Chapter 12Chapter 12Eve’s TesticleEve’s Testicle

There are no distinct rules for There are no distinct rules for gender and sex in naturegender and sex in nature

Presented by Yvonne Cabrera, Angela Sabra, and Adriana SanchezPresented by Yvonne Cabrera, Angela Sabra, and Adriana Sanchez

Biology 203, Spring 2005

I.I. IntroductionIntroduction

Different sexes, physical Different sexes, physical sexual characteristics, and sexual characteristics, and behaviors have been selected for behaviors have been selected for over time due to their adaptive over time due to their adaptive advantages.advantages.

II. Definition of SexII. Definition of Sex

1.1. Specify which gametes can fuse with othersSpecify which gametes can fuse with othersa) a) IsogamyIsogamy:: Gametes have identical morphology Gametes have identical morphology b) b) AnisogamyAnisogamy:: Gametes have different morphology. Gametes have different morphology.c) c) Oogamy:Oogamy: A subset of anisogamy. Production of A subset of anisogamy. Production of eggs and sperm by internal and external fertilizationeggs and sperm by internal and external fertilization(Dusenbery, 2000).(Dusenbery, 2000).

Isogamy, Anisogamy, and Oogamy

III. Evolution of Isogamy to III. Evolution of Isogamy to Anisogamy???Anisogamy???

1.1. Theories for gamete dimorphismTheories for gamete dimorphism::a) Mitochondrial inheritance conflict between gametes (Judson, a) Mitochondrial inheritance conflict between gametes (Judson, 2002).2002).

b) Small motile gametes facilitate finding gametes to fuse with b) Small motile gametes facilitate finding gametes to fuse with (Dusenbery, 2000).(Dusenbery, 2000).

c) Large egg increases survival rate for zygote (Dusenbery, c) Large egg increases survival rate for zygote (Dusenbery, 2002).2002).

d) Large pheromone-producing eggs are easier to find d) Large pheromone-producing eggs are easier to find (Dunsenbery, 2000). (Dunsenbery, 2000).

e) Isogamy evolved in Prokaryotes and anisogamy evolved in e) Isogamy evolved in Prokaryotes and anisogamy evolved in Eukaryotes, related to the organism’s investment in gamete Eukaryotes, related to the organism’s investment in gamete production (Knowlton, 1974).production (Knowlton, 1974).

IV. Evolvement from Zero IV. Evolvement from Zero Sexes to Multiple Sexes???Sexes to Multiple Sexes???

1.1. The absence of sexes allow for inbreeding and hence The absence of sexes allow for inbreeding and hence lead to decreased genetic variation, which is less lead to decreased genetic variation, which is less selected for (Judson, 2002). selected for (Judson, 2002).

2.2. Multiple sexes facilitate finding a suitable mate, Multiple sexes facilitate finding a suitable mate, decreasing the possibility of inbreeding (Judson, decreasing the possibility of inbreeding (Judson, 2002).2002).

3.3. Developing a new sex is beneficial because it can Developing a new sex is beneficial because it can mate with a greater proportion of the population, until mate with a greater proportion of the population, until equilibrium is reached (Judson, 2002).equilibrium is reached (Judson, 2002).

V. What Determines Sex: Male, V. What Determines Sex: Male, female, hermaphrodite, and othersfemale, hermaphrodite, and others

1.1. Genetics, biotic, and abiotic factors Genetics, biotic, and abiotic factors determine sex (Barash & Lipton, 1997).determine sex (Barash & Lipton, 1997).

a) Population density and social milieu a) Population density and social milieu (Judson, 2002). (Judson, 2002).

b) Natural selection: A certain sex may b) Natural selection: A certain sex may have more to offer and hence will be have more to offer and hence will be selected for (Campbell & Reece, 2002). selected for (Campbell & Reece, 2002).

c) Sexual selection: mate can c) Sexual selection: mate can discriminate against morphology of other discriminate against morphology of other mate’s gamete, selecting for preferred mate’s gamete, selecting for preferred traits (Judson, 2002). traits (Judson, 2002).

Green Spoon Worm

Chlamydomonas moewusii

V. Continued…V. Continued…

d) Chromosome d) Chromosome combinations:combinations:

• In mammals, XY= In mammals, XY= male and XX= female. male and XX= female.

• In birds, ZZ=male and In birds, ZZ=male and ZW= female.ZW= female.

• In lizards, ZW= In lizards, ZW= female and XY=malefemale and XY=male

BirdsLions (mammals)

Lizards

V. Continued…V. Continued…

e) Gene combinations: e) Gene combinations: In slime molds, three In slime molds, three

genes determine sex genes determine sex and there are and there are variations of each. variations of each.

• matA, matB, matC.matA, matB, matC.

Physarum polycephalum Physarum polycephalum (Slime mold)(Slime mold)

V. Continued...V. Continued...

f) Environmentf) Environment TemperatureTemperature

In alligators, eggs laid In alligators, eggs laid in cool sand = female in cool sand = female and warm sand = maleand warm sand = male

In snapping turtles, In snapping turtles, eggs laid in sand 20 or eggs laid in sand 20 or 40C = female, 40C = female, anything otherwise = anything otherwise = male. male.

Hatching AlligatorHatching Alligator

Hatching TurtleHatching Turtle

V. Continued…V. Continued…

g) Fate of gametesg) Fate of gametes• In some insects, unfertilized eggs = males. In some insects, unfertilized eggs = males.

h) Pathogenicity h) Pathogenicity • In the tropical insect, In the tropical insect, Stictococcus sjoestedti, eggs , eggs

infected with fungus = female and uninfected = male.infected with fungus = female and uninfected = male.

VI. Why Hermaphrodites, Females VI. Why Hermaphrodites, Females and Males, or Combinations?and Males, or Combinations?1.1. Hermaphrodites have more to offer in Hermaphrodites have more to offer in

small population densities (Judson, small population densities (Judson, 2002).2002).

2.2. Large egg and small sperm lead to Large egg and small sperm lead to female and male sexes.This difference in female and male sexes.This difference in gamete morphology is beneficial gamete morphology is beneficial (Judson, 2002).(Judson, 2002).

3.3. Combinations allow for sharing the Combinations allow for sharing the above benefits (Judson, 2002).above benefits (Judson, 2002).

VII. Misconceptions Related VII. Misconceptions Related to Gender Roles and Sexesto Gender Roles and Sexes

1) Male is responsible for 1) Male is responsible for the upbringing of the upbringing of offspring.offspring.

2) Female Hyaena evolved 2) Female Hyaena evolved male characteristics. male characteristics.

3) Female houses the male 3) Female houses the male for egg fertilization. for egg fertilization.

4) Female dominance over 4) Female dominance over male.male.

Male BatMale Bat

Dyacopterus spadiceus

Crocuta crocutaCrocuta crocutaSpotted HyaenaSpotted Hyaena

Green Spoon Worm

VIII. Conclusion: There are no VIII. Conclusion: There are no rules in nature.rules in nature.

In summary, gender roles and sexes are In summary, gender roles and sexes are not fixed. not fixed.

(Tarzan Comic)

Works Cited Works Cited Barash, D. & Lipton, J. (1997). Barash, D. & Lipton, J. (1997). Making sense of sex, how genes and gender Making sense of sex, how genes and gender

influence our relationships. influence our relationships. Washington DC: Island Press.Washington DC: Island Press.

Campbell, N. & Reese, J. (2002). Descent with modification: A Darwinian view of Campbell, N. & Reese, J. (2002). Descent with modification: A Darwinian view of life. In B. Wilbur (Ed.), life. In B. Wilbur (Ed.), BiologyBiology (pp. 428-442). San Francisco: Benjamin (pp. 428-442). San Francisco: Benjamin Cummings.Cummings.

Dusenbery, D. (2000). Selection for high gamete encounter rates explains the Dusenbery, D. (2000). Selection for high gamete encounter rates explains the success of male and female mating types. success of male and female mating types. Journal of Theoretical Biology, 202Journal of Theoretical Biology, 202, , 1-101-10..

Dusenbery, D. (2002). Ecological models explaining the success of distinctive Dusenbery, D. (2002). Ecological models explaining the success of distinctive sperm and eggs (oogamy). sperm and eggs (oogamy). Journal of Theoretical Biology, 219Journal of Theoretical Biology, 219, 1-7, 1-7..

Judson, O. (2002). Judson, O. (2002). Dr. Tatiana’s sex advice to all creation.Dr. Tatiana’s sex advice to all creation. New York: New York: Metropolitan Books.Metropolitan Books.

Knowlton, N. (1974). A note of evolution of gamete dimorphism. Knowlton, N. (1974). A note of evolution of gamete dimorphism. Journal of Journal of Theoretical Biology, 46Theoretical Biology, 46, 283-285., 283-285.

Works Cited for IllustrationsWorks Cited for IllustrationsBirds. Available from Birds. Available from http://www.mesc.usgs.gov/resources/education/bts/images/bird_sketches/wtgdove.jpghttp://www.mesc.usgs.gov/resources/education/bts/images/bird_sketches/wtgdove.jpg

Chlamydomonas moewusii. Available from http://130.158.208.53/WWW/PDB/Images/Chlorophyta/Chlamydomonas/Chlamydella/samples.jpg

Crocuta crocutaCrocuta crocuta (Spotted Hyaena). Available from http://www.csdyzx.com/swtd/dongwu/jzdwm/images/Feliformia_2d.jpg (Spotted Hyaena). Available from http://www.csdyzx.com/swtd/dongwu/jzdwm/images/Feliformia_2d.jpg

Dyacopterus spadiceusDyacopterus spadiceus (Male Bat). Available from http://www.k12.nf.ca/sptech/bats/researchpage3/batbaby.gif (Male Bat). Available from http://www.k12.nf.ca/sptech/bats/researchpage3/batbaby.gif

Isogamy, Anisogamy, Oogamy. Available from Isogamy, Anisogamy, Oogamy. Available from http://www.biologie.uni-hamburg.de/b-online/ge42/19.jpghttp://www.biologie.uni-hamburg.de/b-online/ge42/19.jpg

Green Spoon Worm. Available from Green Spoon Worm. Available from http://www.entu.cas.cz/berec/image/bonellia.jpghttp://www.entu.cas.cz/berec/image/bonellia.jpg

Hatching Alligator. Available from Hatching Alligator. Available from http://www.no-pest.com/HatchingAlligator.jpghttp://www.no-pest.com/HatchingAlligator.jpg

Hatching Turtle. Available from http://www.dnr.state.wi.us/org/caer/ce/eek/critter/reptile/images/turtleHatching.jpgHatching Turtle. Available from http://www.dnr.state.wi.us/org/caer/ce/eek/critter/reptile/images/turtleHatching.jpg

Lions (mammals). Available from Lions (mammals). Available from http://members.mweb.co.zw/wildlife/mammals/lion/two.jpghttp://members.mweb.co.zw/wildlife/mammals/lion/two.jpg

Lizards. Available from http://www.helodermahorridum.com/images/malefemale.jpgLizards. Available from http://www.helodermahorridum.com/images/malefemale.jpg

Physarum polycephalum Physarum polycephalum (Slime mold).(Slime mold). Available from http://botit.botany.wisc.edu:16080/images/332/Slime_molds_M_Ac_sl_so/Available from http://botit.botany.wisc.edu:16080/images/332/Slime_molds_M_Ac_sl_so/Physarum_folder/Physarum_polycephalum_TJV.gifPhysarum_folder/Physarum_polycephalum_TJV.gif

Tarzan Comic. Available from Tarzan Comic. Available from http://nicolesniche.net/comics.shtml