Reproduction Patterns and Secondary Sexual Characters

What you do

• Name the primary reproductive parts, the gonads, and say what each produces.
• In girls the first sign of puberty at about 10 years is enlargement of the breasts; in boys at about 11 years it is enlargement of the testes.

Challenges to clear

• Sort all twelve cards.
• Fill the secondary sexual character box.
• Fill the Sexual reproduction box — everything that needs two gametes.

The task

Sort each card into the right box.

What this lesson covers

• Asexual reproduction — One parent, no gametes: Amoeba splits into two daughter cells by binary fission (The whole parent cell divides in two and each daughter cell then grows individually. No gametes are involved at any point.); Hydra grows small buds that separate and grow into new organisms (In budding the reproductive unit is just a portion of the parent body, so only one parent is involved.); No gametes are formed, so there is little or no variation in the offspring (Without gametes there is no mixing of genetic material, which is the first difference listed in Table 13.1.); Normally more offspring, produced rapidly in favourable conditions (Table 13.1 lists asexual reproduction as the rapid process that normally yields more offspring.)
• Sexual reproduction — Gametes fuse to form a zygote: Usually two parents are involved and their genetic material mixes (Genetic mixing between two parents is exactly what gives sexual reproduction its increased variation.); Sperm and egg unite to form a zygote (The gametes must normally unite in fertilisation to make a zygote, which then develops into the offspring.); Fewer offspring, and a slower process (Table 13.1 sets this directly against asexual reproduction, which is faster and gives more offspring.); The only method by which human beings reproduce (Bacteria, yeast and many plants can reproduce non-sexually, but in humans reproduction takes place only by the sexual method.)
• Secondary sexual character — Tells the sexes apart from outside: Beard and moustache on a man's face (Distribution of hair on the body and face is a secondary sexual character, brought on by testosterone from the testes at puberty.); Breasts in females (Oestrogens released at puberty cause growth of the mammary glands. This identifies the sex but takes no direct part in reproduction.); Deeper voice in males (Deepening of the voice is one of the changes testosterone brings about in boys at about 11 to 15 years.); Widening of the hips in females (Oestrogens widen the hips and alter the skeletal structure. Skeletal structure is listed among the secondary sexual characters.)

Hint

Secondary sexual characters are not reproductive parts. They serve to identify and attract sex partners, but they do not directly participate in reproduction.