Chapter 18
Viruses
Viruses
Why are viruses considered nonliving?
They cannot reproduce on their own.
What enzyme do retroviruses use to make DNA?
Reverse transcriptase.
What type of cells are bacteria?
Prokaryotic
Why is nitrogen fixation essential to ecosystems?
Makes nitrogen usable for plants.
Why are protists considered evolutionarily diverse?
They evolved from multiple ancestors.
What is the capsid?
Protein coat of a virus.
What does a vaccine trigger in the body?
Antibody production.
Why are Gram-negative bacteria often more drug resistant?
Outer membrane blocks antibiotics.
How can plasmids contribute to rapid evolution?
Transfer genes between bacteria.
How does a contractile vacuole maintain homeostasis?
Pumps out excess water.
What happens to the host cell in the lytic cycle?
It bursts
What does a vaccine stimulate?
Immune response.
How does binary fission limit variation?
Produces identical offspring.
How can plasmids contribute to rapid evolution?
Transfer genes between bacteria.
Why are algae vital to aquatic ecosystems?
They are primary producers.
What is viral DNA called when inserted into host DNA?
Prophage (or provirus).
What determines which cells a virus can infect?
Specific receptors.
Why are endospores important for evolution?
Allow survival through harsh conditions.
Why are bacteria considered key decomposers?
Break down organic matter.
How do protists support higher trophic levels?
Serve as food source.
Why don’t antibiotics work on viruses?
Viruses lack cell structures.
Why do viruses mutate rapidly?
Fast replication and little proofreading.
How do facultative anaerobes have an advantage?
Can live with or without oxygen.
Why are chemoautotrophs important in extreme environments?
They produce energy without sunlight.
Why can some protists survive in extreme environments?
Adapted cellular structures.