Chapter 21- Environmental regulation in animal development

1. 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

2. 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

3. 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

4. 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 _______

5. 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 (typical/induced) No predation until 50% of typical morphs eaten ______ _____ _____ ____ ____

6. 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

7. 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 ________

8. 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

9. Quinine ________ • Alcohol (>2oz/day) ____________________ • Smoking (>20/day) 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 _______________________

10. 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

11. 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

12. 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”

13. 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

14. 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?

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