Unit_2.1.2_Dealing_with_Environmental_Extremes

Unit Overview

• Title: Dealing with Environmental Extremes

• Course: Biology 4415

• Instructor: Dr. Matthew Terry

• Institution: UTRGV

Voltinism

• Definition: Refers to the number of generations (voltinism) an organism produces within a year.

• Types of Voltinism:

  • Univoltine: One generation per year.

    • Example: Species that have a single reproductive cycle annually.

  • Bivoltine: Two generations per year.

  • Multivoltine: Multiple generations per year.

  • Semivoltine: More than one year per generation.

• Life Stages Involved in Voltinism:

  • Ovum: The egg stage.

  • Adult: The mature stage of the organism.

  • Hibernation: A state to survive unfavorable environmental conditions.

  • Pupae: The transitional life stage.

  • Larvae: The juvenile form of the organism.

Diapause

• Definition: A period of suspended development to avoid unfavorable environmental conditions.

• Life Stages:

  • Diapause can occur in all life stages of an organism.

• Types of Diapause:

  • Facultative: Optional diapause based on environmental conditions.

  • Obligate: Required diapause that occurs regardless of conditions.

Cold: Cryoprotection

• Mechanisms of Cryoprotection:

  • Antifreeze Proteins: Proteins that prevent ice formation in cells.

  • Glycerols and Sugars: Compounds that lower the freezing point of bodily fluids.

  • Dehydration: Reducing body water content to avoid ice damage.

• Affected Structures in Species:

  • Hemideina spp. adults, Chilo suppressalis larvae, Eurosta solidaginis larvae, etc.

  • Cellular Structures: Gut, membranes, Malpighian tubules, and fat body cells involved in cryoprotection.

• Unique Behavioral Adaptations:

  • Supercooling: A state of remaining in liquid form below freezing point.

Cold: Freeze Avoidance

• Definition: Adaptations to prevent freezing in extreme cold.

• Examples of Winter-Breeding Species:

  • Notable species include Neplodes costipennis costipennis, Neplodes bowringi, etc.

  • Adaptation to cold climates, particularly in the Appalachian Mountains in the USA.

Heat Stress

• Effects of Heat on Organisms:

  • Thermal Stress: Conditions above optimal temperature leading to stress.

  • Measurements:

    • 40°C: Critical point for many species.

    • 30°C - 35°C: Impact on longevity and mortality in different organisms.

• Physiological Response:

  • Organisms produce Heat Shock Proteins (HSP) to manage thermal stress.

  • Indicators of stress include Reactive Oxygen Species (ROS), Catalase (CAT), Glutathione S-Transferase (GST), and Superoxide Dismutase (SOD).

Aridity Adaption

• Types of Adaptations:

  • Behavioral: Changes in habits to conserve water.

  • Morphological: Physical adaptations (e.g., leaf shape) to minimize water loss.

  • Physiological: Internal processes that enable survival in dry conditions.

Migration

• Definition: Movement of organisms from one habitat to another.

• Characteristics of Migration:

  • Not dispersal: Migration involves a return journey, unlike one-way dispersal.

  • Not range extension: Migration does not expand the geographic range of a species.

  • Cyclical Nature: Seasonal patterns of movement.

  • Direction: Relatively straight routes are often taken to reduce travel time.

  • Population Dynamics: A significant percentage of the entire population participates in migration well defined by behavioral changes.