Invertebrate Diversity and Characteristics Selected topics chosen from Chapters 23-24

Kingdom Animalia Animals are the most physically diverse kingdom of organisms. Animals range in size from 25-meter-long blue whales to microscopic rotifers. Animals are found nearly everywhere on Earth.

Each animal phylum has a unique body plan. Vertebrates have an internal segmented backbone. An endoskeleton allows vertebrates to grow to large sizes. internal made of bone or cartilage Invertebrates do not have a backbone. Invertebrates encompass most animal groups.

Differences in body plans result from differences in the expression of Hox genes. Hox genes tell embryonic cells which body part to become. Mutations in Hox genes led to the vast diversity of animal species. head tail fruit fly genes human HOX-B genes

Animals are grouped using a variety of criteria. 3 criteria are used to categorize animals: body plan symmetry tissue layers developmental patterns gastrovascular cavity mouth mesoglea oral arms tentacles blood vessels brain hearts muscle segment nerve cord mouth digestive track

There are 3 types of body plan symmetry. 1. bilateral symmetry: body divides equally along one plane Animals with bilateral symmetry can be divided equally along only one plane, which splits an animal into mirror-image sides. 2. radial symmetry: body arranged in circle around a central axis (usually the mouth) 3. asymmetry: body has no general plan or central axis. It is irregular in shape. Animals with radial symmetry have body parts arranged in a circle around a central axis.

Bilateral animals have three distinct layers of tissue; radial animals have only two. both animal types have ectoderm (outer layer) and endoderm (inner layer) bilateral animals have mesoderm (middle layer) Animals are divided into two major groups, the protostomes and the deuterostomes. Protostomes form mouth-first, and anus second. Deuterostomes first form the anus and then the mouth.

A comparison of structure and genetics reveals the evolutionary history of animals. Protostomes and deuterostomes are the two major radiations on the animal phylogenetic tree. Porifera Cnidaria Platyhelminthes Annelida Mollusca Nematoda Arthropoda Echinodermata Chordata RADIAL NO TISSUES PROTOSTOMES DUETEROSTOMES jellyfish, coral, anemones sponges flatworms Segmented worms clams, snails, octopuses roundworms insects, spiders crustaceans, sea urchins sea stars, vertebrates lancelets,

Sponges have specialized cells but no tissues. Sponges are the most primitive animals on Earth. 570 million-year-old fossils closely related to group of protists sessile reproduce both sexually and asexually filter feeders

Cnidarians are the oldest existing animals that have specialized tissues. Cnidarians have two body forms. polyps medusas In the polyp form of a coral, the tentacles and mouth face upward. In the medusa form of a jellyfish, the tentacles and mouth face downward.

Flatworms are simple bilateral animals. Flatworms have a solid body and incomplete or absent gut. There are three classes of flatworms. Flukes: Parasites that feed on the body fluids of other animals. Larva penetrate through human skin into blood vessels to settle in human intestine. Treatable. Tapeworms: parasites that live in vertebrate guts. Absorb nutrients from digested food by latching sucker like mouth to intestinal wall. Treatable. Planarians: free-living, nonparasitic flatworm. Lives in ocean.

Mollusks are diverse animals. Mollusks have a complete digestive tract and a mantle. A complete digestive tract has two openings: a mouth and an anus. Mantle is a hard shell to protect animal.

Annelids have segmented bodies. Segmentation refers to the repeated sections of an annelid’s body. The coelom is a fluid-filled space completely surrounded by muscle. There are three groups of annelids: Earthworms, marine worms, leeches blood vessels muscle hearts brain mouth digestive tract nerve cord segment

Roundworms shed their stiff outer skeleton as they grow. Roundworms are protostomes with bilateral symmetry. Roundworms have a tough outer skeleton called a cuticle made of chitin Many roundworms are parasites. Nearly every plant and animal species are parasitized by roundworms. hookworms pinworms Guinea worms Hookworms: feed on host’s blood. Contract it by walking barefoot over contaminated soil. Guinea worms: found in connective tissue of host. Occurs when host drinks contaminated water. Wrap worm around stick and turn it once a day. If worm breaks, it will be difficult to extract from body again. The most common symptom of pinworms is an itchy rectal area. Symptoms are worse at night when the female worms are most active and crawl out of the anus to deposit their eggs. Adults live in gut of host.

Echinoderms have radial symmetry. Echinoderms have a water vascular system a series of water-filled ring canals around central disk canals store water used for circulation and movement changes in water pressure extend and retract tube feet Echinoderms have a complete digestive system. Some echinoderms can regenerate limbs or other body parts. Echinoderm means “spiny skin” tube feet

Arthropods are the most diverse of all animals because they have features that are highly adapted. Arthropods are invertebrates that share several features. exoskeleton (cuticle) made of chitin that will molt jointed appendages segmented body parts Compound eye External sensory organs (antennae and body hairs

Crustaceans—live in oceans, freshwater streams, and on land Trilobites—extinct, bottom feeders; oldest fossils date back 540 million years. Insects—most live on land, have six legs Chelicerates—specialized daggerlike mouthparts Myriapods—long bodies and many pairs of legs

Arthropod exoskeletons serve a variety of functions. Joints are made of stiff and flexible cuticle to allow movement. The exoskeleton is made of many layers of chitin. hard material that protects the body must be shed in order to grow Arthropods have an open circulatory system. Sensory organs such as antennae are made of modified cuticle. Most arthropods have compound eyes.

Crustaceans evolved as marine arthropods. Crustaceans share several common features. two distinct body sections: cephalothorax and abdomen one pair of appendages per segment two pairs of antennae exoskeleton Carapace

Crustacean appendages can take many forms. Crustacean appendages are used for a variety of functions. collecting and manipulating food attracting females protection Appendages include claws, antennae, walking legs, swimmerets, and mandibles. Decapods such as lobsters and crabs have ten legs Barnacles are sessile filter feeders wrapped in a hard shell.

Arachnids include spiders and their relatives. Arachnids are a group of chelicerates that live on land. eight legs fanglike pincers that inject venom silk glands All spiders make silk and produce venom. Arachnids also include mites, ticks, chiggers, and scorpions. horseshoe crabs

Insects are the dominant terrestrial arthropods that show an amazing range of adaptations. Insects are in nearly every ecological niche. Insects have a body with three parts. head thorax abdomen abdomen thorax head Some insects live independently, others live in social colonies.

Insects undergo metamorphosis. In incomplete metamorphosis, insects look like miniature adults when they hatch. There are three life stages of incomplete metamorphosis. larva nymph adult nymph stage larvae adult

In complete metamorphosis, the insect changes form entirely. Larva Egg Pupa Adult There are three life stages of incomplete metamorphosis. egg larva pupa adult

Arthropods and humans interact in many ways by sharing many of the same resources. Many arthropods are herbivores that eat plants that humans depend on. Arthropods cause millions of dollars of crop damage. Insecticides have unwanted side effects.

Scientists have developed safer insecticide alternatives. arthropod-specific insecticides integrated pest management (IPM) reduces pests by managing their ecology. Ex. Use insect traps, physical barriers, or introduce natural predators. genetically modified crops

Some arthropods can spread human diseases. Vectors are organisms that carry disease from one host to another. Diseases spread by arthropods have serious effects on human populations. Bubonic plague is caused by a bacterium carried by fleas. Yellow fever is caused by a virus carried by mosquitoes. Malaria is caused by a protozoan parasite carried by mosquitoes. West Nile virus is caused by a virus carried by mosquitoes.