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F215-Module 4-Responding to the Environment

5.4.1 Plant responses

a. Explain why plants need to respond to their environment in terms of the need to
avoid predators and abiotic stress

Phototropism-Plants grow towards like so they can get more light and
photosynthesise more.
Geotropism-Roots grow pulled down by gravity to anchor…

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d. Evaluate the experimental evidence for the role in auxins in the control of apical
dominance and gibberellin in the control of cell elongation

Apical dominance
o It is when the growing apical bud at the tip of the shoot inhibits the
growth of lateral buds further down the shoot.…

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Auxin inhibits abscission usually by acting on leaves in the abscission zone. But:
o Lead senescence causes auxin production at the tip to drop.
o So it makes cells in the abscission zone more sensitive to ethene whose
production is increased when there is a drop in auxin.
o So…

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5.4.2 Animal responses

a. Discuss why animals need to respond to their environment

Need to react to changes both internally and externally.
They need to be able to coordinate a set of different responses.
They need to respond to stay alive e.g. to run away from predators.
They need to…

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Parasympathetic
o Most active in sleep and relaxation.
o Neurones linked at a ganglion close to the target tissue- longer
pre-ganglionic neurones.
o Post-ganglionic neurones secrete acetylcholine.
o Effects include decreased heart rate, pupil constriction and decreased
ventilation rate.

d. Describe, with the aid of diagrams, the gross structure of…

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e. Describe how coordinated movement requires the action of skeletal muscles about
joints with reference to the movements of the elbow

1. Impulses arrive at the neuromuscular junction.
2. Vesicles fuse with the pre-synaptic membrane.
3. Acetylcholine is released.
4. The acetylcholine binds to receptors on the muscle fibre membrane…

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o Transfer from creatine phosphate in the muscle cell sarcoplasm. The
phosphate group from creatine phosphate can be added to ADP to make
ATP using the enzyme creatine phosphotransderase.

i. Compare and contrast the actions of synapses and neuromuscular junctions

Synapses Neuromuscular junction
Neurone to neurone. Neurone to sarcomere (muscle…

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k. State that responses to environmental stimuli in mammals are coordinated by
nervous and endocrine systems

Systems of both nervous and endocrine continuously monitor the external and
internal environments.
Coordination of responses to stimuli is needed for survival.
Mainly the result of brain activity to access the appropriate response and…

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o It can be positive where the reaction is towards the stimulus or negative
where the reaction is away from the stimulus.
Kinesis
o An orientation response where the rate of movement increases when the
organism is in unfavourable conditions.
o Non-directional response (not in any specific direction).

c. Explain…

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o The young are able to learn through observation and play, where they are
able to learn skills which are essential for when they are older.
o It can lead to the security of a group which leads to the survival and
learning of the young.
o The knowledge and…

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