Classification

Historical Development of Classification  Classification: process of grouping and naming organisms based on evolutionary relatedness.  Classification is important because organized information is easier to use and access. By organizing living things into groups scientists can identify relationships, similarities, and differences easier.  The first attempts at classification where based entirely on physical appearance.  Aristotle was the first person to develop a classification system. His system included two major groups, plants and animals.

Historical Development of Classification  More recently Carl Linnaeus created a classification system with several large groups that where composed of smaller and smaller groups. These groups included kingdom, phylum, class, order, family, genus, and species. Linnaeus also classified organisms based on appearance.  He also created the current system for naming organisms called binomial nomenclature. This system uses the two most specific classifications (genus and species) as the scientific name.

Current Classification  Carl Linnaeus’ system is the bases of the current system of classification.  We currently use the same classification categories plus one new one, domain.  However scientists have changed the bases of classification from appearance to evolutionary relationships.  With the new knowledge about DNA and how it is inherited and the ability to identify how much DNA two individuals have in common, scientists can now establish the evolutionary relationship between organisms.  Those that are closely related share many classification categories.

Assignment  Assignment comparing the classification of many living things like compare a chimpanzee to humans to whales to sharks to birds to crocodile. How related are they?

Dichotomous Key  A series of paired statements that describe physical traits used to identify and classify organism.

Phylogenetic Trees  Phylogenetic trees are used to show the order in which living things branched off from the common ancestor. The more recently two groups branched off from each other the more related they are.  This also allows scientists to identify the order of appearance in history for each group of living things.

Groups of Living Things

Viruses  Not actually a living thing because it is not capable of performing the majority of life functions.  Examples include flu, cold, chicken pox, warts, polio, and small pox.  The structure of a virus is a protein coat (capsid) that surrounds genetic information. The capsid is used to trick cells so the virus can attach and inject the genetic material.

Eubacteria  Bacteria that are found in almost every condition except extremely harsh environments.  Examples include strep throat, tetanus, tuberculosis, and E. coli  Bacteria cells are prokaryotic (no nucleus or organelles). The majority of bacteria are going to be unicellular; however, some bacteria form cooperative groups called colonies. The cell wall contains peptidoglycan.

Archeabacteria  Bacteria that are found in extremely harsh environments. These bacteria are thought to be the ancestors of eukaryotic organisms.  Examples include bacteria that live in hot springs.  Bacteria cells are prokaryotic (no nucleus or organelles). The majority of bacteria are going to be unicellular; however, some bacteria form cooperative groups called colonies. The cell wall does not contain peptidoglycan.

Protists  This is a catch all category. If the cell is eukaryotic (has a nucleus) but the organism cannot be classified as a plant, fungus, or animal for any reason it is classified as a protist.  Examples include ameba, euglena, paramecium, and diatoms.  The cells are eukaryotic and most are unicellular. Some have cell walls. Some have cilia and flagella for movement.

Fungi  Heterotrophic organisms that digest and absorb food from the structures they live on.  Examples include mushrooms, yeast, ringworm, athletes foot, lichens, and mycorrhizza.  The cells have a nucleus (eukaryotic) and a cell wall made of chitin. The bulk of the fungus is a chain of single cells called mycelium that cannot be seen by humans. The visible structure is called the fruiting body and is the reproductive structure of the fungus.

Green Algae  Plants that are made up of individual cells that live in masses. They do not have specialized cells to perform different functions. A large mass of algae is called a bloom. Plants are autotrophic.  Examples include volvox, and fresh water algae.  The cells of algae are plant cells (eukaryotic) with a cell wall made of cellulose and chloroplasts to produce sugars. Some types of algae have cilia and flagella to allow them to move.

Bryophytes  Plants that have specialized cells, but do not have vascular tissue to transport materials around the body, seeds, or flowers. Mosses are very cold tolerant making them the only plant that can live at the poles.  Examples include mosses, liverworts, and hornworts.  Plant cells are eukaryotic with cell walls made of cellulose and chloroplasts to make sugar.

Seedless Vascular Plants  Plants that have vascular tissue (xylem and phloem) but they do not produce seeds or flowers. They reproduce by creating spores. Most are tolerant of low light conditions.  Examples include ferns, club mosses, and horsetails.  Plant cells are eukaryotic with cell walls made of cellulose and chloroplasts to make sugar.

Gymnosperms  Plants that have vascular tissue to transport material and create seeds for reproduction but the seeds are not produced inside flowers, they are made on cones.  Examples include conifers, cycads, ginkgoes, and gnetophytes.  Plant cells are eukaryotic with cell walls made of cellulose and chloroplasts to make sugar.

Angiosperms  Plants that have vascular tissue to transport materials and produce seeds inside of flowers.  Examples include pecan trees, water lilies, grasses, carrots, broccoli, and roses.  Plant cells are eukaryotic with cell walls made of cellulose and chloroplasts to make sugar.

Porifera  Simplest animals. They do not have symmetry (asymmetrical). Some of the cells have cilia or flagella in order to push water through the animal because that is how they will eat, obtain oxygen, and remove waste.  Examples include sponges.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Cnidarians  Radially symmetrical animals that posses nematocysts which are stinging cells.  Examples include jellyfish, sea anemones, and corals.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Platyhelminthes  Animals that have three different layers of tissue, several organ systems, cephalization (organization of nervous tissue creating a head) and sensory organs including eye spots.  Examples include flatworms such as planaria and tapeworms.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Nematodes  Worms that are not segmented but they do posses a one way digestive tract. These worms also have a tough outer skin that must be molted in order to grow suggesting they are more related to arthropods than other worms.  Examples include roundworms and hookworms such as heartworms in dogs.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Annelids  Animals that have segmented bodies, a closed circulatory system (blood stays in blood vessels), and a one way digestive tract.  Examples include leeches and earthworms.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Arthropods  Most varied group of animals that have exoskeletons, segmented bodies, open circulatory systems, and jointed appendages. Many also posses wings.  Examples include:  Crustaceans such as crabs, lobster, and shrimp  Chelicerae such as spiders, ticks, mites, scorpions, and horseshoe crabs.  Uniramia such as centipedes millipedes, and insects.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Mollusks  Animals that have soft bodies and a muscular foot. Some have external shells and some have internal shells that have modified.  Examples include snails, slugs, clams, squid, octopi, and nautilus.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Echinoderms  Animals that have spiny skin and a unique water vascular system to transport nutrients, get rid of waste, and exchange oxygen and carbon dioxide.  Examples include starfish, sea cucumbers, brittle stars, sand dollars, and sea urchins.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Fish  Animals that have scales, paired fins, a lateral line to detect water movement and gills.  Examples include  Jawless fish such as the lamprey and hagfish  Cartilaginous fish such as sharks, skates, and rays.  Boney fish such as perch and sea horses  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Amphibians  Animals that have thin moist skin so that they can move oxygen across it, no scales or claws, and live a double life. As juveniles they live in water with gills and no limbs. As adults they live mostly on land with lungs and strong appendages.  Examples include frogs, salamanders, and toads.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Reptiles  Animals that are exothermic, and have thick dry scaly skin, and claws.  Examples include snakes, turtles, alligators, crocodiles, and lizards.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Birds  Animals that are endothermic, have efficient body systems, are covered in feathers, and have modified front limbs called wings.  Examples include birds of prey, song birds, and water fowl.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.

Mammals  Animals that are endothermic, have efficient systems, have mammary glands to produce milk for young, and have hair.  Examples include  Monotremes such as a platypus and echidna  Marsupials such as kangaroos, koalas, and opossums.  Placental such as humans, bears, and dogs.  Animal cells are eukaryotic cells that lack a cell wall and chloroplasts.