Chapter 21- Environmental regulation in
animal development
1. Many examples of environmental regulation exist
•Red abalone- must bind coralline red algae to begin
___________________
•Mosquito- _________________ triggers egg production
•______________________________
•Algae provides photosynthetic energy to
amphibian eggs when in tight clusters
•A bacterium multiplies only in leaf hopper __________
•No bacterium= embryonic death due to lack
of _________________ development
1. environmental regulation (cont.)
•Nitrogen fixing ________ provide nitrogen to legumous
plants (e.g. bean plants)
•Aphids hatch only _________ in the spring, but
male and female are hatched in the autumn
(mechanism unknown)
•Many insects use __________- a suspension of
development due to harsh conditions (e.g winter
condition)
•Diapause is not triggered by harsh conditions, but
before the harsh conditions arrive
•Gravity/pressure
•A chick embryo requires proper positioning to
_________________________
•Also effects development of bones in chicken
2. ____________________- express distinct
phenotypes depending on circumstances
Termed “______________”
a. _______________
dictates grass hopper
development
Low density
phenotype
High density
phenotype
_________
phenotype
_________
phenotype
Fig. 3.3
Fig. 21.6
b. ______
dictates wing
color in certain
butterflies
2. Phenotypic plasticity- (cont.)
c. ______________dependant sex determination
Recall Temperature-dependent sex
determination in reptiles (Ch. 17)
• Crocodiles- temperature extremes result in female
Advantage- increase sexual reproduction if ____
male:female ratio
Disadvantage- less adaptable to slight environment
change (e.g. ______________)
• Blue headed Wrassse (reef fish) •If wrasse reaches reef with males, it develops into _____
•If wrasse reaches reef without males, it develops into ___
•If male dies, largest female becomes male within _______
d. __________-induced polypheism
a. Organisms change shape in response to soluble
factors released by predators
Fig. 21.13
typical
Predator
induced
Daphnia ??? Barnicle ??? Mollusk Carp
Survival Rate
predation ______
_____ _____ ____
____ No
until 50% of
(typical/induced)
typical morphs
eaten
3. Predator-induced polypheism (cont.)
b. Mammalian immunity
•A foreign object (antigen) is recognized by a one in __
_________ B-cells
•Only the B-cell that recognizes the antigen will
__________ and secrete specific antibody to _________
the antigen
•The immune system “_____________” its foreign invaders
4. Learning is an environmentally induced system
a. New neurons are produced
• in _______ learning a song
• in ________ learning activities
b. Visual pathway development is affected by _______
• A flash of light seen by a cortical neuron right
eye is also “seen” by the corresponding cortical
neuron in the left eye
•Kitten experiments
•If sew right eye of newborn closed for ________,
they were functionally ______ in right eye
•If sew both eyes of newborn closed for 3 months,
vision remains (though weak) in ________
4. Learning is an environmentally induced system
•Kitten experiments (cont.)
•If sew either eye shut after first three months- __
__________
•Thus, synapses have been stabilized by 3 months
•Critical window of development is 4 weeks to 3
months
Thus, not all development is encoded in the ______
• Some is the result of ___________
Two key principles1. ______________ are made prior to when the animal sees
2. __________ plays key role in determining whether
neuronal connections ____________
Also- the _________________ phenomenon is due to learning
5. Environmental disruptions to development
•About _____________ of human conceptions survive to term
•About ____ of human babies have a recognizable deformation
(normally in limbs, lungs or face)
•Abnormalities caused by genetic mutations agents are called
____________ (e.g. Down’s syndrome, aniridia (Pax6 mutation))
•Abnormalities caused by exogenous agents are called ________
Examples•Skunk cabbage induced _______ in sheep
In Humans
•Quinine
________
•Alcohol (>2oz/day)
____________________
•Smoking (>20/day)
_______________________
5. Disruptions (cont.)
a. Retinoic acid as a teratogen
Accutane-for treating severe ____
________ women of childbearing age have used Accutane
1985 study of pregnant Accutane users
•____ “ normal”
•_____aborted spontaneously
•_____ with anomalies- absent ears,
small jaws, cleft palate, and/or CNS
problems
Estimated that__ of pregnancies in America are unplanned
b. Alcohol is a teratogen
CH3CH2OH
Fetal Alcohol Syndrome
•Fetal alcohol syndrome (FAS) is __
most prevalent type of mental
retardation (behind fragile X and
Down Syndrome); ______ children
in USA
•Estimated that _______ of children
born to alcoholic mothers will have
FAS
•FAS children have mean IQ of __; at 16.5
yrs, they have vocabulary of ___ yrs
Misshapen eyes, flat nose,
long upper lip
Huge problem in South Africa due to alcohol-based economy
c. Pathogens as teratogens•______ can cause deafness, heart malformations
•_____________ and cytomegalovirus can cause
deafness, blindness, mental retardation
•Syphilis can cause deafness or death
d. Chemicals as teratogens•________________, and zinc are common ones
•In Kazakhstan (former Soviet Union) nearly __ of
population have extensive chromosome breakage due
to “industrial production at all costs”
e. Estrogen
•DDT is a banned insecticide
that can act like ________
•DDT is linked to increased incidence
of __________ and decreased _____
________
•Dioxin (dumped at Times Beach west of
St. Louis) is linked to increased _____
_____ and decreased ____________
1985-Industrial plant in Italy explodes•Breast cancer ____________in immediate perimeter
•Breast cancer ___________ in surrounding area
e. Estrogen (cont.)
•_____________ (used to harden plastics
used in plumbing and milk/orange juice
containers)- replaces role of estrogen to
induce certain cultured cell to divide
•PCBs (previously used as refrigerants);
banned in 1970 due to cancer-causing
ability in rats; yet remain in environment
•Blamed for reduced reproductive capacities in
seals, mink and fish
Dramatic increase in deformed frogs in US- Due to toxins
in water?
Other teratogens
• ____________(fallout)
• Infectious agents- Herpes simplex II,
cytomegalovirus, rubella
• Drugs- alcohol, aminopterin, chlorophenyls,
tetracyclines, thalidomide
• Other possible teratogens- _______
___________, lithium, zinc deficiency