Characteristics of Life & Viruses Review

Why do viruses need living hosts, such as bacteria or eukaryote cells?

• Viruses have a cellular structure which never require a host.

• Viruses depend on the host cells that they infect to reproduce.

• Viruses depend on a host cell because they lack their own DNA or RNA.

• The host cell is the source of food for the virus.

Viruses are not living, because they

• are not cellular.

• have no DNA.

• do not reproduce.

• lack a nucleus.

Cell theory states:

all living things are composed of one or more cells;

a cell is the smallest unit that still retains the properties of life;

and new cells only come from cells that already exist.

Based on cell theory, which of these answer choices would describe one reason a virus is considered nonliving?

• A virus is too small to be considered a cell.

• A virus does not contain genetic material.

• A virus does not have a nucleus.

• A virus cannot reproduce itself without a host

Which statement describes ALL living things?

• They are composed of one or more cells.

• They must reproduce sexually.

• They have organ systems to carry out the processes of life.

• They are capable of making their own food.

Tags

NGSS.MS-LS1-1

When scientists classify living things, they do not include viruses.

This is because viruses

• do not contain DNA.

• are much smaller than other organisms.

• are not made of one or more cells.

• cause disease.

Viruses CANNOT

• be crystallized.

• live in bacteria.

• cause disease in plants.

• reproduce on their own.

Examine the model of a viral structure shown here. Select the choice that accurately compares and contrasts the structures of viruses and cells.

• Both cells and proteins have capsid structures surrounding their genomes.

• Both cells and viruses have protein molecules.

Examine the model of a viral structure shown here. Select the choice that accurately compares and contrasts the structures of viruses and cells.

• Viruses have enzymes for DNA replication, where cells do not.

• Cells have specialized organelles, where viruses do not contain these structures.

Examine the model of a viral structure shown here. Select the choice that accurately compares and contrasts the structures of viruses and cells.

• Viruses have the ability to maintain homeostasis.

• Both cells and viruses have DNA/RNA.

Is this characteristic define as living organisms, viruses, or both:

The ability to grow.

• Living Organisms

• Viruses

• Both

Tags

NGSS.MS-LS1-5