AP Biology Macroevolution Part 2 Modes of Speciation
AP Biology Macroevolution Part 2
Modes of Speciation Allopatric speciation Sympatric speciation
Geographic Range of west coast salamanders (A ring species)
Galapagos Islands
Galapagos Islands close up
Darwin’s Galapagos Island finches
Modes of Speciation Allopatric speciation Sympatric speciation
Autopolyploidy Failure of cell division in a cell of a growing diploid plant after chromosome duplication gives rise to a tetraploid branch or other tissue. 2 n = 6 Gametes produced by flowers on this tetraploid branch are diploid. Offspring with tetraploid karyotypes may be viable and fertile—a new biological species. 2 n 4 n = 12 4 n
Allopolyploidy Unreduced gamete with 4 chromosomes Species A 2 n = 4 Hybrid with 7 chromosomes Unreduced gamete with 7 chromosomes Viable fertile hybrid (allopolyploid) Meiotic error; chromosome number not reduced from 2 n to n 2 n = 10 Normal gamete n=3 Species B 2 n = 6 Normal gamete n=3
Stephen Jay Gould
. Time Gradualism model Punctuated equilibrium model
Mass extinctions over time 100 600 Millions of years ago 400 300 200 500 80 0 Number of taxonomic families Permian mass extinction 2, 500 2, 000 ) Extinction rate 60 1, 500 40 Cretaceous mass extinction 1, 000 Number of families ( ) 20 500 0 Paleozoic Mesozoic Cenozoic Neogene Paleogene Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian 0 Proterozoic eon Extinction rate ( 100
Snowball Earth
Pangaea By about 10 million years ago, Earth’s youngest major mountain range, the Himalayas, formed as a result of India’s collision with Eurasia during the Cenozoic. The continents continue to drift today. Cenozoic 0 a c eri Eurasia m h. A rt No 65. 5 South America Africa India Madagascar Antarctica Mesozoic 135 Gon a gae Pan 251 Paleozoic Millions of years ago Laurasia dwa na lia stra Au By the end of the Mesozoic, Laurasia and Gondwana separated into the present-day continents. By the mid-Mesozoic Pangaea split into northern (Laurasia) and southern (Gondwana) landmasses. At the end of the Paleozoic, all of Earth’s landmasses were joined in the supercontinent Pangaea.
Asteroid Impact NORTH AMERICA Yucatán Peninsula Chicxulub crater
Example of Descent with Modification and Natural Selection
Evolution of the eye Pigmented cells (photoreceptors) Pigmented cells Epithelium Nerve fibers Patch of pigmented cells Fluid-filled cavity Epithelium Optic nerve Nerve fibers Eyecup Cellular fluid (lens) Pigmented layer (retina) Pinhole camera-type eye Optic nerve Eye with primitive lens Cornea Lens Retina Optic nerve Complex camera-type eye Cornea
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