BIOL 2300 Lecture Notes - Lecture 5: Stoma, Digestion, Cryptobiosis
22 Jun 2018
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LECTRURE 5 ORGANISMS AND ENVIRONMENTAL CHANGE
Organisms & Environmental Variability
Environmental Change
Individual Responses
1. Developmental (years) – irreversible
2. Acclimatory (days – weeks) - reversible
3. Regulatory (seconds – minutes) - reversible
Variability in Regulatory Responses
Temperature Regulation
Ectotherms
Limitations of Ectotherms
Endotherms
Limitations of Endotherms
Energy Conservation - Endotherms
Allometry: Surface Area to Volume Ratio
Consequences of Allometry
Consequence:
Summary
2
Organisms & Environmental Variability
• Physiological Ecology: how an individual responds to its abiotic
environment
o Changes in order to maintain body conditions
o Can be behaviorally or physiologically
• Emphasis: responses of animals to fluctuations in temperature
Environmental Change
• Organisms live in constantly changing environments.
o Many temporal scales: daily (e.g., light-dark), seasonally, annually,
decadal
o Variation may be predictable or unpredictable
• Fitness depends on an individual’s ability to cope with environmental change.
o To maximize fitness – an individual’s response to these changes must
be shorter than the period of change
o E.g., Cryptobiosis – eggs are in state of abiotic which survive for long
periods of intolerable conditions (e.g., no water), and comes back to
biotic state when water is present (i.e., they hatch)
Individual Responses
• Responses to environmental change fall into 3 categories:
1. Developmental (years) – irreversible
• Individual alters its development to produce a phenotype most suitable to a
persistent slow change in environmental conditions
3
• E.g. Wing length in European freshwater Water Striders (genus Gerris) –
inhabiting temporary ponds
o Eggs hatch (spring)
o Adult lifespan is short (reproduce & die during one summer)
o 2 morphs (discrete phenotypes):
▪ Long-winged
• can fly
• move if pond dries up
• more energy into survival than reproduction
▪ Short-winged
• cannot fly
• cannot move if pond dries up
• more energy into reproduction than survival
o If high temperature during egg development… which form do they
develop into? – Long-winged
2. Acclimatory (days – weeks) - reversible
• changes in response to seasonal variations
• e.g. thickening of fur for winter/colour change
• e.g. cold/frost hardening in plants
• = habituation of an organism’s physiological response to environmental
conditions
• Acclimation – applied to laboratory
• Acclimatization – applied to nature
Document Summary
Individual responses: developmental (years) irreversible, acclimatory (days weeks) - reversible, regulatory (seconds minutes) - reversible. Organisms & environmental variability: physiological ecology: how an individual responds to its abiotic environment, changes in order to maintain body conditions, can be behaviorally or physiologically, emphasis: responses of animals to fluctuations in temperature. Individual responses: responses to environmental change fall into 3 categories, developmental (years) irreversible. Individual alters its development to produce a phenotype most suitable to a persistent slow change in environmental conditions. As the external temperature cools down, the body temperature heats up: mechanism that senses the internal condition, means of comparing the actual with the desired internal condition, apparatus that alters the internal condition in preferred direction. Ectotherms: ectotherms: regulate body temperature by gaining heat from external sources, most are poikilotherms, advantage: energy expenditure can be low, disadvantage: growth, reproduction and survival is limited by temperature fluctuations, active only in a narrow range of temps.
