Concept of the Ecosystem - MBBS II

Course Information

• University: Usmanu Danfodiyo University, Sokoto
• College: College of Health Sciences
• Faculty: Faculty of Clinical Sciences
• Department: Department of Community Health
• Programme: MBBS
• Level: UG II
• Session: 2023/2024
• Topic: Concept of the Ecosystem
• Lecturer: Prof. A.U Ka'oje

Outline

• Introduction/definition of terms
• Ecosystem and its fundamental characteristics
• Important ecological concepts
• Food chain, ecological pyramid, food web

Lecture Expectations

• Basic understanding of the ecosystem
• Knowledge of different forms of ecosystems
• Ability to describe food chains

Introduction

• System: regularly interacting and interdependent components forming a unified whole
• Ecology: the study of how organisms interact with each other and their environment of matter and energy
• Ecological niche: the combination of function and habitat for each species (approximately 1.5 million animal species and 0.5 million plant species on Earth)

Ecologists Study Connections in Nature

• Levels of organization:
  • Population
  • Genetic diversity
  • Community
  • Ecosystem
  • Biosphere

Biosphere

• Parts of Earth's air, water, and soil where life exists

Ecosystem

• A community of different species interacting with each other and their nonliving environment

Community

• Populations of different species living in a particular place and potentially interacting with each other

Population

• A group of individuals of the same species living in a particular place

Organism

• An individual living being

Cell

• The fundamental structural and functional unit of life

Molecule

• Chemical combination of two or more atoms

Atom

• Smallest unit of an element exhibiting chemical properties

Earth's Life-Support System

• Four major components:
  • Atmosphere
  • Troposphere: lowest atmospheric layer; 4-11 miles high (depending on latitude)
  • Stratosphere: ozone layer
  • Hydrosphere
  • Geosphere
  • Biosphere

General Structure of Earth

• Biosphere (living organisms)
• Atmosphere (air)
• Crust (soil and rock)
• Hydrosphere (water)
• Lithosphere (crust, mantle, core)

What is an Ecosystem?

• A community of living organisms (plants, animals, microbes) interacting with their nonliving environment

Life on Earth

• Sustained through interactions of many organisms functioning together through physical and chemical environments
• Humans are integral to ecosystems
• Ecosystems sustain life, consist of species and a fluid medium (air, water)
• Ecosystems cycle chemical elements and flow energy
• Biotic and abiotic parts are linked by nutrient cycles and energy flow

Ecosystem Components (Biotic and Abiotic)

• Living parts (biotic): plants, animals, microbes
• Non-living parts (abiotic): water, soil, air, light, temperature

Ecosystem Structure

• Ecosystems consist of biotic (living) and abiotic (non-living) components.
• The biotic and abiotic components are interrelated in an ecosystem
• It is an open system where energy and components can flow throughout the boundaries

Biotic Components

• Autotrophs: produce their own food (e.g., plants)
• Heterotrophs: consume other organisms for food (e.g., herbivores, carnivores, decomposers)

Abiotic Components

• Physical, chemical factors, conditions (e.g., soil, climate, water, temperature)
• Inorganic substances like carbon, nitrogen, etc
• Organic compounds like proteins and carbohydrates

Functional Components/Units of Ecosystems

• Productivity: rate of biomass production
• Energy flow: sequential process of energy transfer between trophic levels (producers -> consumers -> decomposers)
• Decomposition: breakdown of dead organic material; major site = topsoil
• Nutrient cycling: consumption and recycling of nutrients in various forms

Functions of Ecosystem

• Regulates ecological processes, supports life systems, and ensures stability
• Cycles nutrients between biotic & abiotic components
• Balances trophic levels
• Cycles minerals
• Abiotic components support organic compound synthesis; energy exchange

Ecosystem Dynamics

• Ecosystems are always in motion/dynamic
• Changes in one part of the ecosystem often cause changes elsewhere.
• Several important cycles affected by human activity include: hydrologic cycle, carbon cycle, nitrogen cycle, phosphorous cycle, and energy flow.

Energy Flow in an Ecosystem

• Energy flows through ecosystems in food chains and webs.
• Amount of chemical energy decreases at each succeeding feeding level
• Energy transfers are in part degraded as heat (second law of thermodynamics)

Important Ecological Concepts

• Food chain: linkage of who feeds whom. The sun is the ultimate energy source for plants, followed by energy transfer to consumers. Energy & nutrients travel along the food chain through various organisms. Decomposition plays a key role, breaking down matter to elements that support the cycle.
• Examples: grass - grasshopper - mouse - snake - eagle.
• Food web: a network of interconnected food chains

Trophic Levels

• Trophic level is the organism's position in the food chain or web
• Producers (autotrophs) form the base
• Consumers (herbivores, carnivores) are divided into levels based on their trophic level in the food web.
• Decomposers break down dead organisms

Ecological Pyramid

• Graphical representation of the number, energy, and biomass of trophic levels in an ecosystem.
• Most ecosystems have huge numbers of tiny organisms at the base (e.g., plankton). Top levels in the pyramid have relatively few, large individuals.

Food Web

• A network of interlinked food chains.
• Plants lay the foundation of all food chains.
• In a marine environment, phytoplankton is the primary producer

Environment

• Derived from French word "environia" meaning to surround
• Sum total of living and nonliving conditions surrounding something at a given time and space
• Abiotic factors (physical): air, water, soil
• Biotic factors (living): plants, animals, microorganisms

Components of Environment

• Physical environment (abiotic): air, water, temperature, light, noise, etc. key factors influencing living beings
• Divided into atmosphere (gas), hydrosphere (liquid), and lithosphere (solid).
• Biological environment (biotic): plants, animals, microorganisms. Impacted by factors like disease, food availability

Social Component

• Complex of psychosocial factors influencing individual & community health
• As important as physical & biological components to health, morbidity & disease, (e.g. comparing rural & urban health, developing vs developed countries)
• Socioeconomic & political factors are crucial determinants for health