Animal Reproduction Sexual & Asexual By Diana L. Duckworth Rustburg High School Campbell County

Asexual Reproduction Budding – small part of parent’s body grows into new organism Genetically identical clones Simmons/images/hydra2.jpg

Asexual Reproduction Regeneration – parent separates into two or more pieces & each piece forms new organism –In some instances just a new part grows –Sponges, sea stars, jellyfish, planaria –Also be clones

Asexual Reproduction Parthenogenesis – growth & development of embryo without fertilization by male Population all female Many insects; lizards, salamanders, fish, turkeys

Sexual Reproduction – gametes from opposite sexes unite Species with sexual reproduction are said to be dioecous – separate sexes Often exhibit distinct sexual dimorphism – males and females look different Sperm (male gamete) formed by meiosis in testes Eggs (female gamete) formed by meiosis in the ovary

Mating Mating – male & female join together to ensure fertilization; not essential to sexual reproduction %20fauna/pages/Tetraopes%20tetrophthalmus%20m ating.html

External Fertilization Males & females release sperm & eggs into the environment – sperm & egg join outside the body –Males & females may come into close proximity –Eggs & larvae develop outside the body –Many gametes produced; many zygotes formed –Usually aquatic ates/marine_inverts/Arthropoda/Atlantic%20Horseshoe%20 Crab/atlantic_horsehoe_index.htm

External Fertilization – e.g. Salmon m/travel/katmai.html

Internal fertilization Joining of sperm & egg inside the body after mating –Ensures selection of mate (not random); promotes diversity –Parents protect and care for young –Does not require water; can occur on land –Less sex cells produced; increases probability of successful reproduction –Common in birds, reptiles & mammals

Internal fertilization; external development After fertilization, larvae (embryo) are released & development occurs outside female body Example: Barnacles uk.org.uk/mag/indexmag.html? uk.org.uk/mag/artjan99/barnac.html

Internal fertilization & development Females put large amounts of energy into development of embryo – very few in litter or clutch – different schemes Eggs in “shell” are laid and either abandoned or nurtured in nest xtDocument=542

Various levels of parental care lgeographic.com/ani mals/photos/baby- animals/american- crocodile- baby_image.html

Internal fertilization & internal development of eggs; followed by live birth advocates.org/index.php?option=com_content&t ask=blogcategory&id=22&Itemid=46

Internal fertilization, internal development of embryo to fetus, live birth In seahorses, eggs are deposited in the male where they are fertilized and develop. Babies born live.

In most species, it is the female who carries the developing fetus to birth…

Hermaphrodites Organisms that change sex in order to reproduce Crepidula fornicata – a snail ertebrates/Molluscs/Gastropods/Marine- Snails/Crepidulidae/Atlantic-Slipper/Atlantic-Slipper- 1.html