5.5- Plant and animal responses Flashcards
Describe different types of stimuli plants respond to
- biotic and abiotic components of the environment
- Examples- depositing thicker layers of wax on leaves in response to higher temperatures, signifying vascular tissue more heavily when very windy, chemical responses to herbivores
What is the ultimate purpose of plants responding to the environment
Helps plants survive long enough to reproduce
Name 3 different chemical defences in response to the threat of herbivores
- Tannins
- Alkaloids
- Pheromones
Describe Tannins
- toxic to microorganisms and larger herbivores
- in leaves, found in upper epidermis- make leaf taste bad
- in roots, prevent infiltration by pathogenic microorganisms
Describe Alkaloids
- derived from amino acids
- located in growing tips and flowers, and peripheral cell layers of stems and roots
- Bitter taste- feeding deterrent to animals
Describe pheromones
- chemicals released by 1 individual which can affect the behaviour or physiology of another
Describe different categories of plant responses
- tropisms- directional growth response
- positive tropic- plant responds towards stimulus
- negative tropic- plant responds away from stimulus
- nastic- non-directional to external stimuli
Describe an example of nastic responses
- sensitive plant Mimosa podia responds to touch with sudden falling of the leaves
- response is example of thigmonasty
Name different types of tropisms
- phototropism
- geotropism
- chemotropism
- thigmotropism
Describe phototropism
- shoots grow towards light (positively phototrophic)
- enables them to photosynthesise
Describe geotropism
- roots grow towards pull of gravity
- this anchors them in soil and helps them to take up water- needed for support (keeps them turgid), as a raw material for photosynthesis, to help cool the plant, and to carry minerals e.g. nitrate needed for the synthesis of amino acids
Describe chemotropism
- on a flower, pollen tubes grow down to the style, attracted by chemicals, towards the ovary where fertilisation can take place
Describe thigmotropism
- Shoots of climbing plants, such as ivy, wind around other plants or solid structures to gain support
Describe the role of hormones in plant responses
- coordinate plant responses to environmental stimuli
- chemical messengers that can be transported away from their site of manufacture to act in other parts (target cells or tissues) of the plant
- produced in a variety of tissues in the plant (not endocrine glands)
Describe the action of plant hormones
- when they 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
- specific binding means hormones can only act on correct tissues
- some hormones can have different effects on different tissues, some can amplify each other’s effects, and some can cancel out each other’s effects
- can influence cell division, differentiation, or elongation
Name 5 different plant hormones
- Cytokinins
- abscisic acid
- auxins (e.g. IAA- indole 3-acetic acid)
- gibberellins
- ethene
Describe cytokinins (plant hormones)
- promote cell division
- delay leaf senescence
- overcome apical dominance
- promote cell expansion
Describe abscisic acid (plant hormones
- inhibits seed germination and growth
- causes stomatal closure when the plant ios stressed by low water availability
Describe Auxins (plant hormones)
- promote cell elongation
- inhibit growth of site-shoots
- inhibit leaf abscission (fall)
Describe gibberellins (plant hormones)
- promote seed germination and growth of stems
Describe ethene (plant hormones)
Promotes fruit ripening
What is the apex of a plant
The tip
Which plant hormones are responsible for regulating plant growth
Auxins
What happens if you break the shoot tip off a plant
The plant starts to grow side branches from lateral buds that were previously dormant
Describe the scientific research process into auxins
1) Researchers first suggested that auxins from the apical bud prevent lateral buds from growing- when the tip is removed, auxin levels in the shoot drop and the buds grow. To test this, scientists applied paste with auxins to cut end and lateral buds didn’t grow
2) however, scientists manipulation of the plants could have had unexpected effect on exposure to oxygen- cells on end could have produced a hormone that promoted lateral bud growth
3) Because of this, scientists applied a ring of auxin transport inhibitor below the apex- lateral buds still grey
4) Then suggested that a normal auxin level in lateral bids inhibits growth, whereas low levels promote growth
5) however, 2 variables (auxin levels and growth inhibition) may have no effect on eachotehr- could both be affected by 3rd variable
6) Then suggested that auxin levels in lateral bids of kidney bean actually increased when the shoot tip was cut off
7) Now think that 2 other hormones are involved- Abscisic acid and cytokinins
Name 2 hormones other than auxins that are involved in plant growth
- abscisic acid
- cytokinins
Describe the role of abscisic acid in plant growth
- inhibits plant growth
- high auxin in the shoot keeps abscisic acid levels high in the bud
- when the tip (source of auxin) is removed, abscisic acid levels drop and the bud starts to grow
Describe the role of cytokinins in plant growth
- promote bud growth
- directly applying cytokinin to buds can override the apical dominance effect
- high levels of auxin make the shoot apex a sink for cytokinins produced in the roots- most of the cytokinin goes to the shoot apex
- when the apex is removed, cytokinin spreads evenly around the plant
Describe the apical dominance effect
- refers to the inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of a plant shoot
- The lateral buds are more sensitive to auxin than the apical bud
- There is a concentration of auxin at which the apical bud is stimulated to grow while the lateral buds are inhibited
- When the apical bud is removed, the source of auxin is removed
- Since the auxin concentration is much lower, the lateral buds can now grow
- Thus pruning a shoot will cause it to branch
lateral and apical bud diagram
auxin levels in root, apical bud and lateral bud graph
Describe the role of gibberellins in plant growth
- plant hormones which are responsible for control of stem elongation and seed germination
Describe the effects of differing gibberellin levels in plants
- Researchers found higher levels of GA1 in tall pea plants (homozygous for the dominant Le allele) compared to dwarf pea plants (homozygous for the recessive le allele)
- They worked out that the Le gene was responsible for producing the enzyme that converted GA20 to GA1
Describe the research process investigating the effects of gibberellins of plant growth
1) In japan, a fungus causes disease which makes rice grow very tall- fungal compounds involved are gibberellins and include gibberellic acid (GA3)
2) Scientists tested gibberellic acid on many different plants- when they applied it to dwarf varieties of plants e.g. maize/peas or to rosette plants, they grew taller
3) Suggetss that gibberellic acid is responsible for plant stem growth- however, experiment may not have actually investigated a natural phenomenon just because GA3 CAN cause stem elongation, doesn’t mean that it DOES so in nature- experiment needs to work within concentrations of gibberellins naturally found in plants, and in parts of the plant that gibberellin molecules normally reach
4) To reach this criteria, compared GA1 levels in tall pea plants (homozygous for the dominant Le allele) compared to dwarf pea plants (homozygous for the recessive le allele)- found that plants with her GA1 levels were taller
5) To show that GA1 directly causes stem growth, needed to know how GA1 is formed- worked out the Le gene was responsible for producing the enzyme that converted GA20 to GA1
6) Then research chose pea plant with mutation that blocks gibberellin production between ent-kaurene and GA12-aldehyde- those plants produce no gibberellin and grow to only around 1cm tall
7) Researchers grafted a shoot onto homozygous le plant (which cannot convert GA20 to GA1) and it grew tall- such a shoot, with no GA20 of its own, does have the enzyme to convert GA20 to GA1, and it can use the unused GA2- from the normal plant- as thee shoot grew tall confirmed that GA1 causes stem elongation
8) Further studies have shown that gibberellins cause growth in the internodes by stimulating the production of a protein that controls the cell cycle
Synthesis pathway for gibberellins diagram
Gibberellins stem elongation diagram
What else do gibberellins effect
Seed germination
Describe the effects of gibberellins on seed germination
- promote seed germination
- when the seed absorbs water, the embryo releases gibberellin, which travels to the aleurone layer in the endosperm region of the seed
- the gibberellin enables the production of amylase, which can break down starch into glucose
- this provides a substrate for respiration for the embryo, so it goes
- the glucose is also used for protein synthesis
Branches of the nervous system
Autonomic divided into sympathetic and parasympathetic
Outline the central nervous system
- consists of brain and spinal cord
Describe the brain (brief- CNS)
- contains 86 billion neurones
- much composed of relay neurones
- multiple connections enabling complex neural pathways
- Most cells are non-myelinated and tissue looks grey in colour- grey matter
Describe the spinal cord (brief- CNS)
- spinal cord
- many non-myelinated relay neurones making up the central grey matte
- also contains many myelinated neurons making up outer region of white matter- carry action potentials up/down cord for rapid communication over long distances
- Protected by the vertebral column
- Between each vertebra, peripheral nerves enter and leave the spinal cord carrying action potentials to/from the rest of the body.
What is the role of the peripheral nervous system
- ensures rapid communication between the sesnory receptors, the CNS and the effectors
- composed of sensory and motor neurones- usually bundled together in. collective tossie sheath to from nerves
Describe the somatic nervous system
- motor neurones that conduct action potentials from the CNS to effectors
- under voluntary/conscious control
- e.g. skeletal muscles
- myelinated neurones- rapid responses
- always one single neurone connecting CNS to effector
- can only be stimulatory effect
Describe the autonomic nervous system
- motor neurones that conduct action potentials from the CNS to effectors
- not under voluntary control
- includes glands, cardiac muscle, smooth muscle in the walls of blood vessels, airway, wall of digestive system
- mostly unmyelinated neurones- control of many effectors don’t need to be rapid
- at least 2 neurones involved in the connection between CNS and effector
- neurones connected at small swellings- ganglia
- responsible for controlling majority of homeostatic mechanisms- plays vital role in regulating internal environment of body
- contains sympathetic and parasympathetic system
Describe the action of the sympathetic and the parasympathetic neurones
- sympathetic system prepares the body for activity, and the parasympathetic conserves energy
- differ in both structure and action
- antagonistic system- action of one opposes the other
- at rest, action potentials pass along the neurones of both systems at relatively low frequency
- controlled by subconscious parts of brain
- changes to internal conditions or stress lead to changes in the balance of stimulation between 2 systems- leads to the appropriate response
Compare the structure of the parasympathetic and the sympathetic nervous system
- S consists of many nerves leading out of CNS with each reading to a separate effector, whereas P consisted of just a few nerves leading out if the CNS which divide and lead to different effectors
- S has ganglia just outside the CNSm whereas P has ganglia in the effector tissue
- S has short pre-ganglionic neurones, whereas P has long pre-ganglionic neurones (variable in length, dependent upon position of effector)
- S has long post-ganglionic neuornes (variable in length, dependent upon position of effector), whereas S has short post-ganglionic neuones
- S uses noradrenaline as the neurotransmitter, whereas P uses acetylcholine
Compare the action of the parasympathetic and the sympathetic nervous system
- S increases activity to prepare the body for activity, whereas P decreases activity to conserve energy
- S is most active in times of stress, whereas P is most active during sleep or relaxation
- S increases heart rate whereas P decreases it
- S dilates pupils, whereas P contacts them
- S increases ventilation rate, whereas P decreases it
- S reduces digestive activity, whereas P increases it
- S causes orgasm, whereas P causes sexual arousal
name the 4 main areas of the brain
- cerebrum
- cerebellum
- hypothalamus and pituitary complex
- medulla oblongata
Describe the structure of the cerebrum
- has 2 cerebral hemispheres
- connected via major tracts on neurones- corpus callosum
- outermost layer consists of a thin layer of nerve cell bodies called the cerebral cortex
Describe the functions of the cerebrum
More highly developed in humans than any other organism, controls higher brain functions:
- conscious thought
- conscious actions including the ability to override some reflexes
- emotional responses
- intelligence, reasoning, judgement, decision making
- factual memory
Describe different areas about the cerebral cortex
- sensory areas- receive action potentials from the sensory receptors- size of the regions allocated to receive input from different receptors are related to the sensitivity of the area that inputs are received from
- association areas- compare sensory inputs with previous experience, interpret what the input means, and judges an appropriate response
- moor areas- sen action potentials to various effectors (muscles and glands)- sizes of the regions allocated to deal with different effectors are related to the complexity of the movements needed in the parts of the body. Motot eras on the left side control the effectors on the right side of the body and vice versa.
Lobes of the brain diagram and explanation
A- Frontal lobe- concerned with higher brain functions such as decision making, reasoning, planning and consciousness of emotions. It includes the motor cortex which stores information about how to carry out different movements
B- Parietal lobe – concerned with orientation, movement, sensation, calculation and types of recognition and memory.
C- Occipital lobe – Visual cortex, concerned with processing information from the eyes including vision, colour, shape and perspective
D- Cerebellum- coordinates movement and balance
E- Temporal Lobe – concerned with processing auditory information i.e. Hearing, sound, and recognition of speech. Also involved in memory
Areas of the cerebral cortex diagram
Why is the human brain wrinkled
- cerebral cortex has become enlarged to enable the higher processes to occur
- cerebral cortex is only thin layer of cells- has become enlarged by increasing its surface area which is around 2.5 m2 to fit inside the head
Describe the cerebellum
- contains over half of all the neurones in the brain
- involved with balance and coordination of movement
- must receive information from many sensory receptors and process the information accurately
- sensory organs that supply information- retina, balance organs in the inner ear, spindle fibres in muscles which give information about muscle length, and joints
- the conscious decision to contract voluntary muscles is initiated in the cerebral cortex, however, the CC doesn’t provide the complex signals needed to coordinate complex movements
- coordinates fine control of muscular movement e.g. maintaining body position/balance, judging the position of objects/limbs, tensioning muscles to use instruments/tools, coordinating contraction and relaxation of antagonistic skeletal muscles when walking/running
Describe pathways in the cerebellum
- fine control of muscular movement often requires learning
- once learnt, such activities may become second nature and involve much unconscious control
- this sort of coordination requires complex nervous pathways which are strengthened by practice
- means the complex activity becomes programmed into the cerebellum, and neurones from the cerebellum conduct action potentials to the motor areas so that motor output to he effectors can be finely controlled
How are the cerebrum and cerebellum connected?
The pons
Where does growth happen in plants
Meristems
Describe different types of meristems
- Apical meristems- at tips or apices (apex) of roots and shoots- responsible for roots.shoots getting longer
- lateral bud meristems- found in buds- can give rise to side shoots
- lateral meristems- form cylinder near the outside of roots and shoots- responsible for roots/shoos getting wider
- intercalary meristems- in some plants, located between the nodes, where the leaves and buds branch off the stem- growth between the nodes is responsible for the shoot getting longer
Describe the action of auxin in shoots when the light is on one side of the plant
- produced at the apex of the shoot
- travels to the shaded side if the sun is on one side of the plant (move away from the sun)
- causes cell elongation in the shaded side
- this causes the plant to grow in a bend towards the light, as the cells on the shaded side are elongating whereas those in the light aren’t
- the extent to which cells elongate is proportional to the concentration of auxins
Describe the action of auxin in shoots when the light ISN’T on one side of the plant
- when light equal on all sides, the auxins simply promote shoot growth evenly
Describe the action of auxin in roots
- involved in geotropic responses in roots
- in a root lying flat, auxin accumulates on the lower side- inhibits cell elongation
- the upper side continues to grow and the root bends downwards
- INVESTIGATED BY WENT
Compare the action of auxin in the shoots and roots
- in shoots, shoot lying flat bends upwards as auxins promote cell elongation
- in roots, root lying flat bends downwards as auxins inhibit cell elongation
- happens because root and shoot cells in the elongation zone exhibit different responses to the same concentrations of auxin- concentrations that stimulate shoot growth inhibit root growth
Briefly outline the investigation of phototrophic and geotropic responses
- phototropic responses can be investigated by using an experimental plant and a control plant with 10 replicates
- control is illuminated on all sides while the experimental has illumination from just one side
- in each plant, shoots and roots are marked every 2mm at the start
- after several days, the standard mean and standard deviation of the lengths between the marks has increased on the shady side
Briefly outline the investigation of geotropic responses
- control plant is evenly spun slowly by klinostat to ensure the effect of gravity is applied equally to all sides of the plant
- experimental plant- klinostat is not switched on so gravity is only applied to one side
-in the experimental plant, the root bends downwards because the upper side of the root has elongated more than the lower side- the shoot bends upwards, because the lower side of the shoot has elongated more than the upper side - in the control plant, both root and shoot grow horizontally
name experiments into the effect of plant hormones on phototropisms
- Darwin
- Boysen-Jensen
- Went
Describe Darwin’s experiments into the effect of plant hormones on phototropisms
- confirmed that the shoot tip was responsible for phototropic responses
Describe Boysen-Jensens experiments into the effect of plant hormones on phototropisms
- confirmed that water and/or solutes need to be able to move backwards from the shoot tip for phototropism to happen
- when a permeable gelatine block was inserted behind the shoot tip, the shoot still showed positive phototropism
- when an impermeable mica block was inserted there was no phototropic response
Describe Went’s experiments into the effect of plant hormones on phototropisms
- to demonstrate that a chemical messenger existed and could stimulate a phototropic effect artificially, Went found Agard block containing auxin stimulates growth, offset blocks containing auxin stimulate curved growth, and blocks containing no auxin have no effect
Comparison of autonomic and somatic nervous system diagram
Outline the corneal reflex
- mediated by a sensory neurone from the cornea, which enters the pons
- a synapse connects the sensory neurone to a relay neurones, which passes the action potential to the motor neurone
- the motor neurone passes back out of the brain to the facial muscles, causing the eyelid to blink
- this is a very short and direct pathway, so the corneal reflex is very rapid- takes around 0.1 seconds
- usually causes both eyes to blink even if only 1 cornea is affected
table of physiological changes and survival value caused by the fight or flight response
Describe commercial uses of auxins
- can be used to prevent leaf and fruit drop and can promote flowering for commercial flower production (but in high concentrations can also promote fruit drop)- useful if too many small fruit that will be difficult to cell as the plant then produces fewer
- taking cuttings- dipping the end of a cutting in rooting powder before planting it encourages root growth- rooting powder contains auxins and talcum powder
- seedless fruit- treating unpollinated flowers with auxin can promote growth of seedless fruit (parthenocarpy)- applying auxin promotes ovule growth, which triggers the automatic production of auxin by tissues in the developing fruit, helping to complete the developmental process
- herbicides- kill weeds- as they are man-made, plants find them harder to break down- can act within the plant for longer- promote shoot growth so much that the stem cannot support itself, buckles, and dies
Shoot tip diagram
Outline the pathway of the knee-jerk reflex
- spinal reflex- nervous pathway passes through spinal cord rather than through the brain
- only consists of 2 neurones- sensory to motor
- one less synapse so response is quicker
- higher parts of brain informed that reflex is happening, however, as there is no relay neurone, the brain cannot inhibit the reflex, as inhibition relies on rapid myelinated neurones carrying the inhibitory action potential to the synapse before the motor neurone is stimulated
- in the absence of a relay neurone, the motor neurone is stimulated directly by the sensory neurone and there is insufficient delay to enable inhibition
- this is why doctors test reflexed by tapping the tendon below the knee cap- causes immediate response that cannot be inhibited
Outline the mechanism of adrenaline action
Adrenaline is first messenger- amino acid derivate and therefore can’t enter target cell- must cause effect inside the cell, without entering the cell itself:
1) bind to adrenaline receptor on plasma membrane
2) This receptor is associated with a G protein on the inner surface of the plasma membrane, which is stimulated to activate the enzyme adenyl cyclase
3) Adenyl cyclase converts ATP to cyclic AMP (cAMP) - second messenger
4) cAMP causes an effect inside the cell by activating enzyme action- precise effect depends upon the cell that adrenaline has bound to
Fight or flight pituitary hypothalamus hormones diagram
Fight or flight response pathway diagram
Control of heart rate diagram
involuntary (smooth) muscle diagram
involuntary (smooth) muscle microscopy
Cardiac muscle diagram
cardiac muscle microscopy
appears striated when viewed under microscope
voluntary (skeletal/striated) muscle diagram
voluntary (skeletal/striated) muscle microscopy
Comparison of different muscle types microscopy
Describe the events at a neuromuscular junction
1) Action potentials arriving at the end of the axon open calcium ion channels in the membrane
2) Calcium ions flood into the end of the axon
3) Vescicles of acetylcholine move towards and fuse with the end of the membrane
4) acetylcholine molecules diffuse across the gap and fuse with receptors in the sarcolemma
5) those open sodium ion channels, which allow sodium ions to enter the muscle fibre
6) This causes depolarisation of the sarcolemma
7) a wave of depolarisation spreads along the sarcolemma and down transverse tubules into the muscle fibre
Describe the use of an EMG
- when a muscle is stimulated, motor neurone creates action potential in the muscle fibres
- electrodes applied to the surface of the skin detect the combined effects of these action potentials
- a simple contraction of the muscle is seen as a series of apparently disorganised peaks on a trace
- amplitude of EMG recording reflects the number and size of the motor units involved in the contraction- more powerful contraction is seen as a higher amplitude
Comparison of muscle types table
Describe the stricture of the myofibril
- thin filaments- made up by actin- make up the light band (I-band)
- thick filaments- made up my myosin- make up the dark band (A-band)
- Z-Line- holds together thin filaments
- H-Zone- middle of dark band where ether is no overlap between thin and thick filaments
- sarcomere- distance between 2 Z-lines- functional unit of the muscle- at rest around 2.5um
- M-band- where myosin attaches (darker on micrograph)
Describe the thin filaments
- each consists of 2 chains of actin sub-units twisted around each other
- tropomyosin- molecule wound around each actin molecule
- tropomyosin is attached to globular molecules of troponin
- each troponin consists of 3 polypeptides- one bind stop actin, one to tropomyosin, one to calcium when it is available
- at rest, the tropomyosin covers the binding site (actin-myosin binding site) to which the thick filaments can bind, and it is herd in place by troponin
Describe the thick filaments
- consists of bundle of myosin molecules
- each myosin occult has 2 porting heads, which stick out at the end of the molecule
- these heads are mobile and can bind ti actin wen the binding sites are exposed
Briefly outline the sliding filament hypothesis
- during contraction, the light band and the H-zone get shorter
- therefore, the Z lines more closer together and the sarcomere gets shorter
- during contraction, the thick and thin filaments slide past one another
Sliding filaments diagram
Outline the process of muscle contraction
1) When the muscle is stimulated, the action potential passes along the sarcolemma down the t-tubules (transverse tubules) into the muscle fibre
2) The action potential is carried to the sarcoplasmic creticulumn, which stores calcium ions- and causes the release of calcium ions into te sarcoplasm
3) The calcium ions bind to the troponin, which alters the shape pulling the tropomyosin aside- exposes to binding sites on the actin
4) Part of the myosin head acts as ATPase and can hydolyse ATP to ADP and Pi- releasing energy
5) This causes the myosin head to attach to the actin filament, forming a cross-bridge- millions of cross-bridges can be formed between the two filaments
6) The myosin head moves (tilts backwards), causing the thin filament to slide past the thick filament- this is the power stroke
7) During the power-stroke, ADP and Pi are released from the myosin head
8) After the power-stroke, a new ATP molecule attaches to the myosin head, breaking the cross-bridge
9) The myosin egad then returns to its original position (swings forward again) as the ATP is hydrolysed (provides the energy tome this movement occur)
10) The myosin head can now make a New Cross-bridge further along the actin filament
