ECOSYSTEM

Introduction to Interactions and Interdependencies - Topic: Interactions and interdependencies in natural systems; Part One focuses on introduction, ecosystems, and interdependencies.
Ecology

  • Ecology: The study of interactions of organisms with one another and with the physical and chemical environment in which they are found.

Ecosystems

  • An ecosystem is an area that consists of an ecological community where the living (biotic) factors and non-living (abiotic) factors exist and interact with each other.

Biosphere and 'spheres'

  • BIOSPHERE: The sum total of all the ecosystems on Earth.

  • Other Earth spheres mentioned (as part of the system): LITHOSPHERE (crust, mantle), ATMOSPHERE, HYDROSPHERE. Visual cues show interconnections among these components with the BIOSPHERE.

Biodiversity and agricultural context

  • BIODIVERSITY: The variety of life that occurs in one ecosystem/habitat.

  • Examples discussed (conceptual, not exhaustive):

    • Food and cash crops; shade for coffee; nitrogen cycling (intercropping, perishables, medicines, fodder, fruits, timber, herbs, milk, vitamins).

    • Roles of trees and various crops in supporting farm ecosystems (pest control, pollination, soil fertility, manure).

    • Purpose in ecosystems: supports resilience, resource availability, and ecosystem services such as pest control and pollination.

Habitat

  • Habitat: The natural home or environment of a plant, animal, or other organism.

Community and Population concepts

  • COMMUNITY: All the populations living in an area.

  • POPULATION: All the organisms of the same species living in an area.

  • Example illustrations include a lake ecosystem and a community around an oak tree, illustrating how populations group within a habitat.

Species definition

  • SPECIES: A group of individuals that can interbreed and produce fertile offspring.

  • Example: Horses and donkeys are not the same species because they do not produce fertile offspring.

Biotic vs Abiotic factors

  • ABIOtic factors: The non-living parts of an ecosystem (e.g., water, air, light, soil, minerals, temperature, etc.).

  • BIOTIC factors: The living parts of an ecosystem (e.g., animals, plants, protists, bacteria, fungi, and decomposers).

  • Examples listed for biotic factors include various animals (foxes, insectivorous birds, toads, spiders, predaceous insects, squirrels, mice, seed-eating birds).

  • Examples listed for abiotic factors include water, air, light, soil, minerals, temperature, oxygen, carbon dioxide, etc.

Hierarchy of biological organization

  • BIOSPHERE consists of ECOSYSTEMS.

  • ECOSYSTEMS consist of COMMUNITIES.

  • COMMUNITIES consist of POPULATIONS.

  • POPULATIONS consist of INDIVIDUALS/ORGANISMS.

Symbiosis and interdependencies

  • SYMBIOSIS: Close and long-term biological interaction between two different biological organisms.

  • INTERDEPENDENCIES in ecosystems: Living organisms depend on other biotic organisms and abiotic factors.

  • Quick check:

    • Biotic = living

    • Abiotic = non-living

    • Symbiosis types discussed: Mutualism, Commensalism, Parasitism.

Mutualism

  • Mutualism: A symbiotic relationship between two different organisms where both benefit from the relationship.

Commensalism

  • Commensalism: A symbiotic relationship where one party benefits, while the other is neither helped nor harmed.

Parasitism

  • Parasitism: A symbiotic relationship where one party (the host) is disadvantaged while the other (the parasite) benefits.

Activities and practice (classwork/homework references)

  • Activity 3 (pp. 38) and Exercise 3 (pp. 42) involve identifying biotic vs abiotic factors and relationships such as mutualism, commensalism, and parasitism.

  • Example listing of biotic factors: crocodile, hippopotamus, zebra, elephant, giraffe, stork, eagle, birds, seed-eating birds, etc.

  • Example listing of abiotic factors: water, rocks, wind, soil, sun, temperature, oxygen, carbon dioxide, etc.

Producers and consumers

  • Producers (autotrophs): Plants that produce their own food via photosynthesis.

  • Consumers: Organisms that obtain food directly or indirectly from plants; organisms that feed on other organisms.

Feeding relationships (trophic categories)

  • Herbivores (primary consumers): feed on plants.

  • Carnivores (secondary and tertiary consumers): meat eaters; occupy higher trophic levels.

  • Predators: carnivores that hunt and kill; prey are the organisms hunted.

  • Scavengers: carnivores that feed on animals that are already dead.

  • Insectivores: animals that feed on insects and other small invertebrates.

  • Omnivores: diet includes both plants and meat.

  • Detritivores: scavengers that feed on waste/detritus of plants and animals; they help enlarge the surface for decomposers.

  • Decomposers: microorganisms (bacteria and fungi) that break down dead plant and animal material.

Energy flow and balance in ecosystems

  • A food chain starts with a producer and ends with decomposers; energy flows from producers to various consumers.

  • A food web is a network of interconnected food chains.

  • Example chain illustrating energy flow: PRODUCER → PRIMARY CONSUMER → SECONDARY CONSUMER → TERTIARY CONSUMER (and includes decomposers).

  • Trophic levels:

    • 1st level: PRIMARY PRODUCERS (plants).

    • 2nd level: PRIMARY CONSUMERS (herbivores).

    • 3rd level: SECONDARY CONSUMERS (carnivores).

    • 4th level: TERTIARY CONSUMERS (top carnivores).

  • Energy pyramid concept: energy and numbers decrease at higher trophic levels due to energy use by organisms (respiration, reproduction, excretion, etc.).

  • Key rule of energy transfer: Only about 10\% of the net energy production of one trophic level is transferred to the next level. This can be summarized as the rule: \text{Energy transfer efficiency} \approx 0.10 per level, leading to a typical 100% → 10% → 1% → 0.1% progression down the pyramid.

  • Rationale for energy loss includes respiration, heat loss, reproduction, excretion, and egestion (waste).

  • The energy lost as heat is often represented as LOST ENERGY AS HEAT on energy pyramids.

Ecological balance and carrying capacity

  • Ecological balance: a stable balance in the number of each species in an ecosystem; ecosystems can only support as many organisms as resources (food, water, shelter) allow.

  • Ecological balance can be disrupted by natural factors (food shortages, predators, diseases, droughts/floods) or by human factors (habitat destruction, pollution, climate change).

  • Populations may recover or go extinct depending on factors; examples of extinct or threatened species cited include Kwagga, Javan Tiger, Golden Frog.

  • Yellowstone National Park (USA) is cited as an example of interdependence in an ecosystem.

Quick reference: key terms mapped

  • Biosphere → Ecosystems → Communities → Populations → Individuals/Organisms.

  • Biotic factors vs Abiotic factors definitions.

  • Symbiosis types: Mutualism, Commensalism, Parasitism.

  • Trophic levels and energy transfer rule: ~10\% per level; energy pyramids illustrate this flow.

  • Ecological balance depends on resource availability and population size; influenced by natural and human factors.

Notable examples and prompts from the transcript

  • Biodiversity supports ecosystem services such as pest control, pollination, intercropping, and nitrogen fixation through various crop and tree species.

  • A community is all populations in an area; a population is all individuals of a species in an area.

  • Habitat describes the natural environment; the relationship between organisms and their habitat is a focus of ecology.

  • The energy flow diagrams show producers, primary/secondary/tertiary consumers, and decomposers; energy transfer efficiency is a central concept.

  • Exercises and activities (referenced as pages 38, 42, 55, and 61-64) reinforce concepts like biotic/abiotic factors, food chains, food webs, and energy pyramids.