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5a – Surviving Adverse Conditions - Coggle Diagram
5a – Surviving Adverse Conditions
Survival: Dormancy
Predictive
Dormancy
When an organism’s dormancy begins
BEFORE the arrival of adverse conditions.
This is most common where changing conditions are
predictable
.
E.g. Many trees respond to a decreased photoperiod (day length). They shed their leaves and have winter buds that respond in spring to increased photoperiod.
Consequential
Dormancy
When an organism’s dormancy begins
AFTER the arrival of adverse conditions.
It is more common where
conditions are unpredictable,
allowing organisms to
take advantage available resources
.
However, a sudden and severe change may cause death before dormancy.
E.g. Garden Snails secrete a layer of mucus over their openings (except for a small hole for the exchange of gases to avoid desiccation [drying out].
A period in the life of an organism during which metabolic activity is greatly reduced to the minimum needed to keep its cells alive.
Allows it to survive periods of environmental adversity – extreme temperatures, drought or food scarcity.
Hibernation
Response to very cold weather
May last for weeks/months.
Often predictive – animal consumes extra food which is laid down as a fat store.
Metabolic rate drops which results in decrease body temperature.
Slower heart and breathing rate, minimal energy expenditure..
Adverse Conditions & Survival
Survival
- A reduction in metabolic rate allows an organism to avoid using excess energy to try to stay warm in extreme cold or to stay cool in extreme hot.
AC
- Cyclic seasonal fluctuations are not often fatal because animals either have adaptations to survive these OR methods to avoid extreme conditions.
Daily torpor
Animal's rate of metabolism and activity become greatly reduced for part of every 24-hour cycle.
Accompanied by a slowing down of heart and breathing rate and decrease in body temperature.
All of these animals have a high surface area through which heat is lost.
Aestivation
Examples of Aestivation
Lungfish buries itself in a cocoon of dried up mucus in the mud of a dried up pond
In intense heat, garden snails secrete a protective mucus, except for a tiny hole for gas exchange.
The organism
remains
at a
minimum metabolic rate
until
favourable conditions return.
Physiologically similar to hibernation, but
occurs in summer in response to drought or extreme high temperatures
Adaptations
Millions of years of evolution and natural selection have resulted in adaptations that allow organisms to survive, including where necessary to survive adverse conditions.
These can be structural, physiological, or behavioural
Tolerance Limits
Some environments vary beyond the “tolerable limits” for normal metabolic activity of an organism.
The tolerance of an organism is the range of conditions in which it can maintain homeostasis without exhausting its metabolism.