Problem 20 - Biology

Question

The dominant organism in fern is the _____. a. sperm b. spore c. gamete d. sporophyte

Step-by-Step Solution

Answer

d. sporophyte

Step 1: Understand the Question

The question asks for the dominant organism in ferns. Knowing this aspect of the fern life cycle is essential for answering the question correctly.

Step 2: Review Fern Life Cycle

Ferns have a life cycle that includes two main stages: the sporophyte and the gametophyte. The sporophyte is the diploid phase, producing spores, and the gametophyte is the haploid phase, producing gametes.

Step 3: Identify Dominant Stage

Determine which stage is more prominent and longer-lived in ferns. In ferns, the sporophyte stage is the dominant and more visible phase of the life cycle.

Step 4: Select the Correct Answer

Given the options: a. sperm, b. spore, c. gamete, d. sporophyte, the correct answer is d. sporophyte as it is the dominant organism in ferns.

Key Concepts

Sporophyte Stage

In the fern life cycle, the sporophyte stage is the longest and most prominent. This stage is diploid, meaning it has two sets of chromosomes. It begins when the fertilized egg, or zygote, develops into a mature fern plant.
The sporophyte is the leafy green plant most people recognize as a fern. It produces spores through a process called meiosis.
Meiosis creates spore cells that are haploid, containing only one set of chromosomes. These spores are then released into the environment, usually from structures called sporangia. This starts the next phase in the life cycle.

Gametophyte Stage

The gametophyte stage in ferns is less visible but crucial to their life cycle. It is haploid, containing just one set of chromosomes. The stage begins when the spores from the sporophyte land in suitable conditions and grow into tiny, heart-shaped structures called prothalli.
These gametophytes produce both male and female gametes. Male gametes are known as sperm cells and are produced in structures called antheridia. Female gametes are known as egg cells and are produced in structures called archegonia.
The sperm swims through water to reach the egg, leading to fertilization and the formation of a new zygote. This zygote grows into a new sporophyte, completing the cycle.

Dominant Organism

In the context of ferns, the term 'dominant organism' refers to the stage in their life cycle that is most apparent and long-lasting. For ferns, this is the sporophyte stage.
The sporophyte is what you typically see when you look at a fern plant. It is larger, more complex, and lives longer than the gametophyte stage. The dominance of the sporophyte is a significant characteristic of higher plants.
Plants' evolutionary transition has favored the diploid sporophyte stage over the haploid gametophyte stage. This shift likely offers a genetic advantage by having two sets of chromosomes, enabling better genetic diversity and adaptability.