Segmented Worms

• Annelida means “little rings” which is fitting because the bodies of the annelida are divided into similar rings or segments. 
• Although most of the annelids live in salt water, the earthworm is the most common from this phylum. 
• Like roundworms, these have an anus. 
• Along the ventral and lateral surfaces of the earthworm are setae (tiny bristles, four pairs to each segment) that can be retracted into the worm’s body. The worm moves by means of its setae and two muscular layers - a circular layer that makes the worm longer and thinner when contracted and longitudinal to make it shorter and thicker when they contract. Uses the setae as an anchor. 
• Nutrition: 
• Feeds on vegetation refuse and decayed animal matter in the soil. The worm sucks the soil in with its pharynx. It is moved to the gizzard where the food is ground into small pieces. Then moved to the intestine where enzymes break down the food. The nutrients are absorbed by blood circulating through the walls of the digestive tract as it moves through the intestine and out the anus.
• Circulation, Respiration, and Excretion
• The earthworm is the first animal we see with a circulatory system. In this case it is a closed system. It involves a series of vessels containing blood. It has two major vessels, the ventral and dorsal blood vessels. Near the mouth, there are five pairs of thickly muscled vessels called aortic arches that connect the dorsal and ventral blood vessels. These arches help regulate blood pressure.
• There are tiny vessels that bring oxygen absorbed through the epidermis to the rest of the tissues through its circulatory system. The earthworm has a protective cuticle that must be kept moist to allow to permit the passage of oxygen through it, but it can also suffocate if submerged in water, such as during a rain storm.
• To excrete waste, each segment of the worm except for the first three and the last, have nephridia, tubes that filter waste from the blood and expel them through small openings on the animal’s side called nephridiopores. 
• Nervous and Reproductive Systems
• The “brain” of the worm is actually a pair of ganglia, a mass of nervous tissue.
• A double ventral nerve cord extends from the large ganglion to the end of the worm. Along this cord are smaller ganglia, one for each segment of the earthworm.
• Earthworms are sensitive to light, touch, and certain chemicals. They do not have sensory organs, but they have sensory cells distributed all over their body.
• Earthworms prefer to reproduce sexually, although some species can regenerate.
• The earthworm is hemaphroditic. Their male and female sex organs are located in separate segments. 
• In sexual reproduction, like the flatworms, there needs to be cross-fertilization. 
• Some earthworms live to be several years old!

Roundworms

• These are tiny cylindrical worms usually less than 2.5 cm long. But even though they are small, they are plentiful. One shovelful of water could contain a million roundworms. They live in practically all environments and every living thing. 
• They also can live in places where nothing else likes to live such as the arctic, hot springs, mountaintops, and deep parts of the ocean. They are super durable, the most durable of the animal kingdom.
• Specific roundworms like specific hosts. 
• A Typical Roundworm: Ascaris
• The body structure is basically a tube within a tube. Epidermis and cuticle (non-cellular secreted by the epidermis)
• This is the first phylum we have seen that has an anus.
• Ascaris is supported primarily by the organs and the fluid that fills the space between the two tubs. 
• It only possess longitudinal muscles, so it moves in frantic thrashing motions.
• It feeds on digested food matter found in its host’s intestine. It sucks food into its digestive tube where it is absorbed. 
• Respiration and circulation are accomplished on a cellular level. 
• Roundworms reproduce only sexually, but they are the first type of worm we have seen that has specific males and females. The female lays eggs at a rate of 200,000 a day and are egested daily in the host’s feces. 

Flatworms

• The most obvious characteristic that separates this phylum from the other worm pula is that they are flat.
• Some are free-living, but most are parasitic and live on or within other animals.

Free-living Flatworms: The Planarians

• These flatworms usually live in freshwater lakes and streams. They may be black, brown or white. 
• Their body is essentially a strip of flat tissues about a centimeter long that ends in a triangular point.
• This point is the head. There are eyespots on the dorsal side. They do not focus on objects, but are sensitive to the presence and direction of light.
• There are three layers of cells: 
• Epidermis: protection from environment
• Mesoderm: it is similar to the mesenchyme and mesoglea, but this time instead of being an acellular jelly, it is composed of cells. Many of the different organs develop from the mesoderm.
• Gastroderm: lines the digestive tract.
• Movement: 
• Planarians must seek and capture food.
• Able to do locomotion
• Special cells on the ventral surface enable it to move by secreting a layer of slime. Then ciliated cells propel the flatworm over the slime.
• Support: 
• The three layers of cells provide support
• Protective body covering:
• Epidermis
• Nutrients: 
• Usually feed by scavenging pieces of decayed animals or plant matter and eating small organisms when they can catch them
• Their mouth is located on the ventral surface (only one opening for ingestion and excretion)
• A muscular, tubelike pharynx is extended through the mouth where it sucks up food into the intestine. There it is broken down with enzymes. It is then diffused through the body. 
• Excretion/Circulation:
• Any indigestible food that remains in the intestine is egested through the pharynx.
• The cells also excrete waste by diffusion. 
• A system of tubules that extends throughout the planarian’s mesoderm, connected to flame cells, or hollow bulbs containing cilia that beat vigorously to maintain a current, carry waste to excretory pores to be released into the environment.
• Respiration:
• Flatworms have a thin body and therefore do respiration on a cellular level through diffusion.
• Response:
• Flatworms have an elaborate nervous system. 
• They have a mass of nerve tissue that coordinates responses to the environment, control the eyespots and sensory glands that allow them to taste, smell, and touch. 
• There are two longitudinal nerves that extend from the brain down the length of the animal. 
• A number of transverse nerves unite the longitudinal nerves in a ladder-like pattern.
• Reproduction:

• Asexual: regeneration
• Sexual:
• All planarians are hermaphroditic, or have both sets of sexual organs. But they always cross-fertilize. After mating, each will release several fertilized eggs enclosed in a capsule. The capsule then attaches to a rock or plant in the water.
• Larval stages

Parasitic Flatworms

• A parasite feeds off its host, often harming the host. 
• There are some big differences between the free-living flatworms and the parasitic type because they do not need to same things for survival. Parasitic flatworms have:
• Few sensory organs in adults
• No external cilia in adults
• A thick tegument (protective body covering)
• Suckers or hooks or both for attachment to the host. 
• There are two main groups: the flukes and the tapeworms

The Flukes

• The sheep liver fluke is a great example. 
• As an adult it inhabits the liver of sheep or other grazing animals, causing a disease known as “liver rot.” 
• The anatomy is very similar.
• The fluke feeds by sucking the tissue and fluids of the host into its mouth through the pharynx. 
• The adult produces eggs, which pass through the she eps feces. The eggs hatch in water, releasing ciliated larvae, which enter particular species of snail. The snail becomes the intermediary. 
• While in the snail, the fluke undergoes a series of changes while reproducing asexually. 
• Eventually the fluke leaves the snail and attaches to vegetation. The sheep eats the plants and then the fluke is in the sheep again. 

Tapeworm 

• Bears little resemblance to the flukes.
• The pork tapeworm is a human parasite, living in the intestines of humans. 
• The tapeworm has a ribbon-like segmented body with suckers and hooks. It has no mouth or digestive organs. It simply absorbs the already digested nutrients in the host. 
• The tapeworm’s tegument protects it from the digestive juices.
• Most of the tapeworm’s energy is dedicated to reproduction. Each segment of the tapeworm contains both female and male reproductive organs. This means that each segment produces, fertilizes and stores the eggs. Once mature, the segment, containing 1000s of eggs, detaches and is egested with the feces. 
• If a pig eats one of these segments, the tapeworm will burrow into its muscle and wait for an unsuspecting human to eat the pig. If the pork is not completely cooked, the human will ingest the tapeworm and the cycle starts all over again. 

Phylum Cnidaria: Hydras, Jellyfish, Coral, and Sea Anemone

• Cnidarians have to basic forms (which both have radial symmetry)
• Polyp: cup-shaped, tubular cnidarian with a mouth and tentacles at one end and a sticky basal disk for attachment at the other.

Polyp form

• Medusa: has an expanded bell-shaped body and swims freely.
• It contracts and relaxes its body, gliding through the water in jerky upward motion. 

Medusa form



• Even though, some only exist as either a polyp or medusa, many have both polp and medusa stages in their life cycle.
• Cnidarians are divided into three different classes:
• Hydrozoa (Hydras)
• Sycphozoa (Jellyfish)
• Anthozoa (Cora and Sea Anemone)

Hydras (Class Hydrozoa)

Hydra

• Hydra are a small freshwater cnidarian commonly found in quiet lakes and ponds.
• They are often white, green, or brown. Some hydras are green because they ingest algae which produces sugars which the hydra then uses as food. 
• Structure
• Hydra polyp form is a hollow tube with a single opening (or mouth). All cnidarians only have one opening with functions for both ingestion and excretion. 
• Long, movable tentacles, which the hydra uses to catch food, surround the mouth. 
• Like porifera, the hydra has two layers of cells separated by a jelly-like layer. 
• Epidermis, mesoglea, and gastrodermis (which primarily perform digestion)
• The epidermis and gastrodermis have contractile fibers that contract like muscles, allowing them to bend their body, move their tentacles, and contract into a tiny ball when disturbed.
• They can move by a strange somersaulting motion, but usually remain attached by the sticky basal disk.
• Feeding
• While feeding, the hydra hang limply from its underwater base and allow its tentacles to dangle in the water.
• They have stinging cells called cnidocytes lining their tentacles. They contain poisonous barbs (nematocysts), coiled threads, or sticky substance. 
• When a small invertebrate brush against the tentacles, the hydra releases the nematocysts paralyzing their pray and entangling them with the threads or sticky substance.
• The tentacles draw the prey into their gastrovascular cavity where it is then digested. 

• Excretion and respiration are both done on a cellular level. The waste is excreted directly into the gastrovascular cavity and leaves through the mouth.
• Responses and Reproduction
• Hydra have a nerve net that allows them to dramatically react to stimuli.
• Ex. the tentacle reaction to food or contracting into a tiny ball.
• Hydra use budding and regeneration to reproduce asexually.
• When reproducing sexually, the ovum develops and breaks through the body. Then sperm is released from another hydra and fertilizes the ovum. The hydra is dormant during the winter months and then during the spring, forms a new hydra.

Jellyfish (Class Scyphozoa)

• Free-swimming medusa (dominant form) spurts through the water and feeds upon organisms that bump into its oral arms.
• Sperm released and travels into the gastrovascular cavity of the female, fertilizing the ovum.
• Zygote leaves the cavity through the mouth and clings to the oral arms. When the zygote developes into a larva, it leaves the female and swims away, attaching itself to a base. It becomes a small polyp. After months of storing food and producing new polyps by budding, the body develops into the medusa form.

Corals and Sea Anemones (Class Anthozoa)

• Anthozoa means “flower animals” and includes some of the most beautiful cnidarians.

Coral

• Corals are common in the ocean. The actual coral is a polyp that lives in a self-made skeleton or cup. When not feeding the polyp contracts into the cup for protection. 
• They usually stack themselves on top of each other, making colonies of thousands of polyps. They can stretch for miles.

Sea anemone

• Sea anemones, the “flowers” of the sea, live on the sea floor. They attach to rocks and other submerged objects. 
• They use hydrostatic skeletons for support. It depends on two layers of muscles in the body wall and a fluid-filled interior. As the muscles contract, the water pressure in the anemonoe increase, redistributing the water and causing its body to flex and twist in response. 
• They have tentacles that use nematocysts. Most are not harmful to humans.

Phylum Porifera: the Sponges

Colorful Sponge

For years, scientists argued about whether sponges should be considered plants or animals. It wasn’t until the mid-1800s, when stronger microscopes were made available, that scientists were able to determine, based on cell structure and their development from zygotes to mature organism, that they were in fact animals.

Porifera means “pore bearing.” Sponges act as a pump, drawing water into their bodies through tiny openings called ostia and then expelling it through larger openings called osculum.

Sponges range in size from 1 cm to 2 m across. There are more tan 10,000 different species of sponges, with only 150 species being found in freshwater.

Structure of Sponges

• The walls of sponges generally have two layers of cells that are separated by a thin, jellylike layer.
• The first layer of cells is called the epidermis. This protects the sponge from it’s environment.
• The inner layer of cells lines the cavity of the sponge.
• The jellylike layer is called the mesenchyme. Even though the mesenchyme is not composed of cells, it contains some structures that are very important for the survival and function of the sponge.
• Amoebocytes move freely through the mesenchyme and help to transport food and waste. They are also responsible for the production of spicules which are mineral deposits that provide structure for the sponge. The spicules range in shape from hooks, needles, and barbs. 

Life Processes of Sponges

• The sponge consumes microscopic algae, bacteria, and organic debris. Because the sponge cannot move, it must move it’s environment around it in order to bring the food to it. 
• Collar cells, which line the cavities of the sponge, have flagella that beat the water around it to create a current. The water then enters the ostia, leaving through the oscumlum. 
• The collar cells then engulf the food particles and start digesting it. The food is then transported to the amoebocytes to complete the digestion and transport food through the sponge. 
• Sponges perform excretion and respiration at a cellular level by diffusion. This is possible because the wall of the sponge is very thing, therefor all the cells are close to the environment. 

Reproduction of Sponges

• Asexual reproduction: there are various forms of reproduction in sponges. 
• Budding: a group of cells enlarge and separate from the parent to form a new individual. This is the most common type of asexual reproduction in sponges.
• During periods of cold weather or drought, many freshwater sponges form gemmules. These are cells that are encased and protected in a tough, spicule-reinforced coat. Once the harsh conditions kill the parent, the gemmules survive in a dormant state. When favorable conditions return, the gemmules open and new sponges form.

Gemmule

• Regeneration: a small piece of a sponge can regenerate into a new, complete adult. 
• Commercial sponge growers exploit this remarkable ability. By breaking a living sponge into several pieces and spreading them in beds, they cultivate a large number of sponges in the same area.
• Sexual reproduction: this occurs primarily in the spring.
• Sperm released by one sponge can swim and are carried to another sponge. 
• A sperm enters a collar cell, and an amoeboycyte transfers it to an ovum in the mesenchyme. 
• The zygote develops into a larva, leaving the parent sponge to find a suitable place to attach itself and grow.

Sexual Reproduction

Animal Anatomy and Classification

·         Animals have very different shapes and structures. But we can easily describe this in general terms that identify parts of the animal’s anatomy.

·         Symmetry: A symmetrical organism can be cut into equal halves. Some are asymmetrical which means they cannot be cut into half. There are different types of symmetry depending on how one divides the organism:

o   Spherical symmetry: the organism can be divided into equal halves by a cut in any direction as long as the cut passes through the center of the body. These types of animals have no top, bottom, or sides.

o   Radial symmetry: a body pattern that can be divided into equal halves by a cut made through the center of the animal and along its length.

o   Bilateral symmetry: a body pattern that can be divided into equal halves only by a cut that passes longitudinally (top to bottom) and divides the animal into right and left sides.

·         There are some terms that are common when discussing animal anatomy.

o   Cephalic: concerning the head

o   Caudal: concerning the tail

o   Anterior: towards the front, forward

o   Posterior: towards the rear, farther back

o   Dorsal: on or near the upper surface, back

o   Ventral: on or near the lower surface, front

o   Lateral: on or toward the side

o   Medial: on or towards the middle

o   Midline: divides the right and left

o   Transverse: crosses perpendicular to midline

·         The animal kingdom is often divided into two informal groups: invertebrates and vertebrates.

o   Vertebrates, or animals with backbones, would include animals such as fish, birds, snakes, lions, mice, and elephants.

A baby elephant

o   Invertebrates make up 95% of the different species in Kingdom Animalia. These animals have no backbone and usually keep their soft-bodies inside of a cavity such as clams, lobsters, and insects.

Clams

o   The following is a diagram of the breakdown of Kingdom Animalia.

Characteristics of Kingdom Animalia

·         The study of the kingdom Animalia is called zoology.

·         There are more than a million animal species with new species being discovered every day.

·         It is hard to answer the question “What is an animal?” There are so many different types of animals, from worms to people, cows to jellyfish, etc. Even though there are a lot of differences between different animal species, there are some characteristics that are the same no matter what member of Kingdom Animalia.

o   Movement: Most animals are able to do some type of locomotion to obtain their food, but in the case of animals that are fixed in their location; they move the environment around them.

o   Support: Small animals require less structure than larger animals, but nevertheless, all animals have some sort of support system. Some have their support system on the outside (exoskeleton), such as crabs, lobster, and cray fish, while others have it on the inside (endoskeleton).

The cartilage of a squid

Scorpion with its exoskeleton

o   Protective body covering: This protects the animal from the environment, chemicals, microbes, and predators. It can differ greatly between animals: skin, spines, scales, fur, feathers, shells, poisonous secretions, etc.

Armadillo with protective shell

o  Nutrition: All members of Kingdom Animalia are heterotrophs, meaning they depend on other organisms for their food. There are other kingdoms with heterotrophic members. What sets Animalia apart? All members of this kingdom ingest à digest à absorb their food.

o   Excretion: All animals eliminate the waste that their bodies produce.

o   Respiration: Some animals only have respiration at a cellular level, but others exchange CO₂ for O₂ directly with their environments. The means of obtaining oxygen differs depending on the organism. For example, humans have lungs to obtain oxygen from the air while fish have gills to obtain oxygen from water.

o   Circulation: This is the transport of materials throughout the animal. This helps feed and maintain tissues and organs. If there is no circulation to tissues, they can die or be damaged. Blood or a similar fluid is used to transport these materials in either a closed or open system.

o   Response: The ability to perceive and respond to stimuli in the environment. Except for sponges, all multicellular organisms have nerve cells that make response to their environment possible. Some possess brains that are capable of memory and emotion.

o   Reproduction: While some animals can reproduce asexually, sexual reproduction is a characteristic of the animal kingdom. This involves the union of two gametes to form a zygote. The fertilized zygote then goes through embryonic states as it develops into an independent organism. Some animals have larval stages (not like adult) as they mature. 

Fly larva

Embryonic stages of a human

Welcome Students!

Hello Students,

Welcome to the new blog. This is a place where you can check for class notes, updates, homeworks, extra practice, and pictures of things that we have talked about in class.

Miss Cunningham