Fertilisation (in animals) is the process where the male sperm cell fuses with the female egg cell.
Internal fertilisation occurs when the male sperm cell fuses with the female egg cell, in the female’s body.
External fertilisation occurs when the male sperm cell fuses with the female egg cell, outside the female’s body.
The most common mistake made by students is that they believe internal fertilisation occurs in animals that give birth (example mammals) and external fertilisation occurs in animals that lay eggs (example birds and reptiles etc). This concept is wrong.
Internal fertilisation occurs in mammals, birds and reptiles.
In the case of mammals, fertilisation occurs in the female’s body. The new life develops inside the mother’s womb for most mammals.
In the case of birds and reptiles, fertilisation occurs inside the female’s body, and the fertilised egg is then laid. The new life develops outside the mother’s body.
In the case for amphibians and most fishes, fertilisation occurs outside the female’s body and the new life develops outside the mother’s body.
Below are some examples of internal and external fertilisation.
Sunday, April 20, 2008
Common Science Mistake – Internal and External Fertilisation
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tianzhu: PLMSG Q36 ----- For background reading, you may follow this link to find out more about why birds migrate.http://www.closertonature.com/outdoors/bird-migration.htm.In P4 Science, students learn that oil will stick to the feathers of birds and make them clump together, making them unable to swim or fly. I think oil spill is again touched on under environment in P6.In Q36, you are asked to base your observation on the given diagram. I think if you craft your answer around oil affecting the abilities of the birds to fly from their original habitat to Sungei Buloh, you should be able to secure 1 mark.
tianzhu: NYPS P6 Prelim 2009 Q24 ---Option(1) is correct.Light travels in a straight line.If a ray of light is shining at a flat mirror,the angle of incidence is equal to the angle of reflection.Do not worry too much about the technical terms, you'll learn in secondary schools.For this question, just draw a perpendicular line to the flat plane,between the two rays.The angle between the ray and the perpendicular line should be equal.
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