Download orientation responses

ORIENTATION RESPONSES
How organisms position themselves
in relation to their surroundings
Animal Behaviour
• Innate behaviours: also known as instinctive.
These are genetically determined, not
modified by experience. They are inflexible
and stereotyped, “hard-wired”.
• Learnt behaviours: These change as a result
of experience. They are flexible and not rigid.
What are the abiotic stimuli?
STIMULUS
Light
Gravity
Temperature
Water (or Humidity)
Chemicals
Touch
Current (in water)
PREFIX
PhotoGraviThermoHydro- (or Hygro-)
ChemoThigmoRheo-
Simple Animal Orientation Responses
• Taxis
• Kinesis
TAXIS (plural Taxes)
– Orientation and movement of whole
animal towards or away from external
stimulus that is coming from one side only
– Described as positive (toward) or negative
(away from) a stimulus
– Moving toward light = positive photo-taxis
Examples of animal taxes
• Earthworms move away from light back down into
the soil
= Negative phototaxis
• Snails move away when their feelers touch
something ….
= Negative thigmotaxis
• Flatworms and sharks move towards meat
= Positive chemotaxis
Mosquito moves toward warm skin
What’s the advantage?
• Puts the animal in a more favourable position
• Avoids unfavourable conditions (hot, cold etc)
• Increased survival and reproduction
How do animals determine the
direction of the stimulus?
• Two sense organs: By comparing the input
from receptors on each side of the animal at
the same time
• Differences between sides show the direction
of the stimulus (eg. Snail antennae)
• OR One sense organ: Compare the change
from a single sensor over time, using its body
orientation to determine stimulus direction
KINESIS (plural kineses)
= Non-directional response to a change in
stimulus intensity ….. It is not orientating
– Animal may simply turn randomly or change its
rate of movement
– Slater moves more
when it is hot
= thermokinesis
More terms to know
Orthokinesis = the stimulus intensity
determines the organism’s speed of
movement
Klinokinesis = the stimulus intensity
determines the organism’s
rate of turning
Examples of Kineses
• Slaters move faster in bright light and slower
in dim light
= photo-orthokinesis (or photokinesis)
• Woodlice: move faster and turn more in high
humidity vs. low humidity (hygro-)
= hygro-orthokinesis, hygro-klinokinesis
(or hygrokinesis)
• Human body lice turn more at 35°C than at
lower temps
= thermo-klinokinesis (or thermokinesis)
What’s the advantage?
• Puts the animal in a more favourable position
by moving faster or randomly turning
• Eg. Slaters will end up in dark, damp places
which prevents drying out (dessication)
• Avoids unfavourable conditions (hot, cold etc)
• Increased survival and reproduction
BIOZONE questions
• Taxes and Kineses
• Do all the questions on page 5
NCEA 2006 question
• Much of animal behaviour is innate, or inborn. Such
behaviour patterns may be quite simple, or are
produced in response to simple stimuli. They include
kineses and taxes.
• (a) Describe an example of kinesis in a named
animal.
• (b) Explain why this behaviour would be an
advantage to your named animal in its normal
environment.
Plant Orientation Responses
Plants are capable of a number of movements in
response to environmental stimuli.
eg. Temperature, humidity, light, touch, chemicals
1. NASTIC RESPONSES: non-directional rapid
responses to stimuli
2. TROPISMS: Directional slower growth
responses towards or away from a directional
stimulus
Nastic Responses
Rapid, reversible, non-directional movement
responses by parts of a plant to changes in
abiotic factors such as:
– Light intensity
– Heat
– Touch
– chemicals
– Water
– gravity
• Non-directional, so they do not have a
positive or negative aspect to the movement.
• They occur due to changes in the intensity of
the stimulus.
• Generally: the rate or frequency of these
responses increases as intensity of the
stimulus increases.
• They are named with the suffix "-nasty" and
have prefixes that depend on the stimuli
• Eg. Photonasty: response to changing light intensity
Examples of plant responses
• Mimosa pudica: the sensitive plant
• https://www.youtube.com/watch?v=BLTcVNy
OhUc
• Venus fly traps – jaws of death
https://www.youtube.com/watch?v=O7eQKSf0L
mY
Caused by…
• Generally they are caused
by rapid changes in
osmotic pressure in
certain cells.
• This leads to a sudden loss
of turgor pressure
– Eg. mimosa leaves folding
up
What’s the adaptive purpose?
• A nastic response removes a plant, or part of a
plant, from unfavourable environmental
conditions…. Placing it in favourable
environmental conditions.
Eg. Mimosa plant
• When the sensitive leaves are touched, they
droop down and fold up rapidly
• = Thigmonasty
• Advantage: why?
• Reduces the plant’s
Surface area for grazing
And abiotic stress.
Venus Fly Trap Plant
What happened?
What was the stimulus?
Advantages?
Photonasty
• The collapse of leaves when exposed to high
light intensity.
• Eg. the leaves of the Oxalis plant, which are
normally horizontal, collapse and droop
downwards when light increases.
• Why? May prevent damage to the leaf’s cells
from exposure to high light intensities.
Other examples
• Opening/closing of tulip and crocus flowers
due to changes in air temperature
– Called?
PLANT TROPISMS
• Directional growth response that occurs in
response to an external directional stimulus
• May be positive (towards stimulus) or
negative (away from stimulus)
• Tropism comes from a Greek word ‘tropos’
meaning “to turn” or “to change”
Why?
• Plants can alter their growth so they can grow
towards more favourable conditions
(eg. More light, more water etc)
• Must detect where the conditions are better
then alter their growth to "move" in the
appropriate direction
PHOTOTROPISM
= the directional growth response of a plant in
response to a light stimulus.
• Different parts of a plant exhibit different
reactions to light.
• Stems and shoots exhibit positive phototropism
(grow toward light)
• Most roots exhibit negative phototropism (grow
away from light)
GRAVITROPISM
= the directional growth response of a plant in
response to gravity.
• Roots exhibit positive gravitropism (towards)
• Stems and leaves exhibit negative gravitropism.
THIGMOTROPISM
• Thigmotropism is the growth
response of a plant to physical
contact (touch).
• Plants that cling to physical
structures such as sticks exhibit
positive thigmotropism.
HYDROTROPISM
• Directional growth in
response to presence
of water in the soil
• Roots = positive
hydrotropism
(grow toward water)
Note: stronger than
gravitropism
CHEMOTROPISM
• Directional growth in response to a chemical
stimulus
• eg. Roots can grow towards or away from
chemicals in the soil (copper pipe)
• eg. Growth of pollen tube towards ovary in
flowers (ovary releases chemicals)
THIGMOMORPHOGENESIS !!
An alteration in growth patterns caused by touch
(eg. wind, rain)
Type of tropism? Positive or negative?
One Advantage?
1.
2.
3.
4.
5.
6.
7.
8.
Roots of a seedling grow down ……………………..
Stem of vine winds around a branch………………..
Leaves of pot plant turn toward window………..
Roots of willow grow sideways toward water……
Roots grow away from copper pipes in soil….
Shoots of seedling grow upward in dark lab…
Pollen tube in flower grows toward ovary…..
Tree grows sideways on an exposed mountain…
Control of Plant Growth
• Plant growth is controlled by HORMONES
• These are chemicals produced in one part of
the plant and transported to where they
produce a growth response.
Terminology…
Coleoptile
(co – lee – op – tile)
is the protective sheath
covering the emerging
shoot in plants such as oats
and grasses.
Auxins
• A group of hormones that
regulate plant growth
• Indole Acetic Acid, IAA
(the first auxin isolated)
• Made in the tips of the shoots
and roots, and can diffuse to
other parts of the shoots or
roots.
• Causes cell elongation in stems
Phototropism in Coleoptiles….
• Tip of shoot detects light
stimulus, auxin is produced
• Auxin causes cell elongation
in the stem
If light comes from an angle:
• Auxin moves to shaded side
of stem, cells elongate
• Shoot bends towards light
Auxin moves to shaded side and causes cell
elongation - stem bends towards light source
• More auxin on
the shaded side
• Cells elongate
• Stem bends
toward light
over time
The diagram shows the typical results shown by
oat seedlings grown in a box with a light from one
side
Seedlings Results and explanations
A
The tips have been removed. No auxin is
produced and the shoots do not grow longer.
B
The tips have been covered so light cannot
reach them. Auxin is in the same concentration
on both sides of the shoots, so they grow
evenly and longer on both sides.
C
One side of the tips are in more light than the
other side. Auxin is in a greater concentration
on the shaded side, causing the cells there to
grow longer than the cells on the lit side.
Shoot bends towards the light.
TROPISMS….. You tube clip:
Plant Physiology: Phototropic Response
http://www.youtube.com/watch?v=zctM_TWg5Ik
Experiments with Grass/Oat Coleoptiles
•
Shoots and roots respond differently to high
concentrations of auxins:
• cells in shoots grow more
• cells in roots grow less.
Gravitropism in roots
• In roots, perception of gravity appears to depend
on the settling of specialised organelles called
statoliths in root-cap cells. Statoliths are denser
than cytoplasm.
• When the plant is turned, within minutes the
statoliths sink toward the source of gravity, to the
side that is down.
• This signal causes redistribution of auxin streams
in the root cap and root as a whole.
Statoliths
sink
towards
the source
of gravity
(down)
Auxin and root growth
• Auxin builds up on the lower side of the root
cap, causing inhibition of cell elongation and
downwards growth of the root.
(note – auxin causes an opposite effect in roots
compared to shoots)
• Pea shoot time lapse….
https://www.youtube.com/watch?v=eDA8rmUP
5ZM
THIGMOTROPISM
• Growth is inhibited on the side
of stem being touched
• Cells elongate on the nontouching side due to auxin
• Causes the stem to coil around
the object being touched
Worksheet
• Have a go at all
the questions
Terminology time!
COLEOPTILE = the protective sheath covering tip of the first new shoot from a seed
Darwin studied phototropism in canary grass and oat coleoptiles. The coleoptile is a
hollow sheath of tissue which surrounds the apical axis (stem) of these and other
grasses. Darwin demonstrated that these coleoptiles are phototropic in that they
bend toward a light source. When he covered the tips of the coleoptiles, they were
not phototropic but when he covered the lower portions of the coleoptiles, they
were phototropic. Darwin concluded from these and other experiments that (a)
the tip of the coleoptile is the most photosensitive region; (b) the middle of the
coleoptile is responsible for most of the bending; and (c) an influence which
causes bending is transmitted from the top to the middle of the coleoptile.
Read more: Phototropism - History Of Phototropism Research - Coleoptile,
Darwin, Coleoptiles, Plant, Agar, and Light
http://science.jrank.org/pages/5197/Phototropism-History-phototropismresearch.html#ixzz10OQbtO20