Unit 2 KA4 Flashcards
Abiotic factor
A factor in an organism’s external environment, which can fluctuate and affect its internal environment.
eg. temperature, pH, salinity
Conformers
Organisms whose internal environment is dependent on abiotic factors in their external environment.
Conformers have low metabolic costs and are found in stable environments.
They are restricted to narrow ecological niches, and cannot easily adapt to changing environments.
They use behavioural responses (eg. basking in lizards) to respond to variation in their environment.
Regulators
The internal environment of a regulator is independent of the external environment.
Regulators use their metabolism to control their internal environment (homeostasis).
They can exploit a much wider range of ecological niches.
Their metabolic costs are higher, as energy is expended to regulate their internal environment.
Homeostasis
The maintenance of a constant internal environment, within tolerable limits.
Regulation is brought about by negative feedback control, and requires energy.
Negative feedback control
Any change away from a set level is detected by receptors.
Corrective mechanisms (effectors) are set in motion to return conditions back to set level.
The corrective mechanism is then switched off.
Thermoregulation
Control of body temperature
Ectotherms
Conformers, that are unable to regulate their body temperature.
They rely on behavioural thermoregulation. eg. basking in lizards.
Their body temperature depends on the external environment and they obtain most of their heat by absorbing it from their surroundings.
Ectotherms include all invertebrates and some vertebrates - fish, amphibians and reptiles.
Endotherms
Organisms that can maintain their internal temperature at a relatively constant level, which is independent of the external environment.
They have a high metabolic rate, which generates heat, but uses a lot of energy.
They have an efficient metabolism, since body temperature is kept at a level for optimum enzyme activity and diffusion rates.
They can exploit a wide variety of niches and can be active at any time of day or night.
Hypothalamus
The body’s temperature monitoring (thermoregulatory) centre in the brain.
Receives nerve impulses from the skin and internal organs.
Contains internal thermoreceptors which detect changes in blood temperature.
Responds to changes by sending nerve impulses to effectors.
Effectors
Muscles or glands that respond to nerve impulses.
Vasoconstriction
In cold conditions, arterioles leading to the surface of the skin become constricted by contraction of circular muscles.
Blood is redirected away from the surface of the skin, reducing heat loss by radiation.
Vasodilation
In hot conditions, the arterioles leading to the surface of the skin dilate due to relaxation of circular muscles in the arteriole wall.
Blood is diverted towards the skin, and when hot blood flows near to cool air in the environment, heat can be lost by radiation, which cools the blood.
Hair erector muscles
Every hair has its own muscle, known as a hair erector muscle.
In cold conditions, the muscle contracts, pulling the hair upright.
When many hairs stand upright, a layer of air is trapped against the skin, which acts an insulator, reducing heat loss.
This is very effective in organisms with a thick layer of fur or feathers.
Sweat glands
In hot conditions, sweat is released onto the surface of the skin by sweat glands.
Heat energy from the skin is used to turn the sweat into water vapour, which has a cooling effect on the skin.
Shivering
Rapid skeletal muscle contractions in cold conditions generate heat as a result of friction between muscle fibres.
