Lecture 10 BIO 311D 1st EditionOutline of Last Lecture I. Sympatric SpeciationII. Habitat DifferentiationIII. Sexual selectionIV. PhylogenyV. Hierarchal ClassificationVI. Homology and Analogy DifferencesOutline of Current Lecture I. Cell Structure and SpecializationII. Reproduction and DevelopmentIII. Body PlansIV. TissuesV. Protostome and Deuterostome Developments:Current LectureCell Structure and Specialization: • Animals are multicellular eukaryotes• Their cells lack cell walls• Their bodies are held together by structural proteins such as collagen• Nervous tissue and muscle tissue are unique, defining characteristics of animals• Tissues are groups of cells that have a common structure, function, or both• Plants have cell walls, animals do not• So we have collagen in replacement• Animals have specialized cells such as nervous tissues and muscle tissues• Blastula is hallow inside, cells areformed on the outside• Yellow section turns into digestivetract• Outer layered cells are called theectoderm• Inner most cells are the endoderm• Middle layer is mesodermWhy should animals with radial symmetry be better able to do than those with bilateral symmetry?A. Move quickly in one directionB. Detect threats from above or below equally wellC. Deal effectively with food distributed homogeneously in 360 degreesD. Focused attention in a single directionReproduction and Development:• Most animals reproduce sexually, with the diploid stage usually dominating the life cycle• After a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage• Cleavage leads to formation of a multicellular, hollow blastula• The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues• Difference is whether or not they have larva (immature animals that cannot reproduce) or not • Humans are different in that they do not have larva• Humans are similar to other animals such that they have Hox genes• Many animals have at least one larval stage• A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis• A juvenile resembles an adult, but is not yet sexually mature• Most animals, and only animals, have Hox genes that regulate the development of body form• Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphologyBody Plans:- Animals can be characterized by body plans- Zoologists sometimes categorize animals according to a body plan, a set of morphological and developmental traits- Some developmental characteristics are conservative- For example, the molecular control of gastrulation is conserved among diverse animal groups- Animals can be categorized according to the symmetry of their bodies, or lack of it- Some animals have radial symmetry, with no front and back, or left and right- Two-sided symmetry is called bilateral symmetry- Bilaterally symmetrical animals have- A dorsal (top) side and a ventral (bottom) side- A right and left side- Anterior (head) and posterior (tail) ends- Cephalization, the development of a head- Radial animals are often sessile or planktonic (drifting or weakly swimming)- Bilateral animals often move actively and have a central nervous systemAdvantages of body cavities:SpecializationAbsorption of vibrations such as the heart to avoid the whole body from movingTissues:• Animal body plans also vary according to the organization of the animal’s tissues• Tissues are collections of specialized cells isolated from other tissues by membranous layers• During development, three germ layers give rise to the tissues and organs of the animal embryo• Ectoderm is the germ layer covering the embryo’s surface• Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron• Sponges and a few other groups lack true tissues• Diploblastic animals have ectoderm and endoderm• These include cnidarians and comb jellies• Triploblastic animals also have an intervening mesoderm layer; these include all bilaterians• These include flatworms, arthropods, vertebrates, and others• Most triploblastic animals possess a body cavity• A true body cavity is called a coelom and is derived from mesoderm• Coelomates are animals that possess a true coelom• A pseudocoelom is a body cavity derived from the mesoderm and endoderm• Triploblastic animals that possess a pseudocoelom are called pseudocoelomates• Triploblastic animals that lack a body cavity are called acoelomates• Coelomates and pseudocoelomates belong to the same grade• A grade is a group whose members share key biological features• A grade is not necessarily a clade, an ancestor and all of its descendantsProtostome and Deuterostome Developments:• Based on early development, many animals can be categorized as having protostome development or deuterostome development• In protostome development, cleavage is spiral and determinate• In deuterostome development, cleavage is radial and indeterminate• With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo• Indeterminate cleavage makes possible identical twins, and embryonic stem cells• In protostome development, the splitting of solid masses of mesoderm forms the coelom• In deuterostome development, the mesoderm buds from the wall of the archenteron to form the coelom• The blastopore forms during gastrulation and connects the archenteron to the exterior of the gastrula• In protostome development, the blastopore becomes the mouth• In deuterostome development, the blastopore becomes the anus• Zoologists recognize about three dozen animal phyla• Phylogenies now combine morphological, molecular, and fossil data• Current debate in animal systematics has led to the development of multiple hypothesesabout the relationships among animal groupsProtostome and deuterostome development are distinguished by differences inA. Cleavage coelom formation and the fate of the blastoporeB. Cleavage the fate of the blastopore and radial symmetryC. Gastrulation, radial symmetry, and diploblastic animals D. Triploblastic animals bilateral symmetry and indeterminate cleavage What is true of modern animal phylogenies?A. They take no account of an animals body planB. They portray an animals place on the scale of nature (scala