5.1.5 Plants and animal responses Flashcards
What are the similarities in the action of plant and animal hormones in cell signalling?
- Hormones bind to RECEPTORS
- Cause a cascade of enzyme reactions
- May involve in the switching on/off of genes
- Can have an affect on more than 1 TARGET TISSUE
Why are plants able to form more natural reproductive clones than animals?
- Most plant cells are able to retain to differentiate to different cells (TOTIPOTENT)
- Plants have meristems
- Animal cells cant differentiate into all cell types (multipotent)
Mechanism of Photo tropism
- Apical Cells (The apex/Tip of the shoot) produce auxins
- Auxins diffuse down the shoot (through the parenchyma)
- Auxins diffuse to the shaded side
- Causes elongation of the cells of the shaded side
- Bends the plant towards the light source
Mechanism of neuronal communication (steps)
- Stimulus is picked up by the (named receptor)
- Causes depolarisation of the sensory neurone
- Action potentials are sent through the sensory neurone to the CNS (Brain or Spinal Cord)
- Relay neurone relays the response down the motor neurone via action potentials
- Synapses are present throughout the entire process (can explain how they work)
- Motor neurone connects to a neuromuscular junction (receptor: muscle)
- Causes depolarisation of muscle fibres
- Causes muscle contraction
- Actin and myosin slide over each other
3 ways farmers can maximise the efficiency of the transfer of energy up the food chains to primary consumers
- Reduce their metabolic rate by reducing their movement
- Keep them in optimum temperatures (stress free)
- High protein caloric foods
- Slaughter when mature
Physical Plant responses to Herbivory
- Thorns
- Inedible tissue
- Stings
- Barbs
- Hairy Leaves
Chemical Plant responses to Herbivory
- Tannins ( Bitter and Toxic to insects)
- Alkaloids ( Bitter nitrogenous compounds)
- Pheromones ( Warn other plants when under attack, elicits a response in other plants to defend themselves)
Mimosa pudica plant deffences
- Contains a toxic alkaloid
- Stem sharp Prickles
- Quick folding leaves (K+ ion channels water follows causing rigidity)
Why are some plant pheromones not pheromones?
- Volatile Organic Compounds (VOC)
- Similar to pheromones
What tropisms are present in plants?
- Phototropism
- Geotropism
- Hydrotropism
Plant responses to abiotic stress
- Leaf loss
- Stomatal control
- Freezing Prevention
Role of hormones in Leaf loss (deciduous) (steps)
- Lengthening of day triggers a number of changes in the plant
- Falling light levels mean lower amounts of auxins
- The lower concentrations of auxins lead to ethene being produced
- Abcsiion zone on the leaf stalk is sensitive to ethene
- Ethene causes gene switching which results in digestive enzymes being produced weakening the abscission zone
- Vascular bundles going to the leaf are sealed off
- More abiotic stress causes the leaf to fall
Role of hormones in Stomatal control (steps)
- Produce ABA which causes stomatal closure
- ABA binds to the plasma membrane of guard cells
- This causes a decrease in water pressure closing the stomata
Role of hormones in seed germination (steps)
- Water absorption by the seed promotes the production of gibberellins
- This stimulates the production of enzymes that break down food stores
- The plant uses this for growth
Role of Gibberellins
- Stem elongation
- Stimulates the breakdown of food stores (germination)
- Pollen tube fertilisation
Role of Auxins
- Cell elongation
- Prevent leaf fall
- Maintain Apical dominance
- Root growth
Role of ethene
- Leaf abscission in deciduous trees
- Fruit ripening
Role of ABA
- Maintain Dormancy of seeds
- Stimulates stomatal closure
What effects do HIGH concentrations of auxins have?
- Suppress lateral growth
- Allows for apical dominance
- Further down the stem there is less auxins so lateral growth occurs more
What effects do Low concentrations of auxins have?
- Promote root growth
- High concentrations inhibit it
- Allows more lateral growth
Experimental evidence for the role of auxins
- Shoot of the tip removes
- No growth and elongation of the plant
Experimental evidence for gibberellins
- Mutant seeds which don’t produce gibberellins don’t germinate
- When Gibberellin biosynthesis inhibitors are applied the seeds don’t germinate
- Stem elongation which produce elongation in plants
Commercial use of plant hormones
- Ripening Ethene
- Weedkillers Auxins
- Hormonal rooting powder (contains auxins which promote root growth)
What does the CNS consist of?
- Brain and spinal cord
What does the peripheral nervous system consist of?
- Neurones connected to the spinal cord
- Sensory, motor
What are the 2 functional organisations of the nervous system?
- Somatic nervous system
- Autonomic nervous system
Somatic Nervous system
- Under conscious control
Autonomic nervous system
- involuntary responses i.e. heartbeat, digestion, arteriole dilation/constriction
Structure and function of the human brain
- Cerebrum (Control voluntary actions, learning, thought etc)
- Medulla oblongata (Autonomic control of heartbeat breathing)
- Hypothalamus ( regulatory centre for water and temperature balance (produces hormones))
- Cerebellum (Controls unconscious function balance, posture etc) (small bottom of the brain)
- Pituitary gland ( stores and releases hormones also produces some hormones (anterior))
What is the survival value of reflex reaction?
- Present at birth
- Very fast
- Brain isn’t overloaded
- minimises damage to the body
Knee - Jerk reflex
- Spinal reflex
- Stretching of the patellar tendon acts as a stimulus (action potentials generated)
- Sensory neurones carry action potentials to the relay neurone in the spinal cord
- Relay neurone sends action potential to motor neurones which go to effectors in the leg
- Relaxation of Hamstring flexor and Contraction of Quadriceps
- Used to maintain posture and balance
Blinking reflex
- Cranial reflex
- Stimulus i.e light, sound, or touch generates action potentials
- (C5) Sensory neurone carries the impulse to a relay neurone in the lower brainstem
- Impulses are then sent through (C7) motor neurones to close the eyelids
- Consensual response so both eyelids close
- Protect he eyes
Flight or Flight system (mechanism)
- Hypothalamus communicates with the sympathetic nervous system and the adrenal-cortical system
- Adrenal medulla secretes adrenaline and noradrenaline into the bloodstream
- Heart rate increases, Pupils dialate, Blood glucose increases, Smooth muscles in airways relax
- This is to allow for more oxygenated blood, Better vision, Increase in respiration, More air into the lungs
How does adrenaline work on the liver cells?
- Adrenaline (primary messanger) binds to a receptor
- This activates Adenylyl cyclase
- This converts ATP into cAMP (secondary messenger)
- cAMP activates other enzymes through a cascade effect which turn glycogen into glucose
Glycogenolysis
- Break down of glycogen into glucose
Gluconeogenesis
- Production of sugars from fat, pyruvates and lactae etc
Glycogenesis
- Conversion of glucose into glycogen
How is heart rate controlled (nerves include)
- Medulla oblongata is responsible for the control of the heart rate
- Heart rate is DECREASED by the parasympathetic pathway through the vagus nerve connecting to the SAN
- Heart rate is INCREASED through the sympathetic nervous system through the ACCELERATOR NERVE (SAN)
What two receptors can change the heart rate?
- Baroreceptors (detect blood pressure (low - increased heat rate))
- Chemoreceptors (detect CO2 concentration in the blood)
How can hormones such as adrenaline and noradrenaline affect the heart rate?
- Affect the pacemaker reagion in the heart directly
- Increases frequency of impulses produced by the SAN
- This increases the heart rate
Structure of Skeletal muscles
- Straiated
- Multinucleted
- Voluntary
- Cylindrical
Structure of cardiac muscles
- Striated
- Uninucleated
- Involuntary contraction (myogenic)
- Branched shape
Structure of smooth muscles
- No strations
- Uninucleated
- Involuntary
- Spindle shape
What is the mechanism of muscular contrition?
- Wave of depolarisation in the sarcolemma spreads through t - tubules which is connected to the sarcoplasmic reticulum
- This causes Calcium ion channels to open
- Calcium ions flood into the sarcoplasm
- Calcium ions bind to troponin changing its shape
- MYOSIN HEAD BIND TO THE ACTIN FILAMENT FORMING A MYOSIN-ACTIN CROSS BRIDGE
- Myosin head flexes shortening the h-zone ATP molecule fixes to the myosin head causing it to detach
- ATPase hydrolysis ATP back to ADP returning the myosin head back to its original position
- This cycle is then repeated
What is habituation and examples of habituation?
- Repeated stimulation makes the organism accustomed to the stimulus (repolarisation cant occur fast enough)
- Slug withdrawing tentacles
Name a difference between a sensory neurone and motor neurone
- Motor neurones Soma is in the CNS or brain
- Sensory is in the middle of the cell
- Sensory has no dendrites
Give 2 reasons why animals and plants need to respond to changes in the environment
- Accsess to resources
- Avoid predation
