Part 2 is nice and short for you guys, so let’s jump right in:

Framework: Fertilization depends on mechanisms that bring together sperm and eggs of the same species.

Fertilization is the union of sperm and egg. The can be done in two ways:

1. External Fertilization: when the female releases its eggs into the environment and the male then fertilizes them. ( Usually done in moist environment so the eggs don’t dry out or so the fastest sperm can go Michael Phelps on the others)
2. Internal Fertilization: when male deposits his sperm in or near the female’s reproductive tract. ( This can be done in both moist or dry environments)

Some species simply release egg and sperm in the surrounding water without making physical contact. Similarly, some species externally fertilize using a method called spawning. Spawning: Clustered individuals release their gametes at the same time (in other words: an orgy. That’s what it’s called so shut up).

Many species, such as us humans, like to choose out mates and have internal fertilization. This is advantageous because:

1. It increases the probability of successful fertilization (as opposed to releasing sperm and egg all over the place). This is also because the release of sperm and egg can be purposely triggered.
2. The sperm can reach the egg efficiently because it is released straight into the female reproduction system

Mating also involves phermones, chemicals released by organism to influence another’s behavior.

Ensuring the Survival of Offspring:

We all are learning AP Biology because of our extensive parental care as a child that will eventually help us find better mates and survive and reproduce. Ja ja ja ja ja.

Animals usually produce more offspring that will reproduce on their own. External fertilization produces lots of offspring (in the big orgy), but only a small fraction of the offspring survive. Internal fertilization produces fewer offspring, but due to the different parental care mechanisms, offspring have a much better chance of survival:

1. Eggs of many terrestrial animals protect against water loss and physical damage during development
2. Marsupials carry their embryos in their reproductive tract (pouch) and nourish them externally
3. Eutherian (placental) mammals, such as humans, have embryos that develop in the uterus
4. Some fish and shark species have young that development completely internally (That’s freaky)

Gamete Production and Delivery:

Things get interesting. Just kidding.

Gonads: The organs that produce gametes.

Some animals, such as palolo, don’t have gonads, and release gametes through the body wall.

Animals that reproduce sexually have specialized cells in their body that eventually become ova and sperm. Usually, this involves special reproductive systems. Take a look at your figures in the textbook for this (Just do it). I can’t explain it on text.

Here are some terms to know:

Spermatheca: sac that stores sperm for “later use”

Cloaca: common opening to digestive, excretory, and reproductive systems. Ew.