krit.club logo

Biology - Life processes (Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition)

Grade 4IGCSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Movement: An action by an organism or part of an organism causing a change of position or place. While animals move their whole bodies, plants show movement by turning their leaves toward the light.

•

Respiration: The chemical reactions in cells that break down nutrient molecules, such as glucose (C6H12O6C_6H_{12}O_6), to release energy for metabolism.

•

Sensitivity: The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.

•

Growth: A permanent increase in size and dry mass by an increase in cell number or cell size (or both).

•

Reproduction: The processes that make more of the same kind of organism, preventing the species from going extinct.

•

Excretion: The removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), such as carbon dioxide (CO2CO_2), and substances in excess of requirements.

•

Nutrition: Taking in of materials for energy, growth, and development. Plants require light, CO2CO_2, H2OH_2O, and ions; animals need organic compounds and water (H2OH_2O).

📐Formulae

The Mnemonic: M.R.S. G.R.E.N.\text{The Mnemonic: } \text{M.R.S. G.R.E.N.}

Aerobic Respiration: C6H12O6+6O2→6CO2+6H2O+Energy\text{Aerobic Respiration: } C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}

Photosynthesis (Plant Nutrition): 6CO2+6H2O→lightC6H12O6+6O2\text{Photosynthesis (Plant Nutrition): } 6CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2

💡Examples

Problem 1:

If a sunflower turns its head throughout the day to face the sun, which two life processes are most clearly being demonstrated?

Solution:

Sensitivity and Movement

Explanation:

The sunflower senses the light (Sensitivity to a stimulus) and changes its position to track it (Movement).

Problem 2:

In the process of respiration, cells use glucose (C6H12O6C_6H_{12}O_6) and oxygen (O2O_2). What are the two main chemical waste products that must be removed via Excretion?

Solution:

CO2CO_2 and H2OH_2O

Explanation:

Carbon dioxide (CO2CO_2) and water (H2OH_2O) are the by-products of aerobic respiration that the body must excrete if they are in excess.

Problem 3:

A kitten increases in mass from 500g500g to 2kg2kg over several months. Which life process does this represent?

Solution:

Growth

Explanation:

Growth is defined as a permanent increase in size and mass, usually involving an increase in the number of cells.

Life processes (Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition)…