Animal Reproduction Main Idea: Animals have specialized structures for sexual reproduction.

Gonads-specialized reproductive organs that produce sperm or eggs Female Male Ovaries produce egg cells Testes produce sperm

How does animal fertilization occur? Egg cell + sperm cell= diploid zygote

Fertilization Internal Fertilization External Fertilization Happens inside of body-deposit sperm in or near a female’s reproductive system Earth worms, spiders, insects, reptiles, birds, and mammals Happens outside of an animal’s body, in the environment Eggs and sperm released in water Large number of eggs released to ensure survival Jellyfishes, clams, sea urchins, sea stars, some fish and amphibians

How do animal embryos develop? Zygote (mitosis and cell division) embryo (fertilized egg) (diploid organism)

How do animal embryos develop? External Development Internal Development Protected and develops inside an egg Yolk provides food Birds, lizards, snakes Develop inside mother Organ or tissue transfers nourishment from mother to embryo Some snakes, insects, and fishes develop in egg with yolk, while inside of mother

External development continued Metamorphosis- developmental process in which the form of the body changes as an animal grows from the egg to an adult

Gestation Length of time between fertilization and birth of an animal Varies among species and relates to the size of the animal at birth Examples: Mouse 21 days Dog 60 days Humans 266 days Elephants 600 days

Questions Compare internal and external fertilization. Why do animals that reproduce by external fertilization produce more eggs than animals that reproduce by internal fertilization? In your own words, write the definition of metamorphosis.