Animal ReproductionSexual & Asexual

ByDiana L. Duckworth

Rustburg High SchoolCampbell County

Asexual Reproduction

• Budding – small part of parent’s body grows into new organism

Genetically identical clones

http://johnson.emcs.net/life/images/anemone.bmp

http://www.microscope-microscope.org/gallery/Mark-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

http://www.starfish.ch/reef/echinoderms.html

Asexual Reproduction

• Parthenogenesis – growth & development of embryo without fertilization by male

• Population all female

Many insects; lizards, salamanders, fish, turkeys

http://www.nova.edu/ocean/ghri/bbc_virginshark.html

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

http://civilliberty.about.com/od/historyprofiles/ss/news080406_2.htm

Mating• Mating – male &

female join together to ensure fertilization; not essential to sexual reproduction

http://www.hickerphoto.com/elephants-mating-205-pictures.htm

http://www.torreypine.org/animals/reptiles.htmlhttp://www.eeb.cornell.edu/agrawal/photos/milkweed%20fauna/pages/Tetraopes%20tetrophthalmus%20mating.html

http://www.snakesandfrogs.com/scra/lizards/greenanole.htm

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

http://www.biol.andrews.edu/everglades/organisms/Invertebrates/marine_inverts/Arthropoda/Atlantic%20Horseshoe%20Crab/atlantic_horsehoe_index.htm

External Fertilization – e.g. Salmon

http://www.mass.gov/dfwele/dfw/dfwstksl.htm

http://escoberphoto.com/travel/katmai.html

http://www.biology-blog.com/blogs/archives/Biology-blog/520525028-Feb-14-2008.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

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artjan99/barnac.html

http://getfile.ucoz.com/load/9-1-0-578

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

http://www.nps.gov/pais/naturescience/reptiles.htm

http://crd.dnr.state.ga.us/content/displaycontent.asp?txtDocument=542

http://www.fws.gov/archiecarr/photos/index.html

Various levels of parental care

http://animals.nationalgeographic.com/animals/photos/baby-animals/american-crocodile-baby_image.html

http://www.flmnh.ufl.edu/cnhc/potm-mar99.html

Internal fertilization & internal development of eggs; followed by live birth

http://earth-advocates.org/index.php?option=com_content&task=blogcategory&id=22&Itemid=46

http://www.pacfish.org/sharkcon/documents/gruber.html

Internal fertilization, internal development of embryo to fetus, live birth

http://www.abc.net.au/science/scribblygum/march2006/

http://www.seahorse-australia.com.au/pages/seahr_biology.html

In seahorses, eggs are deposited in the malewhere they are fertilized and develop. Babiesborn live.

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

http://www.scienceclarified.com/El-Ex/Embryo-and-Embryonic-Development.html

http://www.sciencedaily.com/releases/2008/04/080410184336.htm

http://humangenetics.suite101.com/article.cfm/three_parent_embryo_mtdna

Hermaphrodites

• Organisms that change sex in order to reproduce

Crepidula fornicata – a snail

http://www.opalesurfcasting.net/la_faune_aquatique/la_crepidule_-_crepidula_fornicata_article1202.html?var_recherche=+bar

http://www.dkimages.com/discover/Home/Animals/Invertebrates/Molluscs/Gastropods/Marine-Snails/Crepidulidae/Atlantic-Slipper/Atlantic-Slipper-1.html