An unknown plant species has separate male and female gametophytes, and releases spores into the environment. Which of the following is the most logical conclusion about the life cycle of this plant?

The plant is a fern, and the gametophyte is its dominant phase.
The plant is a gymnosperm, and the sporophyte is its dominant phase.
The plant is a moss, and the gametophyte is its dominant phase.
The plant is an angiosperm, and the sporophyte is its dominant phase.

Question

An unknown plant species has separate male and female gametophytes, and releases spores into the environment. Which of the following is the most logical conclusion about the life cycle of this plant?

		The plant is a fern, and the gametophyte is its dominant phase.
		The plant is a gymnosperm, and the sporophyte is its dominant phase.
		The plant is a moss, and the gametophyte is its dominant phase.
		The plant is an angiosperm, and the sporophyte is its dominant phase.

anonymous · Answer

The key to answering this question and questions like it is to understand the general trend of plant evolution - and to practice a lot so you know the material!

In this question, you are given two characteristics of a plamt. One is that it's heterosporous (produces two types of spores, which develop into separate gametophytes) and one is that it releases spores into the environment.

Starting with the first characteristic - what types of plants to do we normally associate with heterospory? The answer is: seed plans and ferns. Rather than just memorizing this fact though, try seeing it in the grand evolutionary scale: the specialization of gametophytes due to heterospory paved the way for later specialized structures of angiosperms (carpel vs stamen). The trend of evolution is towards a specialized and smaller gametophyte structure to house the developing seed. 

Okay - on to the second characteristic. Do the flowers you normally see produce spores? No - this characteristic is generally found in your 'lesser' plants, like your mosses and ferns. Again - think in terms of evolution. The seed had many advantages over spores (greater amount of food to store zygote = more resistant, not to mention a protective and hardy coat) which is why seed-plants have become dominant today, and spore production has been relegated to your tiny ferns and mosses.

Hopefully that should be enough info to guide you to the right answer choice! The nice thing about bio is it isn't simply just memorization (as many claim!); application of some logic by thinking in terms of evolution can help with learning the material.

anonymous · Answer

kma we just wanted an answer not a book

anonymous · Answer

@kma230