Evolution Notes 2005
These notes represent the text in the lectures on Evolution
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Deep Time
Vocabulary: geologic evolution organic evolution fossil spontaneous generation heterotroph hypothesis
index fossils correlation geologic time scale
homologous analogous vestigial abiogenesis biogenesis
Evolution
A gradual process in which something changes into a different and usually more complex or better form.
Biology.-theory that groups of organisms, as species, may change with passage of time so that descendants differ morphologically and physiologically from their ancestors.
Evolution the unifying theme in biology
chicken
Over the 4.5 billion year history of the earth the geology has changed-this is geologic evolution: plate tectonics, mountain building, erosion etc
Species have changed and evolved over the time life has existed on earth-organic evolution
Evolution from common ancestors "bushy" branches
Evidence based in part (not in whole) on fossils- trace or remains of an organism preserved by natural processes.
MOST animals die and decay and leave no trace.
Sorry
Occasionally- amber ice
bones and petrification teeth tar (mineralization)
molds casts imprints
Ages of fossils: sedimentary rock (layered) date the layers superposition (relative dates)
Absolute dating radioactive decay C-14 U-238 K-40
Penny Lab-let
Graph the “radioactive” decay of a population of pennies
Given a group of pennies
Count them-record this as zero time
flip them all-remove the tails, recount; record this as 1st half life
Flip them all-remove the tails, recount; record this as 2nd half life
Flip them all-remove the tails, recount; record this as 3rd half life
Etc…
This is due next class. With a conclusion, about (a) how this models radioactive decay (b) how knowing the initial number of pennies and the final number of pennies you can figure out how old something is if you know the ½ life.
Sample problems:
You start with 100 pennies and do the flip/remove every 10 minutes-how long has it been if you have 6 pennies left?
You started with 250,000 pennies and do the flip/remove once a day-How long has it been if you have 37,500 pennies left?
You start with 1,000,000,000 pennies and do the flip/remove once every 1000 years. There are 500,000,000 pennies left. How long?
Include the following problem in the lab report:
You start with 160,000 pennies and do the flip/remove every 3 days. You have 312 pennies left. How long?
(igneous/sedimentary problems: really good "clocks" are in igneous rocks, fossils are in sedimentary rocks)
Correlation of layers from place to place -discontinuities index fossils trilobites foraminifera
Geologic time scale: ERA: Cenozoic Mesozoic Paleozoic Precambrian
Annotated Time Line
Ages, periods, etc first defined by extinctions
Evolution is not linear- many side branches that "didn't make it"
Living organisms also indicate evolution comparative anatomy-structural similarities are evidence for some evolutionary relationships
Embryological similarities Embryos
whales, bats and humans all have 5 bones in the "hand" In the whale flipper the 2 bones of the lower arm (ulna and radius) are larger
These bones are homologous Similar structures, and embryonic development but different functions and forms
Bird wing, insect wing, bat wing analogous structures similar external forms, but different structures internally
Homology evidence for evolution from common ancestor Analogy evidence for evolution along different paths
Vestigial structures no longer useful reduced in size evidence of evolution
coccyx-tailbone-reptilian tail appendix-large digestive sac
Both whales and snakes have vestigial leg bones -4 legged ancestors
Biochemical similarities- -antibody-antigen reactions -DNA hybridization -membranes -DNA code
Extra Credit Do the “paper” lab on pages334-335 on biochemical similarities and evolution
Time Line Assignment Due 4/7,8 home work- 2 time lines Groups no more than 4 people A: 1 mm = 100,000 years 600 mya -> present B: 1 mm = 1,000,000 years 4.5 bya -> present
What should be on your time line? Obviously-eras Probably periods Key events dates! What kinds of organisms were there at that time? Accuracy COUNTS!!!
{Don’t copy this} Given there is a great deal of evidence for evolution, there is still a problem. {copy this} Evolution accounts for descent with modification from a universal ancestor.
Remember cell Theory… All cells come from pre-existing cells.
So…if all cells come from pre-existing cells, where did the first one come from?
Life from non-life spontaneous generation -abiogenesis-
meat exposed to the air generates maggots
Redi-need flies to get the maggots
-Extra Credit- Analyze Redi's experiments identifying manipulated and responding variables etc. -research Experimental Design before doing this.
Microorganisms- water not sterile Pasteur- sterilized flasks - isolated air
OK-SO NOW WHAT
If all cells come from preexisting cells where did the first cell come from?
Early earth chemically different from modern earth
Many organic compounds will synthesize from chemicals that were available in the earth's atmosphere or ocean
Miller & Urey Experiments Muchison Meteorite
Aggregates of organics clumped together (clay, bubbles)
The first "organisms" got their energy by using energy in pre-formed compounds They were heterotrophs
The heterotrophs used up the early chemicals and released CO2
When they ran out of pre-formed compounds-mass extinction- few with primitive photosynthetic abilities survived
These primitive photosynthetic microbes didn't produce oxygen, but rather broke apart other organic compounds in photosynthesis
Eventually since producing oxygen from water is more energy efficient those organisms that did that outgrew their ancestors
Oxygen is toxic to most living reactions.
The oxygen first "rusted" all the iron on the earth's surface
Then as the percentage of oxygen in the air increased the ozone layer developed, and the high energy environment that first led to life disappeared.
As more oxygen became available organisms that could not adapt to it became extinct
This led to the success of heterotrophs that respired oxygen instead of other chemicals.
Evolutionary Theory
-Aside- The word theory in science doesn’t have the same meaning it has in common usage… Gravity is a theory. A theory is a broad conceptual understanding that is believed to be true.
When someone says “I have a theory about that”, what they really mean is “I have an hypothesis about that”
Vocabulary: natural selection variation gene pool adaptation population genetic equilibrium speciation
Given that organic evolution exists (fossils, biochemical evidence etc.), what accounts for the origin of and differences between species.
During the 19th century this was THE question in biology
1809 Jean Baptiste de Lamarck-species not constant, but evolve from pre-existing species; Changes in species caused by a need to adapt to the environment (so far so good)
Two principles: " use and disuse (the more you use something the stronger it gets-and the less you use something the less developed it becomes)
" inheritance of acquired characteristics Characteristics an organism develops in its lifetime can be passed on (like wealth) to offspring
OOPS
By stretching to reach food giraffe necks got longer. They passed these long necks to offspring
(1870) Weismann-mice tails cut off for 22 generations- 23rd generation still had tails.
Cultural evolution may work by Lamarckian means, but not organic evolution.
Charles Darwin-
1831-naturalist on HMS Beagle 5 year expedition collected specimens, made observations
especially in the Galapagos islands
Finches-
setting the stage - Principles of Geology-Lyell (earth old, gradually changing)
On Darwin's return- Malthus-An Essay on the Principle of Population (Human population problems go back a long time)
Malthus-population increases geometrically 2 4 8 16 32 64 128
food can at most increase arithmetically 2 3 4 5 6 7 8
Therefore people starve! To balance population growth and food, millions must die by some means
Excess production of people
Darwin- Malthus also applies to organisms who produce more offspring than could possibly survive (cod-millions of eggs)
1838-idea of "Natural" Selection (as opposed to "Artificial" Selection by breeders)
“Artificial Selection” Evolution of Biomorphs
Darwin spent 20 years collating data, polishing his writing etc.
1858 Wallace wrote an essay based on studies of beetles in Malaysia that was on Natural Selection
Darwin "co-published" with Wallace and then produced his great work
"On the Origin of Species by Means of Natural Selection" 1859
six points: 1-Overproduction 2-Competition 3-Variation 4-Adaptations 5-Natural Selection 6-Speciation
Giraffes-
many more "proto-giraffes" than environment can support (1)
they must compete for resources (2)
some have longer necks than others (3)
A longer neck allows some proto-giraffes to be better adapted (4)
they then produce more offspring than those with shorter necks (5)
In time they become substantially different from the original "proto- giraffe" and a giraffe is born (6)
chicken and egg
Fisherbeast simulation
Flaws-Problems 1-where do variations originate (remember this is 1859) 2-some variations cause by the environment not heredity 3-rate of evolution 4-missing links in fossil record 5-evolution occurs to individuals
Fisherbeasts Lab Report Data Tables Graph Answer Questions KEY POINT-Link as many of Darwins 6 principles to parts of the lab as make sense
Darwinian theory- gradualism
Gould and Eldridge- punctuated equilibria evolution in fits and spurts and environment changes
Adaptations: Structural- body of an organism Physiological- metabolism of organism
Adaptations for protection- camouflage warning coloration mimicry
Types of Selection
Directional Selection- an extreme phenotype becomes a favorable adaptation - population evolves
Stabilizing selection extreme phenotypes "weeded" out of the population reducing variation in a trait -most common-
Disruptive selection (rare) 2 opposite rare phenotypes are favorable, while the average is unfavorable extremes survive 2 sub-populations
Speciation: range-where you find a species
At far reaches of a range a species may have different gene frequencies
Isolation-geographic leading to reproductive isolation
Reproductive isolation-new species- different behavior different time of mating different structures infertility
Adaptive radiation-spreading out into new environments which are different from the original environment w/o large migrations back and forth to mix the gene pool
If the new environment has niches that are open variations will take advantage of these niches
Darwin's Finches
Convergent Evolution Some answers to life's problems are better than others
vertebrate and octopus eye have similar structures although they do not share common "eyed" ancestors
bird and insect wings are similar in shape
Tuna, dolphin (Flipper), sharks, and attack submarines share shape
Co-evolution- bees and flowers ants and acacia trees
Observed Natural Selection (This is difficult since we aren't around for millions or even 10's of thousands of years)
Industrial melanism
Fisherbeast
All began with the same genotype for each gene…what happened?
Values for 1, 2, 3
Insect resistance to pesticides (DDT) Bacterial resistance to antibiotics. TB vancomyocin vs nocosomial infections….
Synthetic Theory Evolution occurs at the population level (not the individual level)
-an individual's genes don't change, but the proportions of particular alleles in a population can
Population=group of organisms of the same species living together (interbreeding)
Study of changes in allele frequencies in populations=population genetics
All the available genes (alleles) in a population make up a gene pool
FCAT Analogy
Genetic Variation (remember-only variation in the gametes effects evolution)
mutation-(De Vries) gene recombination crossing over independent assortment
Migration
Genetic drift -small populations founder effects
Among other things know…. Names-what they did Redi, Pasteur, Weisman, Lamark, Darwin, Malthus, Lyell, Wallace Darwins 6 points Heterotroph Hypothesis Diagrams (gradual/punctuated) 3 types of selection Observed Natural Selection Homologous/Analogous
Warning Warning Warning Heavy math a head You can do it, but you have to try!
Hardy-Weinberg Law If conditions exist such that frequencies don't change a population is in genetic equilibrium
Dominant and recessive have no effect on genetic equilibria if there is no difference in fitness
4 conditions need to be true for H-W to hold true and a population to be in genetic equilibria
1-Population must be large 2-Migration into or out of the population be limited or random 3-mutations don't occur 4-reproduction must be random (fitness for alleles must be the same)
These 4 never really exist, but the theory is useful since we can figure out the rate of evolution from how much a population varies from H-W
Mathematically if p = frequency of one allele and q = frequency of the other allele p + q = 1 and p2 + 2pq + q2 = 1
Math Warning… This is potentially confusing. Copy it carefully! Think about it! Work it out several times for different combinations.
Frequencies-number of individual alleles of a particular type.
In a field of pea plants all the plants are tall. If 10% of plants are heterozygous for stem length the frequency of the allele for tall is .95 (95%) and for short is .5 (5%)
Next problem: (to solve them when presented with % just assume 100 organisms) tt = 5 % Tt = 10 % TT = 85 %
180 plants = 360 alleles 100 plants heterozygous Qq 80 plants homozygous QQ 0 plants homozygous qq (lethal recessive) Q q QQ 80 x 2 = 160 0 Qq 100 x 1= 100 100 x 1 =100 qq 0 0 frequency of Q = 260/360 = 0.72 = 72% frequency of q = 100/360 = 0.28 = 28%
180 plants = 360 alleles 100 plants heterozygous Qq 10 plants homozygous QQ 70 plants homozygous qq Q q QQ 10 x 2 = 20 0 Qq 100 x 1= 100 100 x 1 = 100 qq 0 70 x 2 = 140 frequency of Q = 120/360 = 0.33 = 33% frequency of q = 240/360 = 0.67 = 67%
200 plants = 400 alleles 10 plants heterozygous Tt 15 plants homozygous tall TT 175 plants homozygous tt T t TT 15 x 2 = 30 0 Tt 10 x 1= 10 10 x 1 =10 tt 0 175 x 2 = 350 frequency of T = 40/400 = 0.10 = 10% frequency of t = 360/400 = 0.90 = 90%
Now you do one!
Solutions….-> white board
Solutions….-> white board
Solutions….-> white board
Fisherbeasts Lab Report Data Tables Graph Answer Questions KEY POINT-Link as many of Darwins 6 principles to parts of the lab as make sense
Remove everything from your desks but something to write with, a piece of paper, AND
The notes YOU took on Tuesday. You can use YOUR notes. If you don’t have any, sorry.
On the next screen there will be a table. Copy it, and where there are numbers enter the correct names. ANY other correct information you know for the other columns will improve your grade.