Chapter 4 - Ecology

two options for coping with environmental change:

• tolerance: the ability to SURVIVE stressors

• avoidance: response to stressors that lessent heir effect via some behavior/ physiological activity that minimizes exposure to the stress

physiological ecology: study of interactions between organisms and physical environemtn that influence survival and persistence

the potential geographic range of a species is determined by the physical enviornment

• affects ability to obtain energy and resources

• extreme environmental conditions (physical tolerance limits)

actual distribution doesnt equal potential distribution

climate envelope: range of climate variables (T, humidity, precipitation, SR) that are associated with geographic distribution

acclimation: adjustment of physiology, morphology, or behavior to decrease effect of environmental change and decrease stress (indivudal level)

adaptions: evolutionary change of traits for increased fitness; increase in frequency in populations over time

ecotypes: populations with adaptions to unique environments

• can eventually become separate species

adaptions to environmental stress can cary among poulations

dormancy: a state in which little or no metabolic activity occurs

internal temp is determined by balance between energy gained and lost to/ from environment

biochem rxns are T sensitive - related to catalyst optimal T

• at high T, enzymes denature

• some species produce isoenzymes with diff T optima to acclimate to environmental change

• T also determines rate of processes 

• T influences water availability, impacting terrestrial organism

conduction: direct heat transfer form warmer to cooler

convection: latent heat transfer; protection from SR lower temperature

plants:

• energy inputs: sunlight and IR from surrounding objects; conduction and convention

• energy losses: emission of IR to surrounding environment; conduction and convention (cooler air); transpiration and surface evap (evapotranspiration)

• change in rate of transpiration water loss, leaf color, lead orientation, changes in surace roughness

• pubescnece: presence of ligh colored hairs on leaf -> decreases SR absorbed, but also may decrease effectiveness of conducive heat loss

• small, smooth leaves have small boundary layers and lose heat better than large/ rough leaves

animals: can generate heat internally

• delta(H- animal) = SR + IR(in) + IR (out) +/- H(conv) +/- H(cond) - H(evap) + H(metabolic)

• evaporative cooling: sweating, panting, licking body

• ectotherms: regulate body T primarily via energy exchange with environment

• endotherms: rely primarily on internal heat generation

• larger SA relative to volume = increased heat exchange, but harder to maintain constant internal T

  • SA to volume ratio decreases as body size increases

• avoidance: migration, movement to local microhabitats (burrowing)

• tolerance: minimizing damage from ice formation in cells and tissues

• cost of endotheric: increased demand for food to supply energy to support metabolic heat production

  • smaller = higher metabolic rate = more energy required = increased feedcing rates

• thermoneutral zone: range of T over which endogtherms maintain constant BMR

• lower central T: T at which heat loss of endotherm triggers metabolic heat generation

• torpor: dormancy that allows small endotherms to lower critical T and metabolic rate

• hibernation: torpor lasting for several weeks in winter - possible only for animals that have access to enough food and can store enough energy reserves

organisms must maintain suitable water balance and solute (salt) balance

somotic potential: energy associated with dissolved solutes

water potential: overall energy status of water in a system

barries that increase resistance to heat loss: waxy cutivcle of plants, insects; skin of animals

single celled organisms water balance is dependent on water potential of surrounding environment (mostly osmotic)

• osmotic adjustement: respons that changes solute concentration and thus osmotic potential

plants: rigid cell wall -- cellulose--facilitate positive turgor pressure

• take up water form sources with higher water potential than their own

• cell membranes act as solute filter

• terrestrial: get water form soil via roots and mycorrhizal fungi

• daily cycle of nightime rehydrateion and daytime dehydration

marine inverts are isoosmotic to seawater

marine vets may exchange water and salt with environment via drinking, eating, and gills

freshwater animals: lower evaporative water loss and exposure to water stress via sin or increasing water intake

• inverts: higher tolerance for water loss than verts; amphibians higher tolerance than mammals and birds

• amphibians: gas exchange for water; thin skin with lower resistance to water loss

• reptiles: thick skin = barrier for water loss

dispersal: movement from an area of origin/ high population density

• can lead to range expansion

• core of range is typically most ideal (evolved from there)

limiting factor: limits growth of an organism

tolerance limit: min and max levels a species can withstand

climate envelope: range of climates where a species can occur

niche: habitat and resource used by a species

• physical requirements and biotic interaction

• can go under evolutionary change -> range expansion

generalist: broad niche; variety of habitat and food

specialist: narrow niche; specific habitat and feed off specific things

specialists can occupy niches not available to generalists

fundamental niche: all potential roles and range for a species

realized niche: subset of suitable habitat where a species exists -- restricted by competition

T influences fluidity of cellular membranes: too high = too liquid = falls apart; too low = too rigid = brittle

solution: change concentration of types of lipids

• higher unsaturated = higher fluidity

animals use steroids as fluidity buffers

water emergent properties are important for life:

• expands when frozen

• cohesion and adhesion: high surface tension; capillary action - important for movement of water in plants

• high specif heat: energy required to change something’s T; water high @4.18 J/g per C

  • large bodied organisms are more resistant to T change

• universal solvent: can dissolve positives and negative; mobilizes reactants; can also act as a reactant in metabolic rxns 

osmosis: water travels from high to low potential

• hypotonic: more solutes in cell (lysed
  isotonic: same in and out

• hypertonic: more solutes in solution (shriveled)

organisms maintain correct fluid balance via osmoregulation

• marine invers: conform to osmotic conditions

• freshwater fish: water enters body; produce dilute urine; transport salt to gils

• marine fish: water leaves body; max water intake

• marine fish: scant, concentrated urine and nasal glands to remove slat

• sea mammals: scant, concentrated urine and avoid drinking seawater

• plants: filter, excrete, or store extra salts

• land animals: use mechanisms to decrease water loss

• plant adaptations: waxy cuticle, leaves die back in dry season; decreased leaves and photosyntehic stems; hairs and trichomes; fleshy stems for water storage; shrunken stomata; deep roots; CAM photosynthesis