Chapter 24 Flashcards
What are the key features of Chordates?
All chordates share four distinctive structures: Dorsal Nerve chord, Notochord, Pharyngeal gill slits, and Post-anal Tail
Which 3 clades make up the chordates?
Lancelets, Tunicates, Craniates
What is a Dorsal Nerve Cord?
A dorsal nerve cord is the Nerve Cord of chordates that lies above the digestive tract, running lengthwise along the dorsal (upper) portion of the body.
What is a Notochord?
The Notochord is a stiff but flexible rod that extends along the length of the body, located between the digestive tract and the nerve cord. - Provides support, attachment site for muscles, some chordates have the notochord present only during the early development and dissapear as a skeleton develops.
What is a post-anal tail?
The post - anal tail is a posterior extension of the chordate body that extends past the anus and contains muscle tissue and the rearmost portion of the nerve cord. Other animals lack this kind of tail.
Why do we only have the Nerve Cord?
It is only during embryonic phase that we develop and lose out notochord, gill slits, and post anal tails.
Bilateral organisms develop in one of two ways:
Diverse developmental pathways, however, can be grouped into two categories, known as Protostome and Deuterostome development.
Protostome development:
The body cavity forms within the space between the body wall and the digestive cavity. (Cavity structure varies among phyla)
Body Cavities:
Only in member of animal phyla have fluid-filled cavities between the digestive tube ( or gut where food is digested and absorbed) and the outer body wall. “tube-within-a-tube” body plan.
-Can serve a variety of functions: Earthworm it acts as a kind of skeleton, providing support for the body and a framework against which muscles can act. In other animals, internal organs are suspended within the fluid-filled cavity, which serves as a protective buffer between the organs and the outside world.
Type of body cavity: Coelom
The most widespread type; a fluid-filled cavity that is completely lined with a thin layer of tissue that develops from mesoderm (the layer between the endoderm and the ectoderm) Phyla whose members have a coelom are called coelomates. The annelids (segmented worms), arthropods (insects, spiders, crustaceans) Mollusks (clams and snails) echinoderms and chordates (which include humans) are Coelomates.
Type of body cavity: Pseudocoelom
Body cavity that is not completely surrounded by mesoderm-derived tissue. And phyla whose members have one are collectively known as pseudo coelomates. The roundworms (nematodes) are the largest pseudo coelomates group. Splits in the mesoderm
What is Deuterostome?
In Deuterostome development, the body cavity forms as an out-growth of the digestive cavity. The two types of development also differ in the pattern of cell division immediately after fertilization and in the method by which the mouth and anus are formed. An animal with a mode of embryonic development in which the coelom is derived from outpocketings of the gut.
What are Lancelets: invertebrate
Marine filter-feeders: The 25 species of lancelets (Cephalochordata) form a group of invertebrate chordates.
- Lancelets are small ( 2 inches, or 5 long) fishlike animals that retain all four chordate features as adults. An adult lancelet spends most of its time half-buried in the sandy sea bottom, with only the anterior end of its body exposed. The motion of cilia in the pharynx draws seawater into the lancelet’s mouth. The gils filter food from water that is then transported to the digestive tract.
Tunicates include: invertebrate
Sea squirts and Salps: The tunicates (Urochordata) form a larger group of marine invertebrate chordates. Tunicates are small, with lengths ranging from a few millimeters to 1 foot (30 centimeters). The group includes immobile, filter-feeding, vase-shaped animals known as sea squirts. Pharynx occupies most of his body.
How does a squirt get nutrients?
Water enters the body through an incurrent siphon, passes into the pharyngeal basket at its top, moves through the gill slits, and exits the body through an excurrent siphon. Food particles are trapped in the basket’s mucous lining.
Craniates have a skull:
The craniates include all chordates that have a skull that encloses the brain. The skull may be composed of bone or cartilage, a tissue that resembles a bone but is less brittle and more flexible. Earliest known craniates, whose fossils were found in the 530-million year old rocks, resembled lancelets but had brains, skulls and eyes. However,
What is a cartilage?
The skull may be composed of bone or cartilage, a tissue that resembles bone but is less brittle and more flexible. bone made of calcium.
Many Early craniates lacked what?
Jaws: A movable skeletal element that frame the mouth opening.
Today, the Craniate include the hagfishes and the Vertebrates:
Animals in which the embryonic notochord is replaced during development by the backbone, or Vertebral Column, composed of bone or cartilage.
Craniate- What is a Hagfish?
Slimy residents of ocean floor: Ancestral craniates (Myxini) lack jaws. They use tonguelike, tooth-bearing structure to grind and tear food. Lack a true backbone. - A hagfish’s body is stiffened by a notochord, but its skeleton is limited to a few small cartilaginous elements, like a rudimentary skull. Because they lack skeletal elements such as the nerve cord and the vertebral column, they’re not considered vertebrates. BUT represent the craniate group most related to the vertebrates.
Craniate - How does a Hagfish live?
-20 Species and all exclusively marine; Respire using gills, have a two-chambered heart, and are ectothermic - they depend on heat from the external environment to regulate their body temperature.- (these characteristics are also found in all vertebrate fishes) Have gills-
Live near the ocean floor, often burrowing in the mud, and feed off of worms. However, they eat dying fish, using their teeth to grind or burrow into a fish’s body and consume its soft internal organs. Slime is very slimy and potentially used for medicine.
Craniates- Do vertebrates have a backbone?
The vertebral column of a vertebrate supports its body, provides attachment sites for muscles, and protects th delicate nerve cord and brain. Part of a living internal skeleton that can grow and repair itself. Because its not an armor-like heavy weight of the arthropod exoskeleton, it allows vertebrates to grow a great size. Our backbone can repair bones, the arthropods cannot.
Craniate- The appearance of the Jaw/
Early history of vertebrates was characterized by an array of strange, now-extinct jawless fishes, many protected by bony armor plates. 425 million years ago, jawless fish gave rise to jaws: and allowed to grasp, tear or crush their food, permitting them to exploit a much wider range of food sources than jawless fish could. Most but not ALL vertebrates have jaws.
Craniate- Vertebrate adaptations:
Successful invasion of most habitats: Paired appendages. First appeared as fins in fish and served as stabilizers for swimming. Over millions of years, fins were modified by natural selection into legs that allowed animals to crawl onto dry land, and later into wings that allowed some to take to the air. Another adaptation: increase in the size and complexity of their brains and sensory structures, which allow vertebrates to perceive their environment in detail and to respond to it in a great variety of ways.
Major Groups of Vertebrates:
Lampreys, Cartilaginous fishes, ray-finned fishes, coelacanths, lungfishes, amphibians, reptiles, and mammals.
Vertebrate = What are Lampreys Parasitize Fish?
Jawless. Recognizable by the large, rounded sucker that surrounds its mouth and by the single nostril on the top of its head. Nerve cord protected by segments of cartilage. Considered true vertebrates. Some species are parasitic. They use their tooth-lined mouth to attach itself to a larger fish and excavate a hole in the host’s body wall using teeth on its tongue. Without an effective predatory, they have eliminated some commercial fish populations, including the trout. Control measures of the lamprey population allows for some other fish population to recover.
Cartilaginous Fishes (jaws)
Marine Predators: Chondrichthyes, include 625 marine species, among the sharks, skates, and rays. Unlike hagfishes and lampreys but like all other vertebrates, cartilaginous fishes have jaws. They are predators whose skeleton is formed entirely of cartilage and protected by leathery skin roughened by tiny scales. (some need to swim to regulate water across gills, some just pump water across their gills) In contrast to external fertilization, cartilaginous fishes have internal fertilization in which male deposits sperm directly into a female’s reproductive tract.
How do cartilaginous fishes feed?
Some sharks feed by filtering plankton (tiny animals and protists) most are predators of larger prey such as other fishes, marine mammals, sea turtles, crabs and squids. They use their strong jaws that contain many rows of razor-sharped teeth; the back rows move forward as the front teeth are lost to age and use.
Are sharks dangerous to humans?
Large sharks avoid humans, however they still pose a threat. 30 times more likely to die from a lightning strike that to be bitten by a shark. 60 cases were documented in 08, 4 of them fatal. Very rare to be attacked by a shark. TWO CHAMBERED HEART.
