Adaptations to the Physical Environment

Adaptations to the Physical Environment

Chapter Overview

  • Title: Ecology: Evolution, Application, Integration

  • Author: David T. Krohne

  • Copyright: © 2018 Oxford University Press

How Do Environmental Factors Limit Growth and Survival?

  • Physical Resources:

    • Food

    • Physical (abiotic) Factors:

    • Water

    • Temperature

  • Growth and survival is optimal in a specific range: referred to as "the sweet spot." Under certain conditions, growth is favored.

Shelford’s Law of Tolerance (1913)

  • Definition: There are upper and lower limits to the physical factors that an organism can tolerate.

  • Key Points:

    • Different species experience different limiting factors and have unique ranges of tolerance.

    • Tolerance limits visualized through Venn diagrams for various species.

    • Deleterious effects occur when any physical factor lies outside the tolerance range. Does this mean species like become deleted

    • Example: Drought, flood, hurricane.

    • Fitness compromises result if an organism cannot maintain internal homeostasis in suboptimal conditions.

    • Homeostasis Definition: The ability to maintain physiological systems within certain limits across a range of external conditions. The ability to maintain your physiological systems in the midst of your changing environment.

Role of Evolution in Shaping the Tolerance Curves

How does evolution affect an organism’s tolerance in its environment?

  • Tolerance Curve Representation:

    • Graphically represents the tolerance limits of an entire population.

    • This curve is the summation of the tolerances of individual organisms within the population. It showcases the range of conditions under which the population can thrive, displaying the minimum and maximum thresholds for factors such as temperature, moisture, and nutrient availability.

  • Genetic Variation in Tolerance:

    • Individual tolerances may vary based on genetic predispositions.

  • Evolutionary Implications:

    • Environmental changes affect individuals' ability to tolerate new conditions.

    • Genetically advantageous traits are selected for, shifting the population’s tolerance limits. (Traits that are able to survive in the new conditions)

    • Directional Selection: Natural selection that drives a shift in population tolerance based on environmental changes.

      • (ex?) Bell curve shift over to organisms that are better suited for certain environmental conditions ex) Temperature

Environmental Conditions Change Over Time

  • Predictable Temporal Variability:

    • Events that follow cyclical patterns:

    • Seasonal changes

    • Diurnal patterns

    • Tidal movements

  • Unpredictable Environmental Changes:

    • Variability in conditions poses significant challenges to an organism's fitness.

    • Adaptation is easier in stable environments compared to variable ones.

Upland Habitats Patterns

  • Description: Upland habitats tend to be cooler and wetter compared to adjacent lowlands.

  • Species Adaptations:

    • Upland species exhibit specific physiological adaptations to endure cooler temperatures.

    • Examples of Upland Habitats:

    • Upland coniferous forests in Southern California

    • Upland tropical rainforest in Peninsular Malaysia

Historical Climate Cycles

  • Glacial Cycles Impact:

    • Glacial maximum: Cold temperatures permit the expansion of cool-weather-adapted forests into lowlands.

    • Glacial minimum: Warmer temperatures cause these forests to retreat upslope.

      • Cycle between glacial minimum and maximumresults in significant shifts in biodiversity, leading to the adaptation of species to varying climate conditions and the eventual reestablishment of ecosystems as temperatures stabilize.

  • Climatic Cycling:

    • Occurred 50 times over the last 2.5 million years.

    • Upland regions have been fragmented into "islands" for only 3.5% of this time.

Genetics are effected due to climatic cycling.

Case Studies of Tolerance and Adaptation

  • Ovophis convictus (Egg-laying pitviper):

    • Maintained genetic identity across disjunct populations despite 100 km separation.

    • requires interbreeding, during the last glacial maximum. Species upland moved downslope during higher temps.

  • Pseudocalotes Dragon Lizards:

    • Adapt to cooler temperatures on mountain tops, evolve into new species in isolated conditions.

    • Each isolated population evolved into new species

Pleistocene Drying Trends

  • Impact on Species:

    • Species were confined to upland habitats due to evaporating water resources following drying trends.

    • Those unable to adapt went extinct.

  • Examples:

    • Large-blotched Salamanders: Different species on various mountain tops.

    • Mountain Kingsnakes: Potentially different species across San Jacinto Mountain and Laguna Mountain. Important knowing different species in order to protect them.

The Principle of Allocation

  • Definition: Adaptations to address one challenge can limit adaptations to others (Levins, 1968).

  • Trade-offs in Adaptation:

    • Every adaptive solution has associated costs and benefits, influenced by historical constraints.

    • When you adapt in one way, it limits your ability to adapt in other ways.

NATURE’S TRADE-OFFS - Historical Constraints

  • Cheetahs:

    • Adapted for speed; lack strength and endurance.

    • Tradeoff- poor endurance, can’t defend prey > gave up ability to defend prey.

  • Turtles:

    • Morphologically constrained, unable to adapt significantly beyond their shell design.

    • cant adapt beyond their shell

  • Sea turtles:

    • Adaptations include a hydrodynamically-shaped shell for swimming and beak-like jaws for feeding.

    • Trade off- poor performance on land, must go back to land to lay eggs.

2 Categories of Adaptive Responses to Environmental Changes

  • Avoidance Responses:

    • Behavioral Avoidance: Migration, seasonal movement based on environmental cues.

    • Metabolic Avoidance: Includes metabolic rate depression, hibernation, estivation, and torpor.

  • Adaptations:

    • Traits matching organisms’ tolerance limits through various mechanisms:

    • Morphological adaptations

    • Physiological adaptations

    • Biochemical adaptations

Specific Examples of Avoidance Adaptations

  • Metabolic Avoidance Techniques:

    • Dormancy: Seen in seeds and spores, with certain species capable of indefinite dormancy until conditions improve. Can sit for a while until environment in favorable

    • Examples:

    • Southern Pacific Rattlesnake (Crotalus helleri) uses hibernation for survival in cold.

    • mountain population takes on black color to absorb heat

    • lowland population dont need to hibernate of take on more melanin.

  • Physiological Changes:

    • Populations change their hibernation behaviors based on climatic variations.

    • Torpor

      • typically response to food deficiency or heat

      • ex) Spadefoot Toad in American Southwest, will go into metabollic arrest when the ground isnt moist goes into estivation

Hibernation - Benefits and Costs

Obligate hibernators

  • must go into hibernation each year

  • accumulative significant fat reserves

  • metabollic rate and body temp drop not as deep as obligatory hibernators

Faculatative hibernators

  • Quickly enter torpid state

  • quickly aroused by external stimuli

  • drop in metabol

  • Benefits:

    • Avoids harsh environmental conditions and improves predator avoidance.

    • Generally, higher survival rates than non-hibernators. (Spreading genes)

  • Costs:

    • Energy expenditures and risks of mortality while migrating or interacting with ecological pressures. (Not spreading genes out)

Behavioral Avoidance Adaptations - Migration

  • Types of Migration:

    • Obligate Migration: Species that migrate without choice.

    • Facultative Migration: Migration that may not occur every year.

  • Advantages of Migration:

    • Avoids harsh conditions and provides access to varied resources (breeding/overwintering locations).

  • Costs of Migration:

    • Significant energy costs and potential for increased mortality.

    • ex) willabeast migrating and alligators go.

Benefits and Costs of Migration

  • Specific Examples:

    • Bar-tailed Godwit:

    • Migrates approximately 11,000 km non-stop from Alaska to New Zealand, demonstrating extreme migratory capability.

    • Crystal meth in their heads that allow them to navigate to their destination based on the pols of the earth

Behavioral Thermoregulation in Lizards

  • Adapting to Environmental Conditions:

    • Ectotherms exhibit diverse behavioral thermoregulatory strategies, such as basking and changing posture.

    • Warming up in one spot then going about their day

    • Zebra-tailed Lizards (Callisaurus draconoides):

    • Hypothesis: Use of thermal microhabitats for thermoregulation supported by experimental predictions.

Physiological Adaptations to Adaptations' Impact on Tolerance Limits

  • Overview of Physiological Responses:

    • Physiological adaptations, biochemical characteristics, and morphology determine organism's tolerance limits.

  • Responses to Environmental Changes:

    • Species can develop tolerance for varying internal conditions or mechanisms to counteract external challenges, often at an energetic cost

Temperature and Water Availability

  • Temperature: Essential to physiological and biochemical reactions.

    • Extreme temperatures can lead to protein denaturation or freezing of intracellular water.

  • Water: Crucial for life and biochemical reactions; optimal conditions must be maintained within narrow limits.

  • basis of life

Temperature Adaptations: Selective Pressures and Responses

  • Responses to High Temperatures:

    • Production of heat shock proteins, heat-stable proteins, and increases in G-C content of DNA.

    • prevents DNA breakage

  • Responses to Low Temperatures:

    • Production of low molecular weight cryoprotectants and antifreeze glycoproteins.

    • cryoprotectants in blood keep cells from bursting

Physical Mechanisms of Heat Transfer

  • Mechanisms influencing temperature adaptations: conduction (Transfer of heat), radiation ( getting rid of heat), convection (letting wind cool down surface), evaporation, and metabolic heat regulation. TEST STUFF

  • Thermoregulation can involve:

    • Homeotherms: Maintain constant body temperatures with varying external environments, utilizing mechanisms like sweating and panting.

  • Graph

    • Your metabollic rate increases in extreme heat or cold. You can loose weight

Water Conservation in Desert Mammals

  • Unique adaptations enable desert mammals to mitigate water loss and manage temperature, e.g., eland and oryx have specialized thermoregulatory and metabolic strategies for conserving water.

    • Example: Evaporation of Eland and Oryx

      • Reduce evaporative water loss by rising their temeprature.

      • Keep brain cool by counter current blood flow, transfering heat from warm arteriole blood to cooler venous blood, arteriole blood is 3 degrees cooler when it returns to the brain

    • Kidney structure in mammals have large loops of henley and collecting ducts to absorb as much water as possible.

  • You can gather information on an organisms environment based on their excretion: The dryer the environment, the less fluid their excretion

Water Conservation and Thermoregulation in Desert Birds

  • Birds exhibit behavioral adaptation by seeking shade and utilizing food sources with high moisture content to conserve water.

  • Efficient kidneys minimize liquid excretion, aiding survival without drinking water for prolonged periods.

Species Differ in Degree of Water Homeostasis

  • Two Categories:

    • Osmoconformers: Their osmotic concentrations fluctuate with the environment, e.g., marine invertebrates.

    • blood and cellular osmotic concentrations vary with the environment

    • advantage: no new mechanism to maintain enternal homeostasis

    • Osmoregulators: Maintain constant internal osmotic concentration despite environmental changes, e.g., various saltwater and freshwater animals.

    • Maintain constant internal balance of concentration

Case Study: Crab-eating Frog (Fejervarya cancrivora)

  • This species serves as an osmoregulator with adaptations for surviving in saline environments, regulating its internal composition through various physiological means.

    • does so by maintaining high levels of Urea in the blood

  • Tadpoles adaptations

    • Gills play role in ion transfer

    • Mitochondrial rich cells on gill arches, actively transport seawater derived ions in the blood back into the water (active transport)

    • can withstand temps of 42 degrees.

Excretion of Nitrogenous Waste Entails Water Loss (TEST STUFF)

  • Different organisms process nitrogenous waste differently, affecting water conservation in various environments, from ammonia in aquatic to uric acid in terrestrial species.

  • Depending on environmental conditions, animals will excrete waste differently to conserve water and be able to survivie longer periods of time.

Thermal Adaptations in Plants

  • Morphological Features: Leaf structure and orientation impact temperature regulation and overall plant health in regard to thermal conditions.

  • Water Challenges on Land: Waxy cuticles and effective stomata function allow roots' moisture transport, enabling survival in various terrestrial habitats.

The Photosynthesis Dilemma

  • Plants face a challenge between gas exchange for CO2 and the risk of water loss through stomata opening. In arid conditions, adaptations such as C4 photosynthesis promote efficient carbon fixation while minimizing moisture loss.