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Biology 3466B Study Guide - Azide, Dopamine Receptor, Exaptation


Department
Biology
Course Code
BIOL 3466B
Professor
Yolanda Morbey

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Quantitative Genetics Pages 73-94, 11-15, 319-355
A growing body of evolution, concluded by Darwin,
indicated both fossilized and living organisms were
derived from a common ancestor or a few.
3.1 ARTIFICIAL SELECTION: DOMESTIC ANIMALS AND
PLANTS
Darwin studied mechanism of nature under
domestication; method plant and animal breeders use to
modify crops and livestock
In order to refine a particular breed of pigeon that has,
for example, taller feathers or feathers curl more
elegantly, breeders employ artificial selection
They choose pigeons from the flock with the desirable
traits, let them mate to produce next generation
If the desirable traits are passed from parent to offspring,
the next generation will show the desirable traits in a
higher proportion than existed in the previous
generation’s flock
This theory helps to prove the descent of giant tomatoes
versus small tomatoes
On chromosome 2 of tomatoes, a gene called fw2.2 is
carried. This gene encodes a protein that represses cell
division; high production of this protein, smaller the fruit
Changes in the fw2.2 promoter (on/off switch) alter the
total production of protein
Large tomatoes fw2.2 promoter OFF, less protein
production, cell division not repressed
Small tomatoes- fw2.2 promoter ON, more repressor
protein production, cell division repressed
Farmers take seeds of larger tomatoes and replant them,
eliminating smaller tomatoes
3.2 EVOLUTION BY NATURAL SELECTION
Darwin proposed that the descent of modification is the
outcome of 4 postulates:
1) Individuals within population are variable
2) The variations among individuals are, at least in part,
passed from parents to offspring
3) In every generation, some individuals are more
successful at surviving and reproducing than others
4) The survival and reproduction of individuals are not
random; instead they are tied to variation among
individuals. The individuals with the most favourable
variations, those who are better at surviving and
reproducing, are naturally selected
If these 4 postulates are true, then the composition of the
population changes from one generation to the next.
(The stronger individuals survive at higher rates) (pg.76
fig.3.4)
-Darwinian evolution: gradual change in populations over
time
-Selection happens to individuals, but what changes is
populations.
-When a particular trait survives and is passed on to the
next generation and the next generation has a higher
percentage of this trait in the present generation than
the one before, this is evolution by natural selection
-Darwinian fitness is the ability of an individual to survive
and reproduce in its environment
-Adaptation is a characteristic that increases the fitness
of an individual compared to individuals without the trait

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Quantitative Genetics Pages 73-94, 11-15, 319-355
3.3 THE EVOLUTION OF FLOWER COLOUR IN AN
EXPERIMENTAL SNAPDRAGON POPULATION
-48 snapdragons were tested
Postulate 1: There is Variation among Individuals
-Snapdragons varied in flower colour (75% white with 2
yellow spots, 25% full yellow)
Postulate 2: Some of the Variation is Heritable
-Variation in colour was due to different genotypes.
Genes SS and Ss have white flowers with 2 yellow spots,
ss have full yellow flowers; 12/48 SS, 24/48 Ss, 12/48 ss
Testing Postulate 3: Do Individuals Vary in Their Success
at Surviving or Reproducing?
-Bees pollinated these snapdragons and to monitor
plant’s success at reproducing, the researchers counted
the seeds produced from each fruit.
-Consistent with Darwin’s 3rd postulate, plants showed
considerable variation in reproductive success (as pollen
donors and seed mothers)
Testing Postulate 4: Is Reproduction Nonrandom?
-Bees were more attracted to white flowers wit 2 spots,
and white flowers/2spots had higher success of pollen
donation and seed production
-Flowers that donated more pollen, had higher seed
production
-Consistent with Darwin’s 4th postulate, reproductive
success was no random. Through pollen donation and
seed production, white plants had higher reproductive
success than yellow plants
Testing Darwin’s Prediction: Did the Population Evolve?
-Since bees selected white flowers over yellow and white
have higher reproductive success, and genes determine
flower colour, there would be a higher proportion of
white flowers in the next generation
-Experiment proved Darwin’s theory of evolution, proving
all 4 postulates hold.

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Quantitative Genetics Pages 73-94, 11-15, 319-355
3.4 THE EVOLUTION OF BEAK SHAPE IN GALAPAGOS
FINCHES
-The beak is the primary tool used by birds in feeding, and
the enormous range of beak morphologies among the
Galapagos finches reflects the diversity of foods they eat
-Medium ground finches were studied in an experiment.
These finches are mostly seedeaters, in general, birds
with bigger beaks eat bigger seeds and birds with smaller
beaks eat smaller seeds due to efficiency
Testing Postulate 1: Is The Finch Population Variable?
-Scientists weighed each finch, measured its wing length,
tail length, beak width, beak depth and beak length. All
these traits are variable.
-1st postulate is met; variation among individuals within
populations is practically universal
Testing Postulate 2: Is Some of the Variation among
Individuals Heritable?
-Variation in the amount of food that individual birds ate
as a chick can lead to variation in beak depth among
adults. Injuries or abrasion against hard seeds or rocks
can also affect beak size and shape
-To determine if variation among finch beaks is
genetically based, scientists estimated heritability
-Heritability of a trait is the proportion of the variation
observed in a population that is due to variation in genes.
Heritability ranges from 0-1 (because it is a proportion)
-Based on collective data (fig.3.10, pg. 83), parents with
shallow beaks tend to have chicks with shallow beaks and
parents with deep beaks have chicks with deep beaks.
-This proves large proportion of the observed variation in
beak depth is genetically based and can be passed onto
offspring
-Darwin’s 2nd postulate is met; a substantial fraction of
the variation in beak size is due to variation in genotype
-It is experimentally seen that BMP4 (bone morphogenic
protein 4), a signaling molecule that helps sculpt the
shape of bird beaks, are in larger amounts and are
produced earlier in development for birds with larger
beaks.
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