Chapter 6, Problem 1CT

Some biologists place the seaweeds in the kingdom Plantae; others consider seaweeds to be protists. Assume that a better arrangement is to group the green, brown, and red algae in their own kingdom, which we will call Macrophyta. Characterize the new kingdom by first giving its unique characteristics and then differentiate it from the protists and the true plants. Be sure to consider major exceptions or overlaps.

Summary Introduction

To characterize: The unique characteristics of new kingdom Macrophyta and differentiate it from the protists and the true plants.

Introduction: Many fascinating photosynthetic organisms that have evolved from terrestrial vascular plants populate the ocean and marine environment. They carry many morphological features that originally suit with the adaptations to terrestrial plants. However, they are not the members of the Kingdom Plantae.

Explanation of Solution

A unique feature of protists is that they share some functional and anatomical features that are common to both plants and animals. They are eukaryotic, but most of them are unicellular or they are syncytial and some are multicellular.

The unicellular algae are primarily placed under Kingdom Protista, but now they are grouped under Kingdom Plantae as they possess similarities to the green algae. However, the marine algal forms like seaweeds (green, brown, red algae) can be grouped into a hypothetical kingdom called Macrophyta.

The unique characteristics of new kingdom Macrophyta:

• The hypothetical kingdom Macrophyta consists of organisms that are eukaryotic and mostly multicellular.
• It also consists of some unicellular forms and some with multinucleated thallus.
• All of them are autotrophs (except some specialized parasites that can carry out photosynthesis and synthesize complex carbohydrates by trappings energy from sunlight).
• It can reproduce by both sexual and asexual modes of reproduction.

Differentiation of Kingdom Macrophyta from protists and true plants:

1. 1. Kingdom Protista consists of eukaryotes, but unicellular organism and many of protists are heterotrophs. Macrophytes contain unicellular, multicellular as well as thalloid forms, and all are autotrophs (except some specialized parasites).
2. 2. Except some specialized parasites, all Macrophytes are autotrophs like the plants. However, the Macrophytes lack the complex morphology (true leaves, stem, and root) and well reproductive system as plants.