SPECIATION SPECIATION The process by which once species splits into two or more species Accounts for the diversity of life on earth If no speciation, there would only be species that was continuously evolving to adapt to the environment Eastern Meadowlark Western Meadowlark 2
WHAT IS A SPECIES? Depends who you ask! MORPHOLOGICAL SPECIES: Grouped by common physical characteristics (EX: Fossils, asexual organisms) ECOLOGICAL SPECIES: Grouped by ecological niche (Diet, living space etc) PHYLOGENETIC SPECIES: Grouped by position on evolutionary tree Two different species. 3 BIOLOGICAL SPECIES We will use this definition for class BIOLOGICAL SPECIES: A group of populations whose members can interbreed in nature and produce fertile offspring Biological species are reproductively compatible Reproductive barriers keep species separate 4 2
REPRODUCTIVE BARRIERS Prevent closely related species from interbreeding (sharing genes) PRE ZYGOTIC BARRIERS: Differences in habitat (Ex: land vs. aquatic) Differences in breeding seasons Differences in communication Differences in reproductive parts (Ex: flowers & hummingbirds) Differences in gametes (Ex: sea urchins) 5 REPRODUCTIVE BARRIERS Prevent closely related species from interbreeding (sharing genes) POST ZYGOTIC BARRIERS: Reduced development or survival of hybrids Reduced hybrid fertility (Ex. mules, ligers) If reproductive, hybrids usually have unhealthy or sterile offspring Grizzly bear Polar bear Hybrid grolar bear Hybrid offspring from two different species 6 3
MECHANISMS OF SPECIATION. ALLOPATRIC SPECIATION the formation of a new species due to geographic barriers Formation of mountain ranges Drought (lake subsides) Size of barrier? Depends on the organism in question! Reproductive barriers are still NECESSARY for speciation!! South rim A. harrisii A. leucurus North rim Allopatric populations populations separated by a geographic barrier 7 MECHANISMS OF SPECIATION 2. SYMPATRIC SPECIATION the formation of a new species in the same geographic area due to polyploidy, different habitats, or sexual selection Species A Gamete A A sterile hybrid with a single pair of a bunch of different chromosomes (Can reproduce asexually) Species B Gamete B Polyploidy having more than 2 sets of chromosomes 8 4
SYMPATRIC SPECIATION VIA PLEIOTROPY Errors during cell division result in a reproductive hybrid Common in plants b/c they can self fertilize Instant evolution Has happened with several plants in the last 50 years That sterile hybrid with a single pair of a bunch of different chromosomes Errors during cell division result in a second pair of hybrid chromosomes With an even number of chromosomes, meiosis can happen Wheat! Gamete cells of new species, ready for self-fertilization 9 ADAPTIVE RADIATION Evolution of many diverse species from a common ancestor (sympatric) Common on islands Founder Population migrates to new area and individuals differentiate in behavior, food and habitat Many new species arise each with reproductive barriers Cactus-seed-eater (cactus finch) Tool-using insect-eater (woodpecker finch) Ex: Darwin s Finches Ex: Lake Victoria Cichlid fish Seed-eater (large ground finch) 0 5
HYBRID ZONES Regions where different species mate and produce hybrid offspring allow us to study reproductive isolation Collared flycatcher Collared flycatcher POSSIBLE OUTCOMES ) Reinforcement of reproduction barriers (Ex. Flycatchers) 2) Fusion of two species into one (Ex. Lake Victoria Cichlids) 3) A Stable Hybrid Zone Pied flycatcher Allopatric population Pied flycatcher Sympatric population THE SPEED OF SPECIATION The fossil record show speciation can take 4,000 to 40 million years Punctuated pattern Gradual pattern Time 2 6
THE ORIGIN OF LIFE Early earth and the Big Bang 3 SIMPLE CELLS WERE LIKELY THE ST LIFE Scientists hypothesize that four chemical and physical steps may have resulted in the first life. Abiotic synthesis of small organic molecules (amino acids, nitrogenous bases) 2. Joining of these molecules into proteins and nucleic acids 3. Packaging of these molecules into protocells that maintained an internal chemistry different than the surrounding environment 4. The origin of DNA and RNA or their precursors 4 7
Sparks simulating lightning CH 4 Water vapor NH 3 H 2 2 Atmosphere Electrode Condenser 3 Cold water H 2 O Sea 4 Sample for chemical analysis 5 SIMPLE CELLS WERE LIKELY THE ST LIFE Scientists hypothesize that four chemical and physical steps may have resulted in the first life. Abiotic synthesis of small organic molecules (amino acids, nitrogenous bases) 2. Joining of these molecules into proteins and nucleic acids 3. Packaging of these molecules into protocells that maintained an internal chemistry different than the surrounding environment 4. The origin of DNA and RNA or their precursors 6 8
MACROEVOLUTION The broad pattern of changes of life on earth Hadean eon Archean eon Proterozoic eon Phanerozoic eon Origin of Earth Prokaryotes 3.5 bya Atmospheric oxygen 2.7 bya Multicellular eukaryotes.5 bya Single-celled eukaryotes.9 bya 4.6 4 3 2 Billions of years ago Colonization of land Animals Present 7 RADIOMETRIC DATING By measuring the concentration of radioactive isotopes, we can measure the actual age of rocks Carbon 2 Fraction of carbon-4 remaining 2 4 Carbon 4 (radioactive) 8 6 32 Time (thousands of years) 8 9
THE GEOLOGIC RECORD Phanerozoic eon (we are in it!) Proterozoic eon Precambrian 9 ORGANIZATION OF THE GEOLOGIC / FOSSIL RECORD Eons > Eras > Periods > Epochs > Ages 20 0