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Classification of Organisms. Classification of Organisms. The study of the kinds and diversity of organisms and their evolutionary relationships is called systematics or taxonomy Taxonomy is the work involved in the original description of a species.
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Classification of Organisms • The study of the kinds and diversity of organisms and their evolutionary relationships is called systematics or taxonomy • Taxonomy is the work involved in the original description of a species. • Systematics is the assigning of species into evolutionary groups.
Father of Modern Classification • The modern classification system originated with the work of Carolus Linnaeus • he recognized the different species could be grouped into broader categories based on shared characteristics • any grouping of animals that shares a particular set of characteristics forms an assemblage called a taxon
Modern taxonomists use 7 taxa: • kingdom, phylum, class, order, family, genus and species • as taxa increase organisms get more specific
Binomial Nomenclature: • when a species is talked about only the genus and species names are used • this is called thescientific name • unique to each type of organism • Required by the International Code of Zoological Nomenclature
Writing Scientific Names • the genus names is always capitalized • both names are either italicized or underlined • leave a space in the underline between names ex. Homo sapien Felis leo Quercusrubra
Kingdoms of Life • In 1969, Robert H. Whitaker classified kingdoms based on cellular organization and mode of nutrition • this lead to the formation of the 5 kingdoms
5 Kingdoms of Classification: Monera: comprised of bacteria and cyanobacteria • distinguished by being single cell prokaryotes Protista: comprised of Amoeba, Paramecium etc…. • distinguished by being single celled eukaryotes Plantae: multi-cellular photosynthetic eukaryotes • plants have cell walls and are non-motile
5 Kingdoms of Classification: Fungi: multi-cellular heterotrophic eukaryotes • fungi have cell walls and usually non-motile • digest organic matter extra-cellularly (outside of cell) and absorb the breakdown products Animalia: multi-cellular heterotrophic eukaryotes • animal cells lack a cell wall and usually motile • feed by ingesting other organisms or parts of other organisms
Monera prokaryote single-cell Protista eukaryote multi-cell Plantae eukaryote multi-cell autotrophic Fungi eukaryote multi-cell heterotrophic, external digestion Animalia eukaryote multi-cell heterotrophic, internal digestion
DOMAINS??? • Many taxonomists have pushed the idea that the five kingdom system isn’t enough • they feel that organisms share too much similarities and need to be grouped otherwise • the push has led to the addition of 3 domains
3 Domains • Archae: bacteria that live in extreme conditions • Eubacteria: “true bacteria” • Eukarya: all eukaryotic organisms
Patterns of Organization • Once the kingdom of an organism has been decided other aspects of the organism must be looked at to determine it’s classification • Symmetry: describes how the parts of an animal are arranged around a point or an axis
Types of symmetry • Asymmetry: the absence of a central point or axis around which body parts are equally distributed • characterizes most protists and many sponges • not known to be an adaption or advantage to anything • organisms do not develop complex communication, sensory, or locomotor functions
Types of symmetry • Radial Symmetry: arrangement of body parts such that any plane passing through the central oral-aboral axis divides the animal into mirror images • oral-aboral axis: one point of reference is the mouth (oral end) and a second point of reference is the end opposite the mouth (aboral end) • often modified by the arrangement of some structures in pairs , or in other combinations, around the central oral-aboral axis
Types of symmetry • Bilateral Symmetry: the arrangement of body parts such that a single plane, passing between upper and lower surfaces and through the longitudinal axis of an animal, divides the animal into right and left mirror images. • characteristic of active, crawling, or swimming animals • tend to move in one direction, so one end is generally more complex Cephalization: the development or formation of a distinct head
Planes of symmetry are used to describe the organisms based on the relationships of body parts • Not all animals are easily described and can be confusing if different people try to explain them differently • To make it simpler some terms have been universally adopted.
Terms of Directions: • Aboral: the end opposite the mouth • Oral: the end containing the mouth • Anterior: the head end; usually the end of a bilateral animal that meets its environment • Posterior: the tail end • Caudal: toward the tail • Cephalic:toward the head • Distal: away from the point of attachment of a structure on the body (the toes are distal to the knee)
Terms of Directions: • Proximal: toward the point of attachment of a structure on the body (the hip is proximal to the knee) • Dorsal: the back of an animal; usually the upper surface; synonymous with posterior for animals that walk upright • Ventral:the belly of an animal; usually the lower surface; synonymous with anterior for animals that walk upright • Inferior: below a point of reference (the mouth is inferior to the nose in humans) • Superior: above the point of reference (the neck is superior to the chest) • Lateral: away from the plane that divides a bilateral animal into mirror images • Medial (median): on or near the plane that divides a bilateral animal into mirror images
Other Patterns of Organization • Unicellular (Cytoplasmic) level: all single celled organisms • characteristic body plan of the Protista • is not “simple” • must provide for locomotion, food acquisition, digestion, water and ion regulation, sensory perception, and reproduction all in a single cell • colonies can exist, but show little signs of interdependence, cooperation, or coordination of function
Other Patterns of Organization • Diploblastic Organization: simplest tissue-level organization • tissue is derived from two embryonic layers • Ectoderm: gives rise to the epidermis, the outer layer of the body wall • composed of epithelial and muscular cells • Endoderm: gives rise to the gastrodermis, the tissue that lines the gut cavity • composed of digestive and muscular cells • between the epidermis and gastrodermis is the mesoglea, a noncellular layer • cells in each layer are functionally interdependent
Other Patterns of Organization • Triploblastic Organization: tissues are derived from three embryological layers • like diploblastic, the ectoderm forms the outer layer and the endoderm lines the gut • in between these two layers is the mesoderm: which gives rise to supportive, contractile, and blood cells • most organisms have organ-system level of organization
Triploblastic Subgroups • Based on the presence of and what kind of body cavity they have. Body Cavity: a fluid-filled space in which the internal organs can be suspended and separated from the body wall
Why are Body Cavities advantageous? • Provide more room for organ development. • Provide more surface area for diffusion of gases, nutrients, and wastes into and out of organs • Provide and area for storage. • Often act as hydrostatic skeletons. • Provide a vehicle for eliminating wastes and reproductive products from the body • Facilitate increased body size.
Triploblastic Subgroups: • Triploblastic Acoelemate Pattern: the mesoderm layer is a relatively solid mass of cells between ectodermal and endodermal layers • acoelemate means “without” a “cavity” • some of the mesodermal cells are parenchyma: loosely organized cells not specialized for a specific function
Triploblastic Subgroups: • Triploblastic Pseudocoelemate Pattern: • pseudocoelom: a body cavity not entirely lined by mesoderm • No muscular or connective tissues are associated with the gut tract • No mesodermal sheet covers the inner surface of the body wall • No membranes suspend organs in the body cavity
Triploblastic Subgroups: • Triploblastic Coelemate Pattern: • coelem: a body cavity completely surrounded by mesoderm • peritoneum: thin mesodermal sheet that lines the inner body wall . • serosa: thin mesodermal sheet that lines the outside of visceral organs. • peritoneum and serosa are continuous and suspend visceral organs in the body cavity. • mesentery: the suspending sheets of organisms.
Three major groups of the Animal Kingdom: • Mesozoa: includes phylum Mesozoa, or the mesozoans • Parazoa: includes phylum Porifera, or the sponges • Eumetazoa: includes all other phyla • Eumetazoa are further divided into two groups based on body symmetry • Radiata: animals that have radial symmetry • Bilateria: animals that have bilateral symmetry
Bilateria animals are divided into two group based on embryological characteristics Comparative Embryology: studies based on the observation that embryological events may be similar because of shared ancestry
Two Bilateria Groups: • Protostomes: include animals in the phyla Platyhelminthes, Nematoda, Mollusca, Annelida, Arthropoda, and others • Deuterstomes: include animals in the phyla Echinodermatat, Hemichrodata, Chordata, and others.