What are Kingdoms and Domains? There is far too much structural diversity among organisms to compare them all at the species level. For this reason, biologists look at the kingdom and domain levels for similarities and differences. There are two main cell types that classify organisms into three domains. Feb 5 8:31 PM Prokaryotic cells do not have membrane bound nucleus most species are unicellular no species of prokaryotes are multicellular some live in colonies while others are filamentous Bacteria Archaea Feb 7 11:10 AM
Eukaryotic Cells membrane bound nucleus more complex internal structure usually larger than prokaryotic cells Some are unicellular and some are multicellular Feb 7 11:12 AM The three domains in our current classification system are Bacteria, Archaea, and Eukarya We distinguish among domains in kingdoms through, cell types number structure nutrition reproduction Feb 7 11:17 AM
Domain Bacteria Archaea Kingdom Bacteria Archaea Cell Type Prokaryote Prokaryote Number of Cells Unicellular Unicellular Cell Wall Material Peptidoglycan Not peptidoglycan; occasionally no cell wall Nutrition Primary means of reproduction Autotrophs and Heterotrophs Asexual Autotrophs and Heterotrophs Asexual Feb 7 11:24 AM Domain Eukarya Kingdom Protista Plantae Fungi Animalia Cell Type Eukaryote Eukaryote Eukaryote Eukaryote Number of Cells Unicellular & Multicellu lar Multicellula r Mostly Multicellula r Eukaryote Cell wall Material Cellulose in some; occasionally no cell wall Cellulose Shitin No Cell Wall Nutrition Autotrophs & Heterotrop hs Autotrophs Heterotrophs Heterotrophs Primary means of reproductio n Asexual & Sexual Sexual Sexual Sexual Feb 7 11:30 AM
Learning Check: 1. Which kingdom exhibits a prokaryotic cell plan? a. Animalia d. Protista b. Archaea e. Plantae c. Fungi 2. Why does our classification system divide organisms into large, general groups such as domains and kingdoms, as well as specific groups like species? 3. Three new species are discovered. State which domain each species is in and how you know. a. Species A is multicellular b. Species B is unicellular, has no membrane around its nucleus, and has a cell wall composed of peptidoglycan c. Species C is unicellular and has no membrane around its nucleus. Although Species C doesn't have a cell wall, most representatives of its domain have a cell wall that is not composed of peptidoglycan Feb 7 11:40 AM Using a Dichotomous Key It is easier to consider two options than it is to consider many options at the same time. A dichotomous key allows us to make simple choices, one at a time, to help identify organisms. Dichotomous keys are usually used to help identify a species but can also be used to identify an order, a family, or another rank. Feb 7 11:46 AM
To use a dichotomous key, make the first choice, and follow instructions to other choices This dichotomous key will help identify which kingdom an organism is in. 1a. prokaryotic go to 2 1b. eukaryotic go to 3 2a. peptidoglycan in cell wall Bacteria 2b. no peptiglycan in cell wall Arachaea 3a. chitin in cell wall Fungi 3b. no chitin in cell wall go to 4 4a. unicellular Protist 4b. multicellular go to 5 5a. autotroph Plantae 5b. heterotroph Animalia 1. Which traits tell you that an organism is in the Kingdom Plantae? a) prokaryotic, peptidoglycan in cell wall b) eukaryotic, peptidoglycan in cell wall c) eukaryotic, cell wall made of cellulose d) eukaryotic, no chitin in cell wall, multicellular, heterotroph e) eukaryotic, cell wall made of cellulose, multicellular, autotroph 2. Choice 4 tells you that if the organism is unicellular it is a Protist. Bacteria are also unicellular. What are Bacteria not listed as a possibility in choice 4? 3. Why is the choice between autotroph and heterotroph not made first? Feb 8 8:03 PM This is part of a dichotomous key for species of birch trees. 1a. twigs are fragrant go to 2 1b. twigs are not fragrant go to 3 2a. leaves widest near the middle Betula alleghaniensis 3a. mature bark is dark brown or gray go to 4 2b. leaves are widest near the base Betula lenta 3b. mature bark is white go to 5 4a. Leaves yellowish green and shiny Betula occidentalis 4a. leaves dark green and hairy Betula kenaica You have found a birch tree and want to identify it. a. what is the first thing you need to do? b. The twigs of the birch tree and not fragrant, and the bark is dark brown. What is the next decision you need to make, and what will that tell you about the tree? Feb 8 8:19 PM
Create your own dichotomous key See page 28 of your textbook once you have finished, get another group to test out your dichotomous key Feb 8 8:27 PM