Matter and Energy Cycles, Population Dynamics, and Growth Strategies

Matter and Energy

Matter

• Atoms and molecules
• Everything that has mass and volume
• Law of Conservation of Matter: Matter is neither created nor destroyed, it only transforms.

Energy

• Light, chemical, and heat
• Ability to perform work
• Law of Conservation of Energy: Energy is neither created nor destroyed, it only transforms.
• Second Law of Thermodynamics: Entropy tends to increase in the universe.

Cycles of Matter

We can study matter by the path of the atoms and molecules that constitute it. We consider that each trophic level is a compartment, through which the atoms pass.

Energy Flows

• Energy passes from one level or compartment to another, through trophic networks.
• In each step, a significant part of energy is lost as heat or entropy.
• Energy cycles are not closed and continuous.
• For there to be energy, there is a constant input, through solar radiation.
• The number of levels cannot be high.

Carbon Cycle

• Respiration
• Photosynthesis
• Sedimentation
• Lithification
• Volcanic emissions
• Air-water diffusion

Nitrogen Cycle

• Fixation
• Nitrification
• Ammonification
• Assimilation
• Excretion
• Decomposition
• Denitrification
• River and groundwater transport

Phosphorus Cycle

• Weathering
• Decomposition
• Excretion (guano)

Sulfur Cycle

• Utilization
• Decomposition
• Precipitation
• Volcanic eruptions

Population Dynamics

• Population changes over time.
• They depend on factors:
  • Internal: from the population itself.
  • External: environmental factors and relationships with other species.

Factors

• Population size (N)
• Births (B)
• Deaths (D)
• Population growth (B - D). N1 = N0 + (B - D)
• Birth rate (BR) BR = B/N x 100
• Death rate (DR) DR = D/N x 100
• Biotic potential or growth rate (r) r = BR - DR
• Emigration rate
• Immigration rate

Population Growth Strategies

• Growth depends on environmental factors and resources.
• There are two types of growth:
  • r-Strategists: Exponential growth or population explosion
  • K-Strategists: Stable growth.

Demographic Explosion

• Exponential growth: J-shaped graph
• Without environmental limits and with optimal conditions.

Stable Growth

• Logistic or sigmoid growth: S-shaped graph
• With load capacity (K): depends on the species and the environment

Population Size

• According to the dynamics, we can establish three types:
  • Growing population
  • Stabilized population
  • Regressing population.
• Demographic or age pyramids:
  • They inform about the structure of different populations
• Space distribution:
  • Uniform or regular
  • Random
  • Aggregate