Biology 4 Invertebrates 3 PDF

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INVERTEBRATES* When biologists group animals, they divide them into two categories: vertebrates and invertebrates. The fundamental difference between these two types of animals is that invertebrates to do not have a backbone. But while they do not have a backbone, they have physiological systems which are similar to the vertebrates. They still have to eat, excrete waste, breathe, fight diseases, reproduce, and move. This lesson looks at some of the systems of the invertebrates.

VOCABULARY alveoli

tiny sacs within the lungs which increase the surface available for gas exchange

amylase

a digestive enzyme that breaks down starches and glycogen into sugars

atria

the two thin-walled chambers that receive blood into the heart from the veins

bronchi

the two tubes into which the trachea divide to go into each lung

capillary

a tiny vessel through which diffusion takes place between the blood and the body tissues

ganglia

a mass of nerve tissue not part of the brain

hemolymph

a fluid of lymph and blood that circulates within invertebrates

interferons

protein cells that assist in fighting infection and disease

lymphocyte

type of leukocyte that makes up the specific immunity system; capable of building immunity to a disease

Malpighian tubules

excretory tubules in insects and spiders that empty into the intestine

nephron

the functioning unit of the kidney that produces urine

nephridia

tubes in flatworms and earthworms that excrete waste

phagocyte

type of leukocyte that engulfs foreign material and bacteria; part of nonspecific immunity of an animal

phagocytosis

the process of a cell engulfing its food; literally, "cell eating"

protease

a digestive enzyme that breaks down proteins into smaller polypeptides and amino acids

spiracles

holes that open and close for respiration in insects and spiders

thymus

a gland located in the neck area; aids in the production of lymphocytes

ventricle

the two thick, muscular cavities in the heart that pump the blood

INVERTEBRATE)CIRCULATORY)SYSTEMS) Invertebrate Circulatory Systems The primary functions of the circulatory system are to bring needed materials like food and oxygen to cells and tissues and to remove waste products. As a transport and exchange mechanism to facilitate cellular respiration, it complements external respiration and completes the respiratory cycle. Simple aquatic animals like hydra or jellyfish have a digestive cavity that also conducts its circulation. Most arthropods and some mollusks and tunicates have open circulatory systems. This means that the fluid that transports nutrients and oxygen flows directly in and around internal organs. Other animals, such as echinoderms and vertebrates have a closed circulatory system. These animals have a fluid or blood that is enclosed in vessels for transportation to internal organs and tissues of the body. Arthropods like spiders, lobsters, and insects, certain mollusks like clams and snails, and tunicates have a simple heart that pumps fluid called hemolymph through openended vessels. The hemolymph bathes organs and cavities with nutrients and oxygen and then re-enters the heart through valves The closed circulatory system found in some mollusks like squid and octopus, annelids, echinoderms, and vertebrates has a heart or specialized vessels that pump blood throughout the body in enclosed vessels. The simplest example of a closed system is found in the earthworm. There are two major vessels, one that runs along the topside or dorsal of the body, and one vessel that runs along the bottom or ventral side. Both vessels are connected by capillaries that bring blood to the tissues. The dorsal vessel acts as the pump by contracting and pushing blood throughout the worm's body.

INVERTEBRATE)NERVOUS)SYSTEMS)

Central Nervous System Almost all animals have nerve cells and some type of nervous system or network. Except for sponges, both invertebrates and vertebrates have a nervous system. The simplest of neural networks is found in the cnidarians, like jellyfish. Instead of a brain, these simpler animals have a nerve net which has no structure or central control area. Impulses are transmitted in all directions within the net. Reactions from stimuli are simple, like the retraction of a tentacle. Echinoderms, like a sea star, have a ring-like nervous system. They, too, have no brain, but the nerves in their system are a bit more organized. A nerve, shaped like a ring, surrounds the esophagus, and five other nerves radiate out from it. Many Platyhelminthes, like flatworms, have a nerve net structure. However, the more complex flatworms have a ladder-like nervous system and a simple brain or central control area. From the brain, pairs of nerve cords extend out to the body. These nerve cords are connected in the middle by nerves, resembling a ladder. The simple brain processes incoming and outgoing impulses, but is incapable of conscious thought or emotion. Annelids, like the earthworm, and arthropods, like insects or spiders, have three main structures in their nervous system: a brain, segmented ganglia, and a ventral nerve cord. Similar to the flatworm, a simple brain is located at the head, with one or two nerve cords extending out, but this is a ventral cord, meaning it's located on the bottom or stomach side of the organism. There are also segmented ganglia, or build-ups of nerve tissue at different segments of the animal. Mollusks, like clams and octopus, have varying nervous system structures. A clam, for example, has a ring-like network. The octopus, however, has a large complex brain capable of learning and memory. Their neurons are specialized for quick movements and response to food or threat. The most complex nervous systems, however, are the vertebrates', particularly a human's nervous system..

INTRACELLULAR)DIGESTIVE)SYSTEMS)

Digestion is the process in which food is broken down and absorbed by the body. Digestion can occur within cells (intracellular) or outside of cells (extracellular), or both. Most single-celled protists and sponges conduct digestion intracellularly with the help of lysosomes. In the sponge, food enters the body from the water that flows in through its pores. Collar cells inside the sponge trap food and ingest it by phagocytosis or by the enzymes of lysosomes.

EXTRACELLULAR)DIGESTIVE)SYSTEMS) In more complex animals, extracellular digestion in a digestive system is common. Depending on the animal's complexity and diet, its digestive system and the specialized digestive organs will be more or less complex. For example, flatworms only have one opening to their digestive system: food is taken in and digested and wastes are expelled through the same opening. More complex animals, like birds and humans, have two openings—a mouth and anus—and many other organs that are part of the digestive process.

Digestion occurs mechanically and chemically. Most mammals have teeth to break down foods mechanically by tearing and chewing. In birds and earthworms, a gizzard, containing bits of sand or gravel, is used to mechanically break down food. They also have a crop, which stores and softens food. The muscular stomachs of these animals also help break down food by churning. Throughout the digestion process, food is broken down chemically as well. For example, salivary glands in the mouth produce amylase to break down starches and glycogen; hydrochloric acid and proteases in the stomach help break down proteins. Food churns in the stomach for a while until it is of a soupy texture and then moves to the intestines.

RESPIRATORY)SYSTEMS)

The respiratory system exchanges gases from the internal and external environments of the organism and also works with the circulatory system to oxygenate blood that flows throughout the body. Respiration can occur over skin surfaces, like in earthworms and amphibians. Or respiration can occur using specialized organs. The essential organs that do this are the tracheal system in most insects and spiders, gills in most aquatic animals, and lungs in most land-dwelling animals and mammals. Some spiders and most insects have a tracheal system. Like the trachea or "windpipe" in humans, the tracheal system consists of air-filled tubes that branch out throughout the animal's body. Small holes called spiracles in the exoskeleton can open and close, regulating air flow.

INVERTEBRATE)EXCRETORY)SYSTEMS) The excretory system is the way an animal balances water and salt, and removes metabolic waste. Metabolic waste is different than the waste removed from digestion. Metabolic waste is the waste caused by cellular metabolism and the many chemical reactions involved with it. Thus, simple single-celled organisms excrete by way of the cell membrane, through osmosis, diffusion, and active transport. More complex organisms, like sponges, have a contractile vacuole used for excretion. Fresh water flows into the sponge's body, and excess water is collected by the contractile vacuole, which eventually squeezes it out. Platyhelminthes, like flatworms, and annelids, like earthworms, have excretory organs called nephridia, which filter the body fluids of the organism. Fluids flow through a semipermeable membrane, which holds in larger molecules, like proteins, and excretes smaller molecules like salts and sugars. Some material that is filtered out can be reabsorbed to maintain the right balance of substances. In crustaceans, like lobster and crab, the excretory organ is the antennal gland. The antennal gland consists of a sac, coiled tube, a bladder, and a pore. If you've ever opened the head of a lobster, you might have noticed a green material. This is part of

the antennal gland, also called the "green gland." Fluid from the blood is filtered into the sac, which can reabsorb some of the material on its way into the coiled tube that attaches to the bladder. The bladder stores the waste fluid, similar to the urinary bladder of humans, until it is excreted from the body by the excretory pore. The pore is located at the base of the antenna and excretes mostly water and salts. Insects and other arthropods, like spiders, have Malpighian tubules. These tubes lie within the body cavity, absorbing salts and wastes, which empty into the intestine and out of the body with other digestive waste.

SPECIFIC)IMMUNE)SYSTEMS) Immunity is the protection from disease and infection. There are two main types of immunity: nonspecific and specific. Nonspecific immunity, also called innate immunity, works to keep out anything that is foreign to the body. It is always there, and acts the same way toward any type of invasion. Most are born with this line of defense against infection, which is why it is sometimes called innate immunity. Specific immunity attacks a particular foreign invader. It is sometimes referred to as adaptive immunity because it doesn't fight against an invader until the individual has already been exposed to it. Humans and other vertebrates have both types of immunity and are the only ones with an actual immune system. Invertebrates have only nonspecific immunity. The host cells of invertebrates and vertebrates can attack an invading cell by the process of phagocytosis, in which the host cell encloses the invading cell and engulfs it. The phagocytes, a type of leukocyte or white blood cell, of vertebrates commonly do this, digesting the foreign bacteria. Phagocytosis is the only effective way invertebrates fight disease.

LET'S REVIEW! • • •

To identify major organ systems and organs, To identify the major organ systems in invertebrates; and, Recognize differences in respiratory systems depending on habitat differences....