5.5) Plant and Animal responses Flashcards
tannins?
Plant responses
- toxic to microorganisms and larger herbivores and make the leaf taste bad
- they prevent infiltration by pathogenic microorganisms
- In the leaves, they are found in the upper epidermis
alkaloids?
Plant responses
- derived from amino acids. In plants, scientists think they are a feeding deterrent to animals, tasting bitter
- they are located in growing tips and flowers, and peripheral cell layers of stems and roots
pheremones?
Plant responses
chemicals which are released by one individual and which can affect the
behaviour or physiology of another.
What is tropism?
Plant responses
a directional growth response in which the direction of the response is determined by the direction of the external stimulus.
What is positive and negative tropism?
Plant responses
(+) When a plant grows toward the stimulus
(-) When a plant grows away from the stimulus
What are the 4 main tropisms?
Plant responses
Phototropism 🌞
Stimulus: Light
Example: Plant shoots bend toward sunlight (positive phototropism), while roots grow away from light (negative phototropism).
Gravitropism (Geotropism) 🌍
Stimulus: Gravity
Example: Roots grow downward (positive gravitropism), while stems grow upward (negative gravitropism).
Thigmotropism 🤲
Stimulus: Touch or contact
Example: Vines wrapping around a support (positive thigmotropism), or plant parts avoiding obstacles (negative thigmotropism).
Hydrotropism 💧
Stimulus: Water
Example: Roots growing toward a water source (positive hydrotropism).
hormone binding
Plant responses
- hormones reach their target cells, they bind to receptors on
the plasma membrane. - Specific hormones have specific shapes, which can only bind to specific receptors with complementary shapes on the membranes of particular cells. 3. This specific binding makes sure that the hormones only act upon the correct tissues.
Auxins?
Plant responses
- Stimulate cell elongation (especially in shoots).
- Control tropisms (e.g., phototropism, gravitropism).
- Promote root development in cuttings.
Apical Dominance
Definition: The phenomenon where the main shoot tip (apical bud) inhibits the growth of lateral (side) buds
High auxin levels at the top suppress lateral bud growth.
If the apical bud is removed, auxin levels drop, and side branches start growing.
Commercial use of Auxins
Plant responses
Auxins are used as herbicides to kill weeds.
Because they are man-made, plants find them more
difficult to break down, and they can act within
the plant for longer. They promote shoot growth so
much that the stem cannot support itself, buckles
and dies.
Giberellins?
Plant responses
- Gibberellins regulate growth and development by promoting cell elongation, seed germination and division
- Stem Elongation
- Helps plants like sugarcane and grapes grow longer internodes
Seed Germination
* Breaks seed dormancy, triggering germination.
* Converts stored starch into sugars to provide energy for growth
Promotes early flowering in some plants
* Helps in fruit growth and size expansion e.g, seedless grapes
Commercial use of Gibberellins
Plant responses
- Gibberellins can make apples elongate to improve their shape.
With gibberellins, grape stalks elongate, they are less compacted, and the grapes get bigger - When barley seeds germinate, the
aleurone layer of the seed produces amylase enzymes that break
down stored starch into maltose - Spraying sugar cane with gibberellins stimulates growth between
the nodes, making the stems elongate. This is useful because
sugar cane stores sugar in the cells of the internodes
Cytokinins?
Plant responses
- Promote cell division
- Delay leaf senescence
- Overcome apical dominance
- Promote cell expansion
commercial use of cytokinins
Plant responses
cytokinins can delay leaf senescence, they are
sometimes used to prevent yellowing of lettuce leaves after they
have been picked
Abscisic acid
Plant responses
- Inhibits seed germination and growth
- Causes stomatal closure when the plant is stressed by low water availability
commercial use of abscisic acid
Plant responses
Used in agriculture to improve a plant’s tolerance to drought by regulating stomatal closure, reducing water loss in crops like grapes and wheat.
Ethene
Plant responses
Promotes fruit ripening
Commercial use of Ethene
Plant responses
- speeding up fruit ripening in apples, tomatoes and citrus fruits
- promoting fruit drop in cotton, cherry and walnut
knee jerk reflex
The knee jerk reflex is a spinal reflex - the nervous pathway
passes through the spinal cord rather than through the brain.
The muscle at the front of the thigh (quadriceps)
contracts to straighten the leg. This muscle is attached to the
patella tendon that connects the patella to the
lower leg bones at the front of the knee. When the muscles at
the front of the thigh are stretched, specialised stretch receptors
called muscle spindles detect the increase in length of the
muscle. If this stretching is unexpected, a reflex action causes
contraction of the same muscle.
medulla oblongata
The brain
transfers info to the spinal cord, located in brainstem
* controls heart rate
temporal lobe
The brain
process auditory information, language, memory, and emotions
occipital lobe
The brain
responsible for visual perception, including colour, form and motion
cerebellum
The brain
motor controls, balance, posture , coordination
frontal lobe
The brain
controls voluntary movement, thinking, and social skills
* personality
Parietal lobe
The brain
processes sensory information, such as touch, pressure, pain, and temperature
