1. Biological Rhythms
This is something a
plant or animal
does periodically
(maybe daily,
monthly or yearly).

2. Rhythms
WALT: To understand how circadian
rhythms work in living organisms.
WILF:
State what a circadian rhythm and list
examples. (C)
Describe examples of circadian
rhythms for both plants and animals.
(B)
Explain the importance of
photoperiodism in plants. (A/A*)
Keywords
Circadian
rhythm
Biological
clock
Hormones
Germinate
Photoperiodism

3. Circadian Rhythms
A biological
rhythm that
happens
daily.
How?
Your
biological
clock.
e.g. melatonin (hormone)
Makes you feel sleepy. More of
this hormone is released around
10pm whilst levels decrease in the
morning, helping you to wake up.

4. Circadian Rhythms
A biological
rhythm that
happens
daily.
How?
Your
biological
clock.
e.g. Jet lag
Moving east or west
around the globe our day
to night cycle will either
be earlier or later.

5. 1.A circadian rhythm is…
2.What is a biological clock
and where is it found?
3.Describe 2 examples of a
human circadian rhythm.
Aim Higher! A/A*
The data shown looks at the
concentration of melatonin
against time. Describe the
relationship between these
two variables.
Time
14:00
17:00
20:00
23:00
02:00
05:00
07:00
Blood
melatonin
concentration
(picograms/ml)
8
9
11
28
69
67
9

6. Plants have the rhythm too!
Plants also
have circadian
(daily)
rhythms.
e.g. flowers
opening in the
day and
closing at
night
Day
Night

7. Photoperiodism
This is the response of a plant that changes
as the length of day changes.
Examples
Reproduction
(Flowering)
Germination
Growth
Use page 29 to describe when and why
these examples happen.

8. 3, 2, 1!
State 3 keywords you have learnt
today .
Name 2 examples of circadian
rhythms.
Describe 1 example of
photoperiodism.

9. Photoperiodism
Photoperiodism
Photoperiodism is the way a plant responds to the
of a day.
A plant that flowers in the autumn is called a
-day plant.
During the shorter days of
plants may
not grow at all.
As the days get longer in spring,
__
germinate and start to grow.
During spring and summer a plant will
faster.
A long-day plant flowers as the days get longer in
the
months.
Photoperiodism is the way a plant responds to the
of a day.
A plant that flowers in the autumn is called a
-day plant.
During the shorter days of
plants may
not grow at all.
As the days get longer in spring,
__
germinate and start to grow.
During spring and summer a plant will
faster.
A long-day plant flowers as the days get longer in
the
months.
Photoperiodism
Photoperiodism
Photoperiodism is the way a plant responds to the
of a day.
A plant that flowers in the autumn is called a
-day plant.
During the shorter days of
plants may
not grow at all.
As the days get longer in spring,
__
germinate and start to grow.
During spring and summer a plant will
faster.
A long-day plant flowers as the days get longer in
the
months.
Photoperiodism is the way a plant responds to the
of a day.
A plant that flowers in the autumn is called a
-day plant.
During the shorter days of
plants may
not grow at all.
As the days get longer in spring,
__
germinate and start to grow.
During spring and summer a plant will
faster.
A long-day plant flowers as the days get longer in
the
months.