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The Animal Kingdom Anatomical Positions DORSAL ANTERIOR POSTERIOR VENTRAL Directional Orientation • • • • • • • Anterior vs. Posterior Dorsal vs. Ventral Medial vs. Lateral Distal vs. Proximal Inferior vs. Superior Cephalic vs. Caudal Aboral vs. Oral Anatomical Position Review • Use the proper terms to describe the relationship between the following body parts: – A) hand is ____ to the elbow – B) knee is ____ to the head – C) bellybutton is ____ to the spinal cord – D) heart is ____ to the lungs – E) head is ____ to the neck (2 terms fit here) – F) wrist is ____ to the fingers Characteristics of Animals • Heterotrophic • Multicellular • Movement • Eukaryotic Symmetry • Asymmetry • Radial Symmetry • Bilateral Symmetry Symmetry: Asymmetry • Irregular shapes • Do not move • Sponges Symmetry: Radial • Can divide into equal halves using many planes • Cnidaria (stinging animals) • Echinoderms (sea stars) Symmetry: Bilaterial • Can only divide into left & right halves • Most efficient for movement – Flatworms – Roundworms – Mollusks – Segmented Worms – Chordates Bilaterally Symmetrical Animals • Platyhelminths • Chordates • Fishes • Herps • Birds • Rotifers • Molluscs • Arthropods ALLOWS FOR CEPHALIZATION! Cephalization • The process in animals by which nervous and sensory tissues become concentrated in the "head." • Cephalization evolved several times within the animal kingdom, suggesting that it offers certain inherent advantages • the evolution of an advanced degree of cephalization in animals was associated with the evolution of a predatory lifestyle. Benefits of Cephalization • The anterior end of the animal became most likely to first encounter food, predators, and other important features of the external environment. • Flatworms (platyhelminthes) are the most primitive organisms to show cephalization Loss of Cephalization • Cephalization has been lost in some groups. • Bivalves (Clams, Mussels, etc.) • Echinoderms (Sea Stars) Body Plan of Organisms • General similarities in development and form and function among members of a particular phylum Germ Layers • Germ layer is a collection of cells found in an embryo that will give rise to all of the body’s tissues and organs. 3 Types of Germ Layers • Ectoderm – outside layer • Mesoderm – middle layer • Endoderm – inside layer LAYER ORGAN & ORGAN SYSTEM Ectoderm Nervous system Skin Sensory Organs Mesoderm Muscles Circulatory System Skeletal System Reproductive System Endoderm Lining of gut and respiratory tracts Liver Pancreas Digestive Glands Tissue Layer Body Plans • Diploblastic – ectoderm and endoderm • Triploblastic - ectoderm, mesoderm and endoderm – Acoelomate – Pseudocoelomate – Eucoelomate Animal Development (Embryology) • Stage 1: Fertilization • Sperm (n) meets Egg (n) to create Zygote (2n) Embryology • Stage 2: Initial Cleavage • Cleavage = cell divisions • The single cell begins to divide into a solid mass of cells (morula) Embryology • Stage 3: Blastulation • Interior of morula is pulled away • Forms blastocoel (hole middle) • Once hollow ball of cells is created, it is now known as a blastula. Embryology • Stage 4: Gastrulation • Indentation starts at pole of blastula (blastopore) What the blastopore becomes… • Determines if the organism is a protostome (mouth) or deuterostome (anus) Cleavage: Radial vs. Spiral • In deuterostomes, cleavage is radial • In protostomes, cleavage is spiral Embryology • Stage 5: Determination of Germ Layers • As cells move into blastopore; cells differentiate and creates 2 layers of cells (endoderm & ectoderm) • The horse-shoe shapes ball is called the gastrula Embryology • Stage 6: Coelom Development • In gastrula stage, digestive tract is formed in the middle of the organism • What surrounds that digestive tract is called a body cavity (coelom) determines whether the organism is a acoelomate, pseudocoelomate or coelomate • Gastrulation Video • Invagination • Creation of Primitive Gut Protostomes Body Cavities • Acoelomates – no body cavity – Platyhelminthes • Pseudocoelomates – fake body cavity – Nematodes Deuterostomes Body Cavities • All are Coelomates – true body cavity – Mollusks – Annelids – Arthropods – Echinoderms – Chordates