Chapter 17, Problem 25A

Summary Introduction

To determine:

The correct term to replace the italicized word from the given sentence.

Introduction:

The largest and broadest category of all groups in the classification of life is known as domain. At present, there are three groups at this level, the domainArchaea ,domainBacteria , and  domainEukarya . Each domain has a collection of organisms with similar properties and evolutionary histories, as scientists have organized them according to cell type and structures. Within these domains, there are six kingdoms named, Archaea, bacteria, Protista, Fungi, Plantae, Animalia.

Answer to Problem 25A

The correct term to replace the italicized word from the sentence is Archaea. So, the correct sentence will be “Archeaeare called extremophiles because they grow in extreme conditions”.

Explanation of Solution

Domain bacteria comprises of prokaryotic members whose cell wall is made up of peptidoglycan. Peptidoglycan is a polymer that contains two types of sugars namely, N-acetyl glucosamine and N-acetyl muramic acid that are arranged alternately in the chain. Bacteria can be autotrophic or heterotrophic and also can be aerobic and anaerobic. Examples of bacteria are cyanobacteria, mycobacterium.

Domain Archaea comprises of members which are thought to be more ancient than bacteria and more closely related to our eukaryotic ancestors. Their cell wall is not made up of peptidoglycan but contains some proteins that eukaryotic cell have. They are called extremophiles because they grow in extreme environments such as hot springs, salty lakes, thermal vents, and extremely acidic environments.

Domain Eukarya contains all eukaryotic members called eukaryotes which are further classified into protista, fungi, plantae and animalia on the basis of cell wall, cell structure and mode of nutrition.