Overview

This topic explores how animals reproduce and develop from fertilization to maturity. It covers reproductive strategies, embryonic development, and hormonal regulation, which are essential for understanding continuity of life and evolutionary adaptations.

Key Concepts and Structures

• Sexual Reproduction: Involves the fusion of sperm and egg to form a zygote. Provides genetic diversity through meiosis and fertilization.
• Asexual Reproduction: Occurs without gametes. Methods include budding, fragmentation, and parthenogenesis; produces genetically identical offspring.
• Fertilization: Can be internal (e.g., mammals) or external (e.g., many fish and amphibians). Leads to zygote formation.
• Embryonic Development: Includes stages such as cleavage (cell division), blastula (hollow ball), gastrulation (formation of germ layers), and organogenesis (formation of organs).
• Germ Layers: Ectoderm (skin, nervous system), mesoderm (muscles, bones, circulatory system), and endoderm (digestive and respiratory linings).
• Human Reproductive System: Includes testes and penis in males; ovaries, uterus, and vagina in females. Gamete production regulated by hormones.
• Hormonal Control: Estrogen, progesterone, LH, and FSH regulate the menstrual cycle and pregnancy. Testosterone controls sperm production and male characteristics.
• Placenta: In placental mammals, facilitates exchange of nutrients, gases, and wastes between mother and fetus.
• Reproductive Strategies: r-strategists produce many offspring with low survival; K-strategists produce few offspring with high parental care (e.g., humans).
• Metamorphosis: Developmental transformation (e.g., caterpillar to butterfly, tadpole to frog) seen in many invertebrates and amphibians.

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