Anthropology 5
January 4, 2011
Day 1 Week 1

Teacher: Kate Hanson
Intro to class and natural selection
Course structure
Syllabus
Website
Examples of adaptations
Natural selection logic
What is advantageous?
Tinkering
Read the assigned chapter after the lecture is given
Grading
32% Midterm
34% Final
24% Problem sets
10% Research credit (2 research hours or one assignment
7% Extra credit for correct in-class clicker questions
Timetables of lectures, exams, and problem sets can be found in the syllabus
Problem sets are graded on effort rather than correctness
A correct answer is better because it demonstrates you understand the concept
Need to be typed and turning in on time, have to be in section for 48/50 minutes
The problem set with the lowest grade will be dropped

Good fit
Organisms fit well into their environment both due to their physical structures and their behaviors
They are able to address the problems potentially faced by their environment
Eg. The Western screech owl blends into the trees in which it lives
Even the position they sit in and their location on the tree help camouflage
Eg. The fish mimicking the stones at the bottom of the river it lives in
It lays at the bottom rather than swim through the current
Eg. Baby arctic seals’ white coats help to blend into the snow
A combination between physical traits and behavioral decisions allow for camouflage
Eg. Certain crustaceans blend into the coral near them
Eg. Baby dear hunker down when the mother is away
They do not have a scent and are therefore hard to find
Eg. The caterpillar that “looks like poop”
It is not hidden, but has an undesirable look
Eg. Turkey vultures eat decaying flesh
Aided by a featherless head and feet (feathers wont get covered in parasites if they are absent in particular areas)
Enormous nostrils help to find prey
A big question
How do organisms fit their environment so well?
How do organisms get to a certain point of fitness?
Evolution by natural selection!
Co-authored by Charles Darwin and Alfred Russell Wallace
Darwin theorized the idea as a young man, but didn’t explore it until later
Each came up with the ideas individually
Had friends in common and published the theory together
Step 1: population growth is exponential
Begin with 1 breeding pair (2 individuals)
The pair has 2 offspring…etc.
2, 4, 8, 16, 32, 64, 128, 256, 512, 1024…
Assumptions:
The earlier pairs never die
There are no inbreeding problems
Darwin decided to use a difficult subject to prove his point: elephants
Begin to produce at age 30
Have 1 offspring every 10 years (per breeding pair)
Propagate up to age 90
Making 6 offspring per pair total
Step 2: natural populations remain relatively stable over time
Disease, famine, etc. maintain a low population growth
(1) If population growth is exponential but (2) natural populations remain relatively stable over time, then
Step 3: many individuals must fail to reproduce
Why do some individuals fail to reproduce at the maximum rates?
Step 4: individuals with more advantageous rates are more likely to survive and reproduce
Some traits are better in certain environments than in others
Advantageous traits=well fit to the environment
Step 5: offspring resemble their parents
Parents with advantageous traits are likely to pass on those traits to their offspring
Parents with less advantageous traits (if they have offspring) are likely to pass on those traits to their offspring as well
So if (4) individuals that have more advantageous traits are more likely to survive and reproduce (5) offspring resemble their parents then,
Step 6: advantageous traits (CHECK THE LECTURE)
Evolution: the increase of the frequency of a trait over time
This is a restatement of step 6
If advantageous (CHECK THE LECTURE)
Poor traits are not being passed on or are not being passed on at as high of a rate
What is advantageous?
Different environments present different obstacles
How an organism goes about meeting those obstacles determines what is advantageous and what isn't
Different environments mean difference in what is advantageous
Eg. Long legs of gazelles, no trees mean that speed is better for escaping predators
Eg. Short legs for star nose moles, a need to dig requires short legs
What is advantageous also depends on the rest of the organism’s traits
Eg. Butterflies aren’t very ferocious
Wouldn’t it help butterflies to have fangs?
The other traits of butterflies (a light body for flying) means fangs would be hard to implement
Bottom line
For a trait to be advantageous, then the benefits it provides absolutely always must be greater than the costs
Everything has costs
Growth, maintenance, utilizing it, lugging it around, increased production rates, decreased life expectancy
Adaptation
A trait whose total benefit outweighs its total costs in service of addressing a particular problem within its environment
It has a net positive affect for the organism
It is ultimately in the service of reproduction
Eg. Salmon swimming upstream to spawn (a gigantic fish orgy at a predetermined local)
The first fish (male) to arrive have a monopoly on reproduction
As a result they have more offspring in the next generation
Getting upstream requires energy, stopping to replenish energy takes time
To gain more energy with out stopping the fish liquefy their digestive tracts
This is great for reproduction, but will be detrimental later on
Theoretically survival is only important as long as it keeps you alive long enough to have more reproductive opportunities
Quite obviously the individuals left on the earth result from people who have survived long enough to reproduce
There are two identical organisms
One organism uses its energy to live healthily for quite along time
The other organism spends half of its energy to reproduce
The first organism has no descendants
Regardless of how great traits are, energy must be spent on reproduction
Tinkering
Step 6: advantageous traits will accumulate over time
Natural selection must work with what’s present
There was most likely one single organism that everything evolved from
What’s advantageous either flexes between generations or requires constant progression (long legs for gazelles in one generation may be average in a later generation)
Tinkering doesn’t require building something brand new, but rather small changes depending on the present population and the situation it faces
Small changes add up to much larger changes over time
Eg. Consistency between animal appendages: the arm and forearm of bats are shortened while their fingers are elongated to facilitate flight
Just because an organism has advantageous traits doesn’t mean that those traits are necessarily ideal