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Three different kinds of plants, a cactus, euphorbia and milkweed, have similar adaptations for growing in desert environments - VCE - SSCE Biology - Question 5 - 2008 - Paper 1
Question 5
Three different kinds of plants, a cactus, euphorbia and milkweed, have similar adaptations for growing in desert environments. They all have long, fleshy stems for ... show full transcript
Worked Solution & Example Answer:Three different kinds of plants, a cactus, euphorbia and milkweed, have similar adaptations for growing in desert environments - VCE - SSCE Biology - Question 5 - 2008 - Paper 1
Step 1
a. Draw an evolutionary tree (also called phylogenetic tree or cladogram) to demonstrate this relationship.
Answer
To illustrate the evolutionary relationships among the three plants, we can draw a simple phylogenetic tree:
┌── Cactus
│
────┤
│ ┌── Euphorbia
└───┤
└── Milkweed
This tree shows that both the euphorbia and milkweed share a more recent common ancestor than either does to the cactus, indicating that they diverged more recently in evolutionary terms.
Step 2
b. Name the process by which the ancestral leafy euphorbia plant could have given rise to the desert-adapted species described above.
Answer
The process is known as adaptive radiation. This occurs when a single ancestral species evolves into multiple forms that adapt to different environments, in this case, the transition from leafy plants to desert-adapted species.
Step 3
c. What is a possible explanation for there being so few cactus fossils?
Answer
One possible explanation for the scarcity of cactus fossils could be that their preferred environments, such as arid regions, are less conducive to fossilization compared to more temperate environments. Additionally, the composition of cactus tissues may decompose quickly without leaving robust fossils. Environmental conditions like climate change may have also influenced their fossil record.