Animal Reproduction

• female feed before mating
• 150 to 300 eggs at a time
• St Louis Encephalitis 
• West Nile Virus

creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote

creation of offspring without the fusion of egg and sperm

fission, separation of a parent into two or more individuals of about the same size

new individuals arise from outgrowths of existing ones

• is breaking of the body into pieces some or all of which develop into adults
• must be accompanied by regeneration

regrowth of lost body parts

the development of a new individual from an unfertilized egg

• sexual females have half as many daughters as asexual females
• almost all eukaryotic species reproduce sexually

reproductive handicap

genetic recombination which provides potential advantages

• an increase in variation in offspring, providing an increase in the reproductive success of parents in changing environments
• An increase in the rate of adaptation
• A shuffling of genes and the elimination of harmful genes from a population

• each individual has male and female reproductive systems
• some hermaphrodites can self-fertilize

• XX female
• XY male

• XX female
• XO male

• haploids are male
• diploids are female

• ZZ male
• ZW female

• Many reptiles
• Incubation temperature of the eggs determine the sex

If isolated the individual becomes female, but if in a group it develops as a male

starting out as a female and then later becoming a male

starts as male and will change sex to a female

the union of egg and sperm

eggs shed by the female are fertilized by sperm in the external environment

sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract

the release of mature eggs at the midpoint of a female cycle

• hormones and environmental cues
• Most animals exhibit reproductive cycles related to changing seasons
• Animals may reproduce asexually or sexually, or they may alternate these methods

• parthenogenesis- egg involved in fertilization but no sperm
• No known birds or mammals are parthenogenic in the wild

• Several genera of fishes, amphibians, and lizards reproduce only by a complex form of parthenogenesis that involves the doubling of chromosomes after meiosis
• Asexual whiptail lizards are descended from a sexual species, and females still exhibit mating behaviors

• Komodo sex determination is based on the ZW system –ZW is female, ZZ is male and WW is inviable
• Komodo females produce only males during parthenogenesis

organs that produce gametes

• Some simple systems do not have gonads, but gametes form from undifferentiated tissue
• The most complex systems contain many sets of accessory tubes and glands that carry, nourish, and protect gametes and developing embryos

• male only mates once
• Males and/or females of some species have evolved mechanisms to decrease the chance of their mate mating with another individual

• sperm is stored during copulation
• Queen bees mate over a day or couple of days with multiple drones
• Sperm is stored and used for 2-7 years

• is a common opening between the external environment and the digestive, excretory, and reproductive systems
• A cloaca is common in nonmammalian vertebrates; mammals usually have a separate opening to the digestive tract

The internal organs are a pair of gonads and a system of ducts and chambers that carry gametes and house the embryo and fetus

abdominal cavity

follicles which consist of a partially developed egg, called an oocyte, surrounded by support cells

oogenesis