Question

Problem III. A very large population of a flowering plant species occurs in a lowland meadow. A small population of the same species occurs on a remote mountainous region more than 200 km away.

You collect seeds and raise several plants from each population in the same greenhouse.

You measure flower size on plants of each population and find the following:

Mountainous region: mean flower diameter = 1.2 cm

Lowland meadow: mean flower diameter = 5.2 cm

Now on a plant of each population, you self-pollinate one flower and cross-pollinate another using pollen from a plant from the same population. You collect the seeds that form, grow up the offspring the greenhouse and measure their adult biomass. You find the following:

Mountainous region selfed offspring:                    4.5 g

Mountainous region outcrossed offspring:          4.7 g

Lowland region selfed offspring:                                               2.5 g

Lowland region outcrossed offspring:                     4.8 g

In a short paragraph, provide a plausible evolutionary explanation for the differences you observe between the populations, based on what we have been discussing in class.

This is all the information I was given.

Answer 1

Mean flower diameter for mountain flower is 1.2 cm and mean flower diameter for lowland meadow flower is 5.2 cm. The lowland flowers are bigger than mountain flowers. This is because the mountain flowers do not bigger competition like lowland flowers and so they have more accessibility to attract pollinators. The climate is also cold and there is not bright sunlight to make attractive flowers. The mountain flowers to last longers tend to decrease their surface area unlike lowland meadow flowers which need to be bright and bigger to attract the pollinators.

Mountain region plants that were self pollinated and cross pollinated exhibited the similar biomass - 4.5 g and 4.7 g respectively. This is because they all were homozygous and there were no variants. These flowering plants were much more ancestral in origin and have migrated to lowland meadow and have adapted as an ecological variant. This is the reason the lowland cross pollinated had variation in biomass which is similar to mountain region and is expressed because of cross pollination. The reason for the lower biomass in lowland meadow as in self pollinated offspring with 2.5 g is the presence of ample sunlight and longer photoperiod making the need to prepare lesser biomass like leaves for photosynthesis.