evolved into different forms that have different functions.

Reproduction in arthropods

Terrestrial arthropods have internal fertilization. In some species, males have a reproductive organ that places sperm inside females. In other species, the males deposit a sperm packet that is picked up by the females. Aquatic arthropods may have internal or external fertilization. External fertilization takes place outside the female’s body. It occurs when females release eggs into the external environment and males shed sperm around the eggs.

Respiration in arthropods

Most terrestrial arthropods breathe through a network of branching tracheal tubes that extend throughout the body. Air enters and leaves the tracheal tubes through spiracles, which are small openings located along the side of the body. Other terrestrial arthropods, such as spiders, respire using book lungs. Book lungs are organs that have layers of respiratory tissue stacked liked the pages of a book. Most aquatic arthropods, such as lobsters and crabs, respire though organs called book gills.

Phylum Echinodermata

 

Echinoderms are characterized by spiny skin, five part radial symmetry, an internal skeletion, a water vascular system, and suction-cuplike structures called feet.

The water vascular system carries out many essential body functions in echinoderms, including respiration, circulation, and movement.

Classes of echinoderms include sea lilies and feather stars, seas stars, brittlestars, sea urchins, and sand dollars, and sea cucumbers.

 

 

• A unique feature of echinoderms is a system of internal tubes called a water vascular system, which is filled with fluid, carries out many essential body functions in echinoderms, including respiration, circulation, and movement. It opens to the outside though a sievelike structure called a madreporite. In sea stars, the madreporite connects to a ring canal that forms a circle around extend along body segments.

 

• Attached to each radial canal are hundreds of tube feet, these are structures that operate much like a suction cup. Each tube foot has a sucker on the end. Muscles pull the center of the sucker upwards, forming a cup shape. This action creates suction on the surface to which the foot is attached, so the tube foot pulls on the surface. Hundreds of tube feet acting together create enormous force, allowing echinoderms to walk and even to pull open shelled prey as clams.

Reproduction in echinoderms

Echinoderms reproduce by external fertilization. In most sea star species, the sexes are separate. Sperm are produced in testes, and eggs are produced in ovaries. Both types of gametes are shed into open water, where fertilization takes place. The larvae, which have bilateral symmetry, swim around for some time and the swim to the ocean bottom, where they develop into adults that have radial symmetry.

Respiration in echinoderms

Other than the water vascular system, echinoderms have few adaptations to carry out respiration or circulation. In most species, the thin-walled tissue of the tube feet provides the main surface for respiration. In some species, small outgrowths called skin gills also function in gas exchange.

 

 

Phylum Chordata

Chordates are animals that have

(for at least some stage of their life):

• A dorsal, hollow nerve cord: Which runs along the back part of the body. nerves branch from this cord and connect to organs.
• A Notochord: It is a long supporting rod that runs through the body below the nerve cord.Most chordates only have them when they are embryos.
• Pharyngeal pouches: Paired structures in the throat region.
• A tail that extends beyond the anus.

The most known subphylum of chordates is the vertebrata, which is divided into classes:

• class Osteichthyes
• class Amphibia
• class Reptilia
• class Aves
• class Mammalia

There are two subphyla of chordates that don't have backbones:

Tunicates

Lancelets

Tunicates and lancelets are both soft bodied marine organisms. Even though they have a nerve cord, a notochord, pharyngeal pouches and a tail at some stage of their life, they are non vertebrates.

Classification of the Phylum Chordata

Class Osteichthyes

 

Fishes are aquatic vertebrates that are characterized by paired fins, scales and gills. ifns are used for movement, scales for protection and gills for exchanging gases. Fish are very varied

and adaptations to aquatic life include various modes of feeding, specialized structures for gas exchange, paired fins for locomotion, and even more!

 

Reproduction in fishes


The eggs of fishes are fertilized either externally or internally, depending on the species. In many fish species, the female lays the eggs and the embryos in the eggs develop and hatch outside her body. Fishes whose eggs hatch outside the mother’s body are oviparous. As the embryos of oviparous fishes develop, they obtain food from the yolk in the egg. In contrast, in ovoviviparous species the eggs stay in the mother’s body after internal fertilization. Each embryo develops inside its egg, using the yolk for nourishment. The young are then “born alive”, the way the young most mammals are. A few fish species, including several sharks, are viviparous. In this kind of  animals, the embryos stay in the mother’s body as they do in ovoviviparous species. However, these embryos obtain the substances they need directly from the mother’s body, not from material stored within an egg. The young of viviparous species are also born alive.


Respiration in fishes

Most fishes exchange gases using gills located on either side of the pharynx. The gills are made up of feathery, threadlike structures called filaments. Each filament contains a network of fine capillaries that provides a large surface area for the exchange of oxygen and carbon dioxide. Fishes that exchange gases using gills do so by pulling oxygen-poor water out through openings in the sides of the pharynx.

Some fishes, such as lampreys and sharks, have several gill opening. Most fishes, however, have a single gill opening on each side of the body through which water is pumped out. This opening is hidden beneath a protective bony cover called the operculum.

A number of fishes have an adaptation that allows them to survive in oxygen-poor water or in areas where bodies of water often dry up. These fishes have specialized organs that serve as lungs. A tube brings oxygen from the air to this organ through the fish’s mouth. Some lungfishes are so dependent on getting oxygen from the air that they will suffocate if prevented from reaching the surface of the water.

Class Amphibia

An amphibian is a vertebrate that lives in water as a larva and on land as an adult, breathes with lungs as an adult, has moist skin that contains mucus glands and lacks scales and claws ( however there are some exceptions for this). They have adapted for living enterily on land. The word amphibian means "double life" , these animals live both in water and on land. The larvae are fishlike aquatic animals that respire using gills. In contrast , the adults of most species of amphibians are terrestrial animals that respire using lungs and skin.

Reproduction in amphibians:

Amphibian eggs dont have shells and tend to dry out if they are not kept moist. In most amphibians the female lays eggs in water and then the male fertilizes them externally, in other species  like salamanders, eggs are fertilized internally.
When frogs reproduce the male climbs to the females back and squeezes. The female releases as many as 200 eggs that the male then fertilizes. Frogs eggs are encased and sticky, transparent jelly that attaches the egg mass to underwater plants and makes the eggs difficult for predators to grasp. The embryos are nourished by the jelly until they hatch into larvae that are commonly called tadpoles. tadpoles undergo metamorphosis.

Respiration in amphibians:

In most larval amphibians, gas exchange occurs through the skin as well as the gills. Lungs typically replace gills when an amphibian becomes an adult, although some gas exchange continues through the skin and the lining of the mouth cavity. In many adult amphibians the lungs are reasonably well developed; but some lungless salamanders exchange gases through the thin lining of the mouth cavity as well as through the skin.

CLICK HERE TO SEE FROG DISSECTION VIDEO

Class Reptilia

 

 

 A reptile is a vertebrate that has dry, scaly skin, lungs and terestrial eggs with several membranes, which enables them to live their entire lives out of water, unlike their amphibious relatives.

Well developed lungs, a double loop circulatory system, a water-conserving excretory system, strong limbs, internal fertilization, and shelled, terrestrial eggs are the other adaptations that have contributed to the success of reptiles on land. They can also control their body temperature by changing their environments, which means they are ectotherms. 

 

 

Reproduction in reptiles:

 

All reptiles reproduce by internal fertilization, in which the male deposists sperm inside the body of the female. Most male reptiles have a penis that allows them to deliver sperm unto the female cloaca. when fertilization occurs, the embryo is covered with several membranes and leathery shell by the females reproductive system. This " amniotic egg" is one of the most important adaptations to life in land. creates a protected environment in which the embryo can develop without drying out, and is named after the amnion, one of the four membranes that surrounds the developing embryo, the other ones are the yolk sac, the chorion and the allantois.

 

 

 

Respiration in reptiles:

 

The lungs of reptiles are spongy, many reptiles have muscles around their ribs that expand the chest cavity to inhale and collapse the cavity to force air out. Several species of crocodiles also have flaps of skin that can separate the mouth from the nasal passages, allowing these mouth remains open. Usually reptiles have two efficient lungs to exchange gases with the environment, there are certain species of snakes that have just one lung.

 

 

Class Aves

Birds are reptilelike animals and are endotherms, which means they can generate their own body heat;they have an outer covering of feathers and two legs that are covered with scales and   used for walking or perching, and front limbs modified into wings.The ways in which birds carry outtheir life functions, such as obtaining food and oxygen, contribute to their ability to flight. They have a lot of adaptations that enable them to fly. Some of them are:

• HHighly efficient digestive, respiratory and circulatory systems
• Aerodynamic feathers and wings
• Strong chest muscles

 

Reproduction  in birds:

 

Both male and female reproductive tracts open into the cloaca. The sex organs which are internal. As birds preparate to mate, the ovaries and testes grow larger until they reach the functioning size. Mating birds transfer spermform the male to the female by pressing their cloacas together.

Birds eggs are amniotic, they have hard outer shells.Most birds incubate their eggs until the eggs hatch, when a chick is ready to hatchit makes a small hole in the shell and then it brakes open. The newborn chick allows its feathers to dry and its parents take care of it, providing food.

 

 

 

 

Respiration in birds:

 

When a bird inhales, most air first enters large posterior air sacs in the body cavity and bones. Air flows through the lungs and travels in a series of small tubes, which are lined with specialized tissue, where gas exchange takes place. This system ensures that air flows in a single direction, exposing lungs to oxygen-rich air. As an advantage this helps bird mantain their high metabolic rate. This metabolic rate is needed to mantain body temperature and have enough energy for flight.

 

Class Mammalia

Mammals have hair and the ability to nourish their young with milk thanks to the mammary glands present in female mammals. All mammals breathe air, have four chambered hearts and are endotherms, which means they can generate heat internally and is an example of homeostasis.

Other Characteristics:

• Much higher metabolic rate than most other chordates
• External hair and subcutaneous fat
• Sweat glands that help cool the body

Mammals Body Plan and rat Dissection

Reproduction in mammals:

 

When mammals mate, the male deposits sperm inside the reproductive tract of the female and fertilization occurs. Mammals can be classified according to their modes of development and birth, however all new born mammals feed on their mother´s milk.

Oviparous: egg-laying

Viviparous: live-bearing which means the embryos develop within the mother for a while and then are born alive.

 

Respiration in mammals:

 

All mammals use lungs to breathe, these are controlled by two sets of muscles.

Mammals inhale when muscles in the chest lift the rib cage up and outward, at the same time the diaphragm  pulls the bottom of the chest cavity downward,increasing the volume of the chest cavity and pulling air to the lungs. When the chest muscles lower the rib cage, the diaphragm relaxes and the volume of the chest cavity decreases; pushing the air out of the lungs.

Conclusion: Evolution and Increasing complexity In animals

Invertebrate Evolution:

• As animals became larger and more complex, specialized cells joined together to form tissues, organs, and organ systems that work together to carry out complex functions.
• All invertebrates except sponges have some type of body symmetry ( radial or bilateral)
• Invertebrates with cephalization can respond to the environment more quickly than simpler vertebrates.
• Most invertbrates with bilateral symmetry also have segmented bodies, which over evolution have often become specialized for specidic functions.
• Most animal phyla have a true coelom that is lined completel with mesoderm
• Worms, arthropods and mollusks are protostomes, and echinoderms are deuterostomes. 

 
Vertebrate Evolution:

This derived characteristics increased complexity over  the course of evolution of the vertebrates:

• Bilateral symmetry
• Two pairs of jointed locomotor appendages, which can include fins (pectoral and anal/dorsal fins, as well as the forelimbs and hindlimbs)
• Outer covering of protective cellular skin, which can be modified into special structures such as scales, hair and feathers
•  Metamerism found in skeletal, muscular and nervous system. - structures can include ribs, vertebrae, muscles and ganglia/peripheral nerves.
• Well-developed coelom, or body cavity
•  Well-developed internal skeleton
• Cephalization
• Specialized systems ( circulatory, respiratory, reproductive...)

 

For a better view of the charts visit: http://mail.esdnl.ca/~greg_kent/S05937F3B.32/u02_s04_notes_kingdom_animalia.pdf

SOURCES

Miller, K. R., & J. S. Levine (2010) Biology. Pearson Education., chapters 26-30
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/I/Invertebrates.html

TRENDS IN ANIMAL EVOLUTION

This picture shows evolutionary  traits and relationships among kingdom animalia's phyla. During the course of evolution that produced these different groups, important traits evolved.

Complex animals tend to have high levels of cell specialization and internal body organization, bilateral body symmetry, a front end or head with sense of organs (cephalization), and a body cavity (development of a coelom)!