F). Outline the role of the nervous system in detecting and responding to environmental changes
The nervous system provides rapid coordination of internal organ systems and detects & responds to
environmental changes. The nervous system works to regulate & maintain internal environment and respond
to the external environment.
The nervous system is made up of 2 parts:
 Central Nervous System (CNS): consists of the brain & the spinal cord. The CNS acts as the
CONTROL CENTRE for all of the body’s responses as it coordinates all responses (receives info,
interprets info, initiates a response).
 Peripheral Nervous System (PNS): a branching system of nerves that connects receptors & effectors.
This systm trnsmits messges from the CNS & back, acting as a commnicatn channl.
Example: when the environment temp begins to change (stimuli), temperature sensors in the skin (receptors)
detect the temp change. A sensory neuron conducts a nervous impulse to the hypothalamus (temp. control
centre) found in the brain (part of the CNS). Nerve impulses (part of the PNS) pass this info from the
receptors to effector neurons, then onto effectors, such as blood vessels, sweat glands and muscles.
2). Gather, process and analyse information from secondary sources and use available evidence to develop
a model of a feedback mechanism
The body has some effective mechanisms to alter body temperature. If a mechanism is activated, it will
operate until receptors indicate that the optimum temperature has been reached. In this way, the body can
maintain a stable body temperature.
Keeping Warm (if too cold)
Keeping Cool (if too hot)
Metabolism is increased, producing more heat
Metabolism is reduced, less heat produced
Shiver: muscles contract to generate heat
Sweating: evaporation loses heat
Blood vessels constrict; less blood flow, less
heat loss
Hair muscles erect: trap layer air; insulation
Blood vessels dilate; increased blood supple, more heat lost
Increased appetite
Less exercise
Hair relaxes, less insulation
G). Identify the broad range of temperatures over which life is found compared with the narrow limits for
individual species
The majority of living organisms are found in the - 2oC to +40oC range. Below 0oC, cells risk ice crystals
forming in them, and above 45oC, proteins (enzymes) within cells may denature. However, life in some
form can be found at extremes ranging from - 40oC to +120oC.
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Organisms live in environments with ambient temperatures (external environment temp) ranging
from < 0°C to 100°C.
Individual organisms cannot survive this entire range, e.g. mammals only survive in 0°- 45ºC
The range of temps over which life is found is broad compard to the narrw limits for indivdul species.
Life is found in a wide range of temps, but indivdul species can only be found in a narrw temp range.
H). Compare responses of named Australian ectothermic and endothermic organisms to changes in the
ambient temperature and explain how these responses assist temperature regulation
Ectotherms
 organisms that can’t maintan constant body temp (have limited ability to control their body temp)
 Hence, ectotherms are greatly affected by ambient temps. Body is regulated by heat gained from
the environmnt rather than by heat producd by the organism’s own metabolic processes.
 E.g.s plants, invertebrates, fish, reptiles, amphibians
Responses to changes in the ambient temperature
 Controlling exposure: the goanna controls its body exposure to the sun by sun baking in the cool
morning and staying in the shade during hot hours
 Nocturnal activity: brown snakes can change into nocturnal animals when the temp becomes
very hot. They sleep during the day and are active at night
 Changing colour: the bearded dragon changes colours on its back (to pale), to reflect heat
Endotherms
- organisms that can maintain constant body temp (metabolic processes & adaptive mechanisms
maintain internal body temp, i.e. sweating, insulation-feathers, blubber- hibernation).
- E.g.s birds, mammals
Responses to changes in the ambient temperature
 Migration: the short-tailed shearwater migrates to equatorial regions during winter months, to
avoid cold weather (as the bird only breeds in warm weather)
 Insulation: the superb parrot contracts its muscles controlling feather in cold conditions, fluffing
up its coat. This maintans layer of trapped air as insulation, reducing heat loss
 Evaporation: red kangaroo licks its arms to cool itself (the evaporation of saliva cools skin)
3). Analyse information from secondary sources to describe adaptations and responses that have occurred in
Australian organisms to assist temperature regulation (also see above e.g.s)
Bandicoot: large ears provide a larger SA to pass excess heat when it is burrowng during day heat
I). Identify some responses of plants to temperature change
Plants respond to temp change by:
 Altering their growth rate: e.g. daffodil dies back during harsh conditions
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Closing stomates: in response to high temps, to reduce water loss
Leaves hang vertically: to reduce sun exposure e.g. Eucalypts
Reduced surface area: geraniums have reduced surface areas – less heat is absorbed
Banksia: seed dispersal is stimulated by the extreme heat of a fire (incase of emergency)