Cladistics Cladistics groups organisms by common descent A
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. 26 -11 b Lancelet (outgroup) Lamprey Tuna Vertebral column Salamander Hinged jaws Turtle Four walking legs Amniotic egg Leopard Hair (b) Phylogenetic tree 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. 27 -12 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
Prior Previously Printed • Unit 5 11
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: Bee Pollinating Video: Bat Pollinating Agave Plant 12
Fig. 30 -14 EXPERIMENT Time since divergence from common ancestor “Bilateral” clade “Radial” clade Common ancestor Compare numbers of species Mean difference in number of species RESULTS 3, 000 2, 000 1, 000 0 Bilateral symmetry (N = 15) Radial symmetry (N = 4) 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. 31 -22 15
Prior Previously Printed • Unit 4 16
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 -4 a Prezygotic barriers Habitat Isolation Temporal Isolation Ex. Dirunal vs. Nocturnal Individuals of different species (a) Mechanical Isolation Behavioral Isolation Ex. Different mating behavior Mating attempt (c) (e) (f) (d) (b) 20
• Unit 5 C 26 52&39 C 27 38&54, 43/45&44, 55&73, 67/70&72 C 30 95&96/89/90 C 31 87&88, 98&99 C 34 21
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