Chapter 21- Environmental regulation in animal development

•Red abalone- must bind coralline red algae to begin ___________________

•Mosquito- _________________ triggers egg production

•______________________________ •Algae provides photosynthetic energy to amphibian eggs when in tight clusters

1. Many examples of environmental regulation exist

•A bacterium multiplies only in leaf hopper __________

•No bacterium= embryonic death due to lack of _________________ development

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)

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

•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

2. ____________________- express distinct phenotypes depending on circumstances

a. _______________ dictates grass hopper development

Low density phenotype

High density phenotype

Fig. 3.3

Fig. 21.6

_________ phenotype

_________ phenotype

b. ______ dictates wing color in certain butterflies

Termed “______________”

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

typical

Predator induced

Fig. 21.13

CarpMolluskBarnicle ???Daphnia ???

_____ _____ ____ ____ ______Survival Rate(typical/induced)

No predation until 50% of typical morphs eaten

•The immune system “_____________” its foreign invaders

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

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

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

•Kitten experiments

•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.)

•Critical window of development is 4 weeks to 3 months

Thus, not all development is encoded in the ______• Some is the result of ___________

•If sew either eye shut after first three months- __ __________

•Thus, synapses have been stabilized by 3 months

2. __________ plays key role in determining whether neuronal connections ____________

Two key principles-

1. ______________ are made prior to when the animal sees

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 exogenous agents are called ________Examples-

•Skunk cabbage induced _______ in sheep

In Humans

_______________________

•Quinine ________

•Smoking (>20/day)

•Alcohol (>2oz/day) ____________________

•Abnormalities caused by genetic mutations agents are called ____________ (e.g. Down’s syndrome, aniridia (Pax6 mutation))

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

5. Disruptions (cont.)

•FAS children have mean IQ of __; at 16.5 yrs, they have vocabulary of ___ yrs

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

b. Alcohol is a teratogen

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

CH3CH2OH

Fetal Alcohol Syndrome

Huge problem in South Africa due to alcohol-based economy

Misshapen eyes, flat nose, long upper lip

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