External Fertilisation (Ext. Ferti.)
• Most aquatic organisms (e.g., majority of algae, fishes, amphibians).
• Syngamy occurs in the external medium, usually water — i.e., outside the body of
the organism.
• Organisms show good synchrony in the release of a large number of gametes (seen in
many fishes and frogs).
• Large number of offspring are produced.
• Major disadvantage: Offspring are extremely vulnerable to predators, threatening
their survival until adulthood.
• The zygote is formed in the external medium (water).
Internal Fertilisation (Int. Ferti.)
• Seen in many terrestrial organisms such as:
• Higher animals (reptiles, birds, mammals)
• Majority of plants (pteridophytes, gymnosperms, angiosperms)
• Syngamy occurs inside the body of the organism.
• Male gametes are motile,
Female gametes are stationary.
• Only a small number of eggs are produced (selected offspring type).
• In seed plants (gymnosperms, angiosperms), non-motile male gametes are carried to
female gametes through the pollen tube.
• The zygote is formed inside the body of the organism.
Fungi and Algae
• The zygote has a thick wall, making it resistant to desiccation and other adverse
conditions.
• Both groups have a haploid plant body.
• In some algae and fungi, both gametes are motile.
• Asexual reproduction is common due to their relatively simple organisation.
• Most aquatic organisms (e.g., majority of algae, fishes, amphibians).
• Syngamy occurs in the external medium, usually water — i.e., outside the body of
the organism.
• Organisms show good synchrony in the release of a large number of gametes (seen in
many fishes and frogs).
• Large number of offspring are produced.
• Major disadvantage: Offspring are extremely vulnerable to predators, threatening
their survival until adulthood.
• The zygote is formed in the external medium (water).
Internal Fertilisation (Int. Ferti.)
• Seen in many terrestrial organisms such as:
• Higher animals (reptiles, birds, mammals)
• Majority of plants (pteridophytes, gymnosperms, angiosperms)
• Syngamy occurs inside the body of the organism.
• Male gametes are motile,
Female gametes are stationary.
• Only a small number of eggs are produced (selected offspring type).
• In seed plants (gymnosperms, angiosperms), non-motile male gametes are carried to
female gametes through the pollen tube.
• The zygote is formed inside the body of the organism.
Fungi and Algae
• The zygote has a thick wall, making it resistant to desiccation and other adverse
conditions.
• Both groups have a haploid plant body.
• In some algae and fungi, both gametes are motile.
• Asexual reproduction is common due to their relatively simple organisation.
