ODU Biology 108N: Introduction - Cellular Structure and FunctionBETANS1

Answers to Beta - Introduction

1. All plant cells contain a cell wall which surrounds the living part of the cell. The cell wall consists of cellulose and provides protection, insulation, and structure of plant cells. Animal cells lack a cell wall. This causes animal cells to be more elastic. This elasticity in some cells provides a means of stretching and contracting which allows for relative rapid movement (muscle cells). Animal cells lack the protection which plants cells have; therefore, the organism must expend energy to maintain these cells. The outer surface of your body cells consist of several layers of dead cells which protect the underlining body cells. Plants are autotrophic and must continually display their photosynthetic cells to the sun for energy. Therefore plants are adapted to be stationary in the environment and grow in a manner that its leaves are positioned to receive optimum light intensity.

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2. Animal are capable of movement. All of their cells are heterotrophic; therefore, animals must be able to move about its environment to acquire food. Flexible muscle cells would not have evolved if they had cell walls surrounding the living part of the cell.

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3. The correct hierarchical order is : macromolecules, cells tissues, organs, systems, organisms, species, population, ecological communities, biome, biosphere. Write the definition for these terms in your notes using the glossary.

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4. The correct answer is "d". The first cell types were simply a cell membrane surrounding a liquid cytoplasm containing DNA called protocells. Surprisingly these cells were not photosynthetic. They were heterotrophic fed on organic molecules in the ocean which were formed by lightening strikes in a a reducing atmosphere (methane, ammonia, sulfur dioxide) .

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5. All cells contain a cell membrane which separates the cell's interior from its environment and DNA which causes cell division and controls metabolism.

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6. The correct answer is "e". Viruses are particles consisting of a nucleic acid (DNA or RNA) surrounded by a protein coat. These particles lack a cell membrane and can only reproduce when they are present in a living cell.

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7. The correct answer is "c". Learn to classify organisms you are familiar with as "prokaryote or eukaryote" and "autotrophic or heterotrophic"

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8. The correct answer is "c". Animal cells are not autotrophic.