Animal Body Systems Lecture 3 PDF

Biol 224.3 – Animal Body Systems Lecture 3: Classifying Animals Dr Joan Forder Supplementary Textbook Reading: (5th Edition: Chapter 24, page 603-611) 1  Classifying An...

Biol 224.3 – Animal Body Systems Lecture 3: Classifying Animals Dr Joan Forder Supplementary Textbook Reading: (5th Edition: Chapter 24, page 603-611) 1  Classifying Animals Use of Body Plans to classify animals Describe the way that animals are built Considered the “blueprint” of cellular organization Summary of Body Plans in Animals Fig. 24.5, p. 608  Animal Body Plans Animal body plans are influenced by: Embryonic development pattern (Protostomes vs. Deuterostomes) Germ cell layers (Diploblasts vs. Triploblasts) Body symmetry Body cavity type 4  Sexual Reproduction in Animals Most animals undergo some form of sexual reproduction Germ line cells Note: asexual undergo meiosis to reproduction also produce haploid occurs (e.g., gametes budding in hydra, fragmentation in echinoderms, and Gametes fuse parthenogenesis in during fertilization insects, some to form a diploid reptiles) zygote *We will learn more about animal reproduction later in the course 5  Zygote Cleavage Zygote Cleavage follows fertilization The division of cells in the early embryo Zygotes undergo rapid cell cycles with no significant growth Zygote develops into a compact mass of cells termed morula Morula derives into a hollow sphere of single layer of cells, termed blastula Unique to animals Protostomes and Deuterostomes have different cleavage patterns Morula Blastula 6  Cleavage Patterns in PROTOSTOMES Protostomes exhibit spiral cleavage - newly produced cells lie in the space between the cells immediately below them Each cell’s developmental path is determined as the cell is produced meaning that each blastomere is unable to develop into a complete organism by itself (Determinant Cleavage). 7 Image source: cronodon.com  Cleavage Patterns in DEUTEROSTOMES Deuterostomes exhibit radial cleavage - newly produced cells lie directly above and below other cells of the embryo Developmental fates of the first few cells are not determined Meaning a cell removed from the morula will go on to form a complete organism (Indeterminant Cleavage) 8 Image source: cronodon.com  Gastrulation Gastrulation Follows Cleavage Gastrulation begins at the vegetal pole Blastula invaginates and undergoes further differentiation into 2 or 3 (most animals) germ layers: Ectoderm Mesoderm Endoderm Germ layers differentiate to form tissues and organs 9  Animal Body Plans Animal body plans are influenced by: Embryonic development pattern (Protostomes vs. Deuterostomes) Germ cell layers (Diploblasts vs. Triploblasts) Body symmetry Body cavity type 10  Germ Layers Diploblastic animals (e.g., jellyfish, corals, anemones) have 2 germ layers: Ectoderm and Endoderm Triploblastic animals (e.g., flatworms, chordates) have 3 germ layers: Ectoderm, Endoderm and Mesoderm 11  Primary Cell Layers in Embryos Endoderm Innermost layer Forms lining of gut Mesoderm Between other layers Forms muscles of body wall and most other structures between gut and external covering Ectoderm Outermost layer Forms external covering and nervous system  From Germ Layers to Tissues and Organs Ectoderm – Skin and nervous system Endoderm – Digestive tract Mesoderm – Muscle and skeleton Tissues - Groups of similar differentiated cells specialized for particular functions - Usually isolated from other tissues by membrane layers Questions: 1. Since Diploblastic animals (e.g., jellyfish, corals, anemones) have only 2 germ layers which layer are they missing? 2. Which tissues are missing? 3. How does that affect the function of the animals? 13  Polarity of the Digestive System Blastopore develops Embryonic developmental pattern first Later, another opening at the opposite end of the embryo develops This second opening transforms the pouch-like gut into a digestive tube. Protostomes Deuterostomes 14  Origin of the Mesoderm Protostomes Mesoderm differentiates near the blastopore Coelom (body cavity) originates as a split in the mesoderm (i.e., schizocoelom) Deuterostomes mesoderm originates from outpocketings of the archenteron (primitive gut). Coelom develops from space within the outpocketings (i.e., enterocoelom) 15  Summary of Embryonic Development Differences Protostomes Deuterostomes Cleavage Pattern Spiral Radial Cell Fate Determinant Indeterminant Polarity of Mouth develops from Mouth develops from Digestive Tract blastopore secondary opening Origin of Differentiates near Mesoderm originates from Mesoderm blastopore outpocketings of the archenteron Origin of Coelom Schizocoelom Enterocoelom  Animal Body Plans Animal body plans are influenced by: Embryonic development pattern (Protostomes vs. Deuterostomes) Germ cell layers (Diploblasts vs. Triploblasts) Body symmetry Body cavity type 17  Body Symmetry of Animals Radial symmetry: can be divided Bilateral symmetry: can be divided equally by any longitudinal along a vertical plane at the middle to plane passing through the central create two identical halves axis 18  Animals with RADIAL SYMMETRY Diploblastic (except adult echinoderms) Exhibits no left or right sides Have a top (dorsal) and a bottom (ventral) side Often circular or tubular in shape with a mouth at one end (e.g., cnidarians and ctenophores) 19  Animals with BILATERAL SYMMETRY Triploblastic Balanced duplicate distribution of most body parts Specialized head with feeding and sensory organs (Cephalization) Digestive chamber with two openings, mouth and an anus Most animals with bilateral symmetry contain Segmentation 20  Segmentation Repeated structures along the anterior-posterior axis Seen in annelids, arthropods, chordates Advantages: movement, specialization 21  Animal Body Plans Animal body plans are influenced by: Embryonic development pattern (Protostomes vs. Deuterostomes) Germ cell layers (Diploblasts vs. Triploblasts) Body symmetry Body cavity type 22  Deuterostome Body Cavity (COELOM) In most bilaterally symmetrical animals, a body cavity (coelom) separates the gut from the body Most animals are coelomate wall (= Eucoelomate) A fluid-filled cavity between the intestines and the body wall Formed within the mesoderm of the embryo  Protostome Body Cavities Acoelomate (a = not; koilos = hollow) No body cavity Flat worms (Phylum Platyhelminthes) Note: Diploblasts are all acoelomates Pseudocoelomate (pseudo = false) Pseudocoelum: Fluid-filled or organ-filled space between endoderm and mesoderm Roundworms (Phylum Nematoda) 24 Summary of Body Plans in Animals Fig. 24.5, p. 608  Something to Think About What are the advantages of multicellularity over unicellularity? Why bilateral symmetry is more common in animal kingdom? What are the disadvantages of being an acoelomate animal? 26  Why do we study Animal Diversity & Evolution? Animals (and animal body systems) have a common evolutionary history helps us to learn common principles Animals occupy very diverse types of environments helps us understand environmental adaptations The physiological phenotype is a product of the genotype and the environment. 27 Example of Environmental Constraints Compare Respiratory system adaptations Fish: Flow through Bird: Circular flow Human: Tidal Flow 28  Challenges for Animals What challenges must animals overcome to be able to survive and reproduce? Extract nutrients & O2/energy from the environment Eliminate toxic metabolic wastes from the body Sense the environmental changes and respond favorably Maintain near constant internal body conditions 29  Unifying Concepts Animals are diverse, yet some common principles apply to all animals Physiological processes must: Obey the laws of physics and chemistry Usually tightly regulated (homeostasis) 30  Example: Electrical Laws Electrical laws describe membrane function of all cells including excitable cells such as neurons and muscle cells Neuron Muscles 31  NEXT WEEK Communication & integration in the animal body – Homeostasis. Nervous systems.