Intended Learning Outcomes

At the end of this Lecture, students will be able to

• Discuss different types of ecosystems

• Cite biological components of Ecosystems

• Explain energy flow in Ecosystems


• Ecosystem

• Different types of ecosystems

• Biological components of Ecosystems

• Functions of ecosystem

• Importance of ecosystem

• Energy flow in Ecosystems


The self-sustaining structural and functional interaction between living and non-living components

Ecology: Scientific study of the interactions between organisms and the environment

Types of Ecosystem


1. Terrestrial ecosystems (grasslands, forests, desert ecosystems)

2. Aquatic ecosystem

    a. Lentic (Stagnant water) like lake, ponds etc.

    b. Lotic (Flowing water) like river, ocean, sea, etc


1. A crop land, garden, aquarium, park, kitchen garden

Component of an Ecosystem

An ecosystem consists of two main components

Abiotic or Non-living components

1. Inorganic substances

2. Organic compounds

3. Climatic factors

Biotic or Living components

1. Autotrophs or Producers

2. Heterotrophs or Consumers

3. Decomposers or Saprotrophs

Terrestrial Ecosystems

• Terrestrial ecosystems are ecosystems on land.

• They can be as big as a continent, or as small as an island!

• They make up about 28% of the entire World’s ecosystems.

What Animals Live There?

• Many different animals call terrestrial ecosystems home.

• The most common are:

– Birds

– Mammals of all shapes and sizes

– Insects

What Plants Live There?

• Many plants also call terrestrial ecosystems their home also, we see many of them every day!

• Common plants are:

– Flowering plants, like roses

– Mosses, like moss that grows on rocks

– Conifers, which are pine trees

Examples of Terrestrial Ecosystems

• Forests

• Deserts

• Grasslands

Aquatic Ecosystems

• There is something special about aquatic ecosystems.

• There is actually two different types of aquatic ecosystems.

• One type is freshwater

• The other type is saltwater.

• Both types, however, are ecosystems that are in the water.

Freshwater Ecosystems

• Freshwater ecosystems are places in the water where there isn’t much salt in the water.

• These include places like lakes, rivers, and creeks.

What Animals Live in Freshwater Ecosystems?

• A lot of animals live in freshwater ecosystems.

• Animals include:

– Freshwater fish, these fish can’t live in the ocean because it is too salty for them, so they live in freshwater

– Amphibians, like frogs

– Reptiles, like water snakes

What plants live in freshwater Ecosystem?

• Many plants call freshwater ecosystems their home, even if we can see them from the surface of the water

• Some plants are:

– Cattails

– Grasses

– Trees

Saltwater ecosystems

• Saltwater ecosystems are again in the water, but unlike freshwater ecosystems, saltwater ecosystems have very salty water.

• They also make up the vast majority of the Earth’s ecosystems.

• They are the world’s largest ecosystems.

• Some examples of saltwater ecosystems are oceans and coral reefs.

What Plants are in Saltwater Ecosystems?

• Seaweed is one of the most common types of plants that live in saltwater ecosystems.

• Another plant that lives in the ocean is kelp.

What Animals Live in Saltwater Ecosystems?

• There are so many animals that live in saltwater ecosystems

• Animals that live in saltwater ecosystems include:

– Fish

– Sharks

– Jellyfish

– Whales

Function of Ecosystem

• Producers, the green plants, fix radiant energy (solar energy) and with the help of minerals take from their edaphic (soil where they grow) or aerial environment and build up complex organic matter. These are their food. So, with the help of solar energy they convert the chemical energy of the food to kinetic energy and finally heat energy

• The animals eat up plants and other animals as food. So, the energy is transferred through food to animals

• When plants and animals die, then decomposers (like certain bacteria and fungi) act on their dead bodies and decompose them into simple materials like carbon dioxide, water and minerals which go back to air, water bodies and soil from where they were taken

• The carbon dioxide from air, water and minerals from water bodies and soil are again taken up by green plants along with solar energy to make their food. This process is repeated again and again. This leads to continuous functioning of the ecosystem


• Transfer of energy and matter takes place in the process of predator and prey relationship in a food chain. The original source of energy is the energy from the sun

• Out of the enormous amount of energy continuously radiated by the sun, most of it is reflected or refracted back (by atmosphere, earth surface and object like plants). Only a very small fraction, about one per cent, of the solar energy received by the plant is used through the process of photosynthesis

Importance of Ecosystem

• We know that no living organism can live in isolation. We cannot survive without producers in nature. All living beings depend on other living beings in the biological community. Not only they are dependent on one another, but also each of them exist in a certain proportion. This creates a complete balance in nature amongst living organisms.  This is evident from the study of food chains which operate between living organisms

Ecological balance in nature

• The balance between the living beings and also with the non- living environment is called the Ecological Balance or simply a Balance in Nature

• Unfortunately, however human activities have upset the ecological balance in nature, so it is more essential that balance in nature should be established soon because it is essential for our own existence

Conservation of Ecosystem

• Forests are important components of our environment. Rapid destruction of this important resource is a cause of concern

• Afforestation, preventing reckless cutting of trees and making everyone aware of the need to conserve it will help forest conservation

• Nature enjoys ecological balance only if the relative number of species is not disturbed. So, conservation of wildlife is important for the future

• National parks, wildlife sanctuaries and biosphere reserves are established to protect and conserve wildlife

• Such measures would ensure that the wildlife does not become extinct

• Conservation of aquatic life would be ensured by removal of industries near water bodies

Creating Awareness

Awareness about ecosystem conservation can be done by posters, competitions about ecosystem conservation, arranging T.V. programmes and websites related to ecosystems

Ecosystem Components

• Limiting factors determines distributions

Common limiting factors

• Limiting factors – more important in regulating population growth than other factors.

• Terrestrial ecosystems (on land)

– Precipitation

– Temperature

– Soil nutrients

• Aquatic ecosystems

– Temperature, sunlight, nutrients, dissolved oxygen & salinity

• If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium. That existed ten thousand years ago

• If insects were to vanish, the environment would collapse into chaos


• Self-sustaining structural and functional interaction between living and non-living components

• Types of Ecosystems: Natural and Artifical

• Animals eat up plants and other animals as food. So, the energy is transferred through food to animals

• Original source of energy is the energy from the sun

• Awareness about ecosystem conservation can be done by posters

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