Transcript Behaviour - miss-lovell

Behaviour
Causes of behaviour
Photoreceptors
• Photoreceptors are cells that are sensitive to light.
• Animal photoreceptors sense light with a photopigment
called rhodopsin. Molecules of rhodopsin change
structure when light is absorbed and stimulate nerve
endings, then return to their normal state.
• Photoreceptor cells on their own only detect the intensity
of light, but can provide an image when aggregated into
an organ.
• The greater number of photoreceptor cells, the greater
resolution and detail, allowing more complex responses.
An ommatidium of an insect
compound eye
Each ommatidium ‘sees’ a
point of light – having many of
these in a compound eye
allows an insect to perceive an
image made of many dots of
light of varying intensities.
Orientation responses
Tropisms and nastic responses
Tropisms: Auxin
Darwin’s experiments
Apical dominance
•Auxin at the apical meristem (top of the plant) is produced in high
concentrations, so the shoot is stimulated to grow.
•The lateral buds remain dormant, as high concentrations inhibit their growth.
•As auxin diffuses down the plant it becomes less concentrated, and is
inactivated by enzymes and hormones in the lower parts of the plant.
•Near the bottom of the plant, the concentration is low enough to stimulate the
lateral buds to grow out sideways.
•This causes the triangular shape of trees such as conifers. This process is
called apical dominance.
Geotropism in shoots:
How do plants know ‘how’ to grow?
Geotropism in shoots:
How do plants know ‘how’ to grow?
Nastic responses
• Nastic movements are non-directional responses to
stimuli (e.g. temperature, humidity, light intensity). The
movement can be due to changes in turgor or in growth.
•
Nastic movements differ from tropic movements in that
the direction of tropic responses depends on the
direction of the stimulus, whereas the direction of nastic
movements is independent of the stimulus' position.
• The rate or frequency of these responses increases as
intensity of the stimulus increases.
• Example: the opening and closing of flowers
(photonastic response).
Examples…
Thigmonasty in Mimosa
• When the leaves of the Mimosa plant are touched they droop down and the leaflets
fold up.
• It happens in seconds, due to the loss or turgor pressure in special cells at the joints
of the leaves and leaflets.
• The cells pump out potassium ions, which causes water to be lost rapidly by osmosis.
• The folding effect spreads from the touched leaf to neighbouring leaves.
• The transmission involves an electrical impulse rather like in animal nerve cells, but
may also involve a hormone.
• It takes about 10 minutes to ‘reset’ the cells.
Thigmonasty in the Venus fly trap (MB 19)
Similar mechanism to shut its trap.
Read the information on page 19, and discuss why the trap has a memory.
Sleep movements by runner beans / opening and closing of flowers
• Many legumes (runner beans) lower their leaves in the evening then raise them in the
morning (called sleep movements). Mechanism similar to Mimosa.
• Many flowers open their petals in the morning and close at night; or vice versa.
Mechanism similar to Mimosa.
Why do plants do this?
Watch it on
Photonasty in action:
Protective leaf movements of Oxalis acetosella
Oxalis triangularis Photonasty Timelapse
Summary of Movement
responses
(MB 53)
Taxes
(MB page 52)
A taxis (pl. taxes) is a directional response of the WHOLE organism or cells
(slater, sperm, algae) to a directional stimulus.
Examples include:
Phototaxis…
Thermotaxis…
Chemotaxis…
Hydrotaxis…
Geotaxis…
Rheotaxis…
Tropotaxis: Two or more receptors compare the stimulus simultaneously to
determine the direction to move in.
Examples: (Sharks lateral line system).
Klinotaxis: A single receptor is used to calculate the direction of the stimulus
(maggots larva, light)
Examples:
Tropotaxes and Klinotaxes: an
overview
Tropotaxis: taking simultaneous samples from paired
receptors.
In positive tropotaxis, the animal orients the body axis so
that the stimulus is received by both sense organs at
equal strength, then moves forward. If the stimulus
increases on one side, the animal turns toward this side,
and so moves up a gradient.
Tropotaxis is most common in chemical orientation.
Klinotaxis: A single receptor is used to calculate the
direction of the stimulus (maggot larvae only have one
receptor for light and must keep turning its head from
side to side to detect the intensity of light).
Tropotaxes and Klinotaxes: an
overview
Example: antenna-crossing experiments of Martin
Martin chilled honey bees to keep them from stinging, then glued their
right antennae facing to the left, and their left antenna facing right.
The bees were first trained in a Y maze to follow an odor to a food
source, then given the crossed-antenna treatment and presented
with a choice between the odor previously associated with food and
an unfamiliar control odor in the other arm of the Y.
Control bees with unmanipulated antennae went correctly toward the
conditioned odor, as did bees whose antennae were glued but in the
normal position, as a control for the effect of gluing. Bees whose
antennae were glued in the crossed position always chose the
wrong arm of the maze, proving that they were performing tropotaxis
by simultaneous sampling across both antennae.
If they had been orienting by successive samples in klinotaxis, treating
the input from both antennae as a single sample, they would have
moved correctly despite the crossed antennae.
Kinesis (pl. Kineses): pp. 52-53
A kineses is a non-directional response of the
individual to the intensity of a stimulus.
The rate of turning or speed of the organism
relates to the intensity of the stimulus.,
As the response is nondirectional, we do not
mention positive or
negative when
describing the response
of the organism.
Examples: …
Types of kineses
• Orthokinesis:
• Klinokinesis:
Environmental Stimuli
Behaviour
Advantage to
organism
Response Type
Plant Responses
Animal Responses
Usually part movement
Usually whole org. movement
Stimulus
Tropisms
Protection from
Predator/
desiccation
Nastic Responses
Non-directional
Directional
Kinesis
Taxes
Homing and Migration
HOMING: (MB page 53)
The return to a home base after a journey usually daily in
search of food or mates.
MIGRATION: (MB pages 53 – 54)
The regular, repeated mass movement of animals usually
annually or once in a lifetime for breeding or avoidance
of climatic extremes.
ADVANTAGES:
DISADVANTAGES:
Animals remain in a favourable
temperature
They may get lost or caught up in a
storm
They grow larger
They may get eaten by a predator
They leave more offspring
They may use up too much energy in
the migration, leading to exhaustion
Constant supply of food
They may starve
It may lead to a colonisation of a new
area
It is a HUGE investment in energy
Reduces predation/parasitism disease
Greater genetic mixing
Better breeding conditions
Migration: Triggers (MB page 55)
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•
•
•
Maturation
Environmental clues
Innate Genetic drive
Endogenous circadian rhythm
Questions
Plant responses: Pathfinder, end of Unit 7 (page 26)
Animal orientation responses: Pathfinder, end of Unit 2 (page 8)
Methods of homing and
migration (MB page 55 – 59)
• Methods used to find home are often the same
methods that animals use to migrate long
distances.
• Survival of an animal may depend on the
accuracy of its navigation.
• Navigation can be complex – not fully
understood in some cases. Homing Pigeons can
use more than one sense (e.g. if they were
blind-folded).
• A certain amount of learning involved (e.g.
experienced birds navigate better than young).
Methods Mix-Up
Find the method term, definition and example for each of the three
methods in the table below. Find the meaning of the terms listed in bold.
Grey whales migrate
from Alaska to Baja
California and back
using visual clues
provided by the
pacific coastline of
North America.
Piloting
Determining ones
position relative to
other places, using a
map sense and
sense of timing.
Navigation
Night migrating birds use a
star compass. There is a
point in the northern
celestial pole where the
stars seem too rotate the
least. These birds were
shown to orient towards
the part of the sky that
rotated the least.
An animal can detect compass
direction and travels in a
straight line until it
reaches its destination.
(how?)
When an animal moves from one
familiar landmark to another
until it reaches its destination
using visual clues.
Immature starlings captured in the
Netherlands end released in
Switzerland did not compensate
for the relocation during their
Autumn migration. Instead,
they travelled southwest, their
normal migratory direction, and
ended up in incorrect wintering
areas.
Compass orientation
Methods Mix-Up
Find the method term, definition and example for each of the three
homing and migration methods in the table below.
Grey whales migrate
from Alaska to Baja
California and back
using visual clues
provided by the
pacific coastline of
North America.
Piloting
Determining ones
position relative to
other places, using a
map sense and
sense of timing.
Navigation
Night migrating birds use a
star compass. There is a
point in the northern
celestial pole where the
stars seem too rotate the
least. These birds were
shown to orient towards
the part of the sky that
rotated the least.
An animal can detect compass
direction and travels in a
straight line until it
reaches its destination.
When an animal moves from one
familiar landmark to another
until it reaches its destination
using visual clues.
Immature starlings captured in the
Netherlands end released in
Switzerland did not compensate
for the relocation during their
Autumn migration. Instead,
they travelled southwest, their
normal migratory direction, and
ended up in incorrect wintering
areas.
Compass orientation
Watch it on
‘Supernatural’ powers of ocean animals
Methods used by animals to
navigate (MB 56-59)
Visual clues
Solar navigation
Magnetic fields
Star (stellar) navigation
Chemical navigation
Sound used as sonar
SELF CHECK!
Questions in MB page 61
Requirement for timing
(MB page 62)
Biological clock
This is an internal timing system which continues
without external time cues, and controls the
timing of activities of plants and animals.
Examples:
•
•
•
•
•
Circadian
Circatidal
Circasemilunar
Circalunar
Circannual
Definitions that you need to know:
Period of the rhythm
Phase shift
Free running period
when the biological clock is running without any clues from the environment
Entrainment (resetting)
This is the resetting of the biological clock on a regular basis.
This forces the biological clock to take up the period of the environment, and is done by a
zeitgeber
Zeitgeber (‘time giver’)
This is the environmental agent that resets the biological clock.
This could be light, temperature, tides, etc.
Circa
this means ‘about’.
Photoperiod
the response of plants and animals to the lengths of day and night are called
photoperiodic responses
Advantages of having a
biological clock
• Organisms need a method of sleeping and
waking in constant conditions
• Prediction of events like migration and
hibernation in response to approaching
environmental extremes (winter, drought)
• Physiological readiness and synchronicity
for mating
Biological clocks are used for
five things…
What are they?
(MB page 62)
BIOZONE EXERCISES:
BIORHYTHMS (page 188-189)
Human rhythms (MB page 65-)
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•
•
•
•
•
•
•
•
Sleep
Temperature changes
Heart rate rhythms
Pain rhythms
Alcohol metabolism rhythms
Efficiency curve for learning
Renal rhythms
Birth and death
Endocrine system rhythms
Disturbing the sleep rhythms: Jet lag and Shift work
Actograms
Actogram — a type of graph or chart commonly
used in circadian research to plot activity
(present or absent) against time .
Photoperiodism
Short and long-day plants
Day - neutral plants
Let’s do it…
Biozone:
Plant rhythms
Photoperiodism in plants
The phytochrome system
Phytochrome is a photoreceptor, a pigment that plants
use to detect light. It is sensitive to light in the red and
far-red region of the visible spectrum. Many flowering
plants use it to regulate the time of flowering based on
the length of day and night (photoperiodism) and to set
circadian rhythms. It also regulates other responses
including the germination of seeds, elongation of
seedlings, the size, shape and number of leaves, the
synthesis of chlorophyll, and the straightening of the
epicotyls or hypocotyls hook of divot seedlings. It is
found in the leaves of most plants.
Who? What? Wow!
Other plant hormones
Giberellins
Cytokinins
Abscisic Acid (ABA)
Ethelene gas
Florigen
GIBERELLINS
WHO??
WHAT??
WOW…
A group of more than sixty chemicals.
Gibberella fungikuroi was the first
organism discovered to produce a
gibberellin (GA3). Produced in young
leaves and buds.
Mainly causes rapid internodal
growth. Also causes flowering in LDP,
flowering in biennials, germination,
horticultural uses…
Dwarf plants can grow to ‘normal’
dimensions when sprayed with a
suitable gibberellin!
CYTOKININS
WHO??
WHAT??
WOW…
Produced in the roots (mainly) to
regulate cell division.
Promotes cell division but its effects
are regulated by auxin:
High auxin: root growth
High cytokinin: buds & leaves
Equal proportions: callous
Bonsai trees are created by trimming
roots (cytokinins are produced in the
root tips). Shoot auxin prevents lateral
buds from forming.
ABSCISIC ACID (ABA)
WHO??
WHAT??
WOW…
An inhibiting hormone that functions
as the chemical antagonist of auxin,
cytokinins and gibberellins (which all
promote growth of some sort).
Plays a part in the abscission of the
leaves of deciduous trees in autumn, bud
dormancy, seed dormancy.
ABA may also play a part in plants
withstanding drought conditions.
ETHELENE GAS
WHO??
WHAT??
WOW…
FLORIGEN
WHO??
WHAT??
WOW…
Plant hormones revisited:
Mix & Match…
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Slows down aging in plants
Prevent yellowing and dropping of leaves
Regulate the process of cell division
Promote cell division in intact plants and in tissue cultures
Depending on the hormone: hormone ratio, a callus, roots or shoots will
form
Auxin

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
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
Plays a role in the dropping of leaves in autumn
Helps plants withstand drought conditions (close stoma)
It is in high concentration in seeds
it needs to be washed out before the seed
will germinate (plant ensures favourable conditions)
Cytokinins


Encourages root development
Synthetic forms are used as herbicides


Increases the internode length
Causes flowering of biennials that normally need a period chilling
(vernalisation)
Promotes germination of seeds that normally would germinate with difficulty
Increases the size of seedless grapes; celery stalks longer
Florigen
Ethelene gas


Abscisic acid
‘Theoretical’ hormone that promotes flowering in plants
Gibberellins
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Fruit ripening (bananas, apples, grapes)
Dropping of fruit (cherries, blackberries)
Accelerates aging of tobacco leaves
Rubber in rubber trees flow longer
Plant hormones revisited:
Answers…
Florigen

‘Theoretical’ hormone that promotes flowering in plants
Auxin


Encourages root development
Synthetic forms are used as herbicides





Slows down aging in plants
Prevent yellowing and dropping of leaves
Regulate the process of cell division
Promote cell division in intact plants and in tissue cultures
Depending on the hormone: hormone ratio, a callus, roots or shoots will
form





Fruit ripening (bananas, apples, grapes)
Dropping of fruit (cherries, blackberries)
Accelerates aging of tobacco leaves
Rubber in rubber trees flow
longer





Plays a role in the dropping of leaves in autumn
Helps plants withstand drought conditions (close stoma)
It is in high concentration in seeds
it needs to be washed out before the seed
will germinate (plant ensures favourable conditions)


Increases the internode length
Causes flowering of biennials that normally need a period chilling
(vernalisation)
Promotes germination of seeds that normally would germinate with difficulty
Increases the size of seedless grapes; celery stalks longer
Cytokinins
Ethelene gas
Abscisic acid
Gibberellins

