Ecology: Organisms and Their Environment

• Ecology is the study of interactions among organisms and their environment
• The environment consists of both biotic (living organisms) and abiotic (non-living organisms) components

Origin of the Term Ecology

• German biologist Haeckel coined the term "ecology" in 1869
• Ecology is derived from the Greek words ‘Oikos’ (house, habitat) and ‘Logos’ (to study)
• Danish botanist Eugenius Warming expanded on the concept of ecology

Interactions Studied in Ecology Include:

• Non-living components: light, water, wind, soil nutrients, heat, solar radiation, atmosphere
• Living organisms: plants, animals, microorganisms in the soil

Ecosystem Defined

• A.G. Tansley introduced the term "ecosystem" in 1935
• An ecosystem is a biological community in a specific location and the physical and chemical factors that make up its non-living environment
• Examples include ponds, deserts, forests, and oceans
• Ecosystems are the basic functional units of ecology
• An ecosystem is a community of different species interacting with each other and their non-living environment, exchanging energy and matter

Ecology Focus

• Ecology specifically studies ecosystems
• Animals rely on plants for food, either directly or indirectly

Ecosystem Structure Components

• Ecosystems have biotic (living) and abiotic (non-living) components

Biotic Components

• Biotic components include all living organisms in an ecosystem
• Examples are plants, animals, and microorganisms

Classification of Biotic Components by Food Source:

• Producers (Autotrophs): plants
• Consumers (Heterotrophs): animals
• Decomposers: micro-organisms

Producers (Autotrophs)

• Producers synthesize their own food through photosynthesis
• Examples include green plants and trees

Photosynthesis

• Chlorophyll in plant leaves converts carbon dioxide and water into carbohydrates using sunlight
• The chemical equation is: 6CO2 + 6H2O ----> C6H12O6 + 6O2

Consumers (Heterotrophs)

• Consumers classification:
  • Primary Consumers (Herbivores): Plant eaters like insects, rats, goats, deer, cows
  • Secondary Consumers (Primary Carnivores): Meat eaters that feed on herbivores, such as frogs, cats, snakes, and small birds
  • Tertiary Consumers (Secondary Carnivores): Meat eaters that feed on secondary consumers, such as hawks, eagles, tigers, and lions
  • Omnivores: Organisms that eat both plants and animals, like humans, rats, and birds
  • Detritivores: Organisms that feed on dead organisms, wastes, and partially decomposed matter, like termites, earthworms, and ants

Decomposers

• Decomposers break down dead producers and consumers into simpler compounds releasing inorganic nutrients
• Producers then use these nutrients to synthesize their own food
• Examples: bacteria and fungi

Abiotic Components

• Non-living components (physical and chemical) form the abiotic community
• Examples include climate, soil, water, and air
• Physical components: energy, climate, nutrients, and living space needed by the biological community
• Examples: air, water, soil, and sunlight
• Chemical Components: sources of essential nutrients
  • Organic substances: proteins, lipids, and carbohydrates
  • Inorganic substances: micro (Al, Co, Zu, Cu) and macro elements (C,H, O, P, N, P, K)

Types of Ecosystems

• Natural ecosystems: operate under natural conditions
  • Terrestrial ecosystems: related to land (e.g., grasslands, forests, deserts)
  • Aquatic ecosystems: related to water
    • Fresh water ecosystems:
      • Running water (rivers, streams)
      • Standing water (ponds, lakes)
    • Marine ecosystems: seas and seashores
• Man-made (artificial) ecosystems: maintained by humans (e.g., croplands, gardens)

Ecosystem Functions

• Allow the flow of energy and the cycling of nutrients

Three Main Functions

• Primary: Starch manufacture (photosynthesis)
• Secondary: Distributing energy as food to all consumers
• Tertiary: Cycling, where dead systems decompose

Studying Ecosystem Functioning by Examining

• Energy and material flow
• Food chains
• Food webs
• Food pyramids

Energy Flow in Ecosystems

• Energy flow is the most essential requirement for all living organisms
• Solar energy is the primary source
• Solar energy is converted to chemical energy by plants during photosynthesis
• Plants use some chemical energy for growth, and the rest is transferred to consumers through eating
• Energy enters ecosystems through photosynthesis, passing through different tropic levels or feeding levels
• The flow of energy in an ecosystem follows the laws of thermodynamics

Laws of Thermodynamics

• First law: Energy cannot be created or destroyed, only converted from one form to another
• Energy from the sun is absorbed by plants and converted into chemical energy, then transformed into heat by consumers
• Second law: Energy is lost as heat during transformation
• Energy is transferred between tropic levels as heat due to respiration, work, running, and hunting
• The energy and nutrient flow cycle from abiotic to biotic and back

Food Chains

• A food chain is the sequence of eating and being eaten in an ecosystem, or the transfer of food energy through a series of organisms
• It always starts with plant life and ends with an animal; microorganisms decompose dead organisms into nutrients that plants reuse
• About 80-90% of potential energy is lost as heat at each level

Tropic Levels

• Tropic levels are the steps through which food energy passes
• Green plants (producers) are the first tropic level (T1)
• Herbivores (primary consumers) are the second tropic level (T2)
• Carnivores (secondary consumers) are the third tropic level (T3)
• Tertiary consumers are the fourth tropic level (T4)
• Decomposers are the last tropic level (T5)

Types of Food Chains

• Grazing food chain: starts with green plants and goes to decomposers through herbivores and carnivores; found in grassland and pond ecosystems
• Detritus food chain: starts with dead organic matter and goes to decomposers through herbivores and carnivores; found in grassland and forest ecosystems; grazing and detritus food chains are interconnected

Food Webs

• A food web is the interlocking pattern of various food chains in an ecosystem, where different organisms are connected at different tropic levels
• Food webs offer multiple opportunities for eating and being eaten at each tropic level

Differences Between Food Chains and Food Webs

• In a food chain, if one species is affected or becomes extinct, the subsequent tropic levels are also affected
• In a food web, the impact is less severe due to multiple options at each tropic level

Significance of Food Chains and Food Webs

• Both play a vital role in ecosystems
• Energy flow and nutrient cycling take place through them
• They maintain and regulate population sizes, helping to maintain ecological balance
• They exhibit bio-magnification, where non-biodegradable materials accumulate at increasing concentrations at higher tropic levels

Ecological Pyramids

• Ecological pyramids are graphical representations of the structure and function of tropic levels, starting with producers at the bottom and successive tropic levels forming the apex
• Biomass and the number of organisms decrease from producers to consumers
• Energy is lost as heat at each tropic level, making the pyramid progressively smaller near the top

Types of Ecological Pyramids

• Pyramid of numbers
• Pyramid of energy
• Pyramid of biomass

Pyramid of Numbers

• Represents the number of individual organisms at each tropic level
• In a grassland ecosystem, grasses (producers) are large in number at the lower tropic level
• Rats (primary consumers) are fewer in number at the second tropic level
• Snakes (secondary consumers) are even fewer at the third tropic level
• Eagles (tertiary consumers) are the fewest at the top level

Pyramid of Biomass

• A graphical representation of biomass (mass or weight of biological material) in a unit area at each tropic level
• Shows the relationship between biomass and tropic level

Example

• A forest ecosystem shows a decrease in biomass from lower to higher tropic levels
  • Trees (producers) contribute the most biomass
  • Herbivores (rabbits, deer) and carnivores (snakes, foxes) have less biomass
  • Tertiary consumers (lions, tigers) have the lowest biomass

Pyramid of Energy

• Indicates the amount of energy flow at each level
• Illustrates how much energy is needed to support the next tropic level
• There is always a significant loss of energy