Respiration

Question 1

What is respiration?

Answer 1

Respiration is the process by which an organism exchanges gases between
themselves and the environment.

Question 2

What are different mechanisms of respiration?

Answer 2

1) Aerobic cellular respiration: organisms use oxygen to extract energy from food.
2) Anaerobic cellular respiration: organisms do not use oxygen to extract energy from food but instead use a different compound (e.g. nitrate or sulfur).
3) Fermentation: The anaerobic degradation of a substance such as glucose to smaller molecules such as lactic acid or alcohol with the extraction of energy.

Question 3

Benefits of aerobic and anaerobic respiration

Answer 3

Aerobic respiration
• Releases more ATP molecules than anaerobic respiration
• This may have allowed for the evolution of multicellularity and larger organism size
Anaerobic respiration
• Quickly releases energy
• Can occur in low oxygen environments

Question 4

Where did mitochondria come from?

Answer 4

Mitochondria evolved via endosymbiosis where a host cell engulfed an
prokaryote cell.
There are two hypotheses regarding the types of organisms involved:
1) The traditional view is that a eukaryote host engulfed an aerobic
prokaryote.
2) An alternate view is that a prokaryote host engulfed a facultative
anaerobic prokaryote.
This is part of the endosymbiotic theory.

Question 5

How do bacteria and archae respire?

Answer 5

Bacteria and archaea can respire aerobically, anaerobically or both. Respiration occurs in the cytoplasm of the cell.
1. Obligate aerobic bacteria cannot survive without oxygen.
2. Obligate anaerobic bacteria cannot survive in the presence of
oxygen.
3. Facultative anaerobic bacteria can grow without oxygen but use
oxygen if it is present.
Anaerobic bacteria use other compounds such as hydrogen sulfide or
methane, instead of using oxygen.

Question 6

Aerobic respiration in fungi

Answer 6

Most fungi are aerobic, but some are anaerobic.
In soil, hyphae absorb oxygen from tiny air spaces in between soil particles.
Oxygen and carbon dioxide can move across the thin outer wall of hyphae by absorption.

Question 7

Respiration in plants

Answer 7

All parts of a plant need to respire.
Plants obtain oxygen via diffusion through: 1. stomata (leaves and stems)
2. lenticels (stems of woody plants and
some roots)
Plants also obtain oxygen via absorption through roots.

Question 8

Respiration in plant roots

Answer 8

Roots have adaptations depending on the oxygen environment.
Aerial roots known as pneumatophores are useful in environments with anoxic or waterlogged soil.
Aerenchyma are small air pockets in plant tissue. Allows for exchange of gases from exposed parts of the plant to submerged parts.

Question 9

Respiration in plant leaves

Answer 9

Leaves some stems have stomata which are tiny openings that
allow for gas exchange.
Stomata a present in the sporophyte generation of all land plants (except liverworts).
Stomata can open and close, depending on plant condition and environmental condition.

Question 10

What are the five types of respiration in animals?

Answer 10

Direct diffusion
Integumentary exchange
Trachea
Gills
Lungs

Question 11

What are the four possible stages of respiration in animals?

Answer 11

Breathing
Gas exchange
Circulation
Cellular respiration

Question 12

Why do small animals use direct diffusion whilst large animals do not?

Answer 12

Small animals (<1mm diameter) can obtain oxygen via diffusion.
Direct diffusion of oxygen across the outer membrane can supply oxygen to all cells.
Larger animals cannot use this method because diffusion would not be able to provide oxygen quickly enough.

Question 13

Which animals use integumentary exchange?

Answer 13

Some animals, such as earthworms and amphibians, use their skin as the gas exchange surface.
Gases diffuse directly across the integument (i.e. skin) into the circulatory system.

Question 14

Which animals use a trachea for gas exchange?

Answer 14

Insects have a system of tubes branching throughout their body to provide oxygen to all cells. These tubes are called trachea.
The openings to trachea are called spiracles and these can be opened or closed when needed.
Some insects can ventilate the tracheal system with muscle contractions.
The tracheal system is separate to the circulatory system.

Question 15

Which animals use gills?

Answer 15

Gills are found in molluscs, annelids, crustaceans and fish.
Gills can be found in a cavity or externally on different species.
Gills are highly branched and folded thin tissue filaments. Water passes over the gills and oxygen rapidly diffuses across the gills into the circulatory system or coelomic fluid.
Many gills use a counter current system to gain oxygen and lose carbon dioxide

Question 16

Which animals use lungs?

Answer 16

Lungs are found in amphibians, birds, reptiles and mammals.
Lungs vary greatly across the animal kingdom:
• Amphibians have a simple sac like lung.
• Reptile lungs vary but tend to be sac like,
sometimes subdivided.
• Mammals have branching lungs that terminate in
tiny air filled sacs (alveoli).
• Bird lungs are composed of a parallel series of
tubes, the parabronchi.

Question 17

Weird respiratory systems

Answer 17

Some animals breathe through their butt:
• Sea cucumbers have specialized respiratory trees
in just inside their anus.
• Fitzroy river turtles can obtain up to 70% of its
oxygen needs through its cloaca. This is termed
cloacal gill respiration.
The diving bell spider can hold onto an air bubble as
they dive underwater.
Sloth’s organs are attached to their ribcage so that they don’t press on the diaphragm.