2012 Evolution Basics
Extinction is important -95-99% of species that have ever existed are now extinct -this allows “an opening” for other creatures to develop -the current mass extinction event is not natural which causes a concern for some
Charles Darwin -Chucky D . . . -”Father of evolution” -”discovered” - natural selection and sexual selection
What is “natural selection”? • Variation within a species • Too many babies born than can survive • Competition for limited resources • Selection for those creatures best adapted
Micro vs Macro - evoluvtion • Microevolution – changes within a species • Macroevolution – one species changing into another species • What is a “species”????????
Scientific inquiry vs. Creation science • Scientists did not come up with evolution because they wanted to defend a theory that might offend some people – they came up with it by taking a look at what was actually there, from evidence found in the natural world.
Evidence for evolution #1 • Fossil evidence
Evidence for evolution #2 • DNA – Molecular evidence
Evidence for evolution #3 • Homologous structures
Evidence for evolution #4 • Comparative Embryology
Two competing views . . . • Gradualism - “Darwinism” everything is in a constant slow change over time • Punctuated Equilibrium – everything remains essentially the same for long periods of time and then change rapidly in response to a change in the environment
What is sexual selection? • Not to hard to figure out – if you are the biggest, strongest, smartest, fastest . . . But don’t have the opportunity to mate then “survival of the fittest” does not mean much in the big scheme of things. Some creatures (birds are the best example) need to have special “accessories” or attributes (things that might even compromise their personal safety) to attract a mate.
Chucky D is the man Who came up with the idea of sexual selection
Sexual Selection Concepts • Passing on your genes (if you are a living thing) is a very important part of your limited time on earth. So important that it affects how some organisms both look (physical characteristics) and/or behave. • Two basic methods: • Asexual • Sexual
Advantages/Disadvantages • AsexualSexual • All of your genes are passed -Variation • Generally more offspring • No need to waste time/energy Looking for a proper mate
Sexual Dimorphism Male and Female of the same species look different – includes (but not limited too): Size Color Shape Antlers
Sexual Reproduction Terms • Monogamy – one male and one female reproductive strategy • Polygamy – one male multiple females or one female and multiple males reproductive strategy • Polygyny – one male, multiple females • Polyandry – one female, multiple males
Female Choice • Most scientists think that females being able to choose their mates drives sexual selection • This idea was hard to catch on as the male dominated scientific research arena was convinced females (human or otherwise) had little say in who they were going to share their genes in but as more research happened the idea that female choice ruled the day took hold.
Re: reproduction – who has more “skin in the game”?A. Male B. Female • Sperm are cheap, eggs have value • If the above statement is true then females have a huge stake in who they are combining their genes with and they would tend be very picky about who they mate with
Mating Strategies: • If it is female choice that rules the day then what is the advantage/disadvantage for a female that embraces . . . • Monogamy • Polygyny • Polyandry
“Monogamous” songbirds • "Social" monogamy -- staying together for the sake of the kids -- is one thing. But among birds, scientists are finding, females are sneaking off with other males whose offspring are then raised by the female and her unknowing partner. Why the deception? A leading theory is that it provides a sort of evolutionary insurance policy for the female bird. By adding some male genes from outside her "family," she's adding some genetic variability that could enable some of her offspring to survive if the environment should change. The female appears to choose "high-quality" males endowed with desirable traits for these "extra pair" matings. For example, female great reed warblers of Scandinavia select males with a larger repertoire of songs, which have been shown to father healthier offspring. Studies suggest that monogamy survives when the offspring are so dependent on both parents that it is in their interest not to stray if their offspring are to survive. Such situations, however, are in the great minority.
Prairie Vole – monogamy????? Normal for prairie vole couples to have 3-4 litters with 2-7 young in each one per year. One couple can easily create 20 new babies per year.
Prairie Dogs – Love (and offspring) is worth fighting and even killing for • Infanticide is common while the young are still belowground. Amazingly, females actually kill the juveniles of their kin within the coterie, and 39% of all litters are affected. Males kill as well, but female killing is the most common. Because infanticide is so commonplace, females defend the coterie territory and the burrow containing their juveniles from invaders — even if the invader is from their own coterie. Despite several predictions, the reasons for common infanticide are unknown, and further study is in progress. All of this occurs, yet communal nursing is common once the babies are able to get out of their holes.