Ecosystems: What They Are

Objectives

At the end of the session the students should be able to:

1. Can give definition of ecosystems and how they organized  into larger units.

2. Show the trophic categories of ecosystems and explain how they function together in the food  webs to make a sustainable system.

3. Can discuss how nontrophic relationships like mutualism and competition play in ecosystem.

4. Can identify and explain the types of ecosystems and its subtypes.

Ecosystem 

• An ecosystem is a community of organisms interacting with each other and with their environment.

• The term "ecosystem" was first coined by Roy Clapham in 1930.

• Arthur Tansley fully defined the ecosystem concept in 1935, He defined ecosystems as "The whole system including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment".

Concepts of an Ecosystem

• Biotic and Abiotic 

• Autotrophs and Heterotrophs 

• Lithosphere, Hydrosphere, Atmosphere

• Mutualism, Commensalism, Competition, Parasitism, Predation

• Producer, Consumer, Decomposer

• Carnivores, Herbivores, Omnivores, Scavengers

EARTH’S SPHERES

• LITHOSPHERE – Rock Layer

• HYDROSPHERE – Water Layer

• ATMOSPHERE – Gas Layer

• BIOSPHERE – Living things

Basic interacting components of the ecosystem

Biotic  - living component

• Plants 

• Animals

• Microorganisms 

Abiotic – non-living component

• Atmosphere 

• Climate

• Soil 

• Water

Ecological Level of Organization

1. Individual Species – basic unit

2. Population – group of species

3. Community – group of population 

4. Ecosystem – community + environment

5. Biomes – group of ecosystem

6. Biosphere – part of the earth wherein life is possible

Types of Organisms in an Ecosystem according to Source of Nourishment

• Autotrophs 

  • Self-feeders

  • Producers

  • Manufactured their own food

• Heterotrophs 

  • Other-feeders

  • Consumers 

  • Depend on other organisms for food

Trophic Levels in an Ecosystem

• Producers
  - produce food through photosynthesis

• Consumers

  • Herbivores

  • Carnivores

  • Omnivores

  • Scavengers / Detritus Feeders

• Decomposers

Law of Conservation of Energy

“Energy cannot be created or destroyed, but it can be 

transferred or transformed from one form to another.”

Energy Transfer in an Ecosystem

• Food Chain

  • Simple pattern of food-energy transfer in an ecosystem

• Food Web 

  • Complex pattern of food-energy transfer in ecosystem

  • Consists of more than one food chain

Ecological Relationship

• Mutualism  or symbiosis - both are benefited

Types

Facultative mutualism - both species benefit from the interaction but each can live without the other

Obligatory mutualism - one cannot survive for long without the other

• Competition - two or more organisms strive for the same nutrients

Types

Inter-specific competition – competition between two different species

Intra-specific – competition between same species

• Predation - one is nourished while the other is eaten

Predator – organism that benefits

Prey – organism that is eaten

• Parasitism - one is nourished while the other is harmed

Parasites - organism that is benefited

Host - negatively affected organism

Two Types of Parasites

Ectoparasites 

Endoparasites 

• Commensalism - one is benefited while the other is unaffected

  • Commensal – organism that benefits

  • Host – unaffected organism

Types of Ecosystem

1. Aquatic 

2. Terrestrial

Aquatic Ecosystem

• An ecosystem which exists in a body of water is known as an aquatic ecosystem. 

• Types:

  1. Marine 

  2. Freshwater

Marine Ecosystem

• Marine ecosystems are the biggest ecosystems. 

• They cover around 71% of earth’s surface and also contain almost around 97% of the total water present on earth. 

• High amounts of minerals and salts are generally present in the water in the marine ecosystems.

• Types: 

1. Oceans

2. Coral reefs

3. Estuaries

   • A place where salt water meets freshwater

Freshwater Ecosystem

• The freshwater ecosystems are very small in magnitude as compared to the marine ecosystems as these cover only 0.8%.

• In freshwater ecosytem, the faster moving waters contain more dissolved oxygen than the slow moving waters and hence support greater biodiversity.

• Types:

  1. Lentic

• Slow-moving or still water like ponds or lakes

2. Lotic

• Fast-moving water like rivers and streams

3. Wetlands. 

• Ecosystems where soil remains saturated for a long period of time. 

• Examples: marsh and swamps

• Many different species of reptiles, amphibians, and around 41% of the world’s fish species live in these ecosystems. 

Problems Concerning Aquatic Ecosystems

1. Water Pollution

2. Overfishing 

3. Building on Coastal Areas

Terrestrial Ecosystem

• The ecosystem which is found only on landforms is known as the terrestrial ecosystem.

• The main factor which differentiates the terrestrial ecosystems from the aquatic ecosystems is the relative shortage of water in the terrestrial ecosystems.

• Another factor is the better availability of light in these ecosystems as the environment is a lot cleaner in land than it is in water. 

• Types:

1. Forest

2. Desert

3. Grassland

4. Mountain

Forest Ecosystem

• These ecosystems have an abundance of flora or plants and hence in these ecosystems a large number of organisms live in a small space. 

• These ecosystems have a high density of living organisms. 

• Types:

1. Tropical Rainforests

2. Temperate Forests

3. Cold Forests

Desert Ecosystem

• Desert ecosystems are located in the regions which receive less annual rainfall.

• Almost 17% of all the land on this planet is occupied by the desert ecosystems. 

• The fauna and flora in these ecosystems is generally not much developed because of the high temperatures, intense sunlight and low availability of water. 

• The main vegetations of such regions are the shrubs, bushes and a few grasses and trees. The stems and leaves of these plants are also developed in order to conserve as much water as possible. 

• Camels, reptiles and some insects and birds are the living creatures which are found in such regions.

• Types: 

1. Tropical Desert

2. Temperate Desert

3. Cold Desert

Grassland Ecosystem

• The grasslands are the areas which comprise mainly of the grasses with a little number of shrubs and trees. 

• Grazing animals, insectivores and herbivores are the main types of organisms which are found in these regions. 

• Types;

1. Tropical Grassland

2. Temperate Grassland

3. Polar Grassland

Problems Concerning Terrestrial Ecosystems

1. Deforestation

2. Mining

3. Desertification

4. Land Pollution