Edexcel IGCSE Biology Gas Exchange

This page contains the detailed and easy notes for Edexcel IGCSE Biology Gas Exchange for revision and understanding.

HUMAN GAS EXCHANGE SYSTEM

MECHANISM OF BREATHING

GAS EXCHANGE

ALVEOLI

GREATER SURFACE AREA

SHORTER DIFFUSION DISTANCE

STEEP CONCENTRATION GRADIENT

ORGANISATION IN PLANTS

CELLS

TISSUES

• Xylém and Phloem
• Palisade mesophyll tissue
• Spongy mesophyll tissue

ORGANS – Root, Stem and Leaves

ORGAN SYSTEM – Water Transport System

ORGANISM

TRANSPIRATION

• Transpiration is the loss of water from the surface of the leaves in the forms of water vapours.
• In plants it takes place through the stomata.

FACTORS AFFECTING TRANSPIRATION

MEASURING RATE OF TRANSPIRATION

• Potometer is the device which is used to measure the rate of water uptake or the rate of transpiration.
• The movement of bubble is an indicator of water movement which in turn shows the rate of transpiration

ADAPTATIONS TO LIMIT TRANSPIRATION

• Cuticle layer on the leaf which is waterproof prevent rate of transpiration
• Stomata are present on the lower surface to reduce rate of transpiration.
• Some plants stomata open is night and closes in day.
• In plants like cactus the leaves are reduced to spines to decreases the surface area for water loss.
• Some plants have sunken stomata.

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References:

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