Macroevolution and Modern Classification Microevolution Observing allele frequencies

Macroevolution and Modern Classification

Microevolution • Observing allele frequencies change in a single population over generations Macroevolution • Evolution involving groups larger than a single species

Think “Tree, ” NOT “Ladder/Line”

What is a Cladogram? • A Cladogram is a diagram that represents a hypothesis about how species evolved • It shows common ancestry or phylogenic relationships • It may or may not include derived characters like the one below

Understanding Cladograms • This diagram shows a relationship between 4 relatives. These relatives share a common ancestor at the root of the tree. • Note that this diagram is also a timeline. The older organism is at the bottom of the tree. • The four descendants at the top of the tree are DIFFERENT species. Image courtesy of http: //evolution. berkeley. edu/evolibrary/article/0_0_0/evo_05

• Branches on the tree represent SPECIATION, the formation of a new species. • The event that causes the speciation is shown as the fork of the “V”. Image courtesy of http: //evolution. berkeley. edu/evolibrary/article/0_0_0/evo_05

• Species B and C each have characteristics that are unique only to them. • But they also share some part of their history with species A. This shared history is the common ancestor. Image courtesy of http: //evolution. berkeley. edu/evolibrary/article/0_0_0/evo_05

What is the only thing A and B have in common? Image courtesy of http: //evolution. berkeley. edu/evolibrary/article/0_0_0/evo_05

Counting Clades • A CLADE is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor. • Clades are nested within one another forming a nested hierarchy. • If you cut a branch of the tree, you could remove all the organisms that make up a clade.

• Look at the cladogram at the right. What conclusions can be drawn about the relationship between humans, chimps and bonobos? • How many clades are in this cladogram? SEVEN Video Clip on Constructing Cladograms Image courtesy of http: //evolution. berkeley. edu/evolibrary/article/0_0_0/evo_05

Cladistics (How Biologists Make Cladograms) • First, scientists observe unrelated groups of organisms and compare the presence of derived characters

Cladistics (cont. ) • Then, biologists often use Venn Diagrams to help organize clades, then draw the cladogram • The diagram to the right shows 5 different ways to represent a single line of descent

Cladistics (Cont. ) • Organisms in a clade share a derived character • Ex: horse & monkey have hair and mammary glands so they are in the same clade • If an organism does not share the character that unites a clade, it is placed in broader, inclusive clade • Ex: lizard does not have hair or mammary glands, but does have 4 legs and amniotic eggs

Cladistics (Cont. ) • Some characters can derive in unrelated clades due to convergent evolution (analogies) • However, the simplest scientific explanation that fits the data is the favored hypothesis

Cladograms are used to study the Evolution of Multicellular Organisms and Macroevolution

PATTERNS OF MACROEVOLUTION • ADAPTIVE RADIATION • When a single species or small group evolves into diverse forms that live in different ways (new niches available)

• MASS EXTINCTION • When 80% of species die out or go extinct • Occur under intense environmental conditions like ice ages, asteroids, or many volcanoes

• PUNCTUATED EQUILIBRIUM • Idea that evolution occurs at a rate that involves long stable periods interrupted by brief periods of rapid change

• CONVERGENT EVOLUTION • When unrelated species evolve similarities due to a selective pressure or similar environments • Analogous Structures: structures with different parts, but the same function (wings of birds, bats, and insects)

Convergent Evolution Dolphin shape and Fish shape

Convergent Evolution Wing Structure

• COEVOLUTION • When 2 species evolve in response to changes in each other over time (symbiosis)

CLASSIFICATION Taxonomy is the branch of biology involving the identification, naming, and classification of species

The Linnaean System of Classification • Carolus Linnaeus (1707 -1778) developed a naming system that gave every species a 2 -part Latin name and organized them into broader categories “Binomial Nomenclature” (2 -name naming system) Example: Homo sapiens or Homo sapiens Format - 1 st word capitalized, 2 nd word lowercase - Both words of the name italicized or underlined.

Question : • Which organisms are most similar? Why? • A. Acer nigra • B. Luriodendrum tulipifora • C. Acer palustris • Answer: A+C because they belong to the same genus – Acer

Linnaean Classification Groups (and Human Classification Groupings) • Kingdom • Phylum • Class • Order • Family • Genus • Species - Animalia - Chordata - Mammalia - Primate - Homididae - Homo - sapiens • “Kings Play Chess On Fat Green Stools”

Classification and Evolution • Darwin used Linnaeus’s system to show evolutionary relationships → phylogenic trees • The more homologous structures organisms shared, the more closely related they were • Today we use molecular evidence- fewer differences in DNA or amino acid sequences means closer relatives

Kingdoms and Domains • Biologists use the largest taxons to show common ancestry among all of life on Earth (past and present) • The number of kingdoms and the formation of domains have changed in response to new discoveries and evidence

Classification of Living Things Domain Bacteria Archaea Eukarya Kingdom Eubacteria Archaebacter ia Cell Type Prokaryote Cell Structure Cell walls with peptidoglycan Number of Cells unicellular Mode of Nutrition Autotroph or Heterotroph Streptococcus; E. Halophiles, coli Methanogens Amoeba, Paramecium, slime molds Mushrooms, yeast Examples Protista Prokaryote Fungi Plantae Animalia Eukaryote Cell walls without Some have cell walls Cell wall of Chitin peptidoglycan of cellulose; some have chloroplasts Most unicellular; Most some colonial; multicellular; some Some unicellular multicellular Cell walls of cellulose; chloroplasts No cell walls or chloroplasts multicellular Autotroph Heterotroph Mosses, ferns, Sponges, worms, flowering plants insects, fish