Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped.
While very sudden changes in conditions may lead to a high mortality rate among animals relying on consequential dormancy, its use can be advantageous, as organisms remain active longer and are therefore able to make greater use of available resources.
An animal prepares for hibernation by building up a thick layer of body fat during late summer and autumn that will provide it with energy during the dormant period.
Non-shivering thermogenesis is a regulated process in which the proton gradient generated by electron transport in mitochondria is used to produce heat instead of ATP in brown adipose tissue.
[3] Animals that hibernate include bats, ground squirrels and other rodents, mouse lemurs, the European hedgehog and other insectivores, monotremes and marsupials.
Diapause is common in insects, allowing them to suspend development between autumn and spring, and in mammals such as the roe deer (Capreolus capreolus, the only ungulate with embryonic diapause[citation needed]), in which a delay in attachment of the embryo to the uterine lining ensures that offspring are born in spring, when conditions are most favorable.
While endotherms and other heterotherms are described scientifically as hibernating, the way ectotherms such as lizards become dormant in cold conditions is very different, and a separate term was coined for it in the 1920s: brumation.
[4] It differs from hibernation in the metabolic processes involved: energy is stored in glycogen in addition to or in place of fats, and periodic water intake is required.
Many plant species that exhibit dormancy have a biological clock that tells them when to slow activity and to prepare soft tissues for a period of freezing temperatures or water shortage.
On the other hand, dormancy can be triggered after a normal growing season by decreasing temperatures, shortened day length, and/or a reduction in rainfall.
[citation needed] The two adjacent images show two particularly widespread dormancy patterns amongst sympodially growing orchids: When a mature and viable seed under a favorable condition fails to germinate, it is said to be dormant.
[8] In some species, rest can be broken within hours at any stage of dormancy, with either chemicals, heat, or freezing temperatures, effective dosages of which would seem to be a function of sublethal stress, which results in stimulation of ethylene production and increased cell membrane permeability.
Correlated inhibition is a kind of physiological dormancy maintained by agents or conditions originating within the plant, but not within the dormant tissue itself.
[11] White spruce, like many woody plants in temperate and cooler regions, requires exposure to low temperature for a period of weeks before it can resume normal growth and development.
This "chilling requirement" for white spruce is satisfied by uninterrupted exposure to temperatures below 7 °C for 4 to 8 weeks, depending on physiological condition (Nienstaedt 1966, 1967).
For instance, if a Japanese maple (Acer palmatum) is given an "eternal summer" through exposure to additional daylight, it grows continuously for as long as two years.
[13][14] Many bacteria can survive adverse conditions such as temperature, desiccation, and antibiotics by forming endospores, cysts, or general states of reduced metabolic activity lacking specialized cellular structures.
However, some viruses such as poxviruses and picornaviruses, after entering the host, can become latent for long periods of time, or even indefinitely until they are externally activated.
