An
isolated island of volcanic origin supports a simple community with just
four conspicuous species: a sunflower, a beetle, a spider, and a small bird
that usually eats spiders and beetles, but occasionally takes some sunflower
seeds.
Imagine that many individuals
(healthy males and females) from the mainland (ancestral) bird population
arrive on the island one day, blown far out to
sea from a powerful hurricane hitting the mainland. By pure random chance,
the colonizing individuals have slightly thicker bills than the existing
island population, and tend to spend more time eating sunflower seeds. The
two groups cannot coexist indefinitely eating the same food, in the same
habitat.
It’s
March Madness, and the Cowboys have made it into the final game of the NCAA
championship against the surprise upstarts of the tournament, Evil State University
(ESU). The nefarious Dr. Evil is out to sabotage the Cowboys in this final
game, and he has developed a fastacting neurotoxin that paralyzes human arms
for several minutes. His henchmen (disguised as ESU cheerleaders) have been
using little straws to shoot tiny poison darts at the Cowboys throughout game,
secretly. As a result, the Pokes are shooting terribly, and in the final seconds
of the game, are losing 33-32. With just 5 seconds to go, John Lucas sprints
down the court to shoot one of his characteristic running jump shots, but he
is hit with a dart on the way up: his arm falls limp and he misses the shot.
But wait! He was fouled! A time out is called with 1 second left on the clock.
After the time out, John will have the opportunity to sink two free throws
that will win the game. But what can he do? How can he possibly hit the shots
with his arms paralyzed?
Moments
before returning to the court, International Man of Mystery Austin Powers rips
off his Pistol Pete costume, throws the giant head to the floor and says, “Like,
stop the game, Baby! This is all a plot from Dr. Evil!” Austin then rushes
to John Lucas and gives him an antidote before chasing after Dr. Evil out of
the venue. John’s arms are restored, play resumes, and he sinks both
free throws. The Pokes win thanks to Austin Powers! Say, what was in that antidote
anyway?
Ruminants
are mammals that have stomachs divided into multiple compartments (3-4) that
churn and process the large amount of plant material they eat. Plants contain
cellulose, a complex carbohydrate, in their cell walls. Ruminants by themselves
cannot digest cellulose. The rumen of ruminants harbor simple, single-celled
organisms called protozoa. These protozoans are able to digest cellulose and
convert it into energy that is used to synthesize other organic compounds such
as proteins. Both the ruminant and the protozoa benefit from this relationship.
Tubers
of cassava (Manihot esculenta) are an important food in human nutrition in
tropical Africa. The tubers contain mainly starch. Cassava is a successful
crop because the tubers are resistant to insects. The tubers contain high levels
of cyanide (hydrocyanic acid), which is toxic to humans and other animals.
Cyanide is quickly absorbed from the gastrointestinal tract and acts to bind
and disable the last protein in the electron transport chain in the mitochondria.
Thus, cyanide is lethal because it shuts down the electron transport chain
in cellular respiration. Cyanide can be eliminated from food made from cassava
by removing the outside parts that contain the highest levels of cyanide and
by long cooking at high temperature during which the cyanide evaporates.
Dr.
Dolph Schluter, one of Peter Grant’s former students, has been studying
three-spined sticklebacks in lakes in British Columbia. The marine ancestors
of these freshwater fish were probably isolated in these lakes at the end of
the last ice age. What he has found is that there are two types: a large bottom-dwelling
type with a large mouth that feeds on large prey, and a smaller surface-dwelling
type with a smaller mouth that feeds on the small plankton in open water. Genetic
evidence indicates that these two types of sticklebacks are more closely related
to each other than they are to any other stickleback species.
