Brown algae show great variation in size and form. They are generally

Options

A. simple umbranched, filamentous forms
B. profusely branched forms as represented by kelps
C. unicellular to colonial
D. unicellular to heterotrichous

Answer

**Step-by-Step Solution:**

1. **Understanding Brown Algae**: Brown algae, which belong to the group Phaeophyceae, are a diverse group of multicellular organisms. They are primarily found in marine environments and exhibit a wide range of sizes and forms.

2. **Analyzing the Options**:
- **Option A: Simple unbranched filamentous forms**: This option suggests that brown algae are simple and unbranched. However, this is incorrect because brown algae are generally branched, not unbranched.
- **Option B: Profusely branched forms as represented by kelps**: This option is correct. Brown algae include various forms, from simple branched filamentous types to large, profusely branched forms like kelps, which can grow to significant heights (up to 100 meters).
- **Option C: Unicellular to colonial**: This option is incorrect because brown algae are predominantly multicellular, and colonial forms are not typical for this group.
- **Option D: Unicellular to heterotrichous**: This option is also incorrect since heterotrichy (having two types of branches) is not a characteristic of brown algae but is seen in some green algae.

3. **Conclusion**: After evaluating all the options, the correct answer is **profusely branched forms as represented by kelps**.

**Final Answer**: Brown algae show great variation in size and form; they are generally profusely branched forms as represented by kelps.

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