All animals follow the same process for sexual reproduction. There are 4 steps involved in this process: • Meiosis produces gametes • Male gamete (sperm) combines with female gamete (egg) • Zygote is produced and develops into an embryo • Embryo develops through mitosis
For sexual reproduction to be successful 2 conditions must be met: • both male and female gametes must arrive in the same place at the same time • the zygote must receive adequate food, moisture, warmth and protection
Mating Patterns • Animals have different mating patterns that allow zygotes to form and develop. • Mating is the process by which 2 members of a population come together to reproduce. • Humans can mate at any time however some animals can only mate at certain times in order to ensure survival of their offspring. For example, rabbits, deer and other forest animals can only be born in the spring when the environmental conditions are favorable.
Fertilization Patterns • Fertilization can only occur between sperm and egg of the same species (a rabbit cannot successfully mate with a skunk). • Sperm and egg require moisture to survive therefore they’ll die in a dry environment. • Moisture allows sperm to swim and keeps the egg’s cell membrane soft so that sperm can enter.
Animal fertilization can be internal or external. • External fertilization occurs when the sperm and egg combine outside of the organism. This type of fertilization is common among water dwelling organisms.
Most land animals (reptiles, snakes, turtles, humans etc.) reproduce by internal fertilization. • The sperm leaves the male body and travels into the female body in order to fertilize the egg. • After fertilization, the zygote must develop into an independent organism. • Mammals (humans, deer etc) keep their young inside the female until the fetus is developed enough to sustain life. • Reptiles lay their young in an egg with a leathery shell and a soft inside to protect the developing embryo. Birds also lay eggs but they have a hard shell.
Some insects go through a process known as incomplete metamorphosis in which they resemble the parent at birth but they go through a series of molting before they are adults. • Complete metamorphosis happens in insects that don’t resemble their parents when born; butterflies for example.
Hermaphrodites • Some organisms, like earthworms, have both female and male reproductive organs. • Even though they have both sperm and eggs they must be fertilized by another to reproduce
To Do …. • Using your textbook Pg. 51-59 complete the Sexual Reproduction Worksheet (to be kept in your notes) • Copy, label and describe: • Incomplete Metamorphosis Fig. 2.16 pg. 57 • Complete Metamorphosis Fig. 2.17 pg.58 • Complete # 1-5 on pg. 59