Title: Chapter 21- Environmental regulation in animal development
1Chapter 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
2Nitrogen fixing ________ provide nitrogen to
legumous plants (e.g. bean plants)
1. environmental regulation (cont.)
- 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
- A chick embryo requires proper positioning to
_________________________
- Also effects development of bones in chicken
32. ____________________- express distinct
phenotypes depending on circumstances
Termed ______________
Low density phenotype
a. _______________ dictates grass hopper
development
High density phenotype
_________ phenotype
Fig. 21.6
b. ______ dictates wing color in certain
butterflies
_________ phenotype
Fig. 3.3
42. 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 ____
malefemale 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
_______
5d. __________-induced polypheism
a. Organisms change shape in response to soluble
factors released by predators
Fig. 21.13
typical
Predator induced
Carp
Mollusk
Barnicle
???
Daphnia
???
Survival Rate (typical/induced)
______
No predation until 50 of typical morphs eaten
_____
_____
____
____
63. 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
74. Learning is an environmentally induced system
- 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
- 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 ________
84. 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 principles-
1. ______________ are made prior to when the
animal sees
2. __________ plays key role in determining
whether neuronal connections ____________
Also- the _________________ phenomenon is due to
learning
95. 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. Downs syndrome,
aniridia (Pax6 mutation))
- Abnormalities caused by exogenous agents are
called ________
Examples-
- Skunk cabbage induced _______ in sheep
In Humans
_______________________
105. 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
- _____aborted spontaneously
- _____ with anomalies- absent ears, small jaws,
cleft palate, and/or CNS problems
Estimated that__ of pregnancies in America are
unplanned
11b. 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
12c. 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
13e. 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
14e. 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?
15Other teratogens
- ____________(fallout)
- Infectious agents- Herpes simplex II,
cytomegalovirus, rubella - Drugs- alcohol, aminopterin, chlorophenyls,
tetracyclines, thalidomide - Other possible teratogens- _______ ___________,
lithium, zinc deficiency