A rare orchid has been found in the mountains in China. The orchid has pale yellow flowers.
DNA analysis of the genome shows that it is an ancestral species.
All other present day orchids evolved from this ancestral species millions of
years ago.
One present day species has bright purple flowers.
Describe how an orchid with bright purple flowers may have evolved from the
ancestral species which has pale yellow flowers.
[4 marks]

a mutation in the germinal line changed the phenotype to bright flowers which were capable of attracting more pollinators compared to yellow flowers. Subsequently, this mutation was selected by natural selection, thereby increasing its frequency in the population

Explanation:

A mutation is any change in the nucleotide DNA sequence of the genome of a particular organism. Mutations can be divided into 1-germinal mutations (i.e., mutations that occurred in the gamete cells) which can be passed on to offspring, and 2-somatic mutations (i.e., mutations that occurred in the somatic cells), which cannot be inherited. Moreover, mutations can be neutral, deleterious or beneficial depending on the environment in which the organism lives. When a germinal mutation is beneficial, the organism carrying the mutation will have more chances to survive and reproduce (i.e., a higher adaptive fitness), thereby the organism will have more chance to pass this mutation to the next generation and the mutation will increase its frequency in the population.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .