Unit 4: The World Around Us - Comprehensive Ecology and Environmental Science Notes
Understanding Ecosystems and Environments
Definition of an Ecosystem: An ecosystem consists of a community or group of living organisms that coexist and interact within a specific environment. It is a physically defined space comprising two inseparable components:
The Biotope (Abiotic): This refers to the physical environment characterized by specific abiotic factors. These include physical and chemical traits such as climate, temperature, humidity, pH levels, and the concentration of nutrients.
The Biocenosis (Biotic): This is the set of living organisms, including animals, plants, and micro-organisms, that are in constant interaction and exist in a state of interdependence.
Definition of an Environment: The environment refers to the surroundings or conditions in which a person, animal, or plant lives or operates. It encompasses everything on Earth, including both living (biotic) and non-living (abiotic) elements.
Functions of the Environment:
Providing a supply of resources.
Sustaining life processes.
Assimilating waste products.
Enhancing the overall quality of life.
Major Current Environmental Problems:
Global warming.
Ozone layer depletion.
Air and water pollution.
Destruction of forests (deforestation).
Biotic and Abiotic Factors
Biotic Factors (Living): These include all life forms that interact within an ecosystem.
Examples: Fungi, Plants, Animals, Protists, Archaea, and Bacteria.
Abiotic Factors (Non-Living): These are the physical and chemical components of the ecosystem.
Examples: Soil, Light, Water, Air, Humidity, and Temperature.
Ecological Roles and Classification of Organisms
Ecological Roles (Trophic Levels):
Producers (Autotrophs): Organisms that make their own food from inorganic molecules (e.g., through photosynthesis). They form the base of every food chain.
Consumers (Heterotrophs): Organisms that must eat and digest other organisms to obtain energy.
Primary Consumers: Consist of herbivores that eat producers.
Secondary Consumers: Carnivores that eat primary consumers.
Tertiary Consumers: Carnivores that eat secondary consumers (sometimes called apex predators).
Decomposers (Saprotrophs): Organisms such as fungi and bacteria that break down dead plants and animals into simpler forms of matter, recycling nutrients back into the soil and increasing fertility.
Example Food Chain Sequence:
Grass (Producer) $\rightarrow$ Ants (Herbivore/Primary Consumer) $\rightarrow$ Lizard (Carnivore/Secondary Consumer) $\rightarrow$ Rattlesnake (Carnivore/Tertiary Consumer) $\rightarrow$ Fungus (Decomposer).
Scientific Classification (Linnaeus System):
Developed by Carl Linnaeus, this system groups living things based on physical structures and characteristics.
Hierarchical Divisions: Kingdom, Phylum, Class, Order, Family, Genus, Species. (Mnemonic: "Keep Pond Clean Or Frogs Get Sick").
The Five Kingdoms:
Animals: Multicellular, no cell walls or chlorophyll, heterotrophic.
Plants: Multicellular, have cell walls and chlorophyll, autotrophic.
Fungi: Multicellular, have cell walls, no chlorophyll, saprotrophic.
Prokaryotes: Unicellular, no nucleus (e.g., bacteria).
Protoctists: Unicellular, contains a nucleus.
Binomial Nomenclature:
A system where every species is given a unique two-word scientific name consisting of the Genus (capitalized) and the species (lowercase).
The name is always written in italics or underlined. Example: humans are Homo sapiens.
Importance of the Binomial System:
Global Standardization: Provides a common language for scientists regardless of local language.
Eliminates Ambiguity: Prevents confusion caused by common names (e.g., "starfish" aren't true fish).
Shows Relationships: Species sharing a genus name are closely related and share a recent common ancestor.
Stability and Accuracy: Allows for consistent tracking of research and data.
Bio-Ecological Terminology
Autotrophic Feeder: Makes its own food from inorganic molecules, typically using light through photosynthesis.
Heterotrophic Feeder: Obtains energy by eating and digesting other organisms.
Saprotrophic Feeder: Feeds on decaying matter.
Photosynthesis: The process of using light, , and water to produce glucose.
Species: A group of organisms that can breed together to produce fertile offspring.
Habitat: The specific location where an organism lives.
Competition: The interaction where organisms vie for limited resources.
Energy Flow in Ecosystems
Source of Energy: All ecosystem energy originates from the Sun. Sunlight provides the energy required for photosynthesis.
Energy Transfer Logic:
Energy is stored as organisms eat others.
Energy is used for life processes: movement, cellular respiration, and reproduction.
Energy is lost at each level primarily as heat.
The Rule: On average, only of the energy stored at one trophic level is transferred to the next. The remaining is used for metabolic processes or dissipated as heat.
Trophic Pyramids:
Pyramid of Energy: Always upright because energy is lost as heat at every transfer (e.g., ).
Pyramid of Biomass: Represents the total dry weight of organisms. Usually upright, but can be inverted in aquatic systems.
Pyramid of Numbers: Shows the number of individuals. Can be upright, inverted, or spindle-shaped.
Inverted Pyramid Example: A single large tree (one producer) supporting hundreds of insects (many primary consumers).
The Carbon Cycle
Importance of Carbon:
Regulates Earth's temperature and makes life possible.
Key component of food and a primary fuel source.
Cycle Processes:
Atmospheric Carbon: in the atmosphere is absorbed by plants for photosynthesis.
Underground Storage: Dead organic matter buried over millions of years becomes fossil fuels (coal and oil). Majority of carbon stores are in rocks and sediments ( billion metric tonnes).
Release Mechanisms: is released via human and animal respiration, combustion of fossil fuels, decomposition of organic waste, and volcanic activity.
Carbon Balance Factors:
Reduction factors: Photosynthesis, dissolving in oceans, formation of limestone/chalk, and formation of fossil fuels.
Increase factors: Respiration, combustion of fuels, and decomposition of carbonate rocks via volcanoes.
Human Impact and Mitigation
The Greenhouse Effect:
Natural Effect: A life-sustaining process where atmospheric gases trap sun heat to maintain temperature.
Human Enhanced Effect: Unnatural acceleration caused by high gas concentrations, leading to Global Warming.
Carbon Dioxide (): The most significant long-lived greenhouse gas, responsible for roughly three-quarters of human-caused warming.
Causes of Global Warming: Deforestation, industrialization, burning fossil fuels, automobile pollution, and thermal power plants.
The Ozone Layer:
Located in the stratosphere ( high). Absorbs UV light: of UV-A, of UV-B, and of UV-C.
CFCs (Chlorofluorocarbons): Chemicals discovered in the 1980s as the primary cause of ozone depletion ("ozone holes").
Deforestation: Driven by overpopulation and agricultural expansion. Results in biodiversity loss and the release of when trees are burned.
Conservation and Mitigation Strategies:
Wildlife Conservation: Protecting habitats, preventing extinction, and stopping illegal trafficking.
Recycling: Recycling one aluminum can saves of the energy needed for a new one.
Solar Power: Each kilowatt-hour offsets over of .
LED Bulbs: Use of the electricity of traditional bulbs; can reduce carbon footprint by tons per year.
Planting Trees: One tree's shade can save the energy equivalent of air conditioners running for hours a day.
Symbiotic Relationships
Symbiosis: A close relationship between species where at least one benefits.
Mutualism: Both partners benefit (). Examples: Bees and flowers; digestive bacteria in humans.
Commensalism: One partner benefits while the other is unaffected (). Examples: Barnacles on whales; hermit crabs using dead shells.
Parasitism: One partner (parasite) benefits by harming the other (host) (). Examples: Tapeworms, ticks, and fleas.