Characteristics of living organisms

1. Which list contains only characteristics of living organisms used in this topic?

Answer A: Movement, respiration, sensitivity, growth, reproduction, excretion and nutrition

The complete set is movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. Breathing, hearing, circulation, digestion and feeding may occur in particular organisms, but they are not the seven general characteristic names used here.

2. A closed flower opens its petals at sunrise without changing its location. Which characteristic is directly shown by the petals changing position?

Answer C: Movement

Movement includes an action by part of an organism that changes position. The petals change position as they open, so movement is directly shown even though the flower remains rooted in the same place.

3. A woodlouse travels from a dry area into a damp shelter. Which observation is the clearest evidence of movement?

Answer B: Its whole body changes place.

The woodlouse's whole body changes place as it travels into the shelter, directly matching movement. The other statements concern mass, the environment or reproduction and do not describe the observed movement.

4. Which statement correctly describes respiration?

Answer D: Chemical reactions in cells break down nutrient molecules and release energy.

Respiration consists of energy-releasing chemical reactions in cells that break down nutrient molecules. Ventilation moves air, digestion processes food, and carbon dioxide is commonly a waste rather than the substance needed to store nutrients.

5. Why is breathing not the same process as respiration?

Answer A: Breathing moves air, whereas respiration is a set of chemical reactions in cells.

Breathing is ventilation, a physical movement of air. Respiration is chemical and occurs inside living cells, where nutrient molecules are broken down and energy is released. Plants as well as animals respire.

6. Living germinating seeds warm an insulated flask, while boiled seeds in an identical flask do not. Which conclusion is best supported?

Answer C: Respiration in the living seeds releases energy, and some is transferred as heat.

The comparison supports respiration: reactions in the living seeds release energy and some warms the flask. Seeds do not have lungs, and temperature change alone does not demonstrate growth or reproduction.

7. Which observation most directly shows sensitivity?

Answer B: A pupil narrows immediately after light intensity increases.

The increase in light is a stimulus and the narrowing pupil is the response, so the observation shows sensitivity. The other options are descriptions without a detected change followed by a response.

8. Which sequence gives evidence of sensitivity to an internal change?

Answer D: Body water availability falls, the change is detected, and thirst leads to drinking.

Falling water availability is an internal change, and drinking after that change is detected is a response. The other sequences are passive physical changes in non-living materials and do not show biological detection.

9. Which measurement gives the strongest evidence that a group of seedlings has grown?

Answer A: Their total dry mass increased and remained higher.

A lasting increase in dry mass shows that new biological material has been added and supports growth. Fresh mass can rise temporarily through water uptake, leaf folding is movement, and pot warming can be a passive temperature change.

10. Matched equal-sized groups of seedlings are grown identically. Their average dry masses are 2.4 g per seedling for the group sampled on day 4 and 3.0 g per seedling for the group sampled on day 10. What change occurred relative to the day-4 value?

Answer C: An increase of 0.6 g, which is 25%

The difference in average dry mass is 3.0 - 2.4 = 0.6 g per seedling. Relative to the day-4 value, the increase is (0.6 / 2.4) × 100 = 25%. Because matched groups were sampled and dried separately, the result supports average growth without implying that the same dried seedlings were measured twice.

11. A dry bean absorbs water and swells, then returns to its original mass after drying. Why is the swelling alone not secure evidence of growth?

Answer B: The change is reversible and can be explained by water uptake.

The bean returns to its original mass after losing the absorbed water, so the observed swelling is reversible. Biological growth requires a permanent increase in size and dry mass, not merely temporary water uptake.

12. Which event is reproduction rather than growth or repair?

Answer D: A runner from a parent plant forms a separate new plant.

The runner produces a separate new plant of the same kind, so it is reproduction. Wound repair and an increase in trunk size change an existing organism but do not make another organism.

13. Why is reproduction considered a characteristic of living organisms even though one individual may never reproduce?

Answer A: Reproduction allows the species to continue across generations.

An individual can survive without producing offspring, but reproduction creates new organisms and allows the species to continue across generations. It is not a replacement for respiration, excretion or sensitivity.

14. A strawberry runner develops roots and leaves, then becomes separated from the parent. What observation identifies reproduction most clearly?

Answer C: A separate new strawberry plant has formed.

Formation of a separate new plant is the defining evidence of reproduction. Water uptake, leaf movement and carbon dioxide release can relate to other processes but do not by themselves show that offspring formed.

15. Which is an example of excretion?

Answer B: Removing carbon dioxide produced by respiration

Carbon dioxide is a waste product of metabolic reactions and its removal is excretion. Undigested fibre is egested, saliva is a useful secretion, and taking in nutrients is nutrition.

16. Why is removal of undigested food classified as egestion rather than excretion?

Answer D: The material was not absorbed and was not made as a metabolic waste by cells.

Undigested food remains were never absorbed into the body's cells and were not produced by cellular metabolism. Their removal is therefore egestion, whereas excretion removes metabolic wastes and excess substances.

17. Which removal counts as excretion because the substance is present beyond requirements?

Answer A: Removing excess water in urine

Water is required by the body, but water present beyond requirements may be removed in urine as part of excretion. The other materials are external or were not taken into the body's internal processes.

18. Which statement best describes nutrition?

Answer C: Taking in materials needed for energy, growth and development

Nutrition provides materials needed for energy, growth and development. It is distinct from ventilation, sensitivity and egestion, and it does not mean that energy is released simply when material enters the organism.

19. Which comparison between nutrition and respiration is correct?

Answer B: Nutrition supplies nutrient materials; respiration breaks down nutrient molecules in cells to release energy.

Nutrition concerns obtaining materials needed by the organism. Respiration uses chemical reactions in cells to break down nutrient molecules and release energy. Both plants and animals carry out both processes.

20. An organism moves toward shade after the surroundings become hotter. Which pairing is best supported?

Answer D: Movement and sensitivity

Changing place is movement. Doing so after detecting a rise in environmental temperature is evidence of sensitivity. The observation gives no direct evidence of growth, reproduction, excretion, nutrition or respiration.

21. Which set of observations gives the strongest evidence that an unfamiliar object is a living organism?

Answer A: It takes in materials, responds directionally to change, gains dry mass and produces similar offspring.

The first set combines nutrition, sensitivity, permanent growth and reproduction, providing several coordinated lines of biological evidence. The other sets can be explained by gravity, heating, inflation or a single non-living reaction.

22. A flame spreads, consumes fuel and releases carbon dioxide. Why do these facts alone not prove that it is living?

Answer C: Similar-looking changes can result from combustion rather than coordinated life processes.

Combustion can cause spreading, fuel use and gas production without an organism being present. Evidence for life depends on the biological nature and coordination of several processes, not loose similarities to individual words.

23. A dormant seed shows no visible movement during a short observation. Which conclusion is most scientifically sound?

Answer B: Absence of visible movement in a short period does not show that the seed is non-living.

Dormant organisms may carry out life processes very slowly and show little visible activity. A brief failure to observe movement is not enough to classify the seed as non-living; observations over time and under suitable conditions are more informative.

24. Which evidence-and-characteristic match is incorrect?

Answer D: Undigested fibre leaves the body — excretion

Undigested fibre leaving the body is egestion, not excretion, because it was not absorbed and was not produced as a metabolic waste. The other three evidence-and-characteristic matches use the correct biological meanings.