Presentation on theme: "Cross-Dressing Salmon"— Presentation transcript:
1Cross-Dressing Salmon By Tom Horvath SUNY College at Oneonta
2CQ#1: Which statement best describes natural selection? Survival of the fittest.The strongest individuals get to reproduce.The best adapted individuals survive and reproduce.Survival and reproduction is a matter of luck.
4Typical Salmon Life Cycle Female salmon dig the redd (gravel nest) with tail.Male protects redd from other potential spawners & attracts females.Females deposit eggs while male fertilizes eggs (external fertilization).Embryos hatch and develop into alevins.Alevins emerge as fry from the redd and start actively searching for food.After a period of growth in fresh water, anadromous species will start their downstream migration to the sea.Silvery smolts undergo a series of physiological and morphological changes that acclimate them to the salt water conditions.Smolts feed and grow to fully developed adult salmon.Adult salmon return to their natal stream to spawn (reproduce).Most salmon spawn only once during their lifetime (semelparous).The majority of salmon species die within a week of spawning.
6CQ#2: Out of all the eggs a female lays, how many hatchlings (or smolts) do you think will survive to spawn?50% (50 out of 100)10% (10 out of 100)1% (1 out of 100)0.1% (1 out of 1000)Less than 0.1 %Mass of fertilized salmon eggs
8Which are the lucky few who make it to reproduce? Rhetorical
9Charles Darwin’s Theory of Natural Selection It is not just random luck.Some individuals have a better chance of surviving and reproducing than others.Source:
10CQ#3: Are all these smolts ABSOLUTELY identical? A: Yes B: No
11Variation in salmon translates into variations in survival and reproductive success.
12Theory of Evolution by Natural Selection More offspring produced than survive to adulthood (OVERPRODUCTION).Variation among individuals of a species.
13What good is variation?Talk to your neighbor and list as many characteristics a salmon may posses that helps it survive.
14ADAPTATIONAny characteristic that improves the survival or reproductive success of an organism.Often the result of natural selection.Organisms match closely with their environment.
15Survival is only half the story – you have to reproduce to pass on those good traits that aided survival to this point.
16Theory of Evolution by Natural Selection More offspring produced than survive to adulthood (OVERPRODUCTION).Inheritable variation among individuals of a species.Best adapted individuals survive and reproduce (UNEQUAL REPRODUCTIVE SUCCESS).
18Movie Clip Focus on the male defending redd. Time point in clip is 0:25.
19The most dominant males (usually largest and most aggressive) successfully defend their redds and inseminate the eggs. Smaller males that also have the kype lose out in head-to-head competition with larger males. CQ#4: Are we seeing “survival of the fittest” in action here? A. Yes B. No
20A Different Type of Male Female MimicLack dominant male characteristics (e.g., no kype).Appear more female-like.Disadvantage: They can’t compete head-to-head with dominant males either, but….
21Why do these non-dominant males persist in the population over time Why do these non-dominant males persist in the population over time? Why don’t female mimics get weeded out through natural selection if they are not fit?
22CQ#5: Why are female mimics still found in each generation? Some outcompete the dominant males in the redds.They appear from mutations randomly each generation.They have a different reproductive strategy from dominant males and it works.Some females change into males under stressful environmental conditions.
23Cross-Dressing Salmon Female mimics can stay near the redds because dominant males don’t see them as competition; they think they are females.These fish get a brief chance to inseminate a few eggs before being ultimately bumped out by dominant males.
24CQ#6: Even though female mimics are not dominant, are they fit. A CQ#6: Even though female mimics are not dominant, are they fit? A. Yes B. No
25Survival of the Fittest? Source:Darwinian fitness: contribution an individual makes to the gene pool of the next generation relative to the contribution of others.
26Fitness can be compared with relative values (values from 1 to 0) A fitness value of 1 is assigned to the phenotype with the highest representation.All other phenotypes are assigned based on their reproductive success relative to the dominant type.
27Fitness Value ExampleDominant male phenotype produces 300 male offspring in the next generation.Female mimic phenotype produces 50 male offspring in the next generation.Small male phenotype produce only 5 male offspring.Dominant Male Phenotype – Fitness = 300/300 = 1.0Female Mimic Phenotype – Fitness = 50/300 = 0.17Small Male Phenotype – Fitness = 5/300 = 0.02
28Natural SelectionAnalyzing change in frequency of traits in a population:Three patterns emerge:Directional selectionStabilizing selectionDisruptive selection
29Natural SelectionDirectional Selection -Individuals of one extreme phenotype favored.Stabilizing Selection - Individuals with intermediate phenotype favored;Extreme phenotypes selected against.Disruptive Selection - Both extreme phenotypes favored; intermediate phenotypes selected against.
30Directional Selection Individuals of one extreme phenotype favoredPopulation underdirectional selectionPopulation withno natural selectionFrequencySimilar (and better) images can be found in most text booksBody Size of Salmon
31Stabilizing Selection Individuals with intermediate phenotype favored; extreme phenotypes selected againstPopulation understabilizing selectionFrequencyPopulation withno natural selectionSimilar (and better) images can be found in most text booksBody Size of Salmon
32Disruptive Selection Frequency Body Size of Salmon Both extreme phenotypes favored; intermediate phenotypes selected againstPopulation withno natural selectionPopulation underdisruptive selectionFrequencySimilar (and better) images can be found in most text booksBody Size of Salmon
33CQ#7: Given our fitness value from the example, which pattern of selection would we expect in the salmon population?Directional selectionStabilizing selectionDisruptive selectionUnnatural selection
34CQ#8: Do individuals have to be the “strongest” to be fit? YesNo
35CQ#9: Which of these traits might confer fitness upon an individual? Being sneaky and tricking the dominant males into letting you hang around the spawning females.Having an awesome hook on your jaw and large body size.Having sperm that are extra good at finding and fertilizing eggs.Being extra good at storing fat, which will fuel all that waterfall jumping while migrating upstream.Any of the above will increase fitness.
37Slide 7—Left Slide 9 Slide 10 and Slide 13 Slide 11 Description: Survival chart for an average salmon family.Source: U.S. Fish and Wildlife ServiceLink:Clearance: Public domain, a work of the United States Federal Government under the terms of Title 17, Chapter 1, Section 105 of the US Code.Slide 9Description: Water-colour portrait of Charles Darwin.Author: George RichmondSource: Wikimedia Commons.Link:Clearance: A faithful reproduction of an original two-dimensional work of art from the late 1830s. The work of art itself is in the public domain and its copyright has expired. This applies to the United States, Australia, the European Union and those countries with a copyright term of life of the author plus 100 years or fewer.Slide 10 and Slide 13Description: Salmon smolts.Source: Bonneville Power Administration, United States Department of EnergyLink:Clearance: Public domain, courtesy of BPA.Slide 11Description: Mass of salmon.
38Slide 17 Slide 20 and Slide 33 Slide 22 Slide 23 Slide 25 Description: Male salmon showing hook nose (kype).Source: U.S. Fish and Wildlife ServiceLink:Clearance: Public domain, a work of the United States Federal Government under the terms of Title 17, Chapter 1, Section 105 of the US Code.Slide 20 and Slide 33Description: Male and Female sockeye salmon.Source: Fisheries and Oceans CanadaLink:Clearance: Permissible non-commercial reproduction in accordance with Fisheries and Oceans Canada.Slide 22Description: Illustration of single salmon.Source: USDA Forest Service—Tongass National ForestLink:Slide 23Description: Sockeye salmon spawning in an Alaskan stream.Author: Wyatt RivardSource: Dreamstime.com, IDClearance: Copyrighted, licensed, royalty free.Slide 25Description: .Link: