Lesson Note on Biology SS2 Third Term






















SS2 Third Term Biology Lesson Note 

Below are the 2022 complete SS2 Third Term Biology Lesson Note

Week 1

Topic: Respiratory System



Respiration is defined as a biochemical activity of the cell in which glucose is broken down by a series of reactions controlled by enzymes to release energy.

Your respiratory system is made up of the organs in your body that help you to breathe. Respiration means Breathing. The goal of breathing is to deliver oxygen to the body and to take away carbon dioxide. The lungs are the main organs of the respiratory system.

Oxygen is breathed in and it breaks down the food substances (glucose) to release energy, carbon dioxide and water. Carbon dioxide and water are regarded as waste products of respiration. The energy so released is used by living organisms for various life processes. This occur inside a tiny organelle called the mitochondrion. To learn more, click here

 Week 2

Topic: Mechanism of Respiratory System


Unicellular organisms

There are no special respiratory organs in unicellular and aquatic organisms such as Amoeba and Paramecium. The oxygen that dissolves in water diffuses into the body while carbon dioxide goes out of the body through the entire body surface. The cell membrane acts as the respiratory surface. The concentration of oxygen in water is higher than that inside the body, hence it will diffuse into all parts of the body. On the other hand, carbon dioxide inside the body is higher than that of the water, hence it will diffuse out of the body.   The process of gaseous exchange in unicellular organisms is made possible by simple diffusion. These organisms have a large surface area to volume ratio hence diffusion through the body surface alone is enough to satisfy its gaseous exchange needs. To learn more, click here

Week 3

Topic: Aquatic Habitat


Aquatic habitat is a body of water in which certain organisms live naturally. In other words, aquatic habitats are habitats or places that relate to lives in water. Organisms that live in water are called aquatic organisms. Examples of aquatic organisms are fish, crabs, toads, plants etc.

Types of Aquatic Habitats

There are three types of aquatic habitats. These are marine or salt water habitats, estuarine or brackish water habitats and freshwater habitats


Marine habitats refer to aquatic habitats which contain salt water. Marine habitats include the oceans, lakes, shores and the open seas.

Characteristics of Marine Habitat

The marine or salt water habitat has the following characteristics:

  1. Salinity: Salinity is defined as the degree of saltiness or concentration of salt solution in oceans. The marine habitats have high salinity and its average salinity is put at 35.2 per 1000. In other words, the average salinity of the ocean is 35.2 parts of salts by weight per 1000 parts of water. To learn more, click here

Week 4

Topic: Estuarine Habitats




Estuarine habitat is a body of water formed at the coast as a result of the action of tides which mix salt water from sea with fresh water from the land. The mixing of salt water and fresh water results in the formation of brackish water. This brackish water is what is called estuarine.

Characteristics of Estuarine Habitats

The followings are the characteristics of the estuarine habitats:

Fluctuation in salinity: Salinity fluctuates in this habitat. Salinity is lower at the mouth of a river and gets higher towards the sea. Salinity is also affected by season. While rainy season reduces salinity due to addition of fresh water, dry season increases it. To learn more, click here

Week 5

Topic: Fresh Water Habitats


Freshwater habitat is a body of water formed mainly from inland waters and contains very low level of salinity. Examples of freshwater habitats are rivers, ponds, streams, springs and lakes

Types of Fresh Waters

Freshwaters are classified on the basis of their mobility. Based on this, two types are identified. These are:

  • Lotic fresh waters: These include all running waters which can flow continuously in a specific direction. In other words, these are flowing or running waters, e.g. rivers, springs and streams
  • Lentic fresh waters: These include standing or stagnant waters. These waters do not flow nor move. Examples of lentic fresh waters are lakes, ponds, swamps and dams. To learn more, click here

 Week 6

Topic: Terrestrial Habitats


Terrestrial habitats refer to life on land. The nature of  the soil, rainfall and temperature are the major factors affecting the nature of terrestrial habitats

Most of these habitats are shown in on the map of West Africa indicating the vegetation


The terrestrial habitat is divided into four groups. These are:

  • Marsh
  • Rain forest
  • Savanna or Grassland
  • Arid land. To learn more, click here

Week 7

TopicForest Habitats


A forest is an extensive community of plants dominated by tall trees. These trees are of different species and heights. The distribution of forests is mainly determined by climate, especially rainfall and temperature. The rainforest is the dominant forest in Nigeria.


Characteristics of the RainForest

  1. Presence of broad leaves: Most trees in rain forest usually possess broad leaves which enable the plants to receive abundant light and enhance transpiration
  2. Presence of buttress roots: Most trees because of their large sizes often have buttress roots to support their heavy weight and height
  3. Presence of tall trees: The bulk of the trees in rain forest are tall. Some are even 40 metres and above in height. To learn more, click here

Week 8

TopicGrassland Or Savanna Habitats


A grassland or savanna is a plant community in which grass species are dominant with short but scattered trees and shrubs. The grassland or savanna lies between the forest and the deserts or arid land.


Types of Grasslands

There are two major types of grasslands. These are the tropical grassland (savanna) and the temperate grassland
1. Tropical Grassland or Savanna
The tropical grassland is located around the equator, i.e., between 5o and 20o this North and South of the Equator. Areas, where this grassland is found, include Africa where it is called savanna, in Brazil where it is called campos, and in South America where it is called ilanos. To learn more, click here

Week 9

Topic:  Ecology Of Populations


The term “ecological succession” refers to the progression an ecosystem follows as it changes over time. Scientists refer to individual stages of an ecosystem’s growth as “seral stages,” and they refer to the entire process of succession as a “sere.” Biological succession is a natural process that occurs in all of Earth’s ecosystems. Is the gradual replacement of the community of organisms in one area or another, it may take millions of years. In other words, succession is the process by which communities colonise an ecosystem and are then replaced over time by other communities.

Week 10

Topic: Food Shortage 


In all habitats, producers provide the food that supports all consumers either directly or indirectly. In a well-established habitat, the population sizes of the various species are adjusted to the quantity of food that is available in the habitat. Certain factors can, however, decrease the food supply to the habitat causing food storage.

Causes of Food Shortage

The following factors are responsible  for the shortage of food in a habitat:

  1.  Overpopulation: An increase in population without a corresponding increase in food supply tends to create a food shortage.
  2. Poor storage facilities: Lack of or inadequate storage facilities to store excess produce do result in losses leading to food shortage.
  3. Flood: The occurrence of a flood in a particular year may result in the destruction of crops and farmlands which can also lead to food shortage. To learn more, click here