Asexual Reproduction

1. Asexual Reproduction • Genes all come from one parent • Common to many invertebrates • Advantages • Enables animals to live in isolation – no need to locate mates • Organism can create numerous offspring in a short amount of time – rapidly colonize habitat • Advantageous in __________, favorable environments • Perpetuates successful genotypes precisely

2. Forms of Asexual Reproduction • _____________ • separation of parent into two or more individuals of approximately equal size. • _____________ • new individuals split off from existing ones • __________________ • Broken off body part grows into new individual • Regeneration of body parts • _________________ • Eggs develop without being fertilized Queen Worker Drone

3. Forms of Asexual Reproduction • Parthenogenosis • Egg develops ___________ being fertilized • Adults produced by parthenogenesis are _____________ • Example: drone (male) bees form from single unfertilized egg and do not need to undergo meiosis to make their own new reproductive cells • SOMETIMES, in certain species, whether parthenogenesis occurs may be determined by season/conditions • Favorable conditions leads to asexual repro. • Everythings going well, why change? • Environmental stress leads to sexual repro • If conditions are bad, better hope some variety will come up with a solution!

4. Sexual Reproduction • Creation of offspring by fusion of haploid gametes to form a zygote • Increases genetic variation • Probably enhances reproductive success when pathogens or other environmental factors ________ rapidly • If there’s variety, chances are better than someone will have a genetic solution to an environmental problem

5. Hermaphrodites • Each individual has both male and female reproductive systems • NOT ASEXUAL • Helps when finding a mate is not easy • Every individual encountered is a potential ___________ (as opposed to just ½ the individuals encountered) • Each partner donates sperm to female repro organs of the other.

6. TWO Types of Fertilization • ____________ fertilization Requires environment where egg/zygote can develop without drying out. • The eggs are unprotected and vulnerable to water loss, etc. • Thus, almost always occurs in ____________ areas

7. External Fertilization • Parents may not even make physical contact • Eggs/sperm released into water • Timing is still important • Some do use specific mates and mating behaviors • __________________ are used to draw animals together

8. External Fertilization • GENERAL rule • _______ of zygotes produced • _________ parental care • Have lots of babies and hope at least a few of them survive • Very small proportion of zygotes survive to full development

9. Internal Fertilization • Protects _________________ • Neither sperm nor egg is ever exposed to environment • Sperm placed directly inside the female • Protects _______________ • Embryos develop either: • Inside shelled eggs • Inside the female • Don’t come out until they can survive dry environment

10. Internal Fertilization • ALL internal fertilization requires • Sophisticated reproductive systems including organs that • deliver sperm • receptacles that receive, store and transport sperm to ripe eggs. • Cooperativebehaviors leading to copulation • Uncharacteristic sexual behaviors are eliminated by ____________________________ • Example – female spiders eat males if they don’t use the proper reproductive signals

11. Internal Fertilization • Generally produces _______________ zygotes than external • But proportion of zygotes that develop and survive is ____________. This is because of: • greater protection of eggs/zygotes/embryos • Within a shell OR • Within the female • Due to better parental care of eggs and offspring • Don’t abandon young

12. Internal Fertilization • Two possible outcomes: • _______________ to be laid on land • Reptiles, Birds • And 1 very small mammal group – montremes (platypus and spiny echidna) • Embryos develop _______________________ • Mammals (placental and marsupial) • Both animal types are called ______________ due to the embryonic structures they share in common

13. AMNIOTES • Amniotic eggs • Shell is NOT the only part that protects • EXTRAEMBRYONIC MEMBRANES make the anmiontic egg successful • AMNION • surrounds baby with water • “little ocean” • Yolk Sac • Stored Food • Allantois • Waste sac • Chorion • Functions with allantois in GAS EXCHANGE

14. AMNIOTES Amnion • Internal Development • Mammals – • both placental and marsupial • NOT monotremes (EGG LAYERS!) • Shelled egg not used, but • amnion present and • ________ extraembryonic membranes give rise to ____________, etc.

15. Male Reproductive Organs • Testes • Seminiferous Tubules • Sperm production • Epididymis • Sperm maturation • Vas Deferens • Carry sperm to urethra • Urethra • exit body

16. Seminiferous Tubules • Highly coiled tubes • Sperm are formed HERE • ____________ HAPPENS HERE!! • Also contain cells (Leydig cells) which make male hormones • Testosterone and other androgens Cross section through Sem. Tubule

17. ___________________________ • General term for creation of gametes • SEX CELLS • ___________________ • TWO TERMS • Spermatogenesis • Gametogenesis (meiosis) in males • Oogenesis • Gametogenesis (meiosis) in females

18. Spermatogenesis – MEIOSIS to create sperm Least Mature Also called spermatogonium Testis Epididymis Germ cell (diploid) Coiled seminiferous tubules 1° spermatocyte (diploid) MEIOSIS I 2° spermatocytes (haploid) MEIOSIS II Vas deferens Spermatids (haploid) Meiosis happens Inside Seminiferous tubules Most Mature Spermatozoa Cross-section of seminiferous tubule

19. Spermatogenesis • __________________________ • Products of meiosis • ____ created from each primary spermatocyte • ____________________ • Immature sperm • Tailess • Sertoli cells • Provide nourishment to spermatids as they further develop into sperm at center of seminiferous tubule

20. Mature Sperm • Sperm structure • Head • ___________________ • Contains enzymes to penetrate egg • Nucleus • Males genetic contribution • Mid-piece • Mitochondria • For energy - swimming • Tail • Microtubules • ____________

21. Fertilization • Joining of sperm & egg • sperm head (nucleus) enters egg

22. Female reproductive system • Ovaries • produces eggs & hormones • Uterus • nurtures fetus; lining builds up each month • Fallopian tubes • tubes for eggs to travel from ovaries to uterus • Called OVIDUCTS in every other animal • Cervix • opening to uterus, dilates 10cm (4 inches) for birthing baby • Vagina • birth canal

23. Female Reproductive Organs • Ovaries • Each ovary contains many follicles • ___________________ • One egg cell surrounded by folliclecells • Follicle cells nourish and protect developing egg • Follicle cells also produce primary female sex hormones • estrogens

25. Oogenesis • Oogonia • Cells that create cells that undergo ________ • ________________ • Repeatedly divide to create _______ oogonia • ______________ • Primary oocyte • Cell that has entered into _____________ • Secondary oocyte • Cell that has entered into _____________ • ____________

26. Oogenesis • ________ divisions • Make one really good egg and ___ polar bodies Meiosis 1 completed during egg maturation ovulation Meiosis 2 completed triggered by fertilization

27. Reproductive hormones LH &FSH • ______________ • from testes • functions • sperm production • 2° sexual characteristics • _____________ • from ___________ • functions • egg production • prepare uterus for fertilized egg • 2° sexual characteristics testesorovaries