Vertebrates Week 7
Vertebrates Week 7 BZ 214
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This 9 page Class Notes was uploaded by Kenzie Busick on Sunday March 6, 2016. The Class Notes belongs to BZ 214 at Colorado State University taught by Shane Kanatous in Winter 2016. Since its upload, it has received 22 views. For similar materials see Animal Biology- Vertebrates in Biology at Colorado State University.
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Date Created: 03/06/16
Vertebrates Week 7 03/01/2016 ▯ Transition to land Lobed finned fishes were ancestors to amphibians Ordovician period: start to see plants and arthropods to come onto land Continental movement: start to break up-> begin to see more coastline appearing o The more coastline increases the odds for vertebrates success on land Lung fish: lived in shallow water-> higher temperature-> low oxygen in the water ▯ New challenges on land Feel the effects of gravity much more than they would in water o Have to start supporting their body mass o Beached whales/fish are killed because of the shock of the pressure from gravity for the first time Lobed fin-> early amphibians; increase in bone density- skeleton has to get stronger in order to support the body mass Amphibians->early amniotes; well developed neck/head is free from pectoral girdle loose the ability to create suction when feeding on land change how you breath/circulate blood need to keep from drying out; need to keep moisture inside the body ▯ Skeleton Bony fish: trunk and caudal region Early tetrapod: start to have cervical vertebrae and some vertebrae that supports the caudal region Primitive amniote: clearer separation in cervical vertebrae, trunk is now classified as the thorax, caudal region Mammal like: clear neck, thorax region (ribs), lumbar vertebrae, sacral fused to the pelvis, tail (caudal region) Density of skeleton; bones have to become more dense in order to fight gravity, the larger the organism-> denser the bones to support increased body mass Muscles contract against internal skeleton o Muscles only contract in a single plane-> there is a number of muscles working in order for movement o Increased musculature in the face and head o Primates have the most musculature across the face-> allow for facial expressions ▯ Advantages to land New food resources Avoidance of aquatic predators and competitors Oxygen abundant o Open the door to higher metabolic rates ▯ Disadvantages to land Water become limiting factor in distribution o Have to keep themselves from desiccating (drying out) Gravity o Necessitates new morphological designs o There is gravity in water, but the density of the water counteracts the pressure (increase in the need for energy) Water has high heat capacity-> stable temperatures o Land has huge fluctuation in temperatures The challenge usually comes down to if the organism can get enough food to get the energy they need ▯ Bone Inorganic components of bone comprise 60% of the dry weight and provide the strength of bone; organic compound is primarily collagen (gives bone tensile strength) Important roles o Provides support and movement via attachments for soft tissue and muscle o Protects vital organs o Major site for red marrow for production of blood cells o Plays a role in metabolism of minerals such as calcium and phosphorus Two basic structural types; compact and spongy o Compact: forms the outer shell of all bones and also the shafts of long bones o Spongy: found at the expanded heads of long bones and fills most Irregular bones; allows for compressibility (absorb shock from gravity) Most important thing for blood is the need for blood supply for formation and maintenance Firoblasts form collage, osteoblasts form bone cells and together these form membrane bone (bone deposited directed in a blastema) Osteoblast- membrane and dermal bone Chondroblast- endochondral bone ▯ Intramembranous ossification: is the process of membrane bone formation- dermal bone/flat bones Still have spongy and compact bone associated with it Events that take place in intramembranous bone formation o Increased vascularity of tissue o Active proliferation of mesenchymal cells o Osteoblasts begins to lay down osteoid o Osteoblasts either retreat or become entrapped as osteocytes in the osteoid o The osteoid calcifies to form spicules of spongy bone o Bone remodeling occurs (periosteum and compact bone are formed) This process gave rise to o Bones of the lower jaw, skull and pectoral girdle o Dentin and other bone that develops in the skin o Vertebrae in some vertebrates (teleosts, urodeles, and apodans) ▯ Endochondral ossification: is the process in which bone is deposited in pre extisting cartilage and such bone is called replacement bone Once the majority of the shaft has replaced cartilage with bone, you have epiphyseal plates at each side of the bone that stay cartilage (also called the growth plates) Primary center of ossification o The first site of ossification occurs in the primary center of ossification, which is the shaft Steps for primary center of ossification o Formation of the periosteum: contains a layer of undifferentiated cells which later become osteoblasts o Formation of bone collar: osteoblasts secrete osteoid against the shaft of the cartilage model, serves as support for the new bone o Calcification of matrix: nutrients no longer diffuse if the matrix ecomes sufficiently calcified, this create cavities within the bone o Invasion of periosteal bud: consists of blood vessels, lymph vessels, and nerve. Form hemopoietic cells that later form bone marrow o Formation of trabeculae: osteoblasts use the calcified matrix as a scaffold and begin to secrete osteoid, which forms bone trabucula. Osteoclasts breaks down spongy bone to form the medullary (bone marrow) cavity. Secondary center of ossification o Cartilage is retained in the epiphyseal plate. Located between the diaphysis (the shaft) and the epiphysis (end) of the bone These areas of cartilage are known as secondary centers of ossification o Cartilage cells undergo the same transformation as above, as growth progresses the proliferation of cartilage cells in the epiphyseal plate slows and eventually stops. Only articular cartilage remains o Only articular cartilage remains, continues in adult at a much reduced rate ▯ Skeletal Adaptions Somatic skeleton = axial skeleton (vertebral columm, ribs, sternum, and skull) & appendicular skeleton In evolution of the tetrapod limb, there are several new innovations that increase the load carrying capacity of the limbs as these animals adopt to an increasingly terrestrial environment Vertebral column- vertebrae: consists of a centrum (or body), 1 or 2 arches, plus various processes for muscle attachment o Amphicelous Concave at both ends o Opisthocoelous Concave in front and convex in back o Procelous Concave in front and convex in back o Acelous Flat-ended o Heterocelous Saddle-shaped centrum at both ends Vertebral arches o Neural arch – on top of centrum o Hemal arch – beneath centrum in caudal vertebrae of fish, salamander, most reptiles, some birds, and many long-tailed mammals Vertebral processes o Projections from arches and centra o Some give rigidity to the column, articulate with ribs, or serve as site of muscle attachment Transverse processes o Most common type of process: extend laterally from the base of a neual arch or centrum and separate the epaxial and hypaxial muscles Diapophyses & parapophyses o Articulate with ribs Prezygapophyses (cranial zygapophyses) & postzygapophyses (caudal zygapophyses) o Articulate with one another and limit flexion and torsion of the vertebral column Amphibians Consist of three groups that evolved 50 million years ago Must lay eggs directly in water or in extremely humid areas o Still connected to water Very thin skin, which is maintained moist (vast majority can breath through the skin) 3 extant groups; Urodeles (salamanders), anurans (frogs/toads), gymnophionans (caecilians) modern day amphibians lack true ribs; don’t circle and enclose the body cavity anurans: o elongated hind limbs (for leaping) o more fusion of bones urostyle (stiff for jumping) reducing the amount of work they have to do to keep their body stiff- save energy- less muscles ▯ Shared and derived characteristics Cutaneous gas exchange o Exchange gas across the skin Thin and moist o Vary across the group- toads have fairly dry skin o Skin has no external covering; no scales, hair, feathers to block exchange of air across it o If you can exchange oxygen across the surface-> can also exchange water (reasons they have to stay near water because at risk of drying out) Papilla amphibiorum o A sensory area of the inner ear which is sensitive to sound frequencies below 1000 Hz Wider range of hearing o Papilla basilaris is sensitive to frequencies above 1000 Hz, which is what other vertebrates have, however, amphibians have both Operculum-columnella complex o Bones involved in transmitting sounds to the inner ear o Start to adapt the head to pick up sounds Green rods o In eyes, distinct type of retinal cell o Sensitive to blue light Pedicellate teeth o Teeth that sit on the base of pedicle from which the crown is separated by a fibrous connection Levator bulbi muscle o Pushes the eye out, thin muscle on the floor of the orbit o Helps pull air in and out of the nasal passages because they lack a rib cage Other shared characteristics o Ectothermic (all animals except birds and mammals) o Lack true ribs o Mucous glands in the skin May contain poison o Larval stage and metamorphosis o Adult forms are carnivorous ▯ Salamander Lack hair, feathers, scales which Secrete a moisturizing mucous o Most reliant on cutaneous resp. Salamanders are characterized by Long tails, unspecialized limbs, and A relatively flattened skull Vertebral column in modified to provide skin of salamander Support and flexibility on land Sacral and cervical vertebrae, allows for increased pelvic and head support o Undulatory type of locomotion (moves like a fish on land) ▯ Salamander reproduction Rely on olfaction and vision for mate selection 90% of all salamanders utilize internal fertilization o spermatophore: deposited on a substrate and the female will take it with her cloaca o eggs deposited in water or moist environment ▯ ▯