Chapter – 1 : Basic Properties of Life | Chapter Solution Class 9

(b) Aristotle

Explanation:

Aristotle (384-322 BC) was the first scientist to classify organisms into two broad groups: plants and animals. He is considered the Father of Biology and made significant contributions to early taxonomy and classification of living organisms based on their characteristics.

(d) Lemna leaf

Explanation:

Protoplasmic movement (cyclosis) is observed in microscopic plant cells, particularly in aquatic plants like Lemna (duckweed). The movement of cytoplasm helps in intracellular transport of nutrients and organelles, which can be clearly seen under a microscope.

(c) Anabolism

Explanation:

Metabolism consists of two processes:

• Anabolism – A constructive phase where smaller molecules combine to form complex organic substances (e.g., photosynthesis).
• Catabolism – A destructive phase where large molecules break down into simpler forms (e.g., respiration).

Since the question asks about the constructive phase, the correct answer is Anabolism.

(b) Euglena

Explanation:

• Euglena moves using a flagellum, a whip-like structure that allows it to swim.
• Paramecium moves with cilia (short hair-like projections).
• Amoeba moves with pseudopodia (false feet).
• Hydra shows limited movement by tentacles but does not use flagella for locomotion.

(d) All of these

Explanation:

Living organisms exhibit several characteristics that differentiate them from non-living things. These include:

• Respiration – Energy production through metabolic processes.
• Movement – Physical or intracellular movement in response to stimuli.
• Growth – Increase in size and mass due to cell division and metabolic activities.

Potential energy.

Kinetic energy.

Biological process.

Protobionts.

Coacervates.

False

Explanation:

Stored energy is known as potential energy, not kinetic energy. Kinetic energy is the energy of movement, whereas potential energy is stored within molecules and only converted to kinetic energy when needed for biological processes.

True

Explanation:

Reproduction is a fundamental characteristic of all living organisms. It ensures the continuity of species and is essential for maintaining life. Both sexual and asexual reproduction occur in living organisms.

True

Explanation:

Paramecium is a unicellular organism that exhibits protoplasmic movement (cytoplasmic streaming) inside its cell. This movement helps in the transport of nutrients and organelles within the cell.

False

Explanation:

The constructive phase of metabolism, where complex molecules are built from simpler ones, is called anabolism (e.g., photosynthesis).

Catabolism, on the other hand, is a destructive phase where complex substances break down to release energy (e.g., respiration).

True

Explanation:

Life originated on Earth through chemical evolution, where simple inorganic molecules combined under favorable conditions to form complex organic molecules, leading to the first primitive cells and eventually evolving into different life forms.

Protoplasm.

Aristotle.

Paramecium.

Protein-like molecules formed from amino acids in early Earth conditions.

Enzymes.

Life is a complex organization of molecules that shows growth, development, adaptation, reproduction, mutation, and evolution.

Organic evolution is the gradual process of change in living organisms over generations, leading to the formation of new species.

Coacervates are large colloidal aggregates of organic molecules that formed in early Earth conditions, believed to be precursors of life.

The main steps in the origin of life:

1. Formation of basic inorganic molecules (C, H, O, N).
2. Formation of simple organic molecules (amino acids, sugars).
3. Formation of complex organic molecules (proteins, nucleic acids).
4. Formation of protobionts (primitive cells).
5. Evolution of living cells (prokaryotic → eukaryotic).

The two main sources of variation in life are:

1. Mutation – Sudden and permanent genetic changes.
2. Genetic Recombination – Exchange of genetic material during meiosis.

Life is a complex organization of molecules that has the ability to grow, reproduce, adapt, evolve, and respond to stimuli. Living organisms require energy to sustain various biological processes.

Comparison with a Burning Candle:

Life is often compared to a burning candle because of the following similarities:

1. Energy Usage: A candle burns using oxygen, similar to how organisms use oxygen in respiration.
2. Limited Lifespan: Both life and a candle have a definite lifespan; a candle burns out just as life ends.
3. Metabolic Activity: A candle undergoes combustion, a chemical process similar to metabolism in living organisms.
4. Continuous Process: Just as a candle keeps burning while fuel is available, life continues as long as metabolic activities persist.
5. Light and Warmth: A burning candle emits light and heat, just as life contributes to the environment through various biological activities.

The origin of life on Earth is explained through Chemical and Biological Evolution theories.

1. Chemical Evolution (Abiogenesis)

• Proposed by Oparin and Haldane in the 1920s.
• Life originated from simple inorganic molecules, which formed organic compounds under primitive Earth conditions.
• Stanley Miller’s Experiment (1953) confirmed that amino acids (building blocks of life) could form under simulated early Earth conditions.

2. Steps in the Origin of Life

1. Formation of Basic Inorganic Molecules: Hydrogen (H₂), Oxygen (O₂), Carbon (C), Nitrogen (N), etc., were present in the early atmosphere.
2. Formation of Simple Organic Molecules: Under high temperatures, lightning, and UV radiation, simple molecules like amino acids and sugars formed.
3. Formation of Complex Organic Molecules: Proteins, nucleic acids (DNA, RNA), and lipids developed.
4. Formation of Coacervates (Protobionts): These aggregates of organic molecules showed primitive life functions.
5. Evolution of Cells: First prokaryotic cells appeared, followed by eukaryotic cells that led to complex life forms.

Life has several unique characteristics that differentiate it from non-living objects. Five major characteristics include:

• Growth – Growth is the increase in size and mass of an organism due to cell division and accumulation of substances (e.g., plants growing from seeds).
• Metabolism – Metabolism is the sum of all chemical reactions in the body that provide energy and build necessary substances (e.g., digestion, respiration).
• Respiration – Respiration is the process of breaking down food molecules to release energy (e.g., breathing).
• Reproduction – Reproduction is the process by which organisms produce offspring to continue their species (e.g., animals giving birth).
• Response to Stimuli – The ability of an organism to sense and react to environmental changes. (e.g., plants moving towards light).

Geologic Era and Evolutionary Changes