Chapter 21- Environmental regulation in animal development

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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

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Nitrogen 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

• Gravity/pressure

• A chick embryo requires proper positioning to
  _________________________

• Also effects development of bones in chicken

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2. ____________________- 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
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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 ____
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
  _______

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d. __________-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
_____
_____
____
____
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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

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4. 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

• 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 ________

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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 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
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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. Downs syndrome,
  aniridia (Pax6 mutation))

• Abnormalities caused by exogenous agents are
  called ________

Examples-

• Skunk cabbage induced _______ in sheep

In Humans
_______________________
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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
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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
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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

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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

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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?
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Other teratogens

• ____________(fallout)
• Infectious agents- Herpes simplex II,
  cytomegalovirus, rubella
• Drugs- alcohol, aminopterin, chlorophenyls,
  tetracyclines, thalidomide
• Other possible teratogens- _______ ___________,
  lithium, zinc deficiency