BT101 – Ecology, Biodiversity & Evolution-I

Topic No.1

Introduction to ecology


The termecology was invented by the German biologist;Ernst Haeckel in 1866. Ecology is the study of the interaction between the living components of the earth with the environment. Ecologists study the factors that explain the distribution and abundance of plants and animals. More and more we explore the impact of human activities on these distribution. Understanding the ecological foundation of a system enables the ecologist to predict how future changes may affect the system. Ecology for example is critical for understanding conservation, biodiversity issues, global climate change, human alterations of the environment, and the impact of pollutants on ecological systems.

Major components of ecology are

  • Species
  • Population
  • Community
  • Ecosystem
  • Biome
  • Biosphere


A species is often defined as the largest group of organisms in which two individuals are capable of reproducing fertile offspring, typically using sexual reproduction.For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator.




population is a group of organisms of the same species that live in the same area at the same time. Population ecologists study the size, density, and structure of populations and how they change over time.


A biological community consists of all the populations of different species that live in a given area. Community ecologists focus on interactions between populations and how these interactions shape the community.


An ecosystem consists of all the organisms in an area, the community, and the abiotic factors that influence that community. Ecosystem ecologists often focus on flow of energy and recycling of nutrients.


Biomes are very large ecological areas on the earth’s surface, with fauna and flora (animals and plants) adapting to their environment. Biomes are often defined by abiotic factors such as climate, relief, geology, soils and vegetation. A biome is NOT an ecosystem, although in a way it can look like a massive ecosystem.



The biosphere is planet Earth, viewed as an ecological system. Ecologists working at the biosphere level may study global patterns—for example, climate or species distribution—interactions among ecosystems, and phenomena that affect the entire globe, such as climate change.


Sub fields of ecology are

1) Organismal ecology

2) Population ecology

3) Community ecology

4) Ecosystem ecology

5) Landscape ecology

6) Global ecology


1) Organismal ecology

Organismal ecology is the study of individual organisms’ behavior, physiology, morphology, etc. in response to environmental challenges.

2) Population ecology

Population ecology is a sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment. It is the study of how the population sizes of species change over time and space.

3) Community ecology

Community ecology is the study of the interactions between species in communities on many spatial and temporal scales, including the distribution, structure, abundance, demography, and interactions between coexisting populations

4) Ecosystem ecology

Ecosystem ecology is the integrated study of living (biotic) and non-living (abiotic) components of ecosystems and their interactions within an ecosystem framework. This science examines how ecosystems work and relates this to their components such as chemicals, bedrock, soil, plants, and animals.

5) Landscape ecology

Landscape ecology is the science of studying and improving relationships between ecological processes in the environment and particular ecosystems. This is done within a variety of landscape scales, development spatial patterns, and organizational levels of research and policy.

6) Global ecology

Global ecology is the study of the interactions among the Earth’s ecosystems, land, atmosphere and oceans. Global ecology is very important because it is used to understand large scale interactions and how they influence the behavior of the entire planet, including the earth’s responses to future changes.


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