Animal Morphology Lecture

• Attachment is a strong reciprocal emotional bond between an infant and a primary caregiver

  
• Schaffer and Emerson's 1964 study on attachment aimed to identify stages of attachment and find a pattern in the development of attachment between infants and parents
• Participants in the study were 60 babies from Glasgow, and the procedure involved analyzing interactions between infants and carers
• Findings from the study showed that babies of parents or carers who displayed 'sensitive responsiveness' were more likely to have formed an attachment
• Babies of parents/carers with 'sensitive responsiveness' were more likely to have formed an attachment

  
• Vertebrate formation is influenced by the amount and distribution of yolk, determining where cleavage can occur and the relative size of blastomeres
• Cleavage, a series of mitotic divisions after fertilization, divides the egg cytoplasm into numerous smaller, nucleated cells called blastomeres
• Cleavage patterns include holoblastic (complete cleavage), meroblastic (incomplete cleavage), and discoidal (extreme form of meroblastic cleavage)
• Representative animals for different cleavage patterns include amphioxus and eutherian mammals for microlecithal, lampreys, bowfins, and gars for mesolecithal, and reptiles, birds, and monotremes for macrolecithal
• The blastula is a hollow ball of cells that forms as cleavage continues, with different patterns like mesolecithal and macrolecithal
• Gastrulation involves gut formation, becoming bilaterally symmetrical, elongated, and cephalized, forming three germ layers: endoderm, ectoderm, and mesoderm
• Coelom formation involves the formation of hollow body cavities lined with mesoderm, with functions like providing lubrication for organ movement and freeing organs from the trunk's movement
• Evolutionary trends of gastrula in craniates differ based on the type of eggs, influencing processes like invagination, epiboly, and delamination
• The notochord is the first part of mesoderm that differentiates in the dorsal mid-line of the body

  
• The notochord's appearance is critical as it induces the formation of the neural tube
• Vertebrates cannot skip the neurulation step even if the notochord is not needed later
• During neurulation, the nervous system's formation often occurs concurrently with gastrulation
• Neurulation involves the thickening of the neural plate above the notochord, the formation of neural folds and a groove, the sinking and growth of folds to form the neural tube, and the development of the neurocoel or neural cavity inside the tube
• The brain first expands into enlarged regions as the neural tube grows fastest at its anterior end
• Histogenesis involves the development of epithelium, connective tissue, general connective tissue, and special connective tissue
• Heterochrony is a phyletic change where there is an ontogenic shift in the timing of a feature's appearance in descendant species
• Paedomorphosis refers to juvenile characteristics of ancestors appearing in the adults of descendants
• Peramorphosis is when adult characters of ancestors appear exaggerated in adult descendants
• The integumentary system functions include physical protection, water balance, thermoregulation, locomotion, respiratory exchange, coloration, and secretion
• The vertebrate integument consists of skin, hair, associated glands, and has a complex structure with an ectodermal epidermis and chiefly mesodermal dermis
• The epidermis has several layers of cells including the stratum germinativum (basale) and the stratum corneum, which is the outer layer mainly composed of keratinized cells
• The dermis is a meshwork of fibers, including collagenous and elastic fibers, with an outer vascular stratum spongiosum (laxum) and a deeper thicker stratum compactum
• Chromatophores are pigment cells that vary according to location in the integument
• The integument of fish includes an epidermis with epidermal cells secreting a protective cuticle or mucous slime, and a dermis with denticles and dermal placoid scales
• Primitive fishes like ostracoderms and placoderms had bony plates of dermal armor encasing their bodies in an exoskeleton
• Jawless fishes like lampreys and hagfishes have glandular cells that secrete a protective cuticle or mucous slime
• Chondrichthyes lack dermal bones but have denticles and placoid scales
• Teleosts, or bony fishes, have dermal bones (scales) with layers of loose and dense fibrous connective tissue
• Development of skin derivatives involves a thin basal membrane separating the dermis and epidermis, with induction occurring across the membrane
• Hard tissues like enamel, dentine, and bone are produced by different layers of the embryo and contribute to the integument's structure
• Armor shields, osteoderms, gastralia, and other hard structures evolved from dermal scales provide protection and support in different species
• The transition from aquatic to terrestrial environments poses challenges like desiccation, UV effects, and physical abrasion, leading to adaptations in the integument of tetrapods like frogs
• Amphibians have a unique integument with abundant glands, mucous glands, granular poison glands, and varied stratum corneum for functions like cutaneous respiration, gas exchange, and protection
• Reptiles exhibit keratinized scales, scutes, beaks, rattles, claws, plaques, and spiny crests in their epidermis, with specialized structures for protection and adaptation to their environments
• Birds have a typically reptilian integument with feathers for flight, insulation, recognition, mating, and camouflage, with specialized structures like dermal papilla and feather follicles for feather development