4.1 Classification of Living Things Part 2

WHAT ARE THE THREE DOMAINS?

u Kingdoms used to be the highest level of classification

u Scientists noticed that organisms in two of the kingdoms different greatly from organisms in the other four

u A domain represents the largest differences among organisms

Bacteria

u Bacteria contain all organisms within Kingdom Bacteria

u It is made up of prokaryotes that usually have a cell wall and reproduce by cell division

u Prokaryotes – single-celled organisms that lack a cell nucleus

u They live in almost any environment

Archaeau Archaea include all organisms

in Kingdom Archaea

u Made up of prokaryotes that reproduce by cell division

u They have differences in their genetics and their cell walls when compared to bacteria

u Many live in harsh environments

Eukarya

u Eukaryotes are made up of cells that have a nucleus and membrane-bound organelles

u Eukaryotic cells are more complex than prokaryotic cells and usually larger

u Some eukaryotes like protists and some fungi are single-celled while most others are multicellular

u Eukarya is made up of all eukaryotes

WHAT ARE THE FOUR KINGDOMS IN EUKARYA?

Kingdom Protista

u Protista, called protists, are single-celled or multicellular organisms like algae or slime molds

u Very diverse

u They can have plant-like, animal-like, or fungus-like characteristics

u Some produce sexually (with a partner) or asexually (without a partner)

u Algae are autotrophs (make their own food)

u Some are heterotrophs (eat other organisms for food)

Kingdom Plantae

u Consists of multicellular organisms that have cell walls mostly made of cellulose

u Plants are autotrophs

u Found on land and in water that light can pass through

u Some reproduce asexually (like potatoes) while others reproduce sexually (like flowers with pollen)

u Cannot move by themselves

Kingdom Fungi

u Fungi are heterotrophs

u Cell walls contain chitin

u Fungal cells do not have chloroplasts

u Single-celled or multicellular, includes yeasts, molds, and mushrooms

u They use digestive juices to break down materials around them for food

u Reproduce sexually, asexually, or both ways depending on their type

Kingdom Animalia

u Animalia contains multicellular organisms that lack cell walls

u Do not have chloroplasts

u Heterotrophs

u Have specialized sense organs

u Most can move on their own

u Most animals reproduce sexually but a few can asexually (through budding)

HOW DO CLASSIFICATION SYSTEMS CHANGE OVER TIME?

u Millions of organisms have been identified and classified but millions have yet to be discovered and named

u Scientists are still identifying new species which may not fit into existing categories

u Many scientists argue that protists are so different from one another that they should be classified into several kingdoms instead of one

u The number of kingdoms may change as new data are collected

HOW DO BRANCHING DIAGRAMS SHOW CLASSIFICATION RELATIONSHIPS?u Cladograms: shows relationships among

speciesu Grouped according to common

characteristicsu Usually the characteristics are listed

along a lineu Organisms on branches above each

characteristic have the characteristicu Organisms on branches below lack the

characteristics

HOW CAN ORGANISMS BE IDENTIFIED?Dichotomous Keyu Dichotomous key uses a series of paired statements to

identify organisms

u Each pair of statements is numbered

u When identifying an organism, each pair of statements is read

u Then the statement that best describes the organism is chosen

u Either the chosen statement identifies the organism or it will direct you to another pair of statements

u Some dichotomous keys are set up as diagrams instead of tables