Ecology: Ecosystems and Ecological Organization

Introduction to Ecology: Ecosystems Components

• All things originate from the earth and return to it—Menander

What is Science?

• Science is the process of gaining knowledge and investigating by making observations, posing questions, and testing through experimentation.

Scientific Method

• Hypothetico-deductive method
• Steps:
  • Observation (direct or indirect)
  • Problem definition (within the domain of science; not a "Why?" question)
  • Hypothesis formulation (temporary explanation)
  • Experimentation/data gathering (a series of experiments)
  • Theory formulation (not speculation)

Ecology and Levels of Organization of Matter

• Ecology (from Greek oikos, meaning home) is the study of how organisms interact with one another and their non-living environment (biotic and abiotic components).
• Studies natural connections in air, water, and soil.
• Matter organization:
  • Subatomic particles → Atoms → Molecules → Protoplasm → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere → Planet (Earth) → Solar System → Galaxy → Universe

Ecosystem Organization

• Organism: Composed of cells.
  • Eukaryotic vs. Prokaryotic
• Species: Groups of organisms similar in appearance, behavior, and genetics.
  • Sexual vs. Asexual reproduction
  • 1.5 million named species; likely 10-14 million more.
• Populations: Groups of individuals of the same species.
• Communities: Groups of different populations.
• Ecosystems: Communities of organisms and their environment.
• Biosphere: All ecosystems on Earth.

Subdivisions of Ecology

• Autecology: Study of individual organism life histories and behaviors adapting to environmental conditions.
• Synecology: Study of groups of organisms interacting as a unit.

Fields of Ecology

• Population Ecology: Study of population growth and fluctuations.
• Chemical Ecology: Study of chemical use in animal recognition, trail-making, courtship, and defense.
• Physiological Ecology: Study of individual organism responses to temperature, moisture, light, and environmental factors.
• Evolutionary Ecology: Study of natural selection and evolution of populations.
• Behavioral Ecology: Study of imprinting and instinct's role in animal social lives.

Scientists Who Made Contributions in Ecology

• Theophrastus (300BC): Studied the relationship between organisms and the environment; considered the father of botany.
• Ernst Haeckel: Father of ecology; coined the term ecology from Greek roots.
• Thomas Malthus (1766-1834): Studied populations.
• Charles Darwin (1809-1882): Developed the theory of natural selection.

Laws of Ecology

• 1. Law: Nature knows best; Principle: Balance of nature.
• 2. Law: All forms of life are important; Principle: Diversity and Stability.
• 3. Law: Everything changes; Principle: Change.
• 4. Law: Everything is connected to everything else; Principle: Interdependence.
• 5. Law: Everything goes somewhere; Principle: Pollution and Accumulation.
• 6. Law: Our's a finite resources; Principle: Finiteness of resources.
• 7. Law: There is no such thing as a free lunch; Principle: Energy.
• 8. Law: Nature is beautiful, and we are the stewards of God's creation; Principle: Stewardship

Major Ecosystem Components

• Abiotic components:
  • Temperature, water, moisture, light, soil, wind, precipitation, salinity, and time.
  • Tolerance limits for populations, limiting factors affecting population abundance.
• Biotic components:
  • Producers (plants),
  • Consumers (animals),
  • Decomposers (bacteria, fungi).
  • Biotic interactions (predation, competition, symbiosis, parasitism, commensalism).

Biotic Components of Ecosystems

• Producers (autotrophs): Source of all food; photosynthesis.
• Consumers (heterotrophs):
  • Aerobic respiration, Anaerobic respiration (methane, H₂S).
• Decomposers (matter recyclers): Release organic compounds into soil and water used by producers.

Producers: the First Trophic Level

• Autotrophs ("self-feeders"): Capture solar energy for photosynthesis producing sugars.
  • Green plants, cyanobacteria, algae.
• Chemosynthetic bacteria: Use geothermal energy in hot springs or deep-sea vents to produce food.

Photosynthesis: Function of Producers

• Light reaction: Uses light to produce ATP and NADPH; releases oxygen, happens in grana.
• Dark reactions (Calvin cycle): Uses ATP and NADPH plus CO₂ to produce sugar, happens in stroma.

Overall Reaction of Photosynthesis

• 6CO₂ + 12H₂O + light energy → C₆H₁₂O₆ + 6O₂ + 6H₂O

Consumers

• Primary consumers (second trophic level): Herbivores (deer, grasshoppers) that consume plants.
• Secondary Consumers (third trophic level): Carnivores that prey on primary consumers (wolves, rodents).
• Tertiary Consumers (fourth trophic level): Predators at the highest trophic level; consume secondary consumers (hawks, owls).
• Omnivores: Consume both plants and animals.

Cellular Respiration Overview

• Transformation of chemical energy (organic compounds) in food into usable chemical energy (ATP) for cells.
• Occurs in plants and animals; steps include glycolysis, Krebs cycle, and electron transport.

Detritivores and Decomposers

• Detritivores: Consume non-living organic matter (scavengers of waste or dead bodies); example: millipedes.
• Decomposers: Break down leaf litter and non-living materials; Enhance topsoil and recycle nutrients; example: fungi, bacteria.

Abiotic Components: Temperature

• Affects living things in two ways: (1) affects internal processes; (2) affects behavior in ecosystems.
• Living things function optimally within specific temperature ranges.
  • Minimum temperature: Lower limit, where organisms can still function.
  • Maximum temperature: Highest limit, where organisms can still function.
  • Optimum temperature: Ideal temperature, where organisms function best.
  • Tolerance limits for populations.

Abiotic Components: Water

• Plants and animals maintain a favorable water balance.
• Plant adaptations:
  • Xerophytes (arid conditions): Succulent tissue.
  • Hydrophytes (aquatic): Floating/submerged, air spaces.
  • Halophytes (marine): Succulent tissue.

Abiotic Components: Light

• Main source of energy in ecosystems.
• Important for photosynthesis and the formation of vitamin D in animals.
  • Shade tolerance: Ability of plants to survive & grow in shade.
  • Photoperiodism: Reactions to changes in day length.
  • Ozone: Protects Earth from excessive solar radiation, ozone depletion: Caused by CFCs & NO.

Abiotic Components: Soil

• Formed by mechanical or chemical weathering of rocks plus addition of humus.
• Soil texture: Clay (fine particles), sand (coarse particles), silt (medium), loam (mixture).
• Soil moisture (water content): Affected by texture, rainfall, slope, and underlying rock types.
• Soil acidity: Affected by the presence of lime or granite.
• Soil structure: arrangement of soil particles, creating peds (larger structures) for water and gas drainage.
• Soil color: iron affects color (reddish/brownish or gray).
• Soil profile: Layers (horizons) differ in composition; example: O, A, B, C, R horizons.

Abiotic Components: Wind or Air

• Wind is an agent for pollination and seed dispersal.
• Transpiration in plants and evaporation in animals occur faster in the presence of wind.
• Strong winds can damage ecosystems.

Abiotic Components: Time

• Ecosystems are dynamic and affected by time.
• Factors influenced by time include food-hunting-gathering abilities (affecting predator-prey relationships) and reproductive cycles & mate-finding in organisms. - Important for organisms' movements and locomotion based on time.

Limiting Factors Influence on Land and H₂O

• Terrestrial: Sunlight, temperature, precipitation, soil nutrients, fire frequency, wind, latitude, and altitude.
• Aquatic/Marine: Light penetration (water clarity), water currents, dissolved nutrient concentrations, dissolved oxygen concentrations, and salinity.