Life and the cell
Introduced| English | Meaning |
|---|---|
| cell/sel/ | The smallest structural and functional unit of a living organism. |
| biology/baɪˈɒlədʒi/ | biology |
| prokaryotic/ˌprɒkərɪˈɒtɪk/ | Describing cells that lack a membrane-bound nucleus and other membrane-bound organelles. |
| eukaryotic/ˌjuːkərɪˈɒtɪk/ | Describing cells with a membrane-bound nucleus and other membrane-bound organelles. |
| homeostasis/ˌhəʊmiːəˈstɑːsiz/ | Maintaining a relatively stable internal environment despite external or internal changes. |
A bigger image does not mean a growing cell
- An invented cell 细胞 image is 30.0 mm long; its supplied actual length is 0.0500 mm. Enlarging the image on a screen changes its displayed size, not the cell's actual size.
- Biology 生物学 studies living structures, functions and changes. A still image can show structure, but growth needs observations over time and a defined measure.
Calculate magnification with matching units
- Magnification is image length divided by actual length: $M=L_{\text{image}}/L_{\text{actual}}=30.0/0.0500=600$. It is a ratio, written ×600 without a length unit.
- Convert lengths to the same unit before dividing. If a displayed image doubles to 60.0 mm while actual length stays 0.0500 mm, its displayed magnification becomes ×1200; this is no growth measurement.
An image is 30.0 mm long and actual cell length is 0.0500 mm. What is magnification as a number?
Difficulty 2/5 · 140 coins + a small bonus on first completion today
M = image/actual = 30.0/0.0500 = 600; no length unit.
Doubling the displayed image length while actual cell length stays unchanged proves that the cell grew.
Difficulty 1/5 · 100 coins + a small bonus on first completion today
False: displayed magnification changes, not actual size.
Compare how cells are organised
- Prokaryotic 原核 cells have DNA not enclosed in a membrane-bound nucleus. Eukaryotic 真核 cells typically contain a nucleus and other membrane-bound structures, with specialised exceptions.
- A reliably observed nucleus, wall and chloroplasts support a plant-like eukaryotic interpretation. Not every plant cell has chloroplasts, and a blurry image does not establish that a structure is absent.
Match each cell type to its defining feature.
Difficulty 2/5 · 140 coins + a small bonus on first completion today
The distinction concerns cell organisation, not absence of DNA. Typical eukaryotic structures have specialised exceptions; a poor image does not prove a structure is absent.
Define a growth comparison before collecting data
- A fictional plant study measures stem-height change over seven days. Both groups begin at 4.0 cm; their final mean heights are 6.0 and 5.0 cm under stated comparable conditions.
- The observed mean changes are 2.0 and 1.0 cm. Keep the organisms, period, measurement method and other conditions comparable; the cell image alone supplied none of these growth results.
Growth change follows $\Delta h=h_{\text{final}}-h_{\text{initial}}$. For the first group, $\Delta h=6.0-4.0=2.0\ \text{cm}$. This result concerns the supplied plants and period, not every plant or every life process.
Which records are needed for a fair, bounded growth investigation? Choose all that apply.
Difficulty 2/5 · 140 coins + a small bonus on first completion today
A growth investigation needs a measure, comparable conditions and actual observations. A structural image does not establish a growth result.
Mean stem height starts at 4.0 cm and ends at 6.0 cm. What is the mean height change in cm?
Difficulty 2/5 · 140 coins + a small bonus on first completion today
Δh = final - initial = 6.0 - 4.0 = 2.0 cm.
Connect regulation to a response
- Homeostasis 稳态 regulates internal conditions within suitable limits. A changing response can help control a quantity; the quantity need not remain perfectly constant.
- For example, sweating can help regulate body temperature as water evaporates and removes thermal energy. State both the regulated condition and the response rather than saying the body does nothing.
Homeostasis means internal conditions remain exactly unchanged without regulation.
Difficulty 1/5 · 100 coins + a small bonus on first completion today
Homeostasis involves regulation within suitable limits. A changing response can help maintain conditions without making every value perfectly constant.
Give one example of homeostasis and name the mechanism that does the work.
Difficulty 3/5 · 200 coins + a small bonus on first completion today
Example: “Sweating can help regulate body temperature by increasing evaporative cooling.” State the regulated condition and relevant response, without treating one response as every mechanism.
Match each claim to its evidence
- Keep image structure, magnification, growth and regulation separate. Each needs relevant information; one clear cell image does not establish every function of an organism.
- Hooke's Micrographia (1665) used “cell” for spaces in cork. That historical observation is one contribution, not the whole history of cell theory. Source checked 2 October 2026: Royal Society.
Identify what was observed, calculate only from supplied quantities, and state the limit of the conclusion. Use approved methods and supervision for any real specimen work.
Why does a limited image not establish every life process of an organism?
Difficulty 1/5 · 100 coins + a small bonus on first completion today
Keep observation separate from interpretation. Growth, reproduction or regulation can require different evidence from a structural image.