Adaptation and acclimatisation Flashcards
Acclimatisation
Short term changes in physiology that occur in an organism in response to changes in environmental conditions
Adaptability
The ability of an individual organism to make positive anatomical or physiological changes after short or long term exposure to stressful environmental conditions
Heat
Cultural adaptation- wearing more or less clothing. When people get too hot their body responds by sweating and vasodilatation, this increases blood blow to the surface of the skin and this allows heat from the core of the body to dissipate, aided by sweating. Although people live in many different thermal environments there is no variation in the number of sweat glands in any population. If body temperature reaches higher than 41 degree Celsius.
Cold
If the body’s core temperature drops to 31-32 degree celsius then one may die from hypothermia. In cold environments the body vasoconstrics, reducing blood flow by the skin. Another acclimatisation method is to shiver and this generates heat. Human populations shoe significant variation in response to cold. Subcutaneous fat helps to insulate the core of the body
High altitude
Humans originally evolved in hot, humid and low altitude environments whereas people now live at higher altitudes in environments that are dry and cold. Different altitudes mean different atmospheric pressure and less oxygen. Immediate response to this is higher heart rate and increased breathing rate so that the body can get enough oxygen. The growth is slower in children but the growth period is increased so that there’s no overall decrease in size.
Body size and shape
The colder the climate, the larger the body - they have a smaller surface are to volume ratio to conserve heat. Inuits in the arctic have stocky and short limbed bodies that are structured to conserve heat whereas africans have longer appendages in order to disperse heat.
Composition of skin and its purpose
The skin is composed of the thick dermis and a thinner epidermis. Skin acts as a barrier keeping the body protected from most chemicals in the environment. It’s also a vital component in metabolism of various vitamins.
Skin colour and distribution
Skin colour is largely determined by melanin, a dark pigment made in the epidermis. People with darker skin have more melanin than light skinned people. The distribution of skin colour globally follows a fairly orderly pattern. The darkest skin being in the equator and the tropics as one goes north or south away the shade of skin gets lighter. Migration messes with this pattern, as people who are dark skinned move to northern Europe and light skinned people move to places such as Africa or Australia.
UV
UVR cause sunburn and skin cancer which can cause the destruction of skin cells and edema- collection of fluids under the skin can lead to infection. Melanin blocks and filters UVR so dark skinned people are less susceptible to these issues, an acclimatisation for this is the ability to tan.
Vitamin D
Vitamin D helps the body to absorb calcium and is necessary for the normal development of bones and teeth. Dietary sources of it are rare and vitamin D deficiency leads to the development of rickets, bones are not healthy and can become deformed- bow legged. It varies from mild to death. One can also get vitamin D toxicity but this is almost impossible to get enough. People with dark skin do not synthesise as well as light skinned people but as they’re meant to be in hotter and sunnier climates this doesn’t matter and only becomes a problem when dark skinned people emigrate to colder climates.
Rickets
Was first recognised as a serious health problem in the industrialised cities of northern Europe and North America at the start of the 20th century. Smokey pollution reduced sun exposure and it was very dark and up to 90% of children suffered form some degree of rickets.
