Types of reproduction in animals — A/L Biology

What must I remember about Types of reproduction in animals?

• Reproduction is the biological process by which new individual organisms are produced, classified broadly into Asexual and Sexual reproduction.
• Asexual reproduction involves a single parent producing genetically identical offspring (clones) via mitosis without gamete fusion, advantageous in stable environments with rapid population expansion.
• Major mechanisms of asexual reproduction: Binary Fission (bacteria, Amoeba), Budding (Hydra, yeasts), Fragmentation and regeneration (Planaria, sea stars), and Parthenogenesis (development of unfertilized egg into adult, e.g., honeybee drones, whiptail lizards).
• Sexual reproduction involves the fusion of haploid gametes (sperm and ovum) formed via meiosis to create a genetically diverse diploid zygote (2n), providing evolutionary raw material for natural selection.
• Fertilization modes: External fertilization occurs outside parent's body in aquatic environments, requiring synchronization and massive gamete release; Internal fertilization occurs inside female reproductive tract, requiring copulatory organs and behavioral courtship adaptations.

Test yourself (1 minute)

1. Developmental patterns after fertilization

   Oviparity (eggs laid outside, embryonic development fueled by yolk, e.g., birds, most reptiles); Viviparity (embryo develops inside maternal uterus with placental nutrition, giving live birth, e.g., eutherian mammals); Ovoviviparity (eggs retained in mother's body until hatching, nourished by yolk, e.g., certain sharks, vipers).

2. Hermaphroditism (Monoecy)

   Organisms possessing both male and female gonads (e.g., earthworms, tapeworms); allows self-fertilization in isolated conditions or reciprocal cross-fertilization doubling reproductive output.

3. Evolutionary trade-offs

   Asexual reproduction saves energy and time (no mate seeking, 100% maternal gene transmission); sexual reproduction incurs 'two-fold cost of sex' but purges deleterious mutations and creates environmental adaptation plasticity.

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Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 5

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Year 2 · Term 1