【PEP】Junior High Biology, Grade 8, Volume 1: The "Invisible" Neighbors Around Us

Welcome to the microscopic realm beyond what the naked eye can perceive. All around us exists a special class of life forms —viruses. They are the ultimate "minimalists" in the living world.

Viruses are incredibly tiny, measured innanometers (nm), and can only be seen with an electron microscope. Unlike the plants and animals we've studied before, viruseshave no cellular structure; they consist only of a protein coat and genetic material inside.

Core Survival Strategy: Parasitism and Self-Replication

Viruses cannot live independently; they are pureparasites. When a virus leaves a living cell, it becomes an inert crystal. Once it enters a suitable host cell, it hijacks the cell's machinery and, following its owngenetic instructions, churns out大量 copies of new viruses. This unique mode of reproduction is called "self-replication."

Chapter Learning Objectives

Understand the structural features of viruses: composed of a protein coat and genetic material.
Comprehend the viral reproduction process: must parasitize living cells and reproduce through self-replication.
Take a balanced view of the relationship between viruses and humans: they can cause disease, but they can also benefit humanity in fields like genetic engineering.

QUESTION 1

When you cough or sneeze, droplets from your mouth or nose can travel over 2 meters. Using what you've learned, think about the harm this could cause others if you have a cold.

It's just rude behavior, with no biological harm

Pathogens in the droplets (like the flu virus) spread through the air and can infect others

The water in the droplets can give someone a cold

QUESTION 2

Suppose you have 100 bacteria on your hands right now. If bacteria reproduce once every 30 minutes, how many bacteria will be on your hands after 4 hours, assuming you don't wash them or have any other interference? What does this tell you about personal hygiene?

800; we should exercise more

25,600; we should wash our hands frequently to maintain personal hygiene

1,600; we should disinfect regularly

QUESTION 3

Which of the following statements about antibiotics is correct?

Antibiotics can kill all viruses and bacteria

Antibiotics are substances produced by fungi that can kill or inhibit certain disease-causing bacteria

You should take large doses of antibiotics immediately when you catch a cold

QUESTION 4

Determine whether the following statements are true or false: (1) The main difference between bacteria and plant cells is that bacteria lack a cell wall but have a capsule. (2) A magnifying glass can be used to observe the structure of bacteria.

(1) True; (2) True

(1) False; (2) False

(1) False; (2) True

QUESTION 5

Viruses cannot live independently because their structure lacks:

Genetic material

A protein coat

Cellular structures (such as cytoplasm, energy converters, etc.)