Australian Eucalyptus trees characteristically have two types of leaves, a juvenile (young) form and an adult form - VCE - SSCE Biology - Question 22 - 2008 - Paper 1
Question 22
Australian Eucalyptus trees characteristically have two types of leaves, a juvenile (young) form and an adult form. The juvenile leaves are held horizontally and are... show full transcript
Worked Solution & Example Answer:Australian Eucalyptus trees characteristically have two types of leaves, a juvenile (young) form and an adult form - VCE - SSCE Biology - Question 22 - 2008 - Paper 1
Step 1
A. competition for light.
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Answer
The shape and position of juvenile leaves are primarily influenced by the need to maximize sunlight capture for photosynthesis. Broad and horizontally oriented juvenile leaves can spread out to absorb more light, which helps in their growth during the early stages.
Step 2
B. unpredictable rainfall.
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Answer
While rainfall can affect leaf size and structure in terms of moisture efficiency, it does not directly pressure the juvenile form to evolve specific leaf shapes for maximal light absorption.
Step 3
C. browsing by herbivores.
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Although browsing by herbivores might influence leaf shape to some extent, the primary evolutionary pressure for juvenile leaves is more directly tied to light acquisition.
Step 4
D. high ambient temperatures.
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High temperatures might affect leaf morphology indirectly, but they are not the primary selection pressure that shapes juvenile leaves.
