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Chapter 18 – Classification

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1 Chapter 18 – Classification
Section 18-1: Finding Order in Diversity

2 To study the great diversity found on Earth, biologists give organisms names
Biologists use a classification system to name organisms and group them in a logical manner  this is known as taxonomy

3 Using scientific names makes sure that everyone is talking about the same organism
Larger, more general categories are needed as well as smaller specific categories Organisms in the same group are more similar to one another than organisms in a nearby group

4 Scientists began giving organisms scientific names in the 18th century because common names were just too confusing Latin and Greek were well known languages and were used for scientific naming

5 The first attempts at scientific naming usually described physical characteristics and could end up being very long names This also gave naming some subjectivity because a different scientist could describe the organisms in a different way

6 Carolus Linnaeus developed a two-word naming system called binomial nomenclature
In this system, each species is assigned a 2 part scientific name The name is always written in italics

7 The first word (genus) is capitalized and the second word (species) is not
Ex. The llama is Lama glama Genus = a group of closely related species The species is usually a Latin description of the organism

8 A dichotomous key can be used to help identify unfamiliar organisms - it is a series of paired statements that describe physical characteristics of different organisms

9 Linnaeus’s classification system is hierarchical – it consists of levels
The system includes 7 levels; (largest to smallest) kingdom, phylum, class, order, family, genus, and species In taxonomic nomenclature, each level is a taxon

10 Kingdom is the largest and most inclusive of the categories – there are 6 kingdoms

11 Phyla are made up of several different classes that share at least several important characteristics
The phylum chordate is made up of the classes of Mammalia, Aves (birds), Reptilia, Amphibia, and all classes of fish because they share important body plan features and internal functions

12 Classes are composed of similar orders
The class of Mammalia includes animals that are warm-blooded, have body hair, and produce milk

13 Orders are broad categories made up of similar families
Llamas belong to the order Artiodactyla, which are even toed hoofed animals – this order also includes pigs, hippos, giraffes, antelopes, and sheep as well as others

14 Families are composed of similar genera
Llamas are part of the Camelidae family with other similar organisms like alpacas and camels

15 Modern Evolutionary Classification
Section 18-2: Modern Evolutionary Classification

16 Scientists have tried to group organisms according to biologically important characteristics – however there are some limitations to this Classification was mainly based on visible similarities and differences, but which ones are important?

17 Darwin’s ideas about decent with modification has given rise to the study of phylogeny = the evolutionary relationships among organisms Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical characteristics This method of classification is evolutionary classification

18 In evolutionary classification, species in a genus share a recent common ancestor
Similarly, all genera in a family share a common ancestor

19 The higher the level of taxon, the further back in time the ancestor is
Just because two organisms look similar doesn’t necessarily mean they share a common ancestor – natural selection may just have been working on each organism in similar environments  this is convergent evolution

20 Cladistic analysis identifies and considers only those characteristics of organisms that are evolutionary innovations – new characteristics that have evolved Derived characteristics = characteristics that appear in recent parts of a lineage but not older parts

21 Cladograms are diagrams that show relationships among a group of organisms
They help scientists understand how one lineage branched from another (it is like a family tree for organisms) Characteristics can appear along the branches of the cladograms

22 The genes of organisms show important similarities at the molecular level
Similarities in DNA can help determine classification and evolutionary relationships Genes in very dissimilar organisms can code for proteins with somewhat similar functions

23 DNA sequences can show relationships  the closer the DNA, the closer the evolutionary relationship
DNA can also be used as a “molecular clock” to estimate the amount of time two species have been evolving independently

24 Section 18-3: Kingdoms and Domains

25 When Linnaeus first came up with his classification system, he named only two kingdoms – Animalia and Plantae The view of life was simpler and visible differences were considered

26 As biologists learned more about the natural world, they realized that the two kingdoms didn’t fit for every living organism Microorganisms like bacteria and protists were quite different and given their own kingdom, Protista

27 Mushrooms, yeasts and molds were still different and given their own kingdom, Fungi
Later, scientists realized that bacteria were still different from protists and were given a new kingdom, Monera Only recently did scientists realize that Monera was made of two distinct groups and they were now named Eubacteria and Archaebacteria

28 In summary, the current 6 kingdoms are Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia

29 The three domains are Eukarya, Bacteria, and Archaea
Recent work with RNA lead scientists to create a new taxonomic category – the domain – which is larger and more inclusive that kingdoms The three domains are Eukarya, Bacteria, and Archaea

30 1. Eukarya – includes protists, fungi, plants and animals
All eukarya have a nucleus Protists are any organisms that can’t be classified as animals plants or fungi – they have a very wide range

31 Fungi are heterotrophs that usually feed on dead or decaying matter
Plants are photosynthetic autotrophs and also nonmotile (can’t move from place to place)

32 2. Bacteria – includes eubacteria
They are unicellular and prokaryotic They have thick cell walls They have a wide range from soil bacteria to deadly parasites

33 3. Archaea – includes archaebacteria
Also unicellular and prokaryotic They live in some of the most extreme environments and usually can only survive without oxygen

34 Diseases caused by Bacteria Diseases caused by Viruses
Lyme disease Common cold Tetanus Influenza Tuberculosis Smallpox Diphtheria AIDS Bacterial meningitis Chickenpox Strep throat Measles Tooth Decay Hepatitis (A,B, & C)

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