Chapter 3 – Adaptations to Terrestrial Environments:

  • Nutrients and water is obtained from the soil for most terrestrial plants
  • Photosynthesis: Sunlight provides the energy for this process
  • Adaptations to terrestrial environments poses challenges for the balance of water, salt, and nitrogen
  • Adaptations to different temperatures allow for terrestrial life to exist all around the planet

Soil nutrients:

  • Carbohydrates used to fuel survival and growth for plants
  • Oxygen, carbon, and hydrogen to create carbohydrates
  • Require nitrogen, phosphorus, calcium, and potassium
  • Involved in making proteins, nucleic acids, and other essential organic compounds
  • Ions dissolved in water can provide other nutrients
  • Held in soil
  • Lack of nitrogen tends to result in the limitation of plant production in terrestrial environments
  • Water potential:measure of water’s potential energy
  • Factors affecting potential:
  • Gravity
  • Pressure
  • Osmotic potential
  • Matric potential: Potential energy generated by attractive forces between water molecules and soil particles
  • Value becomes more negative with water scarcity
  • Also known as matrix potential
  • Water and soil molecules are electrically charged, causes attraction
  • Explains why water retention is possible in soil regardless of gravities role
  • Water molecules closest to the surface adhere more strongly than other areas
  • Plant roots take up excess
  • Field capacity: Maximum amount of water held by soil particles against force of gravity
  • Water always moves from high potential, more positive, to low potential, more negative
  • Water extractions for plants – water potential must be lower than that of the soil
  • Wilting point: Water potential at which most plants can no longer retrieve water from the soil
  • This value is roughly -1.5MPa

Osmotic pressure and water uptake:

  • Salinization: Process of repeated irrigation, which causes increased soil salinity
  • Caused by small amounts of water used to hydrate plants
  • Cohesion: Mutual attraction among water molecules
  • Hydrogen bonds cause water to move up xylem of plant
  • Pull other water molecules with it
  • Root pressure:Osmotic potential in roots of plants draws in water from soil and forces it into xylem elements
  • Transpiration: process by which leaves can generate water potential as water evaporates from surfaces of leaf cells into the air spaces within the leaves
  • Cohesion-tension theory: Mechanism of water movement from roots to leaves due to water cohesion and water tension

Sunlight provides the energy for photosynthesis:

  • Stomata: small openings on the surface of leaves
  • Serve as points of entry for CO2 and exit points for water vapour
  • Closes stomata to reduce water loss
  • Occurs when water becomes scarce
  • Prevents CO2 from entering leaves
  • Electromagnetic radiation: Energy from the sun
  • Packed in photons
  • Positively charged
  • Highest energy photon = highest frequency , shortest wavelengths
  • Visible light: wavelengths between infrared and ultraviolet radiation that are visible to the human eye
  • Photosynthetically active region: wavelengths of light that are suitable for photosynthesis
  • Range between 400nm, violet, and 700nm, red
  • Chloroplast: Specialized cell organelles found in photosynthetic organisms
  • General photosynthesis equation
  • Two cycles involved
  • Light reactions
  • Dependent on light energy
  • Absorption of light and production of high-energy compounds and oxygen
  • Calvin cycle
  • Homeostasis: Organisms ability to maintain constant internal conditions in the face of varying external environments
  • Negative feedbacks: Action of internal response mechanisms that restores a system to desired state
  • Balance of water and salt are a big obstacle in terrestrial environments
  • Production of urea as a metabolic by-product for nitrogen
  • Dissolves in water
  • Conserves water through this method, good because water is scarce in terrestrial environments
  • Temperature of the environment exceeds temperature of organism results in the organism gaining heat
  • Radiation: Emission of electromagnetic energy by a surface
  • Primary source form the Sun
  • Conduction: Transfer of kinetic energy of heat between substances that are in contact with one another
  • Dependent on three factors:
  • Surface area
  • Resistance to heat transfer
  • Temperature difference between organism and surrounding
  • Convection: Transfer of heat by movement of liquids and gases
  • Thicker/ bigger boundary layer results in slower heat transfer
  • Hot are moves toward cold air
  • Evaporation:Transformation of water from liquid to a gaseous state with the input of heat energy
  • Helps remove heat from surface
  • Loss of water from organism
  • Thermal inertia: Resistance to change in temperature due to large body volume
  • SA= L2
  • V=L3
  • Larger = volume grows faster than surface area
  • Metabolic rate increases faster than surface area
  • Larger individuals have low surface area to volume ratio
  • Lose and gain heat across surfaces less rapidly than small individuals
  • Higher risk of overheating
  • Heat up more slowly though
  • Thermoregulation: Ability of organism to control the temperature of its body
  • Homeotherm:Organism that maintains constant temperature conditions within its cells
  • Biochemical reactions become more efficient
  • Poilkilotherm:Organism that does not have constant body temperatures
  • Ectotherm: Organism with body temperature that is largely determined by its external environment
  • Have low metabolic rates
  • Reptiles, amphibians, plants, small body sizes – insects
  • Environment determines temperature within
  • Endotherm: Organism that can generate sufficient metabolic heat to raise body temperature higher than external environment
  • Most mammals and birds
  • Regulation of internal temperatures between 36 to 410C
  • Accelerated biological activity in colder climates
  • Blood shunting:Adaptation that allows specific blood vessels to shut off so less of an animal’s warm blood flows to the cold extremities
  • Redirection of blood flow from extremities
  • Countercurrent circulation to combat colder environments