Respiration

Respiration

From Chapter 2, Lesson 10 o the Coach book.

All organisms need to continually exchange gases, such as O2, CO2, and water vapor, with their environment

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Unicellular organisms do this through diffusion; larger organisms need specialized structures, such as gills and lungs

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As an adaptation to life on land, mammals, birds, reptiles, adult amphibians, and some snails have lungs

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​The diaphragm contracts, which increases the volume of the thoracic cavity and pulls in air from the outside. The air passes through bronchi, then through smaller and smaller bronchioles, then fills tiny sacs called alveoli.

The alveoli is surrounded by capillaries, so gas exchange takes place by diffusion - O₂ diffuses from the air, into the blood. CO₂ diffuses from the blood, into the air to be exhaled.​

Multiple Choice

Which of the following describes alveoli?

• They serve as the site of gas exchange in lungs

• They carry blood from the heart to the lungs

• They serve as the site of gas exchange in gills

• They serve as the site of gas exchange in leaves

uGills are specialized tissues containing many blood vessels that can take in O2 dissolved in water.

uA fish takes in water through its mouth. As the water flows over the gills, the blood vessels take in the O2 and release CO2.

uThis happens via diffusion.

uGills are less efficient than lungs at taking in O2, and so many aquatic animals have neat adaptations to get the O2 they need.

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Multiple Choice

Which structures are used for gas exchange by organisms that live in aquatic environments?

• tracheas

• spiracles

• gills

• lungs

Multiple Choice

How do gills exchange gases with water?

• by osmosis

• by fermentation

• by diffusion

• by active transport

Some animals, such as earthworms, which are thin-skinned and fairly small, can exchange gases with the environment through their skin.

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In these cases the skin must stay moist so O2 can diffuse from the air into the skin cells and then to the capillaries. CO2 diffuses from the capillaries out through the skin cells

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Arthropods, such as insects, spiders, mites, and centipedes, use a network of tiny tubes called tracheas the exchange gas. These lead to openings called spiracles on the sides of the abdomen.

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​Other methods in land animals

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uPlants take in both CO2 for photosynthesis and O2 for cellular respiration.

uThey exchange gases through tiny openings on the underside of their leaves called stomata.

uGuard cells on either side of the stomata control when it is open or closed.

uThis is mostly so that the plants do not dry out during the day

uSome aquatic plants have stomata on the upper surface of their leaves and roots adapted for removing dissolved O2 from the water

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​Gas exchange in plants

Multiple Choice

Many plants exchange gases with the air through openings on the underside of their leaves called

• gills

• alveoli

• guard cells

• stomata