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Figure 18 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake - Edexcel - GCSE Biology - Question 8 - 2020 - Paper 1
Question 8
Figure 18 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake. (a) Water lilies have stomata on the upper surface of the leaves. Explain w... show full transcript
Worked Solution & Example Answer:Figure 18 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake - Edexcel - GCSE Biology - Question 8 - 2020 - Paper 1
Step 1
Explain why water lilies have no stomata on the lower surface of the leaves.
Answer
Water lilies possess stomata on the upper surface of their leaves to facilitate gas exchange directly with the atmosphere. The lower surface, being submerged in water, does not come into contact with air. Consequently, there is no gas exchange occurring on the lower surface, meaning stomata are unnecessary and can lead to water loss through transpiration.
Step 2
Step 3
Step 4
Describe how this sugar is transported from the leaves to the flowers of the water lily.
Answer
Sucrose is transported from the leaves to the flowers of the water lily through the phloem. This transport occurs via a process known as translocation, where the sugar is dissolved in the sap and moves through the plant's vascular system.
Step 5
Explain why this non-indigenous plant now covers the whole surface of the lake.
Answer
The water lily plant that was introduced to the lake thrived due to favorable conditions such as abundant sunlight and nutrient availability. It outcompeted native plants for resources, allowing it to grow rapidly and reproduce extensively. Additionally, the absence of natural herbivores that would consume the water lily further facilitated its spread across the lake.
Step 6
Explain how the water lilies will affect the biodiversity of this lake.
Answer
The introduction of water lilies can reduce biodiversity by limiting the variety of plant species in the lake. As the lilies cover the surface, they block sunlight from reaching underwater plants, resulting in fewer plants overall. This decrease can disrupt the food chain, as fewer plants mean less food for herbivores and consequently fewer predators in the ecosystem. Additionally, lower plant diversity can lead to reduced habitat options for aquatic animals.