1. Sexual Reproduction
Involves the union of reproductive cells (gametes) from two different parents, called fertilization and results in the formation of a zygote
The union of the two gametes is called fertilization
Offspring are genetically unique from either parent

2. Sexual reproduction: Pros Cons Genetic diversity among offspring
Allows for evolution (ability to adapt)
Higher survival rate
Recombination can disrupt successful adaptations
Huge amount of energy required to make gametes
Requires more time
Reliance on a mate

3. Hermaphroditism Most animals have distinct sexes (male or female)
Hermaphroditism occurs when one individual has both male and female reproductive structures
They usually still mate with other individuals but self-fertilization is possible during mating or in times of environmental stress that prevents finding a mate

4. Hermaphroditism Simultaneous Hermaphroditism
An organism that has both male and female sexual organs at the same time
For example, earthworms, land snails, and land slugs are simultaneous hermaphroditic species
Most plant species are simultaneous hermaphrodites

5. Hermaphroditism Sequential Hermaphroditism
Occurs when the individual is born as one sex, but then later changes into the opposite sex
It is common in fish, jellyfish, snails, and slugs

6. Hermaphroditism
Protandry describes sequential hermaphroditism in the case where an organism is born as a male then changes to female
Example: Clownfish inhabit a sea anemone and consist of one large reproductive female, a smaller reproductive male, and several even smaller non-reproductive males
If the female is removed, the reproductive male will change sex to become a female and the largest non-reproductive male will become reproductive

7. Hermaphroditism
Protogyny sequential hermaphroditism in the case where an organism is born as a female and then later changes to male
Example: Wrasses are born as either females or male form in the initial form, they look the same and are non-territorial
Terminal Phase males are territorial and have bright colouration
Both initial form males and females can become terminal males

8. External Development
External development is taken to be the ancestral condition and where either unfertilized eggs or fertilized eggs are spawned
No embryonic development takes place within the mother
External Fertilization
the female releases unfertilized eggs into the environment and the male then fertilizes them outside of her body

9. External Development Internal Fertilization
The derived condition where the eggs of a female are fertilized within her body by the male inserting sperm
The female then lays an egg that contains the zygote and a significant yolk to feed the developing embryo
In many species, one of the parents or both will continue to feed the young after hatching from the egg