Physiological Ecology: Response to Environment

Physiological Ecology 1: Behavioural and physiological response to the environment

• Physiological ecology studies the behavioral and physiological responses of organisms to their environment.
• Large-scale environmental effects such as long-distance migration are important aspects of physiological ecology.
• Light-bellied Brent Geese migrate long distances, overwintering in the UK and Ireland.
• Animals migrate in response to resource availability to find food, breeding grounds, and maintain energy balance.
• The geese migrate for approximately 7 months, covering 8000km.
• Resource availability affects breeding, the timing/season of breeding, and body reserves.
• Svalbard deer get immensely fat and then lactate to calves.

Learning Outcomes

• It is important to understand physiological responses to the environment
• The diversity of organism responses that can occur in different organisms should be appreciated
• Physiological responses can be sensitive and reliable indicators of species condition and viability.

Plan of Lectures

• Lecture topics include definitions and an overview of Physiological Ecology.
• It covers broad-scale environmental effects on physiology and behavior.
• It discusses the effects of temperature, light, water, parasites, and pathogens.
• The lectures will also cover anthropogenic causes for changes in physiology, conservation, and management.

Physiology

• Physiology is the study of how living organisms function, including nutrition, movement, and reproduction.
• It examines processes within cells and how tissues and organs work, and are controlled within individuals.
• Organisms respond to their environment.
• For example organisms respond to extremes of temperature (arctic vs. desert) or pressure (deep ocean vs. weightless space).

Behavior

• Behavior is the expression of an effort to adapt or adjust to different internal and external conditions.
• Behavior is an animal's response to a stimulus.
• It is the scientific study of everything animals do.
• It investigates the relationships between animals and their physical environment and to other organisms.
• Topic examples include; how animals find and defend resources, avoid predators, choose mates, reproduce, and care for their young.

The "Environment"

• The environment is the totality of circumstances surrounding an organism or group of organisms.
• It combines external physical conditions and social and cultural conditions affecting nature of an individual or a community.

Physiological Ecology/ Ecophysiology

• Physiological ecology/ecophysiology is the adaptation of an organism's physiology to environmental conditions.
• Biology scales of organization from atoms to the biosphere, with ecology focusing on populations, ecosystems and the biosphere.
• Physiology is the study of organisms, organ systems, organs, tissues and cells.

Physiological Ecology Focus

• Physiological ecology studies the interactions between organisms and their physical environment at the individual level.
• The field intersects with ecology and physiology, and is also known as ecophysiology or eco-physiology.

Physiological Ecology: Top Themes:

• Homeostasis: maintenance of constant internal conditions in varying environments.
• Adaptation: adaptation of organisms to specific environments.

Three Big Problems

• Three major challenges for organisms are; obtaining nutrients, maintaining temperature, obtaining and holding onto water.

Energy

• All organisms require energy to live and reproduce.
• Heterotrophs acquire energy from organic material, either living or dead, with most animals feeding on living organisms and decomposers feeding on dead organisms.
• Autotrophs - acquire energy from sunlight or chemicals.
• Chemosynthetic autotrophs obtain energy from inorganic chemicals like methane or hydrogen sulfide, like sea-vent bacteria.
• Photosynthetic autotrophs combine energy from sunlight and CO2 to make sugars, like many bacteria, some protists (algae), and nearly all plants.

Temperature

• Biological processes speed up as temperatures rise and proteins and other organic compounds may break down.
• Compounds are more stable at cold temperatures, but ice crystals may damage or destroy cells, and life processes slow or stop.
• Homeothermic organisms maintain a 'constant' body temperature like birds and mammals.
• Poikilothermic organisms have varying body temperatures, responding to external temperatures like all other animals.
• Also, poikilothermic animals may regulate their body temperature.

Endothermy and Ectothermy

• Endothermy is when body heat is generated internally.
• Ectothermy is when body heat is generated externally.
• Ectotherms regulate their body temperature by basking, moving between shade/sun, and being active at certain times of day
• Endothermy requires a lot of energy and is considered a 'Wasteful' strategy.
• An alternative to these two strategies is torpor which is a condition of lowered body temperature and activity, or hibernation.

Saving Heat

• Heat can be saved by other means using a countercurrent system.
• The rate of heat loss to environment can be reduced by creating a temperature gradient, which transported from arterial blood leaving the body to venous blood returning to the body.
• Torpor and hibernation conserve energy that would otherwise be used to heat the body.

Organism Optimum

• Each organism has an optimum environment which is a narrow range of environmental conditions to which an organism is best suited.
• 'Biological activity' is the y-axis trait with the x-axis being the given 'environmental condition'.
• These are the conditions determining population and survival rates.

Ecophysiology and Light

• Light is a very important environmental signal entraining organisms.
• The tilted axis creates seasons which dictate the amount of solar radiation.

Circadian Rhythms and the SCN

• The suprachiasmatic nucleus (SCN) in the brain that acts as the master internal clock that regulates circadian rhythms in the body.
• The SCN is active during the day in both diurnal and nocturnal animals.
• The sleep/wake cycle is one of many biological processes impacted by the light dark cycle.

Spiny Mice

• Studies on Spiny mice demonstrated how desert-adapted animals' rhythms change according to salinity and temperature.
• They found that the mice defended water loss rather than body temperature.

Temperature and Rainfall

• Changes in temeprature and rainfall as a result of climate impact animal physiology:
• Purely temperature, or purely light can have major effects on animals' physiology
• Annual rhythms of ambient temperature affect breeding cycles
• Additionally, light "flashes" can stop voles breeding.
• Light at night associates with increased breast cancer rates.

Thermal Balance

• Ecophysiology considers temperature and climate.
• Thermoregulation: For an organism to maintain a somewhat constant body temperature, heat gained by the body must equal heat losses.
• Heat exchange takes place with the surrounding environment through conduction, convection, radiation and evaporation.
• Animals in terrestrial environments are subject to more radical changes in their thermal environment than are aquatic animals.
• Aquatic animals live in a more stable energy environment, but generally have a lower tolerance to temperature changes.
• The heat balance of an organism is described by: Htot = Hc +/-Hca +/- H₁ +/- He +/- Hm

Endotherms and Ectotherms and Metabolic Rate

• Endotherms maintain a high and stable internal temperature
• Ectotherms internal temperature varies with surroundings
• The resting metabolic response of endotherms changes in response to ambient temperature

Desert Adaptations

• Adaptations to deserts focus on ways to keep cool which includes avoiding heat by burrowing during the day, and evaporating water.
• Keep brain cool ('selective brain cooling').

Heat and Water Conservation

• Water can be conserved by not drinking, using metabolic water, and concentrating urine.
• The body core's temperature gradient with the ambient conditions can also be reduced to conserve water.

Temperature Adaptations

• Mt. Carmel Mice on Mt. Carmel face heat and water stress and adapt by using energy and water conserving mechanisms and Tº rhythms.
• Mt. Hermon Mice on Mt. Hermon face cold stress and adapt by maintaining heat production, body temperature, insulation and NST - non-shivering thermogenesis.
• A common response is energy expenditure, thermoregulation, body temperature control.

Physiology and Body Mass

• Basal metabolic rate of various mammals is proportional to body mass raised to the (0.75) power, that is, the higher the mass, the lower the mass-specific metabolic rate.
• An animal's physiology impacts factors such as oxygen consumption and metabolic rates.
• Larger animals typically have lower mass-specific metabolic rates.

Thermal Inertia

• Body mass affects thermoregulatory strategy.
• Thermal inertia as influenced by body mass affects thermal stress during hibernation.

Hibernation

• Hibernation is possible if an animal can store sufficient fat reserves, otherwise short-term torpor is used.
• During bat hibernation, fungal disease manipulates arousals, and bats die because they expend too much energy

Chemicals and Physiology

• Chemicals, toxins and pathogens impact physiology.
• The types of toxins discussed include; food pesticides, aluminum, and hormones.
• Parasites are cellular such as protozoa, helminths and plasmodia - malaria..
• Aceullar factors include Fungi, prokaryotes, viruses, prions.

Chemotaxis

• "Chemotaxis describes the phenomenon in which cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment"
• Use simple rules - "travel perpendicular to line/"contour" of equal concentration).

Chemically Motivated Behavior

• Geophagy: "earth - eating".
• Animals do this to obtain essential nutrients like Phosphorus and Potassium, or sometimes to annul toxins from diet.
• Macaws eat diet all kinds of seeds and exploit geophagy as some are rich in tannins and alkaloids - strong poisons
• One thought is that toxins become absorbed in interstices within kaolin clay structure

Effects of Parasites and Pathogens

• Pathogens are a major influential evolutionary force with a huge impact on organismal biology.
• An discussed example is the effect of Dracunculiasis on Humans.
• Infection occurs by drinking water containing cyclops which contains the juvenile form of Guinea worm: Dracunculus medinensis.
• Guinea worm: Infection acquired by drinking water containing cyclops

Dracunculus medinensis Infection Cycle

• After mating females migrate to skin specifically the legs and feet.
• Pressure of embryos bursts the worm causing a Blister.
• This creates an allergic reaction and intense burning
• The Infected person then seeks water which comes in contact with water and bursts the blister
• Next, 0.5 million Juveniles are released which are eaten by Cyclops.
• The lifecycle involves life in both a mammalian and crustacean host leading to difficulty in diagnosis and eradication.
• Is famously treated by its removal on a stick!
• Cool water is applies and juveniles shed
• Then, up to 5 cm of worm appears and gets wrapped around stick
• Continue process for 3 weeks to remove whole worm

Pollution

• Heavy metal pollution includes; Tributyl tin (TBT)
• TBT is a great anti-foulant to add to paint, namely on warships
• However one effect is to hinder and even render marine molluscs (e.g. Nucella spp.) infertile by stimulating females to grow penises!
• But - it is very PERSISTENT in the environment
• Hormone pollution is another common pollutant like Oestrogens
• Noted that fertility in male fish in rivers near cities decreased then were found to be associated to oestrogen-compounds in water responsible
• Human contraceptive pills are a known factor, however there is recent evidence for lower sperm counts in Humans living near livestock farms.