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 2004-2005

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 2004-2005

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! 2004-2005

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 2004-2005

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. 2004-2005

TWO Types of 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 2004-2005

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 2004-2005

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 2004-2005

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 2004-2005

Internal Fertilization ALL internal fertilization requires Sophisticated reproductive systems including organs that deliver sperm receptacles that receive, store and transport sperm to ripe eggs. Cooperative behaviors leading to copulation Uncharacteristic sexual behaviors are eliminated by ____________________________ Example – female spiders eat males if they don’t use the proper reproductive signals 2004-2005

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 2004-2005

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 2004-2005

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 2004-2005

AMNIOTES Internal Development Mammals – Shelled egg not used, but 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. 2004-2005

Male Reproductive Organs Testes Seminiferous Tubules Sperm production Epididymis Sperm maturation Vas Deferens Carry sperm to urethra Urethra exit body 2004-2005

Cross section through Sem. Tubule 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 2004-2005

___________________________ General term for creation of gametes SEX CELLS ___________________ TWO TERMS Spermatogenesis Gametogenesis (meiosis) in males Oogenesis Gametogenesis (meiosis) in females 2004-2005

Spermatogenesis – MEIOSIS to create sperm Least Mature Also called spermatogonium Epididymis Testis 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 2004-2005

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 2004-2005

Mature Sperm Sperm structure Head Mid-piece Tail ___________________ Contains enzymes to penetrate egg Nucleus Males genetic contribution Mid-piece Mitochondria For energy - swimming Tail Microtubules ____________ 2004-2005

Fertilization Joining of sperm & egg sperm head (nucleus) enters egg 2004-2005

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 2004-2005

Female Reproductive Organs Ovaries Each ovary contains many follicles ___________________ One egg cell surrounded by follicle cells Follicle cells nourish and protect developing egg Follicle cells also produce primary female sex hormones estrogens 2004-2005

2004-2005

Oogenesis Oogonia Primary oocyte Secondary oocyte ____________ Cells that create cells that undergo ________ ________________ Repeatedly divide to create _______ oogonia ______________ Primary oocyte Cell that has entered into _____________ Secondary oocyte ____________ 2004-2005

Oogenesis ________ divisions Make one really good egg and ___ polar bodies Meiosis 1 completed during egg maturation ovulation Meiosis 2 completed triggered by fertilization 2004-2005

Reproductive hormones LH & FSH ______________ from testes functions sperm production 2° sexual characteristics _____________ from ___________ egg production prepare uterus for fertilized egg testes or ovaries 2004-2005