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

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

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

4. 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

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

6. 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

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

8. 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

9. 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.