Chapter 21- Environmental regulation in animal development

1. Many examples of environmental regulation exist

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Red abalone- must bind coralline red algae to begin ___________________

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Mosquito _________________ triggers egg production

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______________________________

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Algae provides photosynthetic energy to amphibian eggs when in tight clusters

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A bacterium multiplies only in leaf hopper __________

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No bacterium= embryonic death due to lack of _________________ development

1. environmental regulation (cont.)

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Nitrogen fixing ________ provide nitrogen to legumous plants (e.g. bean plants)

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Aphids hatch only _________ in the spring, but male and female are hatched in the autumn (mechanism unknown)

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Many insects use

__________-

a suspension of development due to harsh conditions (e.g winter condition)

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Diapause is not triggered by harsh conditions, but before the harsh conditions arrive

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Gravity/pressure

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A chick embryo requires proper positioning to _________________________

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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 b. ______ dictates wing color in certain butterflies

Fig. 3.3

Fig. 21.6

2. Phenotypic plasticity- (cont.) c. ______________ dependant sex determination Recall Temperature-dependent sex determination in reptiles (Ch. 17)

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Crocodiles- temperature extremes result in female Advantage- increase sexual reproduction if ____ male:female ratio Disadvantage- less adaptable to slight environment change (e.g. ______________)

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Blue headed Wrassse (reef fish) -

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If wrasse reaches reef with males, it develops into _____

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If wrasse reaches reef without males, it develops into ___

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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 ???

Survival Rate (typical/induced) Barnicle ???

_____ _____ ____ ____ Mollusk Carp

No predation until 50% of typical morphs

______

eaten

3. Predator-induced polypheism (cont.) b. Mammalian immunity

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A foreign object (antigen) is recognized by a one in __ _________ B-cells

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Only the B-cell that recognizes the antigen will __________ and secrete specific antibody to _________ the antigen

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The immune system “ _____________ ” its foreign invaders

4. Learning is an environmentally induced system a. New neurons are produced

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in _______ learning a song

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in ________ learning activities b. Visual pathway development is affected by _______

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A flash of light seen by a cortical neuron right eye is also “seen” by the corresponding cortical neuron in the left eye

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Kitten experiments

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If sew right eye of newborn closed for ________ , they were functionally ______ in right eye

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If sew both eyes of newborn closed for 3 months, vision remains (though weak) in ________

4. Learning is an environmentally induced system

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Kitten experiments (cont.)

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If sew either eye shut after first three months __ __________

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Thus, synapses have been stabilized by 3 months

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Critical window of development is 4 weeks to 3 months Thus, not all development is encoded in the ______

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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

5. Environmental disruptions to development

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About _____________ of human conceptions survive to term

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About ____ of human babies have a recognizable deformation (normally in limbs, lungs or face)

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Abnormalities caused by genetic mutations agents are called

____________

(e.g. Down’s syndrome, aniridia (Pax6 mutation))

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Abnormalities caused by exogenous agents are called

________

Examples-

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Skunk cabbage induced _______ in sheep In Humans

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Quinine

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Alcohol (>2oz/day) ________ ____________________

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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

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____ “ normal”

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_____ aborted spontaneously

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_____ 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

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Fetal alcohol syndrome (FAS) is __ most prevalent type of mental retardation (behind fragile X and Down Syndrome); ______ children in USA

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Estimated that _______ of children born to alcoholic mothers will have FAS

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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-

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______ can cause deafness, heart malformations

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_____________ and cytomegalovirus can cause deafness, blindness, mental retardation

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Syphilis can cause deafness or death d. Chemicals as teratogens-

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________________ , and zinc are common ones

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In Kazakhstan (former Soviet Union) nearly __ of population have extensive chromosome breakage due to “industrial production at all costs”

e. Estrogen

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DDT is a banned insecticide that can act like ________

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DDT is linked to increased incidence of __________ and decreased _____ ________

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Dioxin (dumped at Times Beach west of St. Louis) is linked to increased _____ _____ and decreased ____________ 1985-Industrial plant in Italy explodes-

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Breast cancer

____________

in immediate perimeter

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Breast cancer ___________ in surrounding area

e. Estrogen (cont.)

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_____________ (used to harden plastics used in plumbing and milk/orange juice containers)- replaces role of estrogen to induce certain cultured cell to divide

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PCBs (previously used as refrigerants); banned in 1970 due to cancer-causing ability in rats; yet remain in environment

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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