5.5 Plant and animal responses Flashcards
What are abiotic components?
compenents of an ecosystem that are non-living.
What are alkaloids?
Organic nitrogen-containing bases that have important phyiological effects on animals; includes nicotine, quinine, strychnine and morphine.
What are biotic components?
Components of an ecosystem that are living.
What are pheromones?
Any chemical substance released by one living organism, which influences the behaviour or physiology of another living thing.
What are tannins?
Phenolic compounds, located in cell vacuoles or in the surface wax on plants.
What is tropism?
A directiona; growth responce in which the direction of the responce is determined by the direction of the external stimulus.
How may a plant respond to higher temperatures?
They may deposit a thicker layer of wax on their leaves.
How may a plant respond to very windy conditions?
They may have a more heavily lignified vasular tissue.
How may a plant respond to the threat of hervibours? (chemical defences)
- Tannins
- Alkaloids
- Pheromones
How are tannins a responce to the threat of herbivores to a plant?
Tannins are toxic to microoganisms and larger herbivores. In leaves, they are found in the upper epidermis, and make the leaf taste bad. In the roots, they prevent infiltration by pathogenic microogranisms.
How are Alkaloids a responce to the threat of herbivores to a plant?
Alkaloids are derived from amino acids. In plants, scientists think they are a feeding deterrent to animals, tasting bitter. They are located in the growing tips and flowers, and periperal cell layers of stems and roots.
How are Pheromones a responce to the threat of herbivores to a plant?
Pheromones are chemicals which are released by ome individual and which can affect the behaviour or physiology of another.
What sort of response are tropisms?
Tropisms are directional responces of plants?
Whar are some examples of tropisms?
- Phototropism
- Geotropism
- Chemotropism
- Thigmotroptism
What is phototropism?
Type of tropism where shoots grow towards light, which enable them the photosynthesis. They are positivly phototrophic.
What is geotropism?
Form of tropism- roots grow towards the pull of gravity. This anchors them in the soil and helps them take up water. There will also be minerals into water, such as nitrates needed for the synthesis of amino acids.
What is chotropism?
Type of tropism- On a flower, pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation can take place.
What is thigmotropism?
Shoots of climbing plants, such as ivy, wind around other plants or solid structures to gain support.
What is it called when a plant responds towards a stimulus?
It’s a positive tropic response.
What is it called when a plant respomds away from a stimulus?
It’s a negative tropic responce.
What are nastic respoces?
Non-directional responces to external stimuli.
What is an example of nastic responces to a stimulus?
Thigmonasty- the nastic response of a plant to touch or vibration. e.g. mimosa plantsresponds to touch by folding it’s leaves
What coorfinates plant responces to enviromentak stimuli?
Plant hormones
Describe plant hormones.
Plant hormones are chemical messangers that can be transported awat from the site of manufacture to act in other parts of the plant. They are not produced in endocrine gands, but in a variety of tissues in the plant. When hormones reach their target cells, they bind to receptors on the plama membrane. Specific hormones are specific shapes, which can only bind to specific receptors with complementary shapes on the membranes of particular cells. This specific binding ensures that hormones act on the right cells.
What are some effects of plant hormones?
- Amplify each others side effects.
- Cancel out each other side effects.
- Induce cell division, cell enlongation or cell diffrentiation.
What are 5 examples of plant hormones?
- Cytokinins
- Abscisic acid
- Auxins
- Gibberellins
- Ethene
What do cytokinins do?
- Promote cell divion
- Delay leaf senescence
- Overcome apical dominance
- Promote cell expansion
What does abscisic acid do?
- Inhibits seed germination and growth
- Causes stomatal closure when the plant is stressed by low water availability
What do Auxins do?
- Promote cell elongation
- Inhibits growth of side shoots
- Inhibits leaf abscission (leaf fall)
What do Gibberillins do?
- Promote seed germination and growth of stems
What does Ethene do?
Promotes fruit ripening.
How do hormones move around a plant?
- Active transport
- Diffusion
- Mass flow in the phleom sap or in xylem vessels.
What is apical dominance?
Inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of the plant shoot.
What are auxins?
Plamts hormones which are responsible for regulating plant growth.
What are gibberellins?
Plant hormones which are responsible for the control of stem elongation and seed germination.
What will happen to a plants side shoots, if you break the shoot tip (apex) off a plant?
The plant side shoots start to grow from lateral buds which were previously dormant.
Which plant hormone prevents lateral buds growing?
Auxins from the apical bud prevent lateral buds growing.
What happens to auxin levels in a plant when a plants shoot tip is removed?
Axins levels drop, causing buds to grow.
How did scientists test their hypothesis that lower levels of auxins caused side shoots to grow?
Scientist applied a paste containing auxins to the cut end of the shoots, and the lateral buds did not grow.
Why did the scientists testing the effect on auxins have to change their original experiment?
The scientists showed if they put a paste containing auxins on the cut shoot, the buds didnt grow. However, this could have been an unexpected effect upron the exposure to oxygen as the cells could have produced a different hormone.
To overcome this, scientists put a ring of auxin transport inhibitor below the apex of the shoot- the lateral buds grew.
Later on, a different scientist suggested 2 hormones are involved in auxin levels and growth inhibition?
- Absisic acid inhibits bud growth. High auxin in the shoot may keep absisic levels high in the bud. When the tip is removed, absisic acid levels drop and the buds start to grow.
- Cytokinins promote bud growth- directly applying cytokinin to buds can override the apical dominance effect. High levels of auxins make the soot apex a sink for cytokinins produced in the roots- most of the cytokinins goes to the shoot apex- when the apex is removed, the cytokinins spread out evenly through the plant.
In Japan, a fungus causes a disease whch makes rice grow very tall. What compound must be in the fungus?
The fungal compounds involoved are gibberellins and include gibberellic acid (GA3).
What happens to a plant when gibberellic acid is tested on it?
It will grow taller.
What is gibberellic acid responsible for?
Stem growth
In an experiment investigating the effects of gibberellic acid (GA3), what must happen?
- Must be tested within concentrations of gibberellins normally found in plants.
- Must be tested in parts of the pplant gibberellins normally reach.
What hormone promotes seed germination?
Gibberellins
How do gibberellins promote seed germination?
When the seed abosrbs water, the embryo releases gibberellin, which travels to the aleurone layer in the endosperm reigion of the seed. The gibberellin enebles the production of amalase which can break down strach into glucose. This provides a substate for respiration for the embryo, as it grows. The glusoce is also used in protein sythesis.
What is geotropism?
A directional responce to gravity.
What is phototropism?
A directional growth responce to light.
Where does growth happen in plants?
In places where in the plant there are immature cells that are still capable of dividing, called merristems.
Where can meristems be found in plants?
- Apical meristems are at the tips of roots or shoots, and are responisble for the roots and shoots getting longer.
- Lateral bud meristems are found in the buds. They can give rise to side shoots.
- Lateral meristems forming a cyclinder near the outside of the roots and shoots are are responsible for the roots and shoots getting wider.
- In some plants, intercalary meristems are located between nodes, where the leaves and buds branch off the stem. Growth between the nodes is responsible for the shoots getting longer.
How can you investigate phototropic responces?
Phototropic responces can be investigated using an experimental plant and a control plats (with 10 replicates). The control plant is illuminated from all side, which the experimental plant has illumination just from one side. In each plant, the shoots and roots are marked enery 2mm at the start.
Look at the results after several days. The shoot that has bent towards the light, because the shady side of the shoot has elongated more than the illuminated side. The mean and standard devistion of the lengths between the marks has in creased on the shady side.
What experiement confirmed that a chemical messenger from the shoot tip is responsible for the phototropic responses?
Darwin did an experiment with blades of grass changing whats happening to to the tip of the plant and observing the plants responce.
What did Boysen-Jenson’s work tell us about phototropism? What did he do?
He confirmed that water and/or solutes need to be able to move back anf forwards from the shoot for the tip for phototropism to occur.
When a permeable genaletine block was inserted behind the shoot tip, the shoot still showed positive phototropism but when an impermeable mica block was inserted, there was no phototropic responce.
What was done in the classic experiment to confirm the role of the shoot tip in producing a chemical messanger that controls phototropic responces?
With blades of grass, differrent situations are set up:
* Control
* Agar-block containing auxin stimulates growth.
* Offset blocks containing auxin simulated curved growth.
* Blocks containing no auxin have no effect.
What results do giving blocks of agar with different concentrations of auxin give to a plant?
Give the same result.
Where is auxin when there is light equal on all sides of a plant? What does this cause?
Axin promotes shoot growth evenly- making the shoot grow staight up.
Where is auxin when light is on one side of a plant? What does this cause?
Causes auxins to be transported to the shady side, causing the cells to elongate more quickly, making the shoot bend towards the light.
What is the extent a plant cell elongates is proportional to?
The concentration of auxins.
What is a role of auxin in the cell walls?
Auxin increases the strechiness of the cell wall promoting the active transport of H+ by an ARPase enzyme on the plasma membrane into the cell will. The resulting low pH provides optiumum conditions for wall-loosening enzymes (expansins) to work.
How do the enzymes expansisns work?
These enzymes break binds within the cellulose so the walls bbecome less rigid and can expand as the cell takes in water.
How does auxin let the cell elongate?
Auxins increases wall stretchyness, promoting the active transport of H+ by ATPase enzymes on the plasma membrane. A low pH is optiumum for expansisn (wall-loosening enzymes) which break down the binds in cellulose. Also, the increased hydrogen ions disrupt hydrogen boonds in the cellulose- soio walls are less rigid- cells can expand when they take in water.
How is auxin involoved in the geotropic responces in the roots?
If a root is lying flat, auzin accumulates on the lower side, where it inhibites cell elongation. The upperside continues to groe and the root bends downwards.
What does the graph look like showing the efffect of auzin concentration on eleongation of shoots and roots compared to controls?
What is the automonic nervous system?
Part of th nervous system responsible for controlling the involuntary motor activities of the body.
What is thr central nervous system?
The central part of the nervous system composed of the brain and the spinal cord.
What is the peripheral nervous system (PNS)?
The sensory and motor nerves connecting the sensory receptors and effectors to the CNS.
What is the somatic nervous system?
The motor neurones uner concious control.
What is the role of the nervous system?
To provide responces, such as:
* Coordinating muscle action
* Control of balance and posture
* temperature regulation
* Coordination with the endocrine system
What 2 categories is the overall nervous split into?
- Central nervous system
- Peripherial nervous system
What is the PNS split into?
- Sensory system
- Motor system
What is the motor system split in to in the nervous system?
- Somatic nervous system
- Autonomic nervous system
What is the autonomic nervous system split into in the nervous system?
- Sympathic system
- Parasympathetic system
What is the organisation of the nervous system?
What does the CNS consist of?
The brain and the spinal cord.
How many neurones does the brain contain?
86 billion neurones
What does a lot of the brain consist of? Decribe these?
Much of the brain is composed of replay neurones, which have multiple connections eneabing complex neural pathways. Most of these cells are non-mylinated cells and there tissues look grey in colour- it’s called grey matter.
What is similar in what the brain the the spinal cord is made up of?
Both contain non-mylinated neurones making up grey matter.
What does the spinal cord contain that thr brain doesn’t? What is it’s function?
The spinal cord contains large numbers of mylinated neurones making up an outer region of white matter. These mylinated neurones carry action potentials up and down the spinal cord for rapid communication over long distances.
What is the spinal cord protected by?
The vertebral column- between each vertebrea, peripheral nerves enter and leave the spinal cord carrying action potentials from the rest of the body.
What is the role of the peripheral nervous system?
To ensure rapid communication between the senesory receptors, the CNS and the effectors.
What is the PNS composed of?
Composed of sensory and motor neurones. These are usuallly bundled together in a connective tissue sheath of form nerves.
Which bit od the sensory neurones enter the CNS?
The sensory fibres entering the CNS are dendrons of the sensory neurones.
On a sensory neurone, where is the cell body on the neurone in the nervous system?
These neurones have their cell body in the dorsal root leading into the spinal cord and a short axon connecting to other neurones in the CNS.
What does the motor nervous system do?
The motor nervous syetm conducts action potentials from the CNS to the effectors.
What are some comnercial uses of auxins?
- Taking cuttings
- Seedless fruit
- Herbicides
Why are auxins used to take cuttings comercially?
Dipping the end of a cutting in rooting powder before planting it encourages root growth. Rooting power contains auxins and talcum powder.
Why are auxins used to make seedless frits comercially?
Treating unpollinated flowers with auxin can promote growth of seedless fruit (parthenocarpy). Applying auxin promotes ovule growth, which triggers automatic production of auxin in tissues in the developing fruit, helping the complete the develpmental process.
Why are auxins used commercially to make herbicides?
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 plants for longer. They promote shoot growth so much that the stem cannot support itself, buckles and dies.
Commercially what plant hormone is used to stop lettuce leaves going yellow after they have been picked?
Cytokinins bacuse they delay leaf senscence.
What are cytokinins used for commercially?
- Used to help mass-produce plants.
- They promotes bud and shoot growth from small pieces of tissue taken from a parent plant- this produces a short shoot with a lot of side branches, which can be split in to lots all small plants to be grown separetly.
How are gibberellins used in commercial fruit production?
- Gibberellins delay leaf senescence in citrus fruit, extending the time the fruit can be pickeds, and making them available to the shops for longer.
- Gibberellins acting with cytokinins can make apples elongate to improve their shape.
- Without gibberellins, bunches of grapes are very compact; this restricts the growth of individual grapes. With gibberllins the stalk enlogates so the grapes get bigger.
How are gibberellins used for commercial brewing?
To make beer, you need malt- when barley seeds germinate, the aleurone layer of the seed produced amylase, enzymes break down the stroed starch into maltose. Usually the gebes for amylase production is switched on for naturally occuring gibberellins. Adding gibberllins speeds up the process- malt is then produced by grying and grinding up the seeds.
How are gibberellins used for comercial plant breeding?
- Gibberellins can spped up artificial selection by inducing seed formation on young trees.
How can gibberellin synthesis inhibitors be useful in comercial plant breeding?
Gibberellin synthesis inhibitors can keeps flowers short and stocky and ensures that the internodes of crop stay short, helping prevent lodging. (this happens in wet summers- stes bend over because of the weight collected on the ripened seed heads, making crop difficult to harvest.
How can ethene be sprayed on a plant?
Ethene is a gas so scientists have developed 2-chloroethylphosphonic acid, which can be prayed in solution, is easily absorbed, is slowly absorbed, and slowly releases ethene inside the plant.
What is ethene used for commercially?
- Speeding up fruit-ripening.
- Promoting fruit drop in cotton and cherry
- Promoting female sex expression in cucumbers, reducing the chance of self fertilisation.
- Promoting lateral growth in some plats, yeilding compact flowering stems.
How can restricing ethenes effect be useful?
Storing fruit at a low temperature, with little oxygen and high carbon dioxide levels, means fruits can be stored for longer.
Can also increase self life of cut flowers.
What does the motor nervous system do?
Conducts action potentials from the CNS to the effectors.
What is the motor nervous system further subdivided into?
- The somatic nervous system
- The autonomic nervous system
Whatv is the somatic nervous system?
The somatic nervous system consists of motor neurones that conduct action potentials from the CNS to the effector that are under volentary control. These neurones are mostly mylinated so reponce is rapid. There is always one single neurone connecting the CNS to the effector.
What is the autonomic nervous system?
Consists of motor meurnes that conduct action potentials from the CNS to effectors that are not under volentary control. Many neurones are non-mylinated as responces don’t have to be rapid. There are at least 2 neurones involved in the connection between CNS and the effector. These neurones are connected at small swellings called gangia.
What is the connection called between neurones going from the CNS to an effector in the autonomic nervous system?
Ganglia.
What are some examples of the autonomic nervous system?
- Glands
- The cardiac muscle
- Smooth muscle in the walls of blood vessles
- The air way
- The wall of the digestive system
What is the autonomic nervous system responsible for controlling?
Responsible for controlling the majority of homeostatic mechanisms and so plays a vital role in regulating the internal enviroment of the body.
What is the autonomic nervous system further subdivided into?
The autonomic nervous system can be divided up in to the sympathic system and and parasympathic system.
What doers the sympathic system do?
Prepares the body for action.
What does the parasympathic system do?
Conserves energy.
Why is the sympathic system and the parasympathic system antagonistic?
The action of one system opposes the other.
At rest, what is happening between the sympathetic and parasympathetic systems in the body?
At rest, action potentials pass along the neurones of both systems at a relatively low frequency- this is controlled subconsciously by the brain.
What leads to changes in the balence of the sympathetic and parasympathetic systems?
Changes in the intenal condiations, or stress.
What are the nerves between the CNS and an effector like in the sympathetic system?
It consists of many nerves leading out of the CNS, each leading to a different effector.
What are the nerves between the CNS and an effector like in the parasympathetic system?
It consists of few nerves leading out of the CNS, which divide up and lead to different effectors.
Where is the ganglia in the sympathetic system?
Just outside the CNS.
Where is the ganglia in the parasympathetic system?
Ganglia is in the effector tissue.
What are the pre-ganglionic neurones like in the sympathetic system?
Short pre-ganglionic neurones.
What are the pre-ganglionic neurones like in the parasympathetic system?
Long pre-ganglionic neurones. (variable in length dependent upro the position of the effector)
What is the neurotransmitter in the sympathic system?
Noradrenaline
What is the neurotransmitter in the parasympathic system?
Acetylcholine
How does the sympathetic system change the activity in the body?
Increases the activity- prepares the body for activity.
How does the parasympathetic system change the activity in the body?
Decreases activity- conserving energy.
When is the sympathetic system most active?
In times of stress
When is the parasympathetic system most active?
During sleep or relaxation
What are the effects of the sympathetic system?
- Increases heart rate
- Dialates pupils
- Increases ventillation rate
- Reduces digestive activity
- Orgasm
What are the effects of the parasympathetic system?
- Decreases heart rate
- Constricts pupils
- Reduces ventillation rate
- Increases digestive activity
- Sexual arousal.
What is cardiac muscle?
Muscle found in the walls of the heart.
What is involentary muscle?
Smooth muscle that contracts without conscious control.
What is a neurotransmitter junction?
The structure at which a nerve meets the muscle; its similaar in action to a synapse.
What is this a diagram of?
Involentary (smooth) muscle.
What is this a diagram of?
Cardiac muscle
Whta is this a diagram of?
Volentary (skeletal) muscle
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Action potentials arriving at the end of the axon open calcium ion channels allowing calcium ions to flood into the axon tip.
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Vesicles of acheltocholine move towards the membrane and fuse.
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Acetocholine molecules diffuse across the gap and bind to receptors.
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Sodium ion channels open and sodium ions enter the muscle fibre causing depolarisation.
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Wave of depolarisation passes along the sarcolemma and down the transverse tubules.
What is this a picture of?
An electromygram.
What is the structure of a thin filament in a myofibril?
Each filament is madeup of 2 actin subunits twisted around eachother. Wound around the actin is a molecule of tropomyosin to which are attatched globular molecules of troponin.
What does a think filament in a myofibril consist of?
Each thick fibril consists of a** bundle of myosin molecules**. Each myosin molecule has 2 protruding heads, which stick out at the end of the molecuyle. These heads are mobile and can bind to actin when these binding sites are exposed.
What lead to the sliding filament hypothesis?
During contraction, the light band and the H zone get shorter. therefor, the** Z lines moze closer** together and the sacromere gets shorter. This observation lead to the sliding filament hypothesis.
