1.1 Characteristics Of Living Organisms
Define movement as a characteristic of living organisms?
An action by an organism or part of an organism; causing a change of position or place.
Give one example of movement in a plant?
Roots growing downwards / shoots bending towards light.
Define respiration?
Chemical reactions; in cells; that break down nutrient molecules and release energy for metabolism.
Distinguish between respiration and breathing?
Respiration is chemical reactions inside cells that release energy from nutrients; breathing is the physical/mechanical movement of air into and out of the lungs.
Explain why respiration is essential for living organisms?
Cells require energy to carry out life processes such as growth and movement; respiration releases this energy by breaking down nutrient molecules.
Define sensitivity as a characteristic of living organisms?
The ability to detect changes in the internal or external environment; and respond to those changes.
Give one example of sensitivity in an animal and one in a plant?
Animal: pupil constricting in bright light / pulling hand from heat; Plant: shoot growing towards light / roots growing towards water.
Define growth?
A permanent increase in size; and dry mass.
Explain why dry mass is used to measure growth rather than wet mass?
Water content of an organism fluctuates / is variable; dry mass gives a more accurate/reliable measure of permanent increases in biological material.
Define reproduction?
The processes that make more of the same kind of organism.
State two types of reproduction?
Sexual reproduction; asexual reproduction.
Define excretion?
The removal of waste products of metabolism; and substances in excess of requirements.
Distinguish between excretion and egestion?
Excretion is the removal of waste products produced by metabolic reactions in cells (e.g. CO₂, urea); egestion is the removal of undigested food that was never absorbed into cells / never part of metabolism.
Identify two waste products that are excreted by the human body?
Carbon dioxide (from respiration); urea (from the breakdown of excess amino acids in the liver).
Define nutrition?
The taking in of materials for energy, growth and development.
Explain why nutrition is essential for living organisms?
Organisms need materials to release energy through respiration; and to provide substances for growth and development / building new cells.