Page 1 of 40
LIFE SCIENCES
Term 3
2025
GRADE 11
These notes have been
compiled using previous
examination papers: SACAI
NOV 2020, SACAI NOV
2021, SACAI NOV 2022. NSC – Grade 11 Topic Test: Cellular Respiration. @WCED Revision
Booklet 2025. LIFE SCIENCES TASK 6: TEST 2_GRADE 11. (EC/NOVEMBER 2023) &
(EC/NOVEMBER 2024)
PLEASE NOTE: Some information is repeated, but I have attached it so you can see the
different ways questions/sources can be presented. Good luck.
Good Luck: Juffrou Ansie.
CONTENTS
1. GAS EXCHANGE 1
2. EXCRETION IN HUMANS 18
3. POPULATION ECOLOGY 27
GAS EXCHANGE
@Juffrou_Ansie
, Page 2 of 40
Nasal cavities
• The two external nasal openings lead to two nasal cavities that are separated by a septum.
• Small, fine hairs in the nasal openings filter larger particles from the inhaled air
• Each nasal cavity is divided into three passages by three curved turbinate bones.
• The nasal cavities are lined with a mucous membrane consisting of ciliated columnar epithelial cells.
• The epithelial cells are richly supplied with capillary blood vessels that warm incoming air.
• Goblet cells the columnar epithelial cells secrete mucus that traps dust particles and germs, is
antiseptic, and humidifies incoming air.
• Cilia on the columnar epithelial cells perform swinging movements in the direction away from the lungs
to transport dust-laden mucus to the outside.
Pharynx
• The nasal cavities open into the
pharynx.
THE VENTILATION SYSTEM
• The pharynx leads to two openings,
the opening known as the glottis
which leads to the trachea, and the
opening which leads to the
esophagus.
Trachea
• The trachea is a long, tubular structure located in front of the oesophagus.
• The larynx, which houses the vocal cords, is located at the top of the trachea.
• The epiglottis is located at the top of the larynx and consists of cartilage.
• The epiglottis closes the glottis during the swallowing process, thus preventing food from entering
the trachea.
• The walls of the trachea are strengthened and kept open by C-shaped cartilage rings.
• The trachea is lined with striated columnar epithelial cells that secrete mucus.
• The mucus moistens the incoming air and traps dust particles.
• Mucus with trapped dust particles is transported to the pharynx by the flapping movements of the
cilia.
@Juffrou_Ansie
, Page 3 of 40
Bronchi, bronchioles and alveoli
• The trachea branches into two bronchi that enter the right and left
lungs respectively.
• The bronchi are also lined with a mucous membrane layer and are
held open by O-shaped cartilage rings.
• The bronchi divide into smaller branches within the lung and form
bronchioles.
• The bronchioles have no cartilage rings and their walls consist of
Lungs smooth muscles that can contract and relax to control airflow.
• The two lungs are in the chest and are • Each bronchiole ends in an infundibulum which consists of a
protected by 12 pairs of ribs. group of alveoli.
• The lungs are spongy and elastic and can
expand and contract during breathing.
• The right lung consists of three lobes,
and the left lung consists of two lobes.
• Each lung is surrounded by a double THE VENTILATION SYSTEM
membrane, called the pleura. PERSECUTE
• The fluid (interpleural fluid) between the
pleura prevents friction when the lungs
expand and contract.
Respiratory muscles and ribs:
Diaphragm:
The diaphragm is a dome-
shaped muscle plate that Ribs:
separates the chest and Intercostal muscles:
abdominal cavities. The ribs are on either side of the
The intercostal muscles occur
The diaphragm contracts and sternum (breastbone) and
between successive ribs and
flattens to change the volume of protect the lungs from injury.
consist of external and internal
the chest cavity and is
intercostal muscles.
important during breathing.
@Juffrou_Ansie
, Page 4 of 40
_______________________________________________________________
DIAGRAM OF AN ALVEOLUS SACAI NOV 2021 & 2020
Blood flow from Blood flow to blood
blood vessel 1 vessel 2
Blood vessel 1= Pulmonary artery / Pulmonary artery / pulmonary artery / pulmonary
artery.
Blood vessel 2= Pulmonary vein / Pulmonary vein / pulmonary vein / pulmonary vein.
1. Named part A represents the gas exchange surface area. Requirements that this
surface must meet to be an effective gas exchange surface. SACAI NOV 2021
↘ Gas exchange surface area must be large
↘ Gas exchange surface must be thin
↘ Gas exchange surface must be permeable and moist
↘ It must be well aerated.
↘ It must have a good transport system that is close to the gas exchange surface.
↘ It must be protected.
2. GAS X = Oxygen
3. GAS Y = Carbon dioxide. SACAI NOV 2021
• Sensory cells in the carotid artery/aorta/base of the brain detect the levels of
carbon dioxide in the blood. This sends a message to the medulla
oblongata/respiratory centre in the brain.
4. The function of fluid B in the alveolus SACAI NOV 2021
• The liquid helps dissolve gases to be absorbed/diffusion can occur.
5. Cell C – *Red blood cell / Erythrocyte
@Juffrou_Ansie
LIFE SCIENCES
Term 3
2025
GRADE 11
These notes have been
compiled using previous
examination papers: SACAI
NOV 2020, SACAI NOV
2021, SACAI NOV 2022. NSC – Grade 11 Topic Test: Cellular Respiration. @WCED Revision
Booklet 2025. LIFE SCIENCES TASK 6: TEST 2_GRADE 11. (EC/NOVEMBER 2023) &
(EC/NOVEMBER 2024)
PLEASE NOTE: Some information is repeated, but I have attached it so you can see the
different ways questions/sources can be presented. Good luck.
Good Luck: Juffrou Ansie.
CONTENTS
1. GAS EXCHANGE 1
2. EXCRETION IN HUMANS 18
3. POPULATION ECOLOGY 27
GAS EXCHANGE
@Juffrou_Ansie
, Page 2 of 40
Nasal cavities
• The two external nasal openings lead to two nasal cavities that are separated by a septum.
• Small, fine hairs in the nasal openings filter larger particles from the inhaled air
• Each nasal cavity is divided into three passages by three curved turbinate bones.
• The nasal cavities are lined with a mucous membrane consisting of ciliated columnar epithelial cells.
• The epithelial cells are richly supplied with capillary blood vessels that warm incoming air.
• Goblet cells the columnar epithelial cells secrete mucus that traps dust particles and germs, is
antiseptic, and humidifies incoming air.
• Cilia on the columnar epithelial cells perform swinging movements in the direction away from the lungs
to transport dust-laden mucus to the outside.
Pharynx
• The nasal cavities open into the
pharynx.
THE VENTILATION SYSTEM
• The pharynx leads to two openings,
the opening known as the glottis
which leads to the trachea, and the
opening which leads to the
esophagus.
Trachea
• The trachea is a long, tubular structure located in front of the oesophagus.
• The larynx, which houses the vocal cords, is located at the top of the trachea.
• The epiglottis is located at the top of the larynx and consists of cartilage.
• The epiglottis closes the glottis during the swallowing process, thus preventing food from entering
the trachea.
• The walls of the trachea are strengthened and kept open by C-shaped cartilage rings.
• The trachea is lined with striated columnar epithelial cells that secrete mucus.
• The mucus moistens the incoming air and traps dust particles.
• Mucus with trapped dust particles is transported to the pharynx by the flapping movements of the
cilia.
@Juffrou_Ansie
, Page 3 of 40
Bronchi, bronchioles and alveoli
• The trachea branches into two bronchi that enter the right and left
lungs respectively.
• The bronchi are also lined with a mucous membrane layer and are
held open by O-shaped cartilage rings.
• The bronchi divide into smaller branches within the lung and form
bronchioles.
• The bronchioles have no cartilage rings and their walls consist of
Lungs smooth muscles that can contract and relax to control airflow.
• The two lungs are in the chest and are • Each bronchiole ends in an infundibulum which consists of a
protected by 12 pairs of ribs. group of alveoli.
• The lungs are spongy and elastic and can
expand and contract during breathing.
• The right lung consists of three lobes,
and the left lung consists of two lobes.
• Each lung is surrounded by a double THE VENTILATION SYSTEM
membrane, called the pleura. PERSECUTE
• The fluid (interpleural fluid) between the
pleura prevents friction when the lungs
expand and contract.
Respiratory muscles and ribs:
Diaphragm:
The diaphragm is a dome-
shaped muscle plate that Ribs:
separates the chest and Intercostal muscles:
abdominal cavities. The ribs are on either side of the
The intercostal muscles occur
The diaphragm contracts and sternum (breastbone) and
between successive ribs and
flattens to change the volume of protect the lungs from injury.
consist of external and internal
the chest cavity and is
intercostal muscles.
important during breathing.
@Juffrou_Ansie
, Page 4 of 40
_______________________________________________________________
DIAGRAM OF AN ALVEOLUS SACAI NOV 2021 & 2020
Blood flow from Blood flow to blood
blood vessel 1 vessel 2
Blood vessel 1= Pulmonary artery / Pulmonary artery / pulmonary artery / pulmonary
artery.
Blood vessel 2= Pulmonary vein / Pulmonary vein / pulmonary vein / pulmonary vein.
1. Named part A represents the gas exchange surface area. Requirements that this
surface must meet to be an effective gas exchange surface. SACAI NOV 2021
↘ Gas exchange surface area must be large
↘ Gas exchange surface must be thin
↘ Gas exchange surface must be permeable and moist
↘ It must be well aerated.
↘ It must have a good transport system that is close to the gas exchange surface.
↘ It must be protected.
2. GAS X = Oxygen
3. GAS Y = Carbon dioxide. SACAI NOV 2021
• Sensory cells in the carotid artery/aorta/base of the brain detect the levels of
carbon dioxide in the blood. This sends a message to the medulla
oblongata/respiratory centre in the brain.
4. The function of fluid B in the alveolus SACAI NOV 2021
• The liquid helps dissolve gases to be absorbed/diffusion can occur.
5. Cell C – *Red blood cell / Erythrocyte
@Juffrou_Ansie
