Invertebrate Zoology

• Genetic engineering is the process used by humans to alter an organism's genome.
• Vectors like plasmids, bacterial chromosomes, or viruses transfer a gene into a host organism, altering its DNA.
• Plasmids, naturally found in bacteria, are useful vectors to transfer DNA into bacterial cells.

Recombinant DNA and Genetically Modified Organisms

• Recombinant DNA contains sequences from multiple species.
• Transgenic organisms contain DNA from different species created through recombinant DNA technology.
• Genetically modified organisms (GMOs) have DNA altered by humans, not necessarily from another species.

Uses of Genetic Engineering

• Genetic engineering is applied in agriculture, medicine, research, and commercial sectors.
• Genetic engineering is controversial due to ethical and environmental concerns about altering organisms' DNA.

Plasmids as Cloning Vectors

• A plasmid is a small, circular DNA molecule separate from a host cell's chromosome, replicating independently.
• Joshua Lederberg coined the term "plasmid" in 1952 to define any extra-chromosomal hereditary element.
• Restriction enzymes are used at restriction sites for plasmid construction.
• Plasmids are mostly circular, varying in size, though some are linear.
• A plasmid includes an origin of replication, a selectable marker, and a region to insert foreign DNA.
• Plasmid integration into a host bacterium can be integrating (episomes) or non-integrating.
• Plasmids are used in cloning, gene therapy, disease models, and protein production, like insulin.
• Recombinant plasmids transfer genes of interest into host cells.
• Virulence plasmids in Escherichia coli and Salmonella enterica are examples of plasmids.

Animal Body Plans and Symmetry

• An animal body plan encompasses specific features and their organization, aiding study, classification, and differentiation in evolutionary and developmental biology.
• Body symmetry differentiates animal body plans by comparing halves.
• Radial symmetry means the halves look the same no matter how the animal is split relative to the center.
• Bilateral symmetry is when the animal halves mirror each other, as in mammals.
• Asymmetry, while rare, is when an animal lacks a specific type of symmetry

Body Cavities, Tissues, and Structural Locations

• Animal body plans are also differentiated by structures like body cavities, tissues, and mouths, as well as the location of structures.
• Location of structures include anterior (head), posterior (tail-end), dorsal (top), and ventral (bottom) locations.
• A coelom is a true body cavity, a pseudocoelom has tissue that doesn't line the entire body cavity, and some animals lack coeloms.
• Eumetazoans are animals with true tissues (specialized cells and tissue).
• Protostomes are animals in which the mouth develops first; deuterostomes are animals in which the anus forms first.

Animal Classification: Vertebrates and Invertebrates

• All animals in the kingdom Animalia are multicellular heterotrophs without cell walls.
• Animals are classified as vertebrates or invertebrates.
• Vertebrates possess a backbone, also called a spinal or vertebral column and are in Phylum Chordata which includes: fish, amphibians, reptiles, birds, and mammals.
• Invertebrates do not have a backbone and constitute over 90% of Earth's animals, divided into over 30 phyla and 1.3 million species.

Common Invertebrate Phyla

• Phylum Porifera: Sponges are sessile filter feeders.
• Phylum Coelenterata (Cnidaria): Stingers like jellyfish, corals, and sea anemones.
• Phylum Ctenophora: Comb jellies with comb-like cilia, slightly more evolved than jellyfish.
• Phylum Platyhelminthes: Flatworms capable of regeneration.
• Phylum Nemertea: Ribbon worms with branched extensions.
• Phylum Rotifera: Microscopic predators.
• Phylum Gastroticha: Hairy bellies with cilia on ventral surface.
• Phylum Nematomorpha: Horsehair worms, often parasitic in insects.
• Phylum Nematoda: Roundworms, often parasites infecting various hosts, including humans.
• Phylum Acanthocephala: Spiny-headed worms attach to host's digestive system with hooks.
• Phylum Bryozoa: Moss animals form moss-like clumps with hard exoskeletons, helping build ocean reefs.
• Phylum Tardigrada: Microscopic water bears that can survive in almost any environment.
• Phylum Brachiopoda: Lamp shells, clam-like with stalk-like anchor and ring of cilia around "mouths."
• Phylum Mollusca: Soft-bodied animals, often with a hard protective shell.
  • Includes gastropods (snails and slugs), bivalves (clams, oysters, and scallops), and cephalopods (octopuses, squids, and chambered nautiluses).
• Phylum Annelida: Segmented worms include earthworms and leeches.
• Phylum Sipunculoidea: Peanut worms with small, pointy head and big rear.
• Phylum Arthropoda: Hard exoskeleton, segmented body, and jointed appendages.
  • Includes arachnids (spiders, scorpions, ticks), myriapods (centipedes and millipedes), crustaceans (crabs, lobsters, crawfish, pill bugs, and shrimp), and insects (beetles, butterflies, ants, bees, crickets, etc.).
• Phylum Chaetognatha: Marine arrow worms with fins.
• Phylum Echinodermata: Spiny skin and complex organ systems.
  • Includes sea stars, sea urchins, sand dollars, and sea cucumbers.
• Phylum Hemichordata: Acorn worms, most similar to vertebrates, possess a primitive proto-backbone.
• Invertebrates play important roles in the ecosystem as food sources, decomposers, and pollinators.

Marine Invertebrates: Sponges and Cnidarians

• Invertebrates, animals lacking a backbone, make up 98% of the world's animal life and millions of marine species.
• Sponges are aquatic invertebrates with squishy, porous bodies found on the seafloor and atop rocks, among Earth's most ancient organisms.
• Sponges filter water to get food (microorganisms) and reproduce through regeneration.
• Cnidarians are a diverse class of aquatic invertebrates include coral and jellyfish, and over 10,000 species.
• Most cnidarians have digestive chambers instead of complete digestive tracts.

Types of Worms and Parasitic Worms

• Flatworms, roundworms, and segmented worms are the three main types of worms.
• Flatworms are flattened with one digestive system opening, such as tapeworms.
• Roundworms are rounded with two digestive system openings, such as hookworms.
• Segmented worms (annelids) have segmented bodies with organ structures in each segment and two digestive tract openings, such as earthworms.
• Parasitic worms (helminths) take nutrients from a host, negatively impacting it. Examples include hookworms and ascaris, which infect humans.

Mollusks: Characteristics and Classes

• Mollusks are soft-bodied, invertebrates in the Phylum Mollusca, mostly in marine, freshwater, and land environments.
• They have a mantle with glands that secrete a substance that hardens into a shell, protecting their soft bodies.
• Mollusks have a large, flat, muscular foot behind the mouth for locomotion.
• Some mollusks have a radula in their mouth.
• The first larval stage in mollusks is trochophore, which develops into veliger larva in many species.
• Mollusks include : Gastropoda, Bivalvia, Cephalopoda, and Polyplacophora (chitons).
  • Gastropods have spirally-coiled external shells (e.g., conch shells), flattened shells, or no shells, such as snails and slugs.
  • Bivalves have two hinged shells (valves) and are filter feeders, such as clams, scallops, mussels, and oysters.
  • Cephalopods have well-developed eyes that can form images and produce a thick black liquid from their ink sac to confuse predators. Ex:squids, octopi, nautiluses, and cuttlefish.

Echinoderms: Characteristics and Classes

• Echinoderms are marine benthic invertebrates with rough or spiny skin.
• They start as free-swimming larvae and become sessile as adults.
• Echinoderms have five classes: Asteroidea (sea stars), Ophiuroidea (brittle stars), Crinoidea (sea lilies and feather stars), Echinoidea (sea urchins and sand dollars), and Holothuroidea (sea cucumbers).
• Most echinoderms have endoskeletons formed by calcium carbonate plates or ossicles.
• Echinoderms lack brains but have neural nets and nerve rings for movement and sensory processing.
• They use a water vascular system to force water into their tube feet to move and feed.
• Echinoderms reproduce sexually by producing sperm cells and eggs.
• Larvae exhibit bilateral symmetry, but adults develop pentaradial symmetry.
• They also reproduce by regenerating when cut through their central disc (fission).
• Many echinoderm species are critical in the food chain, but some, like purple sea urchins and crown-of-thorns sea stars, can be destructive if unchecked.

Arthropods: Characteristics and Groups

• Arthropods are invertebrates with segmented bodies; the name "arthropod" means segmented foot.
• Their exoskeleton is made of chitin, a polysaccharide that gives flexibility and sturdiness.
• The arthropod body is divided into three parts: head (cephalon), thorax, and abdomen.
• Arthropods first appeared during the Cambrian period and were among the first animals to walk on land, but possibly share a common ancestor with annelids (segmented worms) because of nervous system and segmentation similarities.
• There are many known groups of arthropods, the extinct Trilobites and five major ones still around today: Chelicerates (arachnids & horseshoe crabs), Onychophora (velvet worms), Myriapods (centipedes & millipedes), Crustaceans (crabs, lobsters, etc.) and Hexapoda (insects).

Horseshoe Crabs: Unique Features and Medical Importance

• Horseshoe crabs are ancient organisms known for their blue blood and medical importance.
• Horseshoe crab blood lacks white blood cells contains amebocytes that clot around invading bacteria and endotoxins.
• Many migratory birds have timed their Arctic migrations to coincide with horseshoe crab mating season.
• There are four species of horseshoe crab: Tachypleus gigas, Tachypleus tridentatus, Carcinoscorpius rotundicauda, and Limulus polyphemus.
• Horseshoe crab blood is used to test vaccines for sterility in order to detect any bacteria or endotoxin.
• The blood is valuable at around $15,000 a quart, due to no perfect substitute for its use as a vaccination safety test.
• Both the blood and horseshoe crabs themselves are harvested.
• Harvested horseshoe crabs have 30% of their blood taken before being returned to the environment, but 10-15% die.
• During the 1980s and 1990s, little regulation resulted in a crash in the horseshoe crab population, decreasing migratory bird populations like the Red Knot.

Horseshoe Crabs: Anatomy and Classification

• Horseshoe crabs are invertebrate animals from the phylum Arthropoda.
• Evolving over 300 million years ago, four extant species of horseshoe crabs are still found, order Xiphosura and family Limulidae.
• Like other arthropods, bodies are segmented and consist of the prosoma, the opisthosoma, and the telson.
  • The prosoma is the largest part, covered with a hard exoskeleton, the prosoma contains most of the major internal organs: the mouth, the brain, six pairs of walking legs, and ten eyes used for locating prey and sensing changes in light.
  • The opisthosoma represents the middle region of the body. The gills used for breathing are found on the underside of the opisthosoma, along with spines used for defense.
  • The telson is a specialized spine serving as the tail, which can be used to help the horseshoe crab right itself.

Horseshoe Crabs: Habitat and Diet

• Horseshoe crabs are one of the oldest living creatures, that have stayed basically the same for over 300 million years.
• They live along coastlines in the Atlantic, Pacific, and Indian oceans and lay their eggs on sandy beaches.
• Juveniles spend two years in protected shallow waters, until adults, when they move out into deeper ocean water.
• Horseshoe crabs can swim, but they spend most of their lives walking along the ocean floor.
  • The Atlantic horseshoe crab lives along the Gulf coast and eastern coast of the United States, from Texas up to Maine.
  • The Mangrove and Coastal horseshoe crabs live in the Indian and Pacific oceans, along the coasts of India and Southeast Asia.
  • The Chinese horseshoe crab lives along the Pacific coasts of China, Japan, South Korea, and Southeast Asia.
• Horseshoe crabs eat food from the ocean floor, such as marine worms and mollusks, with clams as a major part of their diet.

Horseshoe Crabs: Reproduction and Life Cycle

• Horseshoe crabs have lived on Earth for over 400 million years, they are arthropods related to spiders and scorpions, named for their u-shaped bodies.
• The horseshoe crab body possesses three main parts: the prosoma (head), the opisthosoma (abdomen), and the telson (tail), with a protective exoskeleton made of chitin.
• They live in deep ocean waters, but they reproduce on the sandy shores of ocean beaches: where females release pheromones to alert males that they are reproductively receptive.
• Female horseshoe crabs lay tens of thousands of eggs in nests built on the beach.
• Larval horseshoe crabs hatch from the eggs and move into shallow waters, where they mature and juvenile horseshoe crabs can molt their exoskeleton up to 17 times until they reach reproductive maturity at approximately 10 years of age.

Biological Clocks and Circadian Rhythms

• The reason we sleep and wake is because our biological clocks are programmed to do so and this internal rhythm is calibrated to a daily 24-hour cycle called a circadian rhythm.
• All living creatures have a biological clock, although how the clock is calibrated differs. In mammals, the biological clock is found in the hypothalamus, but we don't know how biological clocks work or where they are located in other animals and plants.
• Biological clocks require environmental cues such as daylight to be calibrated to an exact 24-hour cycle, do not require any stimulus to keep running on their normal, consistant schedule and run on a pre-programmed schedule, ignoring temperature.