Download presentation
Presentation is loading. Please wait.
1
Chap 18- Classification Natural selection and other processes have led to a staggering diversity of organisms Biologists have identified and named about 1.5 million species so far Estimate that anywhere between 2 and 100 million additional species have yet to be discovered
2
Chap 18- Classification Why Classify?
For study purposes, biologists must give each organism a name Must also attempt to organize living things into groups that have biological meaning Biologists use classification system to name organisms & group them in a logical manner
3
Chap 18- Classification In taxonomy, scientists classify organisms and assign each organism a universally accepted name Using scientific name reduces confusion about which organism is being discussed When taxonomists classify organisms, place them into biologically significant groups
4
Chap 18- Classification Science often requires smaller categories as well as larger, more general categories Good system of classification – organisms placed into particular group more similar to each other than to organisms in another group
5
Chap 18- Classification Assigning Scientific Names
By 18th century, scientists recognized that referring to organisms by common names was confusing To eliminate confusion, scientists agreed to a single name for each species Latin & Greek were used for scientific names
6
Chap 18- Classification Early Efforts
1st attempts often described physical characteristics in great detail Some names twenty words long Also difficult to standardize names of organisms since different scientists described different characteristics
7
Chap 18- Classification Binomial Nomenclature
Carolus Linnaeus- Swedish botanist, 18th century Developed two-word naming system called binomial nomenclature Each species assigned a two-part scientific name Always written in italics; 1st word capitalized Homo sapiens
8
Chap 18- Classification Linnaeus’ System of Classification
Hierarchical; consists of levels Seven levels (smallest to largest): species, genus, family, order, class, phylum, and kingdom Each level called a taxon, or taxonomic category
9
Chap 18- Classification Species- group of similar organisms that can breed and produce fertile offspring Genus- group of closely related species Family- group of genera that share many characteristics Order- broad taxonomic category composed of similar families
10
Chap 18- Classification Class- composed of similar orders
Ex.- Order Carnivora placed in class Mammalia (animals that are warm-blooded, have body hair, and produce milk for offspring) Phylum- Several different classes; members may be different from one another, but share important characteristics Kingdom- most inclusive of all taxons
11
Grizzly bear Black bear Giant panda Red fox Albert squirrel Coral snake Sea star KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos
13
Chap 18- Classification Organisms determine who belongs to their species by choosing who to mate with Taxons above the species level are “invented” by taxonomists who decide how to distinguish between one genus, family, or phylum Always tried to group according to biologically important characteristics
14
Chapter 18- Classification
Linnaean system has limitations & problems System uses homologies to group species into larger and more general categories Since Darwin, classification is a way of describing evolutionary relationships
15
Chap 18- Classification Which Similarities Are Most Important?
Linnaeus grouped species into larger taxa mainly according to visible similarities & differences Which are most important? Ex.- Dolphins Fish due to fin-like limbs and live in water? Mammals due to milk and breathe air?
16
Chap 18- Classification Evolutionary Classification
Darwin’s ideas gave rise to study of phylogeny (evolutionary relationships between organisms) Now group organisms into categories that represent lines of evolutionary descent, not just physical similarities Systematics- classification based on evolutionary relationships, not just physical similarities
17
Chap 18- Classification Species within a genus more closely related to each other than to species within another genus Because all members of a genus share a recent common ancestor So, all genera in a family share a common ancestor; much farther in past Higher the taxon level, further back the RCA of all organisms in the taxon
18
Chap 18- Classification Evidence used in Systematic Taxonomy:
Fossil record Morphology Embryological Patterns of Development Similarities in Macromolecules
20
Chap 18- Classification Organisms that appear very similar (like barnacles and limpets) may not share a RCA Natural selection has often caused convergent evolution Barnacles & limpets used to be classified together based on superficial similarities Evolutionary classification now shows barnacles more closely related to crabs than limpets
21
Evolutionary Classification
CLASSIFICATION BASED ON VISIBLE SIMILARITIES Evolutionary Classification Appendages Conical Shells Crab Barnacle Limpet Crustaceans Gastropod
22
Chap 18- Classification Classification Using Cladograms
Refining the process, many biologists now prefer a method called cladistic analysis Identifies and considers only those characteristics of organisms that are evolutionary innovations Characteristics that appear in recent parts of a lineage but not in older members- derived characters
23
Chap 18- Classification Derived characters used to construct a cladogram Diagram that shows evolutionary relationships among a group of organisms Useful tools that help to show how one lineage branched from another in the course of evolution Cladogram represents a type of evolutionary tree
24
CLASSIFICATION BASED ON VISIBLE SIMILARITIES
CLADOGRAM Appendages Conical Shells Crab Barnacle Limpet Crustaceans Gastropod Molted exoskeleton Segmentation Tiny free-swimming larva
26
Chap 18- Classification Similarities in DNA & RNA
All classification methods discussed so far based primarily on physical similarities & differences Organisms with very different anatomies can have common traits Since DNA & RNA so similar across all forms of life, provide method of comparing organisms at genetic level
27
Chap 18- Classification Genes of many organisms show important similarities at molecular level Similarities in DNA can be used to help determine classification & evolutionary relationships
28
Chap 18- Classification Even genes of diverse organisms such as humans and yeasts show many similarities Humans have gene for muscle protein myosin Yeasts also have gene for protein myosin Indicator that humans and yeasts share a common ancestry
29
Chap 18- Classification Can also help show evolutionary relationships of species and how species have changed More similar DNA sequences of two species, more recently they shared a common ancestor More two species have diverged, less similar their DNA will be
30
Chap 18- Classification Tree of Life Evolves
In Linnaeus’ time, scientific view of life was simpler Only known differences among living things were traits that separated animals & plants As biologists learned more about natural world, realized Linnaeus’ two kingdoms did not represent full diversity of life
31
Chap 18- Classification Microorganisms were first given a new kingdom based on significant differences from animals & plants (Protista) Next, mushrooms, yeasts, & molds were separated from the plants & placed into own kingdom (Fungi) Later on, bacteria were realized to be missing membrane-bound organelles and placed into own kingdom (Monera)
32
Chap 18- Classification Recently, as new data about bacteria accumulated, Monera were recognized as being two separate groups As a result, Monera has been split into two new kingdoms: Eubacteria & Archaebacteria Gives us six kingdom system: Eubacteria, Archaebacteria, Protista, Fungi, Plantae, & Animalia
34
Chap 18- Classification Three-Domain System
Some most recent evolutionary trees have been produced using comparative studies of rRNA found in all living things These molecular analyses given rise to a new taxonomic category, the domain The domain is more inclusive category- larger than a kingdom
35
Chap 18- Classification Three domains:
-Eukarya: composed of protists, fungi, plants, & animals -Bacteria: corresponds to kingdom Eubacteria -Archaea: corresponds to kingdom Archaebacteria
36
Classification of Living Things
DOMAIN KINGDOM CELL TYPE CELL STRUCTURES NUMBER OF CELLS MODE OF NUTRITION EXAMPLES Bacteria Eubacteria Prokaryote Cell walls with peptidoglycan Unicellular Autotroph or heterotroph Streptococcus, Escherichia coli Archaea Archaebacteria Prokaryote Cell walls without peptidoglycan Unicellular Autotroph or heterotroph Methanogens, halophiles Protista Eukaryote Cell walls of cellulose in some; some have chloroplasts Most unicellular; some colonial; some multicellular Autotroph or heterotroph Amoeba, Paramecium, slime molds, giant kelp Fungi Eukaryote Cell walls of chitin Most multicellular; some unicellular Heterotroph Mushrooms, yeasts Eukarya Plantae Eukaryote Cell walls of cellulose; chloroplasts Multicellular Autotroph Mosses, ferns, flowering plants Animalia Eukaryote No cell walls or chloroplasts Multicellular Heterotroph Sponges, worms, insects, fishes, mammals
37
Chap 18- Classification Domain Bacteria Unicellular and prokaryotic
Cells have thick, rigid cell walls (contain peptidoglycan) around cell membrane Ecologically diverse Some photosynthesize, others do not Some are aerobic, some anaerobic
38
Chap 18- Classification Domain Archaea Unicellular and prokaryotic
Live in very extreme environments Most are anaerobic Cell walls lack peptidoglycan Cell membranes contain unusual lipids not found in other organisms
39
Chap 18- Classification Domain Eukarya
Consists of all organisms that have a nucleus Protista Composed of eukaryotic organisms that cannot be classified as plants, animals, or fungi Members display great variety
40
Chap 18- Classification Most are single-celled, some are multi-cellular Some are photosynthetic, some are heterotrophic Some share characteristics with fungi, some with plants, others with animals Fungi Heterotrophs Feed on dead or decaying organic matter
41
Chap 18- Classification Secrete digestive enzymes into their food source (unlike other heterotrophs) Most are multicellular, some (yeasts) are unicellular Plantae Multicellular, photosynthetic autotrophs Nonmotile Have cell walls that contain cellulose
42
Chap 18- Classification Includes cone-bearing & flowering plants as well as mosses and ferns Multicellular algae are found in Protista, not Plantae Animalia Multicellular & heterotrophic No cell walls Most animals are motile, for at least part of life cycle
43
DOMAIN EUKARYA DOMAIN ARCHAEA DOMAIN BACTERIA
Kingdoms Eubacteria Archaebacteria Protista Plantae Fungi Animalia DOMAIN EUKARYA DOMAIN ARCHAEA DOMAIN BACTERIA
Similar presentations
