today – 2/20
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Today – 2/20. Test results Critter in the News – Spanish flu Evolution. Administration. 3-pt XC opportunity, 7 pm, Steward Observatory N210, Andrea Ghez on the supermassive black hole at the center of our galaxy Read The Beak of the Finch. Spanish flu of 1918. - PowerPoint PPT PresentationTRANSCRIPT
Today – 2/20Today – 2/20
• Test results
• Critter in the News – Spanish flu
• Evolution
Administration
3-pt XC opportunity, 7 pm, Steward Observatory N210, Andrea Ghez on the supermassive black hole at the center of our galaxy
Read The Beak of the Finch
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Spanish flu of 1918
Killed .6% of all Americans, reduced average lifespan by 10 years!
1998 exhumed Native American female 1918 flu victim from the Alaska permafrost
Sequenced DNA, reconstructed virus, studying how it kills – attacks the lungs, gets the body to attack itself
The evolution happened entirely within birds
Clades: know it, love it, live itA clade is a clade because the critters in that clade share a set of derived characters that are unique to themTherefore, dinosaurs are not defined by their eggs or the holes in their skulls because other reptiles (crocs, lizards, turtles, etc.) lay the same kinds of eggs and/or have the same number of skull holes. The number of holes in the dinosaur skull makes the clade Dinosauria part of the larger clade Diapsida, while the kind of eggs dinosaurs laid makes them part of the much bigger clade Amniota
Clades: know it, love it, live it
A clade says there is something different about these animals from any other creatures that makes them unique and groups them together
For dinosaurs, the hips and ankles and some other things are distinctive. These changes gave them upright posture
Evolutionary relationships between HIV and SIV
Evolution in action: drug resistance
AZT, azidothymidine replaces the T (normal thymidine) in the HIV DNA during replication, ruining the DNA strandA tiny percentage of HIV particles in any generation have a mutation that make them better at screening out AZT, survive and pass the mutation to the next generationThese are less vigorous than normal HIV, but eventually thrive enough to cause AIDSIf AZT goes away, HIV reverts to normal
Evolution key point I
Evolution is not pursuing an ideal goal - it is adapting to current conditions. It is not trying to create a “perfect” organism, it is trying get organisms as perfectly adapted to their current environment as possible. When conditions change, so does the evolutionary pathway
Evolution key point II
Trade-offs: a given trait may have both costs and benefits, so that a change in environment radically changes the competitive edge of the individual that has it. The scientific term for this competitive edge is fitness - the ability of an individual to survive and reproduce in its environment
Evolutionary relationships between HIV and SIV
Trade-off example #2
Virulence kills host faster (less time for transmission to new hosts), but increases ability to transmit easily (so less time may be needed)
Therefore, in populations where the norm is unprotected sex with many partners, virulence is favored. In monogamous populations, more benign strains are favored
Evolution key point III
Parsimony – we assume that the evolutionary pathway that requires the least number of changes is the right one, the Occam’s Razor of evolutionary biology. The simplest explanation is usually the right one
In our example, this means that swim bladders evolved from lungs, not the other way around
Spread of marsupial mammals
Evolution key point IV
Physical processes on and in the Earth drive evolution (in addition to biological interactions). Energy for both physical and biological processes on Earth comes from two sources – the Sun and the interior of the Earth. Energy from the interior drives plate tectonics, energy from the sun drives weather. The two combine to determine the physical environment of Earth’s surface – continental and oceanic positions and climate. This is evolution’s canvass
http://helios.bto.ed.ac.uk/
www.clark-shawnee.k12.oh.us
Yucca and yucca moth
Darwin’s four postulates
1. Individuals within species are variable2. Some of these variations are passed on to
offspring3. In every generation, more offspring are
produced than can survive4. The survival and reproduction of
individuals are not random: the individuals who survive and reproduce the most are those with the most favorable variations. They are naturally selected
Natural selection
Usually associated with “survival of the fittest”. General usage refers to ability to deal with the physical and ecological environment – obtain food, avoid predators, survive winter (summer, around here), etc.
Selective agent is the environment
The Problem of the Peacock
Sexual selectionGuys showing-off to get mates, or battling each other for mates. Trade-off: often leads to traits that are disadvantageous in other ways – makes them more visible and/or vulnerable to predators, less effective hunters, etc.Often leads to two types of guys – very sexy versus very sneakySelective agent is the potential mate or the rivalNatural selection and sexual selection are often at odds
Group work
How does sexual selection work in field crickets?
Is sexual selection happening in European praying mantises?
Work in pairs, read one of the two short chapters, explain it to your partner
2-point quiz