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Three different kinds of plants, a cactus, euphoria 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, euphoria and milkweed, have similar adaptations for growing in desert environments. They all have long, fleshy stems for w... show full transcript
Worked Solution & Example Answer:Three different kinds of plants, a cactus, euphoria 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 represent the evolutionary relationship, the tree should illustrate the common ancestor of euphoria and milkweed from leafy plants. Cactus would branch off further away due to its unique adaptations. The tree can be visualized as follows:
+------ Cactus
|
+-------+
| +------ Euphoria
| |
| +------ Milkweed
| |
| +------ Leafy plants
|
+------- Common ancestor
The branches demonstrate the evolutionary lineage and the differing adaptations of each plant group.
Step 2
b. Name the process by which the ancestral leafy euphoria plant could have given rise to the desert-adapted species described above.
Answer
The process is known as 'adaptive radiation'. This occurs when a species diversifies rapidly into a wide variety of forms to adapt to different environments, such as desert conditions in this case.
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 is that the environmental conditions where cacti often thrive, such as arid deserts, can lead to a lack of suitable sediment that preserves fossils. Cacti have relatively soft tissues which decompose quickly, making fossilization less likely. Additionally, climatic changes could have led to erosion and other disturbances that may have destroyed existing fossil records.