BILD 3 Lecture 10 Notes - Phylogeny & Whales PDF

BILD 3: Lecture 10 (Notes) Phylogeny & Whales ○ Phylogeny was used to determine whether several samples of WHALE MEAT came from LEGALLY HARVESTED SPECIES. ○ Researchers purchased 13 SAMPLES of “whale meat” from Japanese fish markets. They...

BILD 3: Lecture 10 (Notes) Phylogeny & Whales ○ Phylogeny was used to determine whether several samples of WHALE MEAT came from LEGALLY HARVESTED SPECIES. ○ Researchers purchased 13 SAMPLES of “whale meat” from Japanese fish markets. They sequenced part of their MITOCHONDRIAL DNA (mtDNA) from each sample and compared their results with mtDNA from KNOWN SPECIES. To infer the species IDENTITY, they constructed a PHYLOGENETIC TREE. ○ The tree shows how closely related the FISH MARKET SAMPLES are to the IDENTIFIED SPECIES. RESULTS: Of the species in the resulting gene tree, only MINKE WHALES in the SOUTHERN HEMISPHERE can be sold legally in Japan. Phylogeny In Eukaryotes ○ Different genes can evolve at DIFFERENT RATES in the same lineage. DNA coding for RIBOSOMAL RNA changes SLOWLY. It can be used to infer ANCIENT relationships. ○ MITOCHONDRIAL DNA (mtDNA) evolves relatively RAPIDLY. It can be used to explore MORE RECENT evolutionary events. Biological Species Concept ○ The biological species concept emphasizes REPRODUCTIVE ISOLATION The word SPECIES is Latin for “KIND” or “APPEARANCE.” These are comparisons of PHYSIOLOGY, BIOCHEMISTRY, and DNA SEQUENCES. Those comparisons will generally confirm that MORPHOLOGICALLY DISTINCT species are DISCRETE GROUPS. Species ○ A group of populations whose members can: Have the potential to INTERBREED IN NATURE Produce VIABLE/FERTILE offspring DO NOT produce offspring with members of other such GROUPS. ○ GENE FLOW between populations holds a species together GENETICALLY. Darwin & Species  ○ He was fascinated by SPECIATION, the process by which ONE SPECIES splits into TWO SPECIES. Speciation occurs as a RESULT of ADAPTIVE RADIATION. It produced the TREMENDOUS DIVERSITY of life and helps explain its UNITY. New Species From Old Ones ○ Three populations are connected by GENE FLOW. However, a BARRIER to gene flow is then ESTABLISHED, and it is usually REPRODUCTIVE. Due to that BARRIER, ONE of the populations begins to DIVERGE GENETICALLY. This one is now REPRODUCTIVELY ISOLATED, and it formed a NEW SPECIES. ○ THERE IS NO INTERBREEDING. Reproductive Isolation ○ These are BIOLOGICAL BARRIERS that impede members of two species from INTERBREEDING and producing FERTILE OFFSPRING. These will limit the formation of HYBRIDS. That is OFFSPRINGS that will result from INTERSPECIFIC MATING. ○ These can be BEFORE FERTILIZATION (Pre-Zygote) or AFTER FERTILIZATION (Post-Zygote). Pre-Zygotic Barriers ○ These will block the fertilization from occurring by: IMPEDING different species from ATTEMPTING TO MATE Preventing the successful COMPLETION of mating HINDERING fertilization is mating is SUCCESSFUL Habitat Isolation  ○ Two species that occupy DIFFERENT HABITATS within the SAME AREA may encounter each other RARELY, if AT ALL. Example: Apple Maggot Flies (A) are isolated from Blueberry Maggot Flies (B) because they FEED/LAY EGGS on different fruits. Temporal Isolation ○ Species that breed at DIFFERENT TIMES of the DAY/DIFFERENT SEASONS/YEARS cannot mix their gametes. Example: Western Spotted Skunks (W) mate in SUMMER and Eastern Spotted Skunks (E) mate in WINTER. Behavioral Isolation ○ COURTSHIP RITUALS and other behaviors UNIQUE to a species are effective barriers to MATING. Example 1: Blue Footed Boobies They will mate only AFTER a unique courtship DISPLAY. FEMALE blue-footed boobies are actively looking at the FEET of the MALES. ○ The LIGHTER SHADE OF BLUE the feet are, the more HEALTHY and likely to SURVIVE the male is. ○ Females HEAVILY look for this, as it ensures that the MALES eat well and their children will ALSO eat well. Example 2: Frigate Birds The MALE species will inflate their RED THROAT SACS and they will engage in a particular CALL. The FEMALE species are likely to choose males that match the RITUALS of their OWN species. ○ They will choose the ones that match their own SPECIES display/rituals. Mechanical Isolation ○ Mating is ATTEMPTED, but morphological differences prevent its SUCCESSFUL COMPLETION. Example 1: Snails The GENITAL OPENINGS of the snails in the genus BRADYBAENA do NOT align if their SHELLS spiral in OPPOSITE directions.  Gametic Isolation ○ SPERM of ONE species might be unable to FERTILIZE THE EGGS of ANOTHER species. Example 1: Sea Urchins The SURFACE PROTEINS on the SPERM and EGGS of DIFFERENT SEA URCHIN SPECIES will bind POORLY to each other. ○ This will prevent FUSION and ZYGOTE formation. Post Zygotic Barriers ○ These will prevent HYBRID ZYGOTES from developing into viable/FERTILE adults through: Reduced Hybrid VIABILITY Reduced Hybrid FERTILITY Hybrid BREAKDOWN Reduced Hybrid Viability ○ Genes of different PARENT SPECIES might interact in ways that IMPAIR the hybrid’s DEVELOPMENT/SURVIVAL in its environment. Example 1: Salamanders The HYBRID OFFSPRING of DIFFERENT subspecies of salamanders of the genus ENSATINA will not usually complete DEVELOPMENT. Reduced Hybrid Fertility ○ Meiosis might FAIL to develop NORMAL GAMETES, resulting in STERILITY, if the parent species have chromosomes of different NUMBER/STRUCTURE. Example 1: Mules The HYBRID offspring of a MALE DONKEY and a FEMALE HORSE is a MULE. ○ The mule is ROBUST but STERILE (2N = 63) Hybrid Breakdown ○ The FIRST-GENERATION hybrids are VIABLE/FERTILE, but offspring in the NEXT GENERATION are STERILE. Example 1: Cultivated Rice Hybrids between CERTAIN strains of cultivated rice are FERTILE. ○ However, members of the NEXT GENERATION are SMALL and STERILE.  The Limitations Of Biological Species Concept ○ There is a LIMITED NUMBER of species to which the BIOLOGICAL SPECIES CONCEPT can be APPLIED. Fossils Asexual Organisms (Including ALL Prokaryotes) Mating can be HARD TO OBSERVE Morphological Species Concept ○ Species are defined by MORPHOLOGICAL TRAITS alone. ○ PALEONTOLOGISTS use these to DEFINE FOSSILS. However, others will use them when REPRODUCTIVE BIOLOGY is NOT available. Ecological Species Concept ○ Species are defined by the ECOLOGICAL NICHES they occupy. ○ Niches select for DIFFERENT ADAPTATIONS Due to this, this concept will often OVERLAP with the MORPHOLOGICAL SPECIES concept. Biological Species Concept ○ Emphasizes the ABSENCE of GENE FLOW, but gene flow occurs between many MORPHOLOGICALLY and ECOLOGICALLY DISTINCT species. Example 1: Grolar Bears Grizzly Bears and Polar Bears are DISTINCT species, but they can OCCASIONALLY mate to produce GROLAR BEARS. Speciation ○ Speciation occurs in TWO WAYS: ○ Allopatric Speciation Populations are GEOGRAPHICALLY isolated ○ Sympatric Speciation Populations are NOT geographically isolated Allopatric Speciation ○ Example 1: Flyless Cormoran Vs. Marine Iguana  Geographic isolation prevented GENE FLOW with the MAINLAND POPULATIONS. Then, NATURAL SELECTION acted on both populations by providing traits that were better suited for their ENVIRONMENTS. One lives near a WATER SOURCE, while the other lives near an ISOLATED ISLAND. Allopatric Speciation (P2) ○ When populations STOP interbreeding (NO GENE FLOW), they begin to DIVERGE. Reason: If the environments DIFFER, each population will adapt DIFFERENTLY to its LOCAL ENVIRONMENT via NATURAL SELECTION. ○ This local adaptation is the MAIN reason why populations DIVERGE. Note: MUTATIONS and GENETIC DRIFT can also contribute. Example 2: Isthmus Of Panama ○ The Isthmus of Panama USED to be OPEN WATER. Due to the formation of a LAND BRIDGE between NORTH and SOUTH AMERICA, it closed 3 MILLION YEARS AGO. That land bridge SPLIT the populations of marine organisms from ONE into TWO. Allopatric Speciation Test ○ Nancy Knowlton of the SMITHSONIAN INSTITUTE ran a test of ALLOPATRIC SPECIATION. She tested SNAPPING SHRIMP, known for having the gene, ALTHEUS. The species of this gene are found on BOTH SIDES of the ISTHMUS. ○ Result: The ISTHMUS OF PANAMA led to allopatric speciation in SEVERAL snapping shrimp species. Mechanisms Of Sympatric Speciation ○ POLYPLOIDY IN PLANTS This is a COMMON MECHANISM of SYMPATRIC SPECIATION. ○ Example 1: Habitat Differentiation  The APPLE MAGGOT FLY is known for utilizing the HAWTHORN plant for its SURVIVAL. This plant holds SMALL RED FRUITS and it is the ANCESTRAL FLY HOST. However, flies are currently using APPLES, which were INTRODUCED to the species about 150 YEARS AGO. Apple Maggot Flies are common in EASTERN and MID-WESTERN US. There is a STRONG ASSOCIATION between FLIES and FRUIT HOSTS. Flies on EACH HOST are now GENETICALLY DISTINCT, despite their SYMPATRY.