This document summarizes notes from chapters 7 and 8 of a biology class. It discusses several genetics concepts, including multi-gene traits, polygenic traits, sex-linked traits, and environmental effects on phenotypes. It also covers evidence of evolution from experiments on fruit flies showing changes in starvation resistance over generations through natural selection. Key figures discussed include Charles Darwin, Jean-Baptiste Lamarck, and Georges Cuvier in the context of the development of the theory of evolution by natural selection.

1. Day 12 October 16th CH 7+8
Dr. Amy B Hollingsworth
The University of Akron
Fall 2014

2. 7.11 Multi-gene Traits
How are continuously varying traits
such as height influenced by genes?
Old wives’ tales suggest a couple of ways for predicting height:
if the baby is a boy, they say to add five inches to the mothers’
height and average that with the father’s height. Or if it is a
girl, subtract five inches from the father’s height and average
that with the mother’s height. Alternatively, the lore says to
just take the child’s height at two years and double it.

3. Additive Effects
The Tall Gene –
hormones and
bone length
and growth
factors – oh
what happens when the effects of alleles
from multiple genes all contribute to the
ultimate phenotype
my!

4. Polygenic Trait
 A trait that is influenced by many different
genes
Mind-blowingly
complicated!!!

5. Why might computer nerds
be more likely to have
autistic children?
•Autism involves 10 or 20 different genes!
•Unusual abilities of perception, analytical
skills, and focus. This idea—called the “geek
theory of autism”
•May be compounded by environmental
effects

6. What is
the
benefit of
“almost”
having
sickle cell
disease?

7. 7.12 Pleiotropy: How can one
gene influence multiple traits?

8. The SRY Gene
 “Sex-determining Region on the Y-chromosome”
 Causes fetal gonads to develop as testes
shortly after fertilization.
 Following the gonads’ secretion of
testosterone, other developmental changes
also occur.

9. 7.13 Why are more men
than women color-blind?
Sex-linked traits differ in their
patterns of expression in males
and females.

11. If a man is color-blind, did he
inherit this condition from his
mother, his father, or both
parents?

12. men only get
one chance to
inherit the
normal version
of the gene

13. 7.14 Environmental
effects: Identical twins are
not identical.

15. Drinking diet soda can be
deadly if you carry a
single bad gene.
What gene is it and why is
it so deadly?

16. Could you create a
temporarily spotted Siamese
cat with an ice pack?
Why?

18.  Genotypes are not like blueprints that
specify phenotypes.
 Phenotypes are a product of the
genotype in combination with the
environment.

19. 7.15 Most traits are passed on as
independent features: Mendel’s law
of independent assortment.
Mendel didn’t know that genes were carried on chromosomes, so he believed that they
were all just free-floating entities within cells. Given this perspective, it made sense to him
that the inheritance pattern of one trait wouldn’t influence the inheritance of any other
trait. He believed all genes behaved independently.

20. 7.16 Red hair and freckles
Genes on the same
chromosome are sometimes
inherited together.

22. Chapter 8: Evolution and Natural Selection
Darwin’s dangerous idea: evolution by natural selection
Lectures by Mark Manteuffel, St. Louis Community College ; Clicker Questions by Kristen Curran, University of Wisconsin-Whitewater

24. Evolution in Action
8.1 We can see evolution occur
right before us. Therefore,
evolution is a scientific process.

25. Could you breed
fruit flies who could
live longer than 20
hours on average?

26. Populations
are studied

27. When these eggs hatch, do you think
the flies in this new generation will
live longer than 20 hours without
food?

28. Make a prediction: A population of fruit flies was starved until
80% of the flies were dead. The remaining flies were fed and
offspring were produced. What do you expect to see in the next
generation if you repeat the starvation experiment?
1. More flies will be alive after 20 hours.
2. Fewer flies will be alive after 20 hours.
3. Fruit flies fed after 80% of the population is dead
will lay more eggs.
4. No change in the average number of fruit flies
that were alive after 20 hours.

29. Make a prediction: A population of fruit flies was starved until
80% of the flies were dead. The remaining flies were fed and
offspring were produced. What do you expect to see in the next
generation if you repeat the starvation experiment?
1. More flies will be alive after 20 hours.
2. Fewer flies will be alive after 20 hours.
3. Fruit flies fed after 80% of the population is dead
will lay more eggs.
4. No change in the average number of fruit flies
that were alive after 20 hours.

31. After 60 generations the average starvation
resistance of fruit flies was 160 hours! What
has happened to this population of fruit flies?
1. They are genetically identical to
the original population.
2. The are genetically different from
the original population.

32. After 60 generations the average starvation resistance
of fruit flies was 160 hours! What has happened to
this population of fruit flies?
1. They are genetically identical to the
original population.
2. The are genetically different from the
original population.

33. What happened?
 Evolution
• a genetic change in the population
 Natural selection
• the consequence of certain individual organisms in
a population being born with characteristics that
enable them to survive better and reproduce more
than the offspring of other individuals in the
population

34. Does evolution occur?
 The answer is an unambiguous: YES.
We can watch it happen in the lab
whenever we want.
Recall from our discussion of the scientific method
that for an experiment’s results to be valid, they
must be reproducible.

35. Experiments
 Dogs?
in Evolution
 Rabbits?

36. In Nature -

37. Why are camels a successful species?

38. Evolution
 How does evolution occur?
 What types of changes can evolution
cause in a population?
 Five primary lines of evidence
 Evolution by natural selection

40. Darwin’s Journey to an Idea
8.2 Before Darwin, most people
believed that all species had been
created separately and were
unchanging.

41. Button started the debate by suggesting the Earth
had to be at least 75,000 years old!

42. Jean-Baptiste Lamarck
 Biologist, early 1800s
 Living species might change over time.
(Was wrong about the mechanism - he thought that change came about
through the use or disuse of features)

43. Charles Lyell
 Geologist
 1830 book Principles of Geology
• Geological forces had shaped the earth and were
continuing to do so.
 Gradual but constant change
This idea that the physical features of the earth were constantly changing would most
closely parallel Darwin’s idea that the living species of the earth, too, were gradually—
but constantly—changing.

44. We know the Earth is constantly
changing
• Fossils of shells have been found high in the
Andes Mountains
• Forest fires wipe out entire species of plants and
animals.
• Rivers flow, and carve out rock, creating two
distinct shores, where different species live.
• Lakes dry up, killing all marine life inside.
• Pollution and Toxic spills kill organisms.
• Volcanoes.
• Humans are changing the earth.

45. In the 1790s, Georges Cuvier began to explore the bottoms
of coal and slate mines and found fossils

46. Why were fossils such a problem for
people at that time?
• This was highly troubling for people at the
time.
http://www.bspcn.com/2009/04/03/11-extinct-animals-that-have-been-photographed-alive/

47. Extinction
• five mass extinctions on earth, and four in the
last 3.5 billion years - many species have
disappeared in a relatively short period of
geological time.
• The "Great Dying" about 250 million years ago,
which is estimated to have killed 90% of species
existing at the time.
• Most extinctions have occurred naturally, without
human intervention: it is estimated that 99.9% of
all species that have ever existed are now extinct.