Characteristics of Living Organisms Practice Questions

Correct answer: Metabolism

Metabolism is a defining property because it occurs in all living organisms and never in non-living objects. Growth and reproduction have exceptions (e.g., mountains grow by accretion, and mules are sterile), while self-consciousness is limited to humans.

Correct answer: Growth and reproduction

In higher organisms, growth (increase in body mass/size) and reproduction are distinct biological processes. In contrast, for unicellular organisms, growth and reproduction are synonymous as cell division leads to both.

Correct answer: Non-living objects like mountains also grow by accumulation of material.

Non-living objects like snow mountains and sand dunes increase in mass through extrinsic growth (accumulation from outside). Since a defining property must be exclusive to living beings, growth fails this criterion.

Correct answer: Neither living nor non-living, but living reactions

Metabolic reactions in a test tube are not 'living things' because they lack cellular organization. However, they are 'living reactions' because they mimic the biochemical processes that occur within a living system.

Correct answer: The capacity to sense the surroundings and respond to stimuli

Consciousness, the ability to sense and respond to stimuli (physical, chemical, or biological), is found in all organisms from prokaryotes to eukaryotes. It is considered the most sophisticated and defining feature of life.

Correct answer: Fungi, filamentous algae, and protonema of mosses

Filamentous organisms like many fungi, filamentous algae, and the protonema of mosses easily multiply by breaking into fragments. Each fragment then grows into a new individual.

Correct answer: Planaria

Planaria (flatworms) possess a high capacity for true regeneration, where a fragmented organism regenerates the lost parts of its body and becomes a new individual. Lizards only show partial regeneration of the tail.

Correct answer: Metabolism

Metabolism is the aggregate of all biochemical reactions (both constructive anabolism and destructive catabolism) taking place inside a living cell or organism. No non-living object exhibits metabolism.

Correct answer: Seasonal breeders, both plants and animals

Photoperiodism is the physiological reaction of organisms to the length of day or night. It significantly influences the reproductive cycles of seasonal breeders in both the plant and animal kingdoms.

Correct answer: Because they respond to stimuli and maintain internal stability

Living systems are capable of sensing changes and responding to them to maintain a steady state (homeostasis). This interaction between internal components and external stimuli defines their self-regulating nature.

Correct answer: All of the above

Mules, sterile worker bees, and certain infertile human couples are living organisms that do not produce offspring. This is why reproduction is a characteristic of life but not a defining property.

Correct answer: Humans

While all living organisms possess consciousness (awareness of their surroundings), humans are the only organisms that possess self-consciousness, the awareness of their own existence and state.

Correct answer: Submicroscopic molecular level

Biological organization begins at the molecular level where various biomolecules interact to form organelles and eventually cells. It is the foundation upon which all higher biological structures are built.

Correct answer: Interactions among the molecular components

Emergent properties at any level of the biological hierarchy arise from the interactions between the constituent parts of the lower level. The properties of an organelle are due to the specific organization and interaction of its molecules, not the molecules in isolation.

Correct answer: Indefinite, Definite

Plants exhibit indeterminate (indefinite) growth throughout their life span due to meristematic tissues. Animals exhibit determinate (definite) growth, which stops after a certain age once they reach their adult size.

Correct answer: Reproduction

Reproduction ensures the continuity of species from one generation to the next, allowing life to persist on Earth despite the limited lifespan of individual organisms.

Correct answer: All life forms

Cellular organization is the fundamental defining feature of all living organisms. Every living being, whether unicellular or multicellular, is composed of cells and cell products.

Correct answer: A patient in a coma supported by machines

A patient in a coma lacks self-consciousness and clear responses to external stimuli, yet is kept alive by machines. This makes classification difficult, as they occupy a grey area between living and non-living when consciousness is used as the defining property.

Correct answer: Photosynthesis

Anabolism refers to biosynthetic processes where complex molecules are formed from simpler ones. Photosynthesis (forming glucose from CO2 and water) is an anabolic process, while the others listed are catabolic (breakdown) processes.

Correct answer: Mass, number of individuals

Increase in mass and increase in the number of individuals (cell population) are the twin characteristics of growth as defined in biological terms.