AP BIOLOGY
Essential Knowledge 2.A.1:
All living systems require
constant input of free energy.

2.A.1.d.2:
Reproduction and
rearing of offspring
require free energy
beyond that used for
maintenance and growth.
Different organisms use
various reproductive
strategies in response
to energy availability.
Life-history
strategy
•Reproductive
diapause
Did you know that the female European roe deer
(Capreolus capreolus) uses embryonic diapause to
control when her fawn will be born? From the latesummer mating through the end of December, the
embryo remains at about the 30-cell stage in a state of
diapause. This delays implantation of the fertilized egg
until a more ideal time for birth.
SO! What is
reproductive
diapause?
Diapause is a genetic switch that results in
suspended animation in which embryonic cell growth
and development are reversibly stopped or slowed.
Diapause occurs in a diverse range of vertebrates
and invertebrates that includes insects, copepods
(crustaceans), fish, birds, rodents, and marsupials
(animals with pouches, such as the kangaroo) and
other mammals, including deer.
Temperature-dependent diapause
In chicken eggs, development stops whenever the hen gets off the egg
and the eggs cool down and starts back again when the hen returns to
her nest.
Environmentally triggered diapause
Diapause differs dramatically from hibernation and aestivation in that
during diapause, every cell ceases growth, achieving dormancy. In
hibernation and aestivation, metabolism only slows as a survival reaction
to harsh conditions. Diapause, on the other hand, begins before these
severe conditions occur and is brought about by environmental triggers.
During diapause, cell growth and development are reversibly stopped or
slowed. Annual killifish eggs in diapause can survive for months or even
years! Recent findings suggest that the female killifish, in response to
environmental cues, relays a message to the egg to stop growing for a
fixed amount of time. Essentially, the biological clock stops. These
“sleeping” embryos can remain alive for periods two times longer than
their normal life expectancy! When diapause is broken and the embryo
“wakes up,” it continues to develop and hatch – as if time had stood
still until then!
Read about some examples!
http://malawicichlids.com/mw11001a.htm
http://www.ansci.wisc.edu/jjp1/ansci_repro/misc/project_websites_07/thur
07/embryonic_diapause/index_files/Page311.htm
What about cicadas? Do they experience diapause?