faculty.ycp.edu

https://www.youtube.com/watch?v=rDK3IT29uoQ

Friday Lecture: HUM 15
Deep Time
Radiometric Dating
Google Map Exercise

Friday Lab: Faculty Lounge
Animals in Cinema

(Tomorrow afternoon practice)

- Natural Selection
- Sexual Selection Darwin
- Kin Selection

- Group Selection (20th century)

- Standard Darwin
- Sexual Selection (Darwin)
- Kin Selection (Darwin)
- Group Selection

“I have called this principle, by which each slight
variation, if useful, is preserved, by the term of
Natural Selection, in order to mark its relation to
man’s power of selection. We have seen that man
by selection can certainly produce great results,
and can adapt organic beings to his own uses,
through the accumulation of slight but useful
variations, given to him by the hand of Nature. But
Natural Selection, as we shall hereafter see, is a
power incessantly ready for action, and is as
immeasurably superior to man’s feeble efforts, as
the works of Nature are to those of Art.”

Origin – Chp 3

- Standard Darwin
- Sexual Selection (Darwin)
- Kin Selection (Darwin)
- Group Selection

Darwin saw traits that didn’t make sense
in terms of standard natural selection

Long-tailed widow bird …. MALE!!

Male Female

STAG
BEETLES

Male Stag Beetles

“And this leads me to say a few words on
what I call Sexual Selection. This
depends, not on a struggle for existence,
but on a struggle between the males for
possession of the females; the result is not
death to the unsuccessful competitor, but
few or no offspring.”

Origin, Chp 4

SEXUAL SELECTION

2 types:
1) Intersexual Selection - males advertise their worthiness

in the presence of potential mates.

Many female animals choose their reproductive partners.
Males with particular appearances or courtship behaviors
gain advantage over other males.

superb bird of paradise A bird of paradise
Watch the females (New Guinea)

Male satin bowerbirds (Australia) build BOWERS to attract females
… females “check out” many bowers and are extremely picky.

BOWER

BOWER

Adornments

Female’s rMuanlweasyoMfintathoelethgerGebarot ewboeawrteBrboirdwbeuirldbairpdaved
Location
MLaargleersrobcuksiladreapplaacevdefdarpthaerthfrolmeathdeing
Display boeugtinonifntghe bower into a “court”
Court
An illusion of uniform stones is created.

Male uses a rock size gradient

Done intentionally!

An optical illusion of uniform
stone size is created

female

What is the female bowerbird really choosing??

Proper Stone Gradient?? -r

+r

Some males do very well … others don’t

Nice Bowers
Good Dancers

Number Problem Bowers
of Mates Poor Dancers

JACKPOT 0 Offspring

2) Intrasexual Selection (= “male rivalry”) involves direct
competition to gain control over females.

EXAMPLES: kangaroos, bighorn sheep, elephant seals

Sexual selection results in sexual DIMORPHISM ---
differences in size, appearance, & behavior.

EXAMPLES: lions, spiders, humans, elephant seals

Elephant seals … large males do better

Intrasexual Selection

Body Size Dimorphism
& Harem Size

13 species of Marine Mammals

polygyny

monogamy

Intrasexual Selection

6 satellite
males…

Dominant following
Male 1 dominant
male…
Female
and the
female he
controls



A male black-winged damselfly removes another
male’s sperm before depositing his own.

M

F

Intrasexual Selection

SPERM COMPETITION

Intrasexual Selection

Sperm-removal spines
on damselfly penis

- Standard Darwin
- Sexual Selection (Darwin)
- Kin Selection (Darwin)
- Group Selection

Q

Order Isoptera

Sterile Workers

“This difficulty [social insects], though appearing
insuperable, is lessened, or, as I believe,
disappears, when it is remembered that selection
may be applied to the family, as well as to the
individual, and may thus gain the desired end.”

Origin, Chp 7

Darwin foreshadowed a huge
20th century advance:
SOCIOBIOLOGY



Order Hymenoptera

WHY?

Honeybee Abdomen

Why?

http://www.youtube.com/watch?v=IwfCf1LEgaE

Suicidal ant (Camponotus saundersi)
Workers possess a gland that fills their abdomen.
Arrival of an invader elicits massive abdominal contractions.
Body explodes spraying invader with sticky GOO.

WHY??

NAKED MOLE RATS
- Underground colonies of up to 300 nmr
- 1 Queen + 2-3 mating males
- Everyone else is a worker

WHY?

VOCABULARY

A special type of natural selection ….
Kin Selection – evolutionary effects of aid given
to both offspring and other relatives
i.e., effects of supporting those who share your genes

VOCABULARY

Fitness – genes contributed by an individual to the next generation

DIRECT fitness – genes contributed to the next generation by an
individual through personal reproduction

INDIRECT fitness – genes contributed to the next generation by
helping relatives other than offspring succeed

INCLUSIVE fitness = DIRECT +
INDIRECT

**** Sociobiology Theory: Natural Selection acts to increase inclusive
fitness ****

CONCLUSION: Sacrificing for a very close relative
is no sacrifice!!

If your sacrifice promotes a relative’s success,
your genes are being propagated.

PROFOUND CONCLUSION

You don’t need to reproduce to be
genetically successful!!

- Standard Darwin
- Sexual Selection (Darwin)
- Kin Selection (Darwin)
- Group Selection

Unrelated group-living animals will make
self-sacrifices for the good of the group.

Groups consisting of altruists will be strong.

Evolutionary biologists have often dismissed
Group Selection … WHY??

(Does group selection apply to humans??)

ASSIGNMENT: Explore the attractiveness of
this idea … Find the main argument
against it.

the



PEPPERED
MOTHS



http://www.nature.com/nature/journal/v505/n7485/full/nature12853.html
Pitnick and Pfennig 2014

Female mated with 3 unrelated males … or 3 brothers

Line
thickness = intensity

Kin selection?
Inclusive fitness?



Today: Current views of natural selection
Wednesday: Current views of speciation
Friday: Phylum Arthropoda

Long-tailed widow bird …. MALE!!



Female bowerbirds will usually
mate once per season



Male Female

STAG
BEETLES

Dung beetle males fight for mates
Trade-off: horns vs eyes

Cloaca-pecking in the
(European dunnock

3 Paving Possibilities Why does the male
create this illusion?
by female
?? Because females
like it ??

Because successful
mating requires it