Chapter 21- Environmental regulation in animal development

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
•Diapause is not triggered by harsh conditions, but
before the harsh conditions arrive
•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
Low density
High density
Fig. 3.3
Fig. 21.6
b. ______
dictates wing
color in certain
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
Daphnia ??? Barnicle ??? Mollusk Carp
Survival Rate
predation ______
_____ _____ ____
____ No
until 50% of
typical morphs
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
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
•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
Estimated that__ of pregnancies in America are unplanned
b. Alcohol is a teratogen
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 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