Chapter 17, Problem 32A

Summary Introduction

To predict:

The domain of newly discovered photosynthetic organism that has cells without membrane- bound organelles and no peptidoglycan

Introduction:

The most widely used biological system of classification has six kingdoms within three domains.

There are three domains: Bacteria, Archaea, and Eukarya. Within these domains are six kingdoms. Domain Bacteria and Domain Achaea has one kingdom each but Domain Eukarya has four kingdoms: Protista, Fungi, Plantae and Animalia.

Answer to Problem 32A

Domain Archaea

Explanation of Solution

Since the newly discovered organism has cells without membrane bound organelles, it cannot be placed in Domain Eukarya as members of Eukarya have cells with membrane- bound organelles. The newly discovered organism is a prokaryote so it can be placed either in Domain Bacteria or Domain Archaea. Members of Domain Bacteria have cells with cell walls containing peptidoglycan. Hence it cannot belong to Domain Bacteria.

Hence a newly discovered photosynthetic organism that has cells without membrane- bound organelles and no peptidoglycan should be placed in the Domain Archaea.

Archaea are thought to be more ancient than bacteria and yet more closely related to eukaryote ancestors. They can live in extreme environments; hence also called extremophiles. These have been found in hot springs, salty lakes, thermal vents on ocean floor and in marshes. They can be autotrophic but most are heterotrophic. Their cells walls do not contain peptidoglycan.