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Internal and External Fertilisation

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Introduction

Internal and External Fertilisation Sexual reproduction > union of male and female gametes (sperm and ova)> two parents donate genes to the young > genes are donated through a process called fertilisation > offspring with a mix of inherited genes. Two mechanisms by which fertilisation can take place: External - (The eggs are fertilised outside of the body). Internal - (The eggs are fertilised within the female reproductive tract). External Fertilisation Characteristics: Gametes Large numbers of male and female gametes produced. Union Occurs in open water environments. Conception Mechanism Simultaneous release of gametes. Chance of fertilisation Low chance of fertilisation because male gametes are released into a large open area where there is less chance of successfully uniting with female gametes. ...read more.

Middle

Number of offspring/zygotes After many zygotes perish a smaller number of offspring survive; however, the number of offspring produced is usually larger compared to internal fertilisation. Breeding frequency Will breed more frequently compared to internal fertilisation due to the lower fertilisation success rate. * An advantage of external fertilisation is that it results in the production of a large number of offspring. * One disadvantage is that environmental hazards such as predators greatly reduce the chance of surviving into adulthood. Internal Fertilisation Characteristics: Gametes Large number of male gametes and fewer female gametes produced. Internal fertilisation is practiced by species that lay shelled eggs or have a period of internal embryonic development. ...read more.

Conclusion

Conception Mechanism Male needs to insert the sperm into the female's reproductive tract via penis or cloaca (copulation). Chance of fertilisation High chance of fertilisation because male gametes are released into a confined space where there is more chance of successfully uniting with female gametes. Environment for zygote Zygote usually develops in a very protected environment inside the female's body. Temperature is controlled there I less chance of predation, infection and loss of zygote from the area. Number of offspring/zygotes Smaller number of zygotes produced because very few perish (higher success rate), therefore, smaller numbers of offspring compared to external fertilisation. Breeding frequency Will breed seasonally and less frequently due to higher fertilisation success rate. * This extra protection increases the chances of survival because mom supplies everything that the embryo needs ?? ?? ?? ?? ...read more.

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