Climate Flashcards
What is human variation the result of?
Genetic drift, gene flow, genetic adaptation (through natural selection) to environmental conditions both past and present, physiological and cultural responses
Human plasticity
Includes physiological/cultural responses to environmental changes
Environmental Stress
Environmental Stress is any condition that disturbs the normal functioning of an organism, this eventually disturbs the organism’s homeostasis
Homeostasis
Homeostasis is when the body of an organism has a consistent and relatively stable internal environment and is maintained by feedback loops
Common forms of environmental stress
Ultra violet radiation Heat stress Humidity Stress Cold Stress Altitude Nutritional Stress Disease Stress Population Pressures
Hot and cold stress
- Both ancient stresses on humans
- Cause less loss of life than malnutrition and disease
- Because humans are better adapted to hot and cold stress
Ideal Internal Core Temperature
37-37.6: ,more than a few degrees either direction from this range is fatal
Ways of adapting to hot and cold stress
Adaptation: Evolutionary change
Accommodation: responses that ensure survival but many have a long term cost
Developmental adjustment: Adjustments to physiology in response to the environment during developmental stages
Acclimatisation (acclimation): gradual, reversible adjustments in response to changes in environments
Behavioural/Cultural responses: responses that are learnt and culturally and environmentally specific e.g wearing warm clothing or sun cream
How can the body heat up when cold?
- Increased metabolism
- exercise or shivering
- hormone-induces increase in metabolism
- infection (i.e. fever) - Non-shivering thermogenesis (induced by hormones)
- Conduction (touching hot things)
- Convection (contact with hot air)
- Radiation (receiving infrared waves)
What increases your risk of freezing to death
-Highest mortality rate in infants, the elderly, the poor, alcoholics and those who are in water
What else can help warm you up?
- Subcutaneous fat (developmental adjustment?)
- Muscle (developmental adjustment?)
- Avoiding cold (behavioural/cultural response)
- Wearing protective clothes (behavioural/cultural response)
- Favourable body proportions (developmental adjustment)
- Higher resting metabolic rate (adaptation, behavioural response)
- Lower core temp, delayed shivering, increased non-shiveering thermogenesis (acclimatisation-within 5-10 days)
- Hunters waves (adaptation, accommodation?)
- Protruding, narrow nose (adaptation)
Body Proportions
Bergmann’s Rule (1847)
-People closer to the equator are less bulky than people who live in cold areas
Allen’s rule (1877)
-People closer to the equator have longer limbs than people who live in cold areas
What increases your risk of heating to death
Infants, elderly, the poor, elite athletes, workers
Heat and metabolism
Humans produce a lot of heat constantly through metabolism, whether exercising or not
This means when core body temperature is high, physical activity adds stress (the opposite of what happens with cold exposure)
Responses to heat
Involves vasodilation, conduction, radiation, evaporation and behaviour/culture
- Internal heat moves by conductance and vasdilation to the body surface where it can radiate away
- Sweat glands produce sweat which evaporates to cool the skin (more difficult in humid climates)
- Ventilation
- Early/Late working and siestas
- Clothing styles
