Nalanda College Grade 10 Science Unit 08: Characteristics of Living Organisms Study Guide

Cellular Structure: Viruses are unique because they possess no cellular structure. They are considered non-cellular or acellular entities.
Metabolic Activity: Metabolic activities do not occur within viruses when they are outside of a living host cell.
Enzymatic Content: Viruses do contain enzymes which are utilized during their life cycle within a host.
Genetic Material:
- Every virus contains genetic material, but a single virus does not contain both DNA and RNA simultaneously.
- Incorrect Statement Check: A common misconception is that viruses contain both DNA and RNA; in reality, they contain either DNA or RNA.
Living and Non-Living Features:
- Viruses exhibit characteristics of both living organisms and non-living matter.
- The only living feature shown by viruses is reproduction, which occurs exclusively when they are inside a living host cell.
- They remain inactive/inert when outside of a living cell.

Definition of Cell Growth: The growth of cells is defined specifically as the increase in the dry weight of the cells.
Characteristics of Growth:
- Growth is an irreversible process.
- The maximum level of growth is not equal for every cell; it varies based on cell type and function.
Cell Division: This process typically occurs after the growth of the cell reaches its maximum limits.
Multicellular Start: The life of a multicellular organism begins as a single cell known as a Zygote.
Hierarchy of Biological Organization:
- Cell: The basic unit of life.
- Tissue: A group of cells modified to perform a specific function (e.g., Xylem tissue in plants).
- Organ: A collection of tissues working together (e.g., Lungs, Liver, Kidney, Skin).
- System: A group of organs performing a complex body function.
- Organism: The complete living individual.

Irritability: This is the biological ability of an organism to respond to stimuli received from the environment.
Stimulus:
- A stimulus is defined as a change that will bring about a biological response.
- Changes can be classified as either internal or external.
- Stimuli are detected by specialized sensory organs.
Experimental Observation of Plant Response:
- In setups used to observe plant characteristics (such as growth or movement), an indicator is often used.
- Observation: After a period (e.g., one hour), the point of the indicator may move, signifying a response or growth.
- Advantage of using a long indicator: A long indicator acts as a lever to magnify small movements, making them easier to observe and measure accurately.

Metabolic Waste Products: Excretion involves the removal of waste products produced by metabolic reactions within the body. Examples include:
- Sweat
- Carbon dioxide ( $CO_2$ )
- Water ( $H_2O$ )
Non-Excretory Products: Feces are not considered a waste product of a metabolic reaction; rather, they are the undigested remains of food (egestion).
Excretory Organs in Animals:
- Lungs (removes carbon dioxide).
- Kidneys (removes nitrogenous wastes).
- Skin (removes sweat).
- Note: While the liver processes toxins, the lungs, kidneys, and skin are primary organs of elimination.
Excretion in Plants: The primary structures used by plants for the gaseous exchange and release of certain metabolic by-products are the Stomata.

Metabolism: This is the term used to explain all the biochemical reactions taking place within a living body. It is divided into two categories:
- Anabolism: Processes that build up complex molecules.
- Catabolism: Processes that break down complex molecules to release energy.
Nutrition Categories:
- Autotrophic Nutrition: Organisms producing food by themselves.
- Categories of Autotrophism:
  1. Photoautotrophism: Using light energy (e.g., Acalypha/Kuppamenia, Asparagus, Loranthus).
  2. Chemoautotrophism: Using chemical energy.
Specific Plant Examples:
- Photoautotrophic: Acalypha (Kuppamenia), Asparagus, and Loranthus (which is semi-parasitic but still performs photosynthesis).
- Non-photoautotrophic: Cuscuta is a parasitic plant that does not perform photosynthesis.

Cellular Respiration: A series of biochemical reactions necessary for producing energy within cells for their metabolism.
Equation for Photosynthesis: $\text{Carbon dioxide} + \text{Water} \xrightarrow[\text{Chlorophyll}]{\text{Light}} \text{Glucose} + \text{Oxygen}$
Experimental Setup for Respiration ( $CO_2$ Release):
- Components: Potassium hydroxide ( $KOH$ ) solution, lime water, and a living organism (e.g., a frog or germinating mung seeds).
- Function of Potassium Hydroxide ( $KOH$ ): It is used to absorb carbon dioxide from the air entering the apparatus. This ensures that any carbon dioxide detected later in the experiment is produced solely by the organism and was not already present in the atmosphere.
- Test for Carbon Dioxide: Lime water is used. If it turns milky, it confirms the presence of $CO_2$ .
- Observation: In an apparatus where air passes from the organism into lime water, the lime water turns milky because the organism (frog or germinating seeds) releases $CO_2$ during respiration.
- Control Variables: If the water level in a control apparatus (e.g., apparatus 'B') does not change significantly, it suggests that no gas is being consumed or produced that affects the pressure, or that the process being tested is absent in that specific setup.