Cladistics Cladistics groups organisms by common descent A clade is a group of species that includes an ancestral species and all its descendants Clades can be nested in larger clades, but not all groupings of organisms qualify as clades 1

Fig b Hair Hinged jaws Vertebral column Four walking legs Amniotic egg (b) Phylogenetic tree Salamander Leopard Turtle Lamprey Tuna Lancelet (outgroup) 2

Transformation and Transduction A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria) 3

R Plasmids and Antibiotic Resistance R plasmids carry genes for antibiotic resistance Antibiotics select for bacteria with genes that are resistant to the antibiotics Antibiotic resistant strains of bacteria are becoming more common 4

Conjugation and Plasmids Conjugation is the process where genetic material is transferred between bacterial cells Sex pili allow cells to connect and pull together for DNA transfer A piece of DNA called the F factor is required for the production of sex pili The F factor can exist as a separate plasmid or as DNA within the bacterial chromosome Cells containing the F plasmid function as DNA donors during conjugation Cells without the F factor function as DNA recipients during conjugation The F factor is transferable during conjugation 5

Fig Sex pilus 1 µm 6

Kingdom Bacteria Bacteria include the vast majority of prokaryotes of which most people are aware Diverse nutritional types are scattered among the major groups of bacteria 7

Diverse nutritional and metabolic adaptations have evolved in prokaryotes Phototrophs obtain energy from light Chemotrophs obtain energy from chemicals Autotrophs require CO 2 as a carbon source Heterotrophs require an organic nutrient to make organic compounds These factors can be combined to give the four major modes of nutrition: photoautotrophy, chemoautotrophy, photoheterotrophy, and chemoheterotrophy 8

Kingdom Archaea Archaea share certain traits with bacteria and other traits with eukaryotes Some archaea live in extreme environments and are called extremophiles Extreme halophiles live in highly saline environments Extreme thermophiles thrive in very hot environments 9

Methanogens live in swamps and marshes and produce methane as a waste product Methanogens are strict anaerobes and are poisoned by O 2 In recent years, genetic prospecting has revealed many new groups of archaea Some of these may offer clues to the early evolution of life on Earth 10

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Evolutionary Links Between Angiosperms and Animals Pollination of flowers and transport of seeds by animals are two important relationships in terrestrial ecosystems Clades with bilaterally symmetrical flowers have more species than those with radially symmetrical flowers This is likely because bilateral symmetry affects the movement of pollinators and reduces gene flow in diverging populations Video: Bat Pollinating Agave Plant Video: Bat Pollinating Agave Plant Video: Bee Pollinating Video: Bee Pollinating 12

Fig Common ancestor Radial symmetry (N = 4) Bilateral symmetry (N = 15) Compare numbers of species Time since divergence from common ancestor “Radial” clade “Bilateral” clade 3,000 2,000 1,000 0 EXPERIMENT RESULTS Mean difference in number of species 13

Fungus-Animal Symbioses Some fungi share their digestive services with animals These fungi help break down plant material in the guts of cows and other grazing mammals Many species of ants and termites use the digestive power of fungi by raising them in “farms” 14

Fig

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Adaptive Radiations Adaptive radiation is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities 17

Darwin’s Galapagos Finches 18

Reproductive Isolation Reproductive isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring Hybrids are the offspring of crosses between different species Reproductive isolation can be classified by whether factors act before or after fertilization 19

Fig. 24-4a Habitat IsolationTemporal Isolation Ex. Dirunal vs. Nocturnal Prezygotic barriers Behavioral Isolation Ex. Different mating behavior Mating attempt Mechanical Isolation (f) (e) (c) (a) (b) (d) Individuals of different species 20

Unit 5C26 52&39C27 38&54, 43/45&44, 55&73, 67/70&72C30 95&96/89/90C31 87&88, 98&99C34 21