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OUTCOMES
recall what happens in sexual reproduction
recognise the differences between external and internal fertilisation
describe how scientific ideas are supported.
Most frogs normally reproduce in May and June. You can sometimes hear them ‘croaking’ at this time. Only the males croak and they do this to attract females. Each male frog finds an area (called a territory) on the bank of a pond. The male frogs will fight any other frogs that come into their areas.
Each different sort (species) of frog has its own croak and so females are only attracted to males of the same species. In bullfrogs, the females are most attracted to the bullfrog males with the deepest croaks.
When a female frog of the right species has come into a male frog’s territory, the male doesn’t mess around! He leaps onto her back and holds on very tightly. The two frogs go into the water and the female releases her egg cells. As she does this the male releases sperm cells onto them. The egg cells are then fertilised by the sperm cells.
The fertilised egg cells then grow into embryos. The egg cells have a jelly coating on them. This provides a source of food for the developing embryo. After two or three weeks the tiny tadpoles break out of the jelly coat. The tadpoles have gills to take oxygen out of the water. They feed on tiny plants. Over a period of months, the tadpoles grow. They then lose their tails and gills and change into frogs. Adult frogs eat insects and breathe using lungs.
1 Write down four key points about frog reproduction. You should write four short sentences only. You may not write more than 25 words.
2 a What happens during fertilisation?
b Do frogs use external or internal fertilisation?
3 How do male frogs make sure that they attract female frogs of the same species?
4 a How would you collect evidence to test the theory that male frogs only attract females of the same species?
b What observations would you make?
5 Write down one way in which frog reproduction is similar to human reproduction.
6 Write down one way in which frog reproduction is different to human reproduction.
7 Female frogs often release hundreds or thousands of eggs into the water. Suggest two reasons why less than half of these ever turn into tadpoles.
8 The turning of a tadpole into an adult frog has a special name. Find out what it is.
Citations
1. https://www.pearsonschoolsandfecolleges.co.uk/secondary/Science/AssessmentforLearning/ExploringScienceHowScienceWorks/Buy/Buy.aspx
2. https://i.ytimg.com/vi/MKSYqMfH2Qk/maxresdefault.jpg
3. https://dingo.care2.com/pictures/greenliving/uploads/2011/05/tadpole-swimming.jpg
4. https://images-na.ssl-images-amazon.com/images/I/71yNrXLjwHL._SL1500_.jpg
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