Echinoderms and chordates

• Deuterostomes are a diverse group in General Biology II(BIO202).
• Chapter 34 focuses on Deuterostomes

Chapter Outline

• Phylum Echinodermata will be covered
• Phylum Chordata will also be covered

Echinoderm Phylogeny

• Echinodermata and Chordata are within Deuterostomes
• Other Phylogenies include Lophotrochozoa and Ecdysozoa from Protostomes

Echinoderms

• Echinoderms include:
  • Sea urchins, sea stars, and brittle stars
  • Sand dollars
• They display radial symmetry as adults
• Their larvae exhibit bilateral symmetry

Phylum Echinodermata

• Echinodermata are exclusively marine organisms
• Characterized as coelomates with a deuterostome pattern of development
• They possess an endoskeleton made of calcium carbonate plates
  • the plates are covered by living tissue
• Adult echinoderms have pentaradial symmetry
  • They have five axes of symmetry.
• Includes sea stars, brittle stars, sea urchins, sand dollars, and sea cucumbers
• Origin is unclear but are thought to have evolved from bilaterally symmetrical ancestors
  • The larvae are bilaterally symmetrical
• Adult sea stars exhibit pentaradial symmetry

Echinoderm Body Plan

• Echinoderms uniquely feature a hydraulic system
  • Aids in movement and feeding
• The water-vascular system is a modification of coelomic spaces
  • It is composed of a central ring canal with extending radial canals.
• The madreporite serves as the entrance to the water vascular system.
• Radial canals transport liquid to the tube feet
• The ampulla in each tube foot contracts,
  • This results in the tube foot extending and attaching to the substrate
• Muscle contractions in the tube feet cause bending and pulling the animal forward
• Echinoderms have pentaradial symmetry as adults and bilateral symmetry as larvae.
• Their oral surface defines the mouth
• All systems are organized with branches radiating from the center.
• The nervous system consists of a nerve ring with branches but has no centralization of function.

Phylum Chordata

• Chordate endoskeletons differ significantly from those of echinoderms
• Chordate endoskeletons are internal
• Echinoderm endoskeletons function similarly to arthropod exoskeletons
  • Serve as a hard shell with muscles attached to the inner surface
• Chordata includes fishes, amphibians, reptiles, birds, and mammals.
  • They are closely related to Echinodermata

The Chordates

• The chordates are deuterostomes.

Chordate Characteristics

• All chordates have 4 key characteristics at some point
• Nerve cord:
  • Differentiates into the brain and spinal cord in vertebrates
• Notochord:
  • Flexible rod that may be replaced by the vertebral column
• Pharyngeal slits:
  • Connect the pharynx with the external environment
• In terrestrial vertebrates, they are termed pharyngeal pouches, not connected to the outside
• Postanal tail:
  • Exists at least during embryonic development
• This is unlike most other animals, which have a terminal anus

Other Chordate Characteristics

• Other traits distinguish chordates such as:
  • Chordate muscles arranged in segmented blocks called somites
  • Internal skeletons against which muscles work

The 3 Chordate Subphyla

• There exist two nonvertebrate subphyla (1 & 2):
  • They do not form vertebrae or other bones
• There exists one vertebrate phylum:
  • Urochordata (Tunicates) and
  • Cephalochordata (Lancelets)
    • The notochord persists throughout the animal's life
  • Vertebrata.

Tunicates

• Most tunicates are immobile as adults
  • Only the larvae possess a notochord and nerve cord
• Larvae have a tadpole-like form with an oval body and broad tail
  • They also have the ability to move freely
• As adults, they typically lose the tail, notochord, and nerve cord

Characteristics of Chordates

• Vertebrates, tunicates, and lancelets
  • All are chordates, coelomate animals with a flexible notochord that provides muscle contraction resistance
  • Aids in rapid lateral body movements
• Exhibits:
  • Pharyngeal slits or pouches that reflect their aquatic ancestry
  • Hollow dorsal nerve cord
  • The vertebral column replaces the Notochord during embryonic development in nearly all vertebrates.

Subphylum Vertebrata

• Vertebrates:
  • Defined as chordates with a spinal column
• Distinguished from nonvertebrates by:
  • Vertebral column enclosing and protects the dorsal nerve cord
  • Heads that Contains distinct and well-differentiated sensory organs

Vertebrates Also Have

• Exhibits:
  • Neural crest: Forms many vertebrate structures
  • Develops from the neural tube
  • Internal organs
    • Liver, kidneys, endocrine glands, heart, and a closed circulatory system
  • Endoskeleton.
    • Made of cartilage or bone
    • Makes possible great size and extraordinary movement

Major Characteristics of Vertebrates

• Adult vertebrates are characterized by:
  • An internal skeleton which is cartilage or bone
  • Vertebral column and skull
• Other internal and external features

History of the Vertebrates

• First vertebrates appeared in the oceans about 545 MYA with a mouth and fin.
• It has progressed throughout evolutionary history:
  • Jawed fishes soon became dominant.
  • Amphibians invaded the land.
  • Then reptiles replaced amphibians as the dominant land vertebrates
  • Birds and mammals became dominant after cretaceous mass extinction
• This period was around 65 MYA

Phylogeny of the Living Vertebrates

• Key characteristics that evolved among the vertebrate groups are displayed in this phylogeny

Patterns of Evolution

• Divergent Evolution:
  • Populations from a common ancestor evolve a different phenotype
• Convergent Evolution:
  • Populations with different ancestors evolve similar phenotypes
• Homologous Structures:
  • Features that have same evolutionary origin but differ in structure and function
• Analogous Structures:
  • Features of different origin used for the same purpose

Mono/Para/Polyphyletic Animal Groups

• Monophyletic:
  • Includes most recent common ancestor and all descendants
• Polyphyletic:
  • Does not include the common ancestor
• Paraphyletic:
  • Includes most recent common ancestor but not all descendants

Fishes

• Most diverse vertebrate group
• They include species across different classes
• Over half of all vertebrates are fishes
• Provides evolutionary basis for invasion of land by amphibians

Fishes Characteristics

• Vertebral column
  • Hagfish and lamprey exception
• Jaws and paired appendages
  • Hagfish and lamprey exception
• Internal gills
  • Have tissue rich in blood vessels allowing for gas exchange
• Single-loop blood circulation
  • (heart → gills → body → heart)
• Nutritional deficiencies
  • Inability to synthesize aromatic amino acids has been inherited by all their vertebrate descendants.
  • Fishes must consume aromatic amino acids in their food

History of the Fishes

• First fishes had no jaws.
  • Agnatha includes all jawless fishes.
    • These are extant as hagfish (class Myxini) and lampreys (class Petromyzontida)
• Ostracoderms are extinct
• In the late Silurian period, jaws developed
• They evolved from the anterior gill arches of cartilage

Evolution of the Jaw

• Jaws evolved from the anterior gill arches of ancient, jawless fishes

Two Major Groups of Bony Fishes

• Two types, cartilagenous fish will be described in the lab
• Ray-finned fishes:
• Parallel bony rays support and stiffen each fin. - There are no muscles within the fins
• Lobe-finned fishes:
• The fins consist of a long fleshy muscular lobe - A central core of bones supports with rays and articulated joints
• Amphibians most likely came from these
• The coelacanth:
• It is a lobe-finned fish that was a group of fishes thought to have been extinct for about 70 million years
• The coelacanth was discovered in the western Indian Ocean in 1938

Inquiry Question

• Lobe-finned fishes can move their fins independently
• Ray-finned fishes must move their fins simultaneously
• “Walking” helps lobe-finned indicate that were likely ancestors to amphibians

Class Amphibia

• Class amphibia were first vertebrates to walk on land.
• They are direct descendants of fishes.

Orders of Amphibians

• Anura,
  • Includes frogs and toads
  • They have Compact, tailless bodies, large heads fused to the trunk
  • Rear limbs are adapted for jumping
• Caudata,
  • Includes salamanders and newts
  • Slender body
  • Possess logs tails and right angled limbs
• Apoda,
  • Includes Caecilians
  • Has snake-like body, lacks limbs, and have little or no tail

Distinguishing Amphibian Features

• Legs adaptation for life on land
• Lungs Most possess a pair of lungs
• Cutaneous respiration Supplements lungs.
• Pulmonary veins Aids with separate pulmonary circuit
• Partially divided heart
  • Improves separation of pulmonary and systemic circuits

Successful Invasion of Land by Vertebrates

• Adaptations:
  • Legs to support body's weight
  • Lungs were for extracting oxygen from air
  • Redesigned heart and circulatory system were to drive larger muscles
  • Reproduction to occur in waster to prevent eggs from drying
  • A system to prevent whole body desiccation.

Ichthyostega

• Ichthyostega Is one of the first amphibian
  • Amphibians evolved from Lobe-finned fish
• Sturdy forelegs, flipper-shaped hindlimbs
• Long, overlapping ribs form solid cage for lungs and heart.
• Its movement was that of Seal

Tiktaalik

• 2006: fossil found and considered to be in transition between fish and Ichthyostega
• Had gills and scales like a fish and exhibited neck that was amphibian-like
• Forearm, shoulder, and wrist bones were like those of amphibians
• End of the bone was a lobed fin and not actual toes.

Class Reptilia

• Contains about 10,000 living species
• Have three key features:
  • Amniotic eggs which are watertight
  • Dry skin It covers body and prevents water loss
  • Thoracic breathing increasing the lungs capacity

Major Orders Of Reptiles

• Reptilia is classified as a Class
• Main orders of reptiles include.
  • Squamata,
  • Serpentes,
  • Rhynchocephalia,
  • Chelonia

Major Orders of Reptiles (continued)

• Additional Orders are defined by their key characteristics such as
  • Crocodylia
  • Ornithischia
  • Saurischia
  • Pterosauria
  • Plesiosaura
  • Ichthyosauria

Amniotic Eggs

• Amniotes
  • Reptiles, birds, and mammals
• Characteristics:
  • Amniotic egg with four membranes
    • Chorion
      • The outermost layer, allows for gas exchange
    • Amnion
      • Encloses the embryo in fluid-filled cavity
    • Yolk sac:
      • Provides food via blood vessels
    • Allantois:
      • Contains excreted wastes from the embryo

Anapsids, Synapsids, and Diapsids

• Reptiles dominated the Earth for 250 million years
  • Distinguished by # of holes on sides of skull behind eye orbit=
  • 0 (anapsids)
  • 1 (synapsids):
    • Rise to dominance first and are now mostly extinct except for mammals
  • 2 (diapsids):
    • Biggest species to that point and the first bipedal animal
    • gave rise to crocodiles, pterosaurs, dinosaurs, and birds

Dinosaurs

• • Dinosaurs have dominated for over 150 million years

• Became extinct 65 MYA due to Asteroid's impact
  • Only except bird descendants

Modern Reptiles

• Modern reptiles have developed two important traits • internal fertilization

• Sperm must fertilize egg before protective membranes are formed
• Improved circulation
  • Oxygen must efficiently be provided to the body
  • Septum in heart extended to create partial wall which occurred most notably in Mammals, birds, and crocodile

Birds (Class Aves*)

• More than 10,000 species exist
• Unique structure is key to success which is feathers
• Feathers developed from reptilian scales

Birds and Reptiles

• Birds retain many reptilian traits
• All birds still lay amniotic eggs. and exhibits scales on lower legs and feet
• There are two main distinguishing Traits
  • Feathers
    • Modified scales of keratin. providing lift for fight and also conserves heat
  • Flight skeleton
    • Bones are thin and hollow
    • Fusion occurs for rigidity which anchors strong flight muscles
      • Breastbone provides places for attachment of flight muscles

Feathers

• Are a linked structure that provides a flexible but sturdy shape.
• Developed from reptile scales

Archaeopteryx

• First known bird and displays Skull with teeth and long reptilian tail
• Displays feathers on wings and tail –One theropod line evolved to become bird .
• Feather most likely evolved to assist with insulation.
• Nearly identical to forelimbs of theropods

Theropod Descendants

• Most paleontologists agree that birds are the direct descendants of theropod dinosaurs

Class Mammalia

• About 5,000 species of Mammals exist.
• There is a lowest count among all previously discussed group in these notes
• Almost 4,000 are Bats, Rodents, shrews or moles.

Fundamentally Mammalian Traits

- Hair
    - Long, keratin that extends from hair follicles:
    - provides Insulation, camouflage, and sensory structure
- Mammary glands
    - Females exhibit mammary glands that secrete milk

History of Mammals

• They’ve been around for about 220 MYA
• Small, nocturnal shrew-like creatures that consumed treedwelling insects
• Over the last 15 million years the total count decreased dues to climate

Subclasses of Mammals

• Prototheria:
  • Most primitive
  • Lay shelled eggs (oviparous)
  • Small number of monotremes in this group
• Theria:
  • Gives live birth (Viviparous )
• 2 categories of living groups
  • Placental Mammals Largest group (Dogs, cats, humans, horses)
    • Consists of Marsupials= Animals like Kangaroos, Opossum, and Kola Bears

Monotremes

• Shells eggs
• Only three extant spices exists
• They can like reptiles exhibit Cloaca for a single opening for urine, feces and Reproduction.
• Lack well-developed nipples

Marsupials

• pattern for the pattern of embryonic development is a major difference from reptiles
• has a short life line in placenta and they can crawl to continue developing. In a Pouch That possesses Nipples
• Most notably opossums in North America and Kangaroos in australia.

Placental Mammals

• Has a True, Nourishing Placenta throughout period for Embryo Development
• Exhibits both fetal and maternal tissues
• They are Born Undergoing a considerable period of Development
• Humans exist in these numbers along with other animals like dolphins and lions

The Placenta

• Placenta has its membranes evolve From amniotic Egg
• Its serves as intestines ,kidneys and lungs throughout the mixing fetal and maternal Blood.
• Umbilical has its cord evolve the allantois for nutrients.

Evolution of Primates

• Evolved arboreal
  • Primates are the mammals that gave rise to our own species
    • insectivores that have grasping toes fingers
    • Exhibits a thumb for opposition for precise grappling and grasping
• Vision is important. They have shifting eyes for distances and binocular vision

Living Primates Anthopoids

• Most all primates had diurnal tendencies • They change depending on eye design and are highly social with each other

Anthropoid History

• 30 MYA
  • New Monkeys of the World Were known to Exist
    • All known monkeys were found in trees
      • Old World monkeys were found in Africa

Hominoids Include

• Hominoids

• apes with gibbons, chimpanzees, gorilla, and orangutan -Larger brains do exist Than Monkeys They Lack Tails
  • Apes were the largest example of this with all known species of Old World monkeys
  • Known as apes were grouped

A Primate Evolutionary Tree

– A lot evolutionary process

Within Hominoids: Apes Vs Hominins

    - The common known ancestor hominins +orangs + gorillas and +chimes are and Is though of as Arborael Climber
    - Humans Vertebral is more curved then Apes, is shorter and in the lower Limbs
    = It Exits From the skull Bottom rather then the other Animals Backbone

Early Hominins

- Genus Australopithecus Has About 7 Species And A Small Brain
   - It's The Genus Homo Contains Abot7 Different Counts
           - It is The Hominins Are Bipedal And Evolves
              - and older linenges are considered in many studies

MODERN HUMANS

• First appeared in Africa 700 thousand to 800 Years prior to modern times, roughly.
• Three species are thought to Evolves
• A variety of species are discussed in humans but all are closely related.
  • A mix of all species is a good example of how they can work together

Human Races

• Human Are are a differentiated Species with traits spreading
• Races have evolved From Mating. And It Leads to a Visually strong Race . This Aides in Visual Cues

Homo Sapiens

• Are a Surviving species with tool use
• The expansion of language and Culture and lead to a modern world.

Groupings of Humans

• Based on skin tone or features Are grouped. This can lead to Genetic Variety

Explore the unique characteristics of echinoderms, including their pentaradial symmetry and water vascular system. Investigate chordate features such as the notochord and neural crest. The relationship between echinoderms and chordates sheds light on deuterostome development.