# The effects of light on plant and animal species: answers and explanations

Cambridge IELTS 5, Test 4, Reading Passage 3

Source: Passage, questions and answer key from Cambridge IELTS 5, Test 4, Reading Passage 3. © Cambridge University Press & Assessment. Used for educational practice. Explanations and evidence notes are written by Testmigo.

## Answer key

| Q | Answer | Proof |
| --- | --- | --- |
| 27 | TRUE | the amount of experimental evidence for this phenomenon is considerable. |
| 28 | TRUE | some species of birds' breeding can be induced even in midwinter simply by increasing day length artificially |
| 29 | NOT GIVEN | In the temperate zone in spring, temperatures fluctuate greatly from day to day, but day length increases steadily by a predictable amount. |
| 30 | FALSE | For example, desert annuals germinate, flower and seed whenever suitable rainfall occurs, regardless of the day length. |
| 31 | FALSE | remain in a vegetative state for many years and then suddenly flower, fruit and die |
| 32 | TRUE | The climatic trigger for this flowering cycle is not yet known |
| 33 | FALSE | Shade-tolerant plants have lower photosynthetic rates and hence have lower growth rates ... eastern hemlock seedlings are shade-tolerant |
| 34 | temperatures | temperatures fluctuate greatly from day to day |
| 35 | day-neutral | regardless of photoperiod, are known as day-neutral plants. |
| 36 | food | because this is a point when adequate food resources will be assured. |
| 37 | insects | Long-day plants are adapted for situations that require fertilization by insects |
| 38 | rainfall | flower and seed whenever suitable rainfall occurs |
| 39 | sugarcane | others, like sugarcane, never reach a maximum |
| 40 | classification | This classification is commonly used in forestry and horticulture. |

## Why these answers are right

**27. TRUE.** The statement says there is plenty of scientific evidence for photoperiodism. The passage says "the amount of experimental evidence for this phenomenon is considerable", where the phenomenon is photoperiodism, "considerable" matches "plenty" and "experimental" matches "scientific", so TRUE.

**28. TRUE.** The statement says some birds can be made to breed out of season. The passage reports that some species' breeding "can be induced even in midwinter simply by increasing day length artificially", and midwinter lies outside their normal breeding time, so the statement is TRUE.

**29. NOT GIVEN.** The statement says photoperiodism only happens in certain geographic areas. The passage uses temperate-zone examples, where day length rises steadily in spring, but never says photoperiodism is limited to those regions or missing elsewhere, so the answer is NOT GIVEN.

The why and the trap for questions 30 onwards are free with an account on the [answers page](https://testmigo.com/ielts/reading/the-effects-of-light-on-plant-and-animal-species/answers).

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