Biological rhythms - photoperiodism and circadian rhythms

What is a circadian rhythm?
Changes in an organism which follow a 24-hour cycle.
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What is photoperiodism?
The functional or behavioural response in an organism to the length of day or night.
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How does photoperiodism affect germination?
When days get longer, plants germinate and begin to grow shoots. Light is needed for photosynthesis and therefore energy for growth.
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How does photoperiodism affect flowering?
Most flowers open in the day when they can be pollinated by insects. The moon flower opens at night to be pollinated by night-flying moths.
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How does photoperiodism affect growth?
Some plants will grow more when the days are longer in the Summer, as they have more resources to grow. Other plants, such as pumpkins, grow faster at night than in the day, as they use up the products of photosynthesis for growth.
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Vertebrates have a ___________ located in the hypothalamus
Biological clock
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Internal circadian rhythms are called
Endogenous cues
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An example of an endogenous cue is
The sleep/wake cycle regulated by melatonin
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External circadian rhythms are called
Exogenous cues
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An example of an exogenous cue is
In Red Deer, the duration of light triggers a hormone which controls sexual function
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Card 2

Front

What is photoperiodism?

Back

The functional or behavioural response in an organism to the length of day or night.

Card 3

Front

How does photoperiodism affect germination?

Back

Preview of the front of card 3

Card 4

Front

How does photoperiodism affect flowering?

Back

Preview of the front of card 4

Card 5

Front

How does photoperiodism affect growth?

Back

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