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
http://www.microscope-microscope.org/gallery/MarkSimmons/images/hydra2.jpg
Genetically
identical
clones
http://johnson.emcs.net/life/images/anemone.bmp
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
http://www.nova.edu/ocean/ghri/bbc_virginshark.html
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
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.snakesandfrogs.com/scra/lizards/greenanole.htm
http://www.torreypine.org/animals/reptiles.html
http://www.eeb.cornell.edu/agrawal/photos/milkweed
%20fauna/pages/Tetraopes%20tetrophthalmus%20m
ating.html
http://www.hickerphoto.com/elephants-mating-205-pictures.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/Invertebr
ates/marine_inverts/Arthropoda/Atlantic%20Horseshoe%20
Crab/atlantic_horsehoe_index.htm
External Fertilization – e.g. Salmon
http://escoberphoto.co
m/travel/katmai.html
http://www.biology-blog.com/blogs/archives/Biology-blog/520525028-Feb-14-2008.html
http://www.mass.gov/dfwele/dfw/dfwstksl.htm
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.microscopyuk.org.uk/mag/indexmag.html?http://www.microscopyuk.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://crd.dnr.state.ga.us/content/displaycontent.asp?t
xtDocument=542
http://www.fws.gov/archiecarr/photos/index.html
http://www.nps.gov/pais/naturescience/reptiles.htm
Various levels of parental care
http://animals.nationa
lgeographic.com/ani
mals/photos/babyanimals/americancrocodilebaby_image.html
http://www.flmnh.ufl.edu/cnhc/potm-mar99.html
Internal fertilization & internal development
of eggs; followed by live birth
http://earthadvocates.org/index.php?option=com_content&t
ask=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.seahorse-australia.com.au/pages/seahr_biology.html
In seahorses, eggs are deposited in the male
where they are fertilized and develop. Babies
born live.
http://www.abc.net.au/science/scribblygum/march2006/
In most species, it is the female who carries the
developing fetus to birth…
http://humangenetics.suite101.com/article.cfm/three_parent_embryo_mtdna
http://www.sciencedaily.com/releases/2008/04/080410184336.htm
http://www.scienceclarified.com/El-Ex/Embryo-and-Embryonic-Development.html
Hermaphrodites
• Organisms that change sex in order to
reproduce
http://www.dkimages.com/discover/Home/Animals/Inv
ertebrates/Molluscs/Gastropods/MarineSnails/Crepidulidae/Atlantic-Slipper/Atlantic-Slipper1.html
Crepidula fornicata – a snail
http://www.opalesurfcasting.net/la_faune_aquatique/la_crepidule_-_crepidula_fornicata_article1202.html?var_recherche=+bar