Evolution
Lec 14 18Feb02
http://life.uiuc.edu/animalbiology/105/
ID: eee105
Password: prAIRie
Plant-animal coevolution
Plant-animal coevolution
Why aren’t all the plants eaten?
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
e.g. the flavors of vegetables
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
milkweed is toxic
but a few insects have evolved resistance
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
milkweed bug is toxic
and has evolved warning coloration
milkweed is toxic
but a few insects have evolved resistance
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
monarch butterfly
caterpillar is
toxic
milkweed is toxic
but a few insects have evolved resistance
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
monarch butterfly
is toxic too
and has evolved bright warning colors
milkweed is toxic
but a few insects have evolved resistance
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
a mimic
viceroy butterfly
is not toxic
but has evolved bright warning colors
milkweed is toxic
but a few insects have evolved resistance
Why aren’t all the plants eaten?
Plants have evolved chemical defenses
milkweed is toxic
but a few insects have evolved resistance
Plant-animal coevolution
plants evolved fruits
Plant-animal coevolution
plants evolved fruits
to “persuade” animals to disperse seeds
Are humans evolving?
Yes but in surprising ways
Darwin’s Descent of Man
and Selection in Relation to Sex
Sexual selection
bizarre, “useless” ornamentation
secondary sexual characteristics
Sexual selection
bizarre, useless ornamentation
secondary sexual characteristics
Sexual selection
bizarre, useless ornamentation
secondary sexual characteristics
Sexual selection
rainbow
darter
bizarre, useless ornamentation
secondary sexual characteristics
Sexual selection
in humans
bizarre, useless ornamentation
secondary sexual characteristics
Sexual selection
female choice
Sexual selection
female choice
the naked ape ?
racial differences?
Sexual selection
female choice
male combat
why mammalian males are larger
than females
Sexual
Sexual selection
selection
female choice
male combat
Sexual selection
female choice
male combat
why mammalian males are larger
than females
in most species females are
the larger sex
in most species females are
the larger sex
Sexual selection is a type of
natural selection
but there is another mechanism of
evolution
Genetic drift
random changes in gene frequencies
(1) gene flow by immigration
humans are exceptional migrators
% B bloodtype
Gene flow by immigration
e.g. Asian invasions of Europe
Sexual selection is a type of
natural selection
but there is another mechanism of
evolution
Genetic drift
random changes in gene frequencies
(1) gene flow by immigration
humans are exceptional migrators
(2) population bottlenecks
Population bottlenecks
In small populations
random changes in gene frequencies
change the population
e.g. small, inbred human populations
e.g. polydacytyly
the founder effect
Population bottlenecks
World population of cheetahs is small
20,000
genetically identical
Are humans evolving?
Yes
sexual selection
genetic drift
natural selection
e.g. lactose intolerance
Most adult humans are lactose intolerant
Only cattle-herding peoples digest milk easily
Are humans evolving?
Yes
sexual selection
genetic drift
natural selection
But humans vigorously oppose natural
selection
Civilization