Biology Ecology Review: Cycling of Materials and Ecosystems

Page 1

• Topic: Cycling of materials in ecosystems (Earth as a closed system).

• Water cycle: Evaporation, Condensation, Precipitation, Percolation, Transpiration.

• Carbon cycle: CO₂ removed from atmosphere by photosynthesis to make glucose (C₆H₁₂O₆); plants store carbon as carbohydrates; plants respire returning CO₂; carbon moves through food chains as organisms are eaten; respiration returns CO₂ to the air; decay and detritus recycling; combustion of wood and fossil fuels releases CO₂ back to the atmosphere.

• Key idea: Matter is recycled through living and non-living spheres; cycles rely on organisms and processes like photosynthesis, respiration, decay, and combustion.

• Snapshot formulas/elements: glucose in plants is a storage form; photosynthesis uses CO₂ to form carbohydrates.

Page 2

• Materials cycle continues: when organisms die or waste is produced, detritus feeders and microorganisms recycle materials back into the environment.

• Decay is faster in warm, moist, aerobic conditions; microorganisms drive decay.

• In a stable community, inputs and outputs of materials are balanced, keeping nutrient availability relatively constant.

• Summary concept: The cycle is a CONSTANT CYCLE of matter through living systems and the environment.

Page 3

• Abiotic vs Biotic factors:

  • Abiotic: non-living factors (e.g., moisture, CO₂ level, light intensity, temperature, wind, oxygen, soil pH/minerals).

  • Biotic: living factors (e.g., predators, pathogens, competition, food availability).

• Environmental changes affect population sizes by altering abiotic or biotic factors.

• Examples: decreases in light, temperature, or CO₂ reduce photosynthesis and plant growth, lowering population sizes.

• Sensor tools: light meter (lux), pH meter (pH scale), thermometer (°C), humidity sensor.

Page 4

• Key ecological terms:

  • Habitat: where an organism lives.

  • Population: all individuals of one species in a habitat.

  • Community: populations of different species in a habitat.

  • Ecosystem: interaction of a community with its non-living environment.

• Organisms compete for resources (light, space, water, minerals, food, mates).

• Interdependence: species depend on others for food, shelter, pollination, seed dispersal.

• Stable communities have balance among species and environmental factors; changes can have far-reaching effects.

Page 5

• Adaptations: features that help survival in different environments; can be structural, behavioural, or functional.

  • Structural: body features (e.g., fur, camouflage, body shape) to avoid predators or conserve heat.

  • Behavioural: actions (e.g., migration, hibernation) that improve survival.

  • Functional: internal processes (e.g., metabolism, water conservation strategies).

• Examples: Arctic fox camouflage, desert water conservation, migration; extremeophiles adapted to extreme conditions.

Page 6

• Food chains and energy flow:

  • Producers: make own food (green plants/algae) via photosynthesis; biomass stored as plant matter.

  • Primary consumers eat producers; Secondary consumers eat primary; Tertiary consumers eat secondary.

  • Predators vs. prey: prey increases predator response; predators reduce prey, creating interdependence.

• Biomass/energy transfer:

  • Energy transfer between trophic levels is limited; roughly around 10% of energy is transferred to the next level; the rest is lost as heat, movement, or undigested material.

  • Biomass transfer efficiency can be expressed as \text{Efficiency} = \frac{\text{Biomass at next level}}{\text{Biomass at previous level}} \times 100.

• Decomposers break down waste and remains, returning nutrients to the ecosystem.

Page 7

• Abundance and distribution: measured with quadrats.

• Quadrats: square frames (e.g., 1 m²) used to sample a known area.

• Practical steps:
  1) Place a 1 m² quadrat at a random point in a sample area.
  2) Count organisms inside the quadrat.
  3) Repeat several times to get a mean.
  4) Do the same in a second sample area and compare means.

Page 8

• Transects: assess distribution along a line.

• Practical approach:
  1) Stretch a line across the study area.
  2) Collect data along/along intervals (e.g., count organisms touching the line or place quadrats at intervals).
  3) Estimate percentage cover or abundance along the line.

Page 9

• Decay and environmental change:

  • Environmental changes alter distribution by affecting water availability, temperature, and pollutant levels.

  • Water cycle: energy from the Sun causes evaporation, vapor transport, condensation into clouds, precipitation, and return to oceans.

  • Lichens as pollution indicators: Foliose (tolerant of pollution) and Crustose (more pollution-sensitive) indicate air quality.

Page 10

• Decay and energy flow:

  • Decay is decomposition of organic matter by microorganisms; compost is decomposed material used as fertiliser.

  • Conditions for decay: water, oxygen, warmth.

  • Biogas: anaerobic decay produces methane; produced in digesters (batch vs continuous).

Page 11

• Investigating decay (example experiment):

  • Enzyme lipase digestion of milk as a model for decay rate.

  • Rate is connected to time for a colour change to stop (pink to colorless) at a given temperature.

  • General rate concept: \text{Rate} = \frac{\text{amount decomposed}}{\text{time}}; experiments vary temperature to see effects on rate.

Page 12

• Biodiversity and waste management:

  • Biodiversity: variety of species; essential for ecosystem stability and human survival.

  • Human actions (waste, deforestation, warming) reduce biodiversity.

  • Population growth increases resource use and waste; pollution affects water, air, and land.

Page 13

• Global warming and deforestation:

  • Greenhouse gases (CO₂, methane) trap heat, altering Earth's energy balance.

  • Consequences: climate change, shifts in species distribution, ice melt, sea-level rise, rainfall changes.

Page 14

• Deforestation and peat bogs:

  • Deforestation reduces CO₂ uptake and biodiversity; burning trees releases CO₂.

  • Peat bogs store carbon; draining/burning releases CO₂.

  • Loss of habitat worsens biodiversity loss.

Page 15

• Maintaining biodiversity: programs and policies

  • Breeding programs to prevent extinction.

  • Habitat protection and restoration (hedgerows, field margins).

  • Government regulations to limit deforestation and pollution.

  • Conflicting pressures: costs, livelihoods, food security, development.

Page 16

• Trophic levels and energy flow basics:

  • Trophic Level I: Producers (plants/algae).

  • Level II: Primary consumers (herbivores).

  • Level III: Secondary consumers (carnivores that eat herbivores).

  • Level IV: Tertiary consumers (carnivores that eat other carnivores).

  • Apex predators: top of the chain with no natural predators.

  • Decomposers (bacteria, fungi) recycle nutrients from waste and dead matter.

Page 17

• Biomass transfer and pyramids:

  • Pyramids of Biomass show the mass of living material at each trophic level.

  • Each successive level typically has less biomass due to energy loss, so bars shrink up the chain.

  • Construct to scale if numerical data are given; label each level.

Page 18

• Biomass and energy efficiencies:

  • About 1% of solar energy is captured by plants as biomass (photosynthesis).

  • About 10% of energy/biomass is transferred to the next trophic level; the rest is lost as heat or used for metabolism and movement.

  • Biomass transfer efficiency . {Efficiency}=\frac{\text{Biomass at next level}}{\text{Biomass at previous level}}\times100 .

Page 19

• Food security and farming:

  • Threats: growing population, changing diets, pests/pathogens, high farming costs, conflict.

  • Overfishing reduces fish stocks and affects ocean food chains.

  • Solutions: sustainable fishing (quotas, mesh size rules), temperature-controlled rearing, improved farm practices.

Page 20

• Biotechnology in food and medicine:

  • Mycoprotein: fungal-derived protein used as food.

  • Insulin production: bacteria engineered to produce human insulin via recombinant DNA.

  • Steps (high level): extract plasmid, cut insulin gene with restriction enzymes, insert insulin gene into plasmid, transform bacteria, culture in controlled vats to produce insulin.

Page 21

• GM crops and biotechnology ethics:

  • GM crops can be pest-resistant and more drought-tolerant; potential to improve nutrition.

  • Controversies: dependence on seed companies, unequal access, ecological risks.

  • Biotechnology definition: manipulating living systems/processes to produce useful products.

• Takeaway: Biotechnology offers tools for food security but requires careful management of risks and equity.