Biological Classification Taxonomy the science of naming and

Biological Classification Taxonomy = the science of naming and classifying species Taxon = a category that organisms are placed into Ex: species or kingdom or class

Biological Classification Systematics – includes taxonomy but considers biological diversity in an evolutionary context – Focuses on tracing ancestry of organisms

Biological Classification, cont’d Basic unit of classification is a species Species differ from each other in at least one characteristic and do not interbreed freely with other species

Binomial Nomenclature Biological names are necessary for scientific exactness Developed by Carolus Linnaeus (1759) Used two words to describe an organism, the genus name and the species name Ex: Dianthus caryophyllus = carnation No other genus may use the same name, no other species name can be used more than once within a genus Names are the same (Latin) in all languages!

Taxonomic Classifications King Phillip Came Over For Good Spaghetti Kingdom-Phylum-Class-Order-Family. Genus-Species – Categories are based on homologies – Note that plant kingdoms have divisions instead of phyla – Bacterial species tend to be placed into groups called strains

Taxonomic Classifications, cont’d Species that share several characteristics are grouped into a genus, several genera that share some characteristics are grouped into the same family, several families that share some common characteristics are grouped in the same order, etc. Only a few common characteristics are shared at the kingdom level/ Think about what characteristics organisms in the kingdom Animalia have in common

Taxonomic Classifications, cont’d Taxonomic classifications are the result of interpretations of data and are subject to change Taxonomists can differ in how they interpret evidence A five kingdom classification system is proposed in many textbooks. Some other texts present six or seven kingdom systems.

Domains A recently added taxon above the level of kingdom in many texts is the domain Did King Phillip Come Over For Good Spaghetti? Domain-Kingdom-Phylum-Class-Order. Family-Genus-Species There are three different domains – Eubacteria, Archaea, and Eukaryota

Figure 27. 2 The three domains of life

3 Domain System Characteristics (see also TB p. 541) Feature Membrane Enclosed Organelles Peptidoglycan Cell Wall RNA Polymerase Introns Inhibit Protein Synthesis with Antibiotics Bacteria Archaea Eukaryota Absent Present Absent One type Absent Inhibited Several kinds Present in some Not Inhibited Present Not Inhibited

Classification by Homology Structure provides one consistent and useful basis for classifying organisms – Note similarity of limb patterns in birds, reptiles, amphibians, mammals

Classification by Homology, cont’d Biochemical homologies (DNA and protein sequences) are becoming increasingly important in determining relationships among species – The greater the similarity in DNA or protein sequences, the more closely related two organisms are thought to be – Ex: chimpanzees determined to be more similar to humans than to gorillas

Classifications Cells are the basic units of structure and function of living things Several criteria are used when classifying organisms. The two most basic include: Cell Structure – All organisms are classified as either prokaryotic or eukaryotic based on their cell structure Nutritional Status – Autotrophs Another name for a producer/can make its’ own food – Heterotrophs Another name for a consumer

Prokaryotes No membrane bound organelles so no nucleus Single circular chromosome (and sometimes a plasmid) Cell division without mitosis (binary fission) Cell walls contain proteins and sugars (peptidoglycan) Simple cytoskeleton / No cytoplasmic streaming Usually unicellular but may be multicellular No nervous system Locomotion is possible in some species

Eukaryotes – Have a nucleus – Contain membrane bound organelles – May be unicellular or multicellular – Contain chromosome pairs – Cell division by mitosis/cytokinesis – Have a complex cytoskeleton – Cell walls if present are made of cellulose or chitin – Have cytoplasmic streaming

Endosymbiotic Hypothesis Eukaryotic cells originated from a symbiotic relationship of prokaryotic cells Focuses on the origin of mitochondria and chloroplasts – These organelles are the same size as eubacteria – They reproduce by binary fission like bacteria – Their ribosomes are more similar to prokaryotic ribosomes than eukaryotic ribosomes

The Five Kingdom System Monera Protista Fungi Plantae Animalia

Kingdom Prokaryotae (or Monera) All prokaryotes may be grouped into one kingdom or divided into archaea and eubacteria Ex include: bacteria, blue-green algae

Kingdom Prokaryotae (or Monera), contd See previous prokaryote listing Monera can be classified in a number of ways Nutritional Classification – May be autotrophs or heterotrophs – Autotrophic prokaryotes may produce food through photosynthesis, but may use different raw materials than plants/may use alternative energy sources to drive chemosynthesis – Many heterotrophic bacteria are involved in decay processes (saprobes)

Kingdom Prokaryotae (or Monera), contd Classification by Reactivity with Oxygen – Obligate aerobes require oxygen for cellular respiration / they must have oxygen to grow – Obligate anaerobes must live in the absence of oxygen – Facultative aerobes can live in either the presence or absence of oxygen

Kingdom Prokaryotae (or Monera), contd Classification as Archaebacteria or Eubacteria Archaea include bacteria that live in extreme environments – Methanogens Adapted for anaerobic conditions, produce methane as a by-product – Halophiles Adapted to high salt conditions – Thermophiles Adapted for high temperature & acidic conditions

Eubacteria May be categorized by mode of acquiring nutrients, mechanism of movement, their shape, etc, Three basic shapes include: – Bacilli = Rod-shaped bacteria – Spirilla = Spiral-Shaped bacteria – Cocci = Sphere-shaped bacteria

Gram Negative vs Gram Positive Bacteria

Eubacteria Some important groups of bacteria to be familiar with Proteobacteria (= gram negative bacteria) Gram-positive bacteria Cyanobacteria (blue-green algae) Spirochetes (cause of syphilis, Lyme disease) Chlamydias (gram - / parasitic) Chemosynthetic bacteria (S bacteria) Nitrogen-fixing bacteria (more to follow in ecology unit) Mycoplasma (only bacteria to lack cell walls)

Kingdom Protista Includes wide variety of organisms including algae and seaweed (plant-like protists), protozoa (animal-like protists), and slime molds (funguslike protists) Are eukaryotic May be microscopic or large May be unicellular or multicellular May be autotrophs or heterotrophs No nervous system Locomotion is possible in some species

Animal-Like Protists Animal-like protists ingest food Some names to know…. – Rhizopoda (amoebas) unicellular, asexual, move via pseudopods, eat via phagocytosis – Foraminifera Marine protists with a calcium carbonate shell, typically live in symbiotic relationship with photosynthetic algae – Actinopoda Make up part of plankton – Apicocomplexa Parasitic, have both sexual and asexual stages, best known example is plasmodium, the cause of malaria – Zooflagellates – Ciliophora (Ex: paramecium)

Fungus-Like Protists Fungus-like protists ingest food Some names to know…. – Myxomycota Plasmodial slime molds Brightly colored but not photosynthetic Live in a clumped mass of single cells – Acrasiomycota Cellular slime molds – Oomycota Water-mold protists Cell wall is made of cellulose May be parasitic or saprobes

Plant-Like Protists Plant-like protists that are mostly photosynthetic Some names to know…. – Dinoflagellata Important producers in many aquatic food chains – Golden Algae Chrysophyta Swim among plankton – Diatoms Major component of plankton Cell walls made of silica

Plant-Like Protists – Green Algae (Chlorophyta) Primarily found in fresh water Contain chlorophyll a and b Considered to be the ancestors of plants – Brown Algae (Phaeophyta) Marine, multicellular Ex: kelp and seaweed – Red Algae (Rhodophyta) Red pigment = phycobilin Marine, live in deep waters. Can absorb nonvisible light for photosynthesis

Kingdom Fungi Ex: yeast, mold, mushrooms Heterotrophic eukaryotes (decomposers) Develop directly from spores Absorb small molecules from their surroundings through their outer walls/extracellular digestion Most are multicellular (except yeast which are unicellular) Reproduction may be sexual or asexual Most are haploid rather than diploid No nervous system/no locomotion Cell walls usually contain chitin

Representative Fungi Zygomycetes – Includes bread molds Basidiomycetes – Have fruiting bodies that bear basidia which produce basidiospores – Ex: mushroom stalk and cap are fruiting bodies Ascomyscetes – Form asexual spores in asci, sac-like structures resulting from conjugation Lichens – Fungi that live symbiotically with green algae Molds (Deuteromycota) – Asexual, quick growing Yeasts – unicellular, , may reproduce sexually or asexually

Kingdom Plantae Ex: mosses, ferns, cone bearing and flowering plants Autotrophic, multicellular eukaryotes Contain chloroplasts Store food as starch Develop from an embryo that lacks a blastula stage Have cellulose in cell walls Most reproduce sexually Produce bulk of world’s food and oxygen No locomotion/no nervous system

Kingdom Plantae, cont’d Divided into – Bryophytes (non-vascular plants) Ex: mosses, liverworts, and hornworts – Tracheophytes (vascular plants) Ex: ferns, trees, flowering plants

Evolutionary Trends in Plants dominant gametophyte →dominant sporophyte generation nonvascular → vascular seedless → seeds motile sperm → pollen naked seeds → seeds in flowers Chlorophytes → bryophytes → seedless vascular plants → gymnosperms → angiosperms

Kingdom Animalia Heterotrophic multicellular eukaryotes Grouped into 35 phyla Typically classified based on anatomical features (homologous structures) and embryonic development Develop from an embryo that has a blastula stage Very diverse in form Most reproduce sexually with a dominant diploid stage Most have nervous systems that aid in locomotion Contains both vertebrates and invertebrates

Nine Important Animal Phyla Porifera (sponges) Cnidaria (hydra, jelly fish) Platyhelminthes (flat worms – planaria, tapeworms) Nematoda (round worms) Annelida (segmented worms) Mollusca (squid-octopi-slugs, snails) Arthropoda (insects, crustaceans, arachnids) Echinodermata (sea stars, sea urchins) Chordata (fish, birds, reptiles, amphibians, mammals)

To classify animals need to know… Germ Layers – Main layers that form the various tissues and organs of the body – Formed early in embryonic development – Ectoderm – Mesoderm - Endoderm – Two germ layers = diploblastic Ex: porifera and cnidarians – Three germ layers = triploblastic Ex: platyhelminthes through chordata

To classify animals need to be able to distinguish radial and bilateral symmetry

To classify animals need to know… Radial Symmetry– Top & bottom but no right or left Bilateral Symmetry – body organized along a longitudinal axis with right and left sides that mirror each other – Also have an anterior (front end) and posterior (rear end) – Animals with bilateral symmetry are triploblastic – Note: echinoderms are bilateral as larvae and revert to radial symmetry in adulthood

To classify animals need to know… Coelomate – A fluid filled body cavity arising from mesoderm that provides space for elaborate body systems (transport, respiratory, digestive, etc) Acoelomate – Organism with no body cavity except a digestive cavity – Primitive animals porifera (sponge), cnidaria (jellyfish), and platyhelminthes (flatworms) Pseudocoelomate – Nematodes (roundworms) – Fluid-filled tube that acts as a hydrostatic skeleton

To classify animals need to know… Coelomates are further divided into two groups: – Protostomes – first opening (blastopore) becomes the mouth Annelids, mollusks, and arthropods – Deuterostomes – second opening becomes the mouth and first opening (blastopore) becomes the anus Echinoderms and chordates

Trends in Animal Development From the Primitive - No symmetry or radial symmetry - Two cell layers: ectoderm & endoderm - No coelom - No true tissues - Life in water - Sessile - Few organ systems To the Complex - Bilateral symmetry with a head end and complex sensory apparatus - Three cell layers - Pseudocoelom to coelom - True tissues and organs - Life on land all modifications it requires - Motile - Many organ systems and much specialization

Porifera Sponges No symmetry Sessile – do not move/no nerves or muscles Filter nutrients from water drawn through central cavity called a spongocoel Consists of two layers ectoderm and endoderm connected by noncellular mesoglea

Porifera, cont’d Have no true tissues or organs but have different cell types – Choanocytes are collar cells that line the body cavity and have flagella that circulate water – Spicules are for support, classify sponges by what makes up the spicules – Amoebocytes are cells that move on their own Evolved from colonial organisms Reproduce asexually by fragmentation as well as sexually/are hermaphroditic

Cnidarians Hydra and Jellyfish Radial Symmetry Body plan is the polyp (vase shaped) or the medusa (upside down bowl) Life cycle – some go through a planula larva (free-swimming) stage then go through two reproductive stages; asexually reproducing (polyp) and sexually reproducing (medusa)

Cnidarians, cont’d Two cell layers ectoderm and endoderm connected by noncellular mesoglea Have a gastrovascular cavity where extracellular digestion occurs Also carry out intracellular digestion inside body cells, carried out in lysosomes All members have stinging cells called cnidocytes

Platyhelminthes Flatworms (Ex: tapeworms) Simplest animals with bilateral symmetry, an anterior end, and 3 distinct cell layers Digestive cavity has only one opening for both ingestion and egestion so food cannot be processed continuously Acoelomate - solid body with no room for true digestive or respiratory system to circulate food molecules or oxygen/Solved problem by – Flat body plan which keeps the body cells in direct contact with oxygen in the environment – Branched digestive cavity that spreads food to all regions of the body

Nematodal Roundworms – Unsegmented worms with bilateral symmetry but little sensory apparatus Protostome coelomates Pseudocoelom transports nutrients but no room for a circulatory system Many are parasitic – Trichinella from uncooked pork causes trichinosis – C. elegans is used as a model system to study genes and development

Annelida Segmented Worms: Earthworms, Leeches Protostome coelomates Digestive tract is a tube within a tube consisting of a crop, gizzard, and intestine Nephridia for excretion of nitrogenous waste, urea Closed circulatory system – heart consists of five pairs of aortic arches Blood contains hemoglobin and carries oxygen Diffusion of oxygen and CO 2 through moist skin Are hermaphroditic but the animal does not self fertilize

Mollusca Squids, Octopi, Slugs, Clams, & Snails Protostome coelomates Have a soft body often protected by a hard calcium containing shell Bilateral symmetry with 3 distinct body zones – Head-foot contains both sensory and motor organs – Visceral mass contains organs of digestion, excretion, and reproduction – Mantle a specialized tissue that surrounds visceral mass and secretes the shell

Mollusca, cont’d Radula, a movable, tooth-bearing structure, acts like a tongue Open circulatory system with blood-filled spaces called hemocoels; most have gills and nephridia

Arthropoda Insects, Crustaceans (crabs), Arachnids (spiders) Protostome coelomates Jointed appendages Segemented: head, thorax, abdomen Chitonous exoskeleton protects the animal and aids in movement Open circulatory system with a tubular heart and hemocoels Malpighian tubules for moving nitrogenous wastes, uric acid Air ducts called trachea bring air from environment into hemocoels

Echinodermata Sea Stars & Sea Urchins Deuterostome coelomates Most are sessile or slow moving Bilateral symmetry as an embryo but reverts to primitive radial symmetry as an adult Water vascular system which is a modified coelom creates hydrostatic support for tube feet, the locomotive structures Reproduce sexually/fertilization is external Also reproduce by fragmentation or regeneration May contain an endoskeleton consisting of calcium plates

Chordata Fishes, Amphibians, Reptiles, Birds, and Mammals Deuterostome coelomates Have a notochord – a rod that extends the length of the body and serves as a flexible axis Dorsal, hollow nerve cord Tail aids in movement and balance – the coccyx bone in humans is a vestige of a tail May be homeotherms (maintain consistent body temp such as birds & mammals) or poikilotherms (“cold-blooded” such as fish, amphibians, and most reptiles)