Chordates By Olivia, Eva, and - PowerPoint Presentation

Chordates By Olivia, Eva, and Anais [Untitled photograph of a giraffe]. ( n.d.). Retrieved February 20, 2014, from http://wakpaper.com/large/Giraffes_wallpapers_331.jpg Elephants. (n.d.). Retrieved February 25, 2014, from http://www.wildaid.org/elephants

Structure of ChordatesNotochord - provides a dorsal, flexible rod that functions as a support. Replaced by bone during development in most chordates.Dorsal hollow nerve cord - forms the basis for the nervous system. In some chordates, the nerve cord becomes the brain and spinal cord. Pharyngeal gill slits (pharyngeal pouches) - provide channels across the pharynx to the outside of the body. In some, the slits become gills for oxygen exchange or filter feeding, while in others, they disappear during embryonic development.Muscular tail (post-anal tail) - extends beyond the digestive tract. In many, such as humans, the tail is lost during embryonic development.

Flowchart . (n.d.). Retrieved February 25, 2014, from http://bioweb.uwlax.edu/bio203/s2012/stauder_abig/classification.htm

Cephalochordates, commonly called amphioxus or lancelets, are marine invertebrate and a very small branch of the animal kingdom. It’s a phylum of about 25 different species of animals. They inhabit mostly shallow tropical and temperate oceans. Chordata-Subphylum Cephalochordata – “Acrania”

StructureShape- slender, laterally compressed, translucent animals about 5 to 7 cm in length.Parts of the organism- Small, eel-like having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development.

[The  dorsal nerve cord  is supported by a muscularized rod, or notochord. The pharynx is perforated by over 100 pharyngeal slits or "gill slits", which are used to strain food particles out of the water. The musculature of the body is divided up into V-shaped blocks, or  myomeres, and there is a post-anal tail. All of these features are shared with vertebrates. On the other hand, cephalochordates lack features found in most or all true vertebrates: the brain is very small and poorly developed, sense organs are also poorly developed, and there are no true  vertebrae.] Alligator and fetus – Chapter 35. ( n.d. ). Retrieved February 25, 2014, from http://highered.mcgraw-hill.com/sites/0073532223/student_view0/chapter35/image_powerpoint_for_students.html

DiversityThere are more than 20 species of fish-like marine chordatesAbout 25 species inhabiting shallow tropical and temperate oceansCephalochordates are a very small branch of the animal kingdom.

How nutrients are obtain: Water is drawn in to the mouth by the beating of the cilia located on the wheel organ(a set of ridges lying inside the mouth). Water gets filtered by the oral cirri (slender projections that surround the opening of the mouth). It then passes through the gill slits. These gill slits are enclosed by metapleural(fin-like folds) folds of the body wall, to form a body cavity known as the atrium. Food particles in the water are trapped by mucus, while water goes through the slits and out of the atrium through the  atriopore, located towards the posterior end. The rest of the digestive system is fairly simple: a pouch or hepatic caecum secretes digestive enzymes, and actual digestion takes place in a specialized part of the intestine known as the iliocolonic ring.Mechanisms of Metabolism: Cephalochordates have a well-developed circulatory system and a simple excretory system composed of paired nephridium(nephridia for plural).Mode of Nutrition

Sexes are separate, both male and female have multiple paired gonads(organ that makes gametes). Eggs are fertilized externally & develop into fish-like larvae.Lancelet sexes are separate and asexual reproduction does not occur.Eggs and sperms are sperm are shed directly into the water, where fertilization occurs.Reproduction

Ecological significanceComparison between cephalochordate and vertebrates genomes has allowed us to postulate a picture for the genome of the last common ancestor of all chordates. Their significance has to do with their place in evolution, as invertebrates transitioned to vertebrates providing clues for the history of human lineage. Aleksandr Kowalevsky first shown the connection in 1867, with embryological evidence that was influential in establishing that evolution has in fact occurred. More recently, the relationship has been well-supported by gene sequence comparisons. Lancelets have a structure that illustrates the characteristic features of chordates in simple form.

UniquenessSince cephalochordates have no hard parts, their fossil record are extremely sparse. three unique features of chordates found in all of them are: the notochord, composed of gelatinous tissue and bound by a tough membrane; a tubular nerve cord (or spinal cord), located above the notochord;gill slits leading into the pharynx, or anterior part of the digestive tract (the throat, in higher vertebrates). In addition, all have blood contained in vessels, and the tunicates and vertebrates have a ventrally located heart. All have a post-anal tail, that is, an extension beyond the anus of the notochord or backbone and of the body-wall musculature, containing no internal organs . 

Examples

Subphylum UrochordataCharacteristics of Chordates: tunicates and salps (salpa) Diversity: 1250 species of marine animals immobile as adults

StructureOnly the larvae having a notochord and nerve chordBody has more than two cell layers and includes tissues and organs. Mode of NutritionD o not feed and have a poorly developed gutBody wholly enclosed in a 'tunic' of secreted protein and cellulose-like material. ReproductionAre hermaphroditic, normally with only one ovary and testis. Can reproduce sexually or asexually. Ecological significance All are filter feeders. Live in marine environments. UniquenessHas a nervous system composed of a anterior ganglion from which individual nerves issue. Has no excretory organs. Has a distinct larval stage.

Examples

Subphylum Vertebrata

Reproduce sexuallyFeatures: Vertebral column - the notochord is replaced during embryonic development by a vertebral column, head - distinct and well-differentiated head with three pairs of well-developed sensory organs, neural crest - a unique group of embryonic cells and they participate in the development of many different structures, internal organs - liver, kidneys, and endocrine glands. All have a heart and a closed circulatory system, endoskeleton - made of cartilage or boneFishes, amphibians, reptiles, birds, and mammals

Fishes:5 characterists: vertebral column of bone or cartilage, jaws, paired appendages, internal gills, and a closed circulatory system.Sharks, rays, and skates are cartilaginous fishes. Bony fish: Actinopterygii (ray-finned) or Sarcopterygiin (lobe-finned fishes)Amphibians: 5 features: legs, lungs, cutaneous respiration, pulmonary veins, and a partially divided heart.Anura (frogs and toads) lack tails as adults, many have a larval tadpole stage. Caudata (salamanders) have tails as adults and larvae similar to the adult form. Apoda (caecilians) are legless.

Reptiles:3 characteristics: watertight amniotic egg; dry, watertight skin; and thoracic breathing. Modern reptiles practice internal fertilization and are ectothermic. Synapsids gave rise to the therapsids that became the mammalian line. Diapsids gave rise to modern reptiles and the birds.Chelonia (turtles and tortoises), Rhynchocephalia (tuataras), Squamata (lizards and snakes), and Crocodylia (crocodiles and alligators) Birds:Characteristics: Feathers and a lightweight skeleton. Feather is a modified reptilian scale. Birds evolved from theropod dinosaurs. Birds have efficient respiration and circulation and are endothermic.

Mammals:Characteristics: hair, mammary glands - provide milk to feed their young, and other characteristics - like being endothermic. Evolved from therapsids (synapsids - reptiles) and reached maximum diversity about 15 mya. Modern mammals - 3 groups: monotremes (lay shelled eggs), marsupials (an embryo completes development in a pouch), and placental mammals (produce a placenta in the uterus to nourish the embryo).  Vertebrates are both predator and prey.

ReferencesInc, A. (2012, january 8). Tunactes. Retrieved from Ocean Observations: http://oceanobservations.blogspot.com/2012/01/tunicates.html Britannica, E. (2014). Cephalochordate. Retrieved from The Encyclopedia Britannica: http://www.britannica.com/EBchecked/topic/103023/cephalochordateChen, J.-Y. D.-Q. (1995). A Possible Early Cambrian Chordate. Nature 377:720-722.Encyclopedia, T. C. (2012). The Columbia Electronic Encyclopedia, Sixth Edition. Retrieved from http://www.infoplease.com/encyclopedia/science/chordata.html Raven, P. H., Johnson, G. B., Mason, K. A., Losos, J. B., & Singer, S. R. (2011). Biology, Ninth Edition. The McGraw-Hill Companies, Inc.Ruppert, E. E., & Bames, R. (1994). Invertebrate Zoology, Sixth Edition. Saunders College Publishing, Fort Worth.