Plant and Animal Responses, 5.5 Flashcards Preview

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Flashcards in Plant and Animal Responses, 5.5 Deck (135):

What is a biotic factor?



What is an abiotic factor?

Non - living


How do plants respond to stimuli?

Respond using plant hormones known as growth factors


Where are growth factors made?

In tissues all over the plant


What are the 3 main types of plant growth?

Cell division. Cell elongation. Cell differentiation.


What are tannins?

Toxic to microorganisms and herbivores. Prevent infiltration by pathogenic microorganisms. Found in leaves - makes them taste bad.


What are alkaloids?

Derived from amino acids. Make plant bitter. Found in flowers and growing tips.


What are pheromes?

Chemicals released that affect the physiology or behaviour of another


What is tropism?

The movement of part of a plant in respond to eternal stimulus. Direction growth -pos. or neg.


Give some examples of a stimulus and a tropism.

Light - phototropism. Gravity - Geotropism. Chemical - Chemotropism. Water - hydrotropism.


Where does plant growth occur?

Occurs at meristems in meristematic tissue.


What is apical meristem?

Found in stems and roots, growth increase length at tips


What are intercalary meristems?

Between the tip and base of stems and leaves. Growth increase between nodes..


What are lateral meristems?

Sides of stems and roots, growth increase diameter.


What are some substance that affect plant growth?

Auxins. Gibberellins. Cytokinins. Abscisic acid. Ethene.


Where are auxins (IAA) produced?

In shoot or root tips


What are the effects of auxin?

Promote stem elongation. Stimulate cell division. Maintain apical domination. Prevent leaf fall.


What does the terminal bud contain?

The apical meristem


How does the auxin travel down the stem?

By diffusion or active transport.


What does auxin do?

Inhibits the sideways growth form lateral buds. Means plant will grown upwards


What happens if you remove the apical meristem?

The lateral buds will grow


What does abscisic acid do?

Inhibits bud growth. High auxin levels keeps high abscisic levels.


What do cytokinins do?

Promote bud growth


What are Gibberellins?

Responsible for stem elongation and seed germination


What does Gibberellin (GA) do?

Increases length of internodes. Stimulates cell division. Stimulates cell elongation.


What can happen if a plant lacks the gene for producing GA?

It will be a dwarf variety


How does Gibberellin work?

1. DELLA protein binds to a transcription factor
2. GA causes the breakdown of DELLA protein
3. Therefore transcription can occur and growth is able to happen


How does GA affect germination?

A seed contains a store of starch which cannot be used until its broken down. Gibberellins enable the production of amylase which breaks starch into glucose. Provides a substrate for respiration for the embryo.


What is leaf abscission?

In temperate countries trees shed their leaves in autumn


Why does leaf abscission occur in trees?

Survival advantage. Not as much sunlight in winter to provide energy. Colder - enzymes will work more slowly. Reduced transpiration. Avoids frost damage.


What are the stages of leaf abscission?

1. As leaf ages rate of auxin production declines
2. Leaf more sensitive to ethene production
3. More ethene produced which inhibits auxin
4. Abscission layer begins to grow at base of stalk
5. Tree grows protective layer were the leaf will break off


What is the abscission layer?

Thin wall of cells. Weakened by enzymes that hydrolyze polysaccharides. Leaf is weak it falls off.


What does the cell wall contain? And what does this prevent?

Suberin. Prevents the entry of pathogens.


What are the commercial uses of auxin?

- Sprayed onto developing fruits to prevent abscission
- Sprayed onto flowers to initiate fruit growth - seedless fruits
- Applied to the cut end of a shoot
- Synthetic auxins used as selective herbicides


What are the commercial uses of ethene?

- Used to ripen fruit
- Fruits can be harvested before they're ripe and transported
- Bananas produce lots of ethene


What are the commercial uses of Gibberellin?

- Promotes growth in fruit crops
- Allows citrus trees to keep fruit on them longer
- Sprayed onto sugar cane to increase sucrose yield
- Used in brewing, makes seeds germinate


What are the commercial uses of Cytokinins?

- Delay leaf senescence, stops leaves yellowing
- Can be used in tissue culture


What does the effect of plant growth factors depend on?

Concentration. The tissue being acted on. The developmental stage of the plant. Species. What other growth factors are present.


Define photoreceptors.

Structures or pigments that are sensitive to light


Define phototropins

Group of photoreceptors primary response for triggering phototropisms


How does auxin effect the stretchiness of the cell wall?

Increases it. Promotes the active transport of H+ by an ATPase enzyme. Lowers the pH providing optimum conditions for wall loosening enzymes called expansins.


How do the enzymes expansins work?

Break bonds within the cellulose and the increased H+ ions disrupt hydrogen bonds so the walls become less rigid.


How did Darwins experiment with shoot tips work?

1. With a tip it bent towards the sun
2. Without a tip in didn't bend
3. With a shaded tip it didn't bend


What conclusions can be drawn from Darwins experiment?

Shoot tip contains auxin and is responsible for phototropic responses. Growth stimulus is transmitted to the zone of elongation


How did Boyson-Jensens experiment with shoot tips work?

1. Sheet of mica inserted on the shaded side - didn't bend. Sheet of mica inserted on the sunny side - did bend
2. Tip cut off and block of gelatin inserted. There was normal curvature


What conclusions can be drawn from Boyson-Jensens experiment?

Water/solutes/auxin travel backwards from the shoot tip for phototropism to happen. Gelatin is permeable to water whereas mica isn't.


How did Wents experiment work?

Tips placed on agar. Block place on stem with tip removed. Bent towards the sun.


What did Wents experiment show?

Demonstrated that a chemical messenger (auxin) existed. Could stimulate effect artificially. Angle of curvature relates to number of tips used.


What two systems is the nervous system separated into?

The central nervous system (CNS) and the peripheral nervous system (PNS)


What does the CNS consist of?

The brain and the spinal cord.


What type of neurones does the brain mainly contain?

Relay neurones - have multiple connections. Most are non-myelinated and look grey.


What does the spinal cord mainly contain?

Has large numbers of myelinated cells - looks white. Which carry action potentials up and down the spinal cord


What does the PNS contain?

Motor system and the sensory system. Ensures rapid communication between sensory receptors, the CNS and effectors. Mainly sensory and motor neurones


What is the sensory nervous system?

Sensory fibres entering the CNS are dendrons of the sensory neurones - conduct action potentials. Have their cell body in the dorsal root leading into the spinal cord.


What is the motor nervous system?

Conducts action potentials from the CNS to effectors. Contains the somatic nervous system and the autonomic nervous system.


What is the somatic nervous system?

Motor neurones which conduction action potentials - under VOLUNTARY control. From the CNS to effectors eg skeletal muscles. Myelinated.


What is the autonomic nervous system?

Motor neurones that conduct action potentials INVOLUNTARYILY. eg glands, cardiac and smooth muscle. Does not require rapid response - mostly unmyelinated neurones.


What two systems can the autonomic nervous system be split into?

Sympathetic nervous system and the Parasympathic nervous system


What can sympathetic and parasympathetic nervous systems be described as?

Antagonistic systems. Have the opposite effects on an unconscious process.


What does the Sympathetic Nervous System do?

Prepares body for activity. eg Increases heart rate, dilates pupils, increases ventilation rate, reduces digestive activity - times of stress.


What does the Parasympathetic Nervous System do?

Conserves energy. eg Decreases heart rate, constricts pupils, reduces ventilation rate, increases digestive activity - during sleep or relaxation.


What does the sympathetic nervous system consist of?

Many nerves leading out of CNS each to separate effector. Ganglia outside CNS. Short pre-ganglionic neurones. Long post ganglionic neurones.


What neurotransmitter does the sympathetic nervous system release?



What does the parasympathetic nervous system consist of?

A few nerves leading out of the CNS. Ganglia in effector tissue. Long pre-ganglionic neurones. Short post ganglionic neurones.


What neurotransmitter does the parasympathetic nervous system release?



What are the four main parts of the Brain?

Cerebrum. Cerebellum. Hypothalamus and Pituary. Medulla Oblangata.


What is the cerebrum?

Largest. Organises highest thought processes, Conscious thought. Memory. Emotional responses. Actions. Judgement.


What are the two cerebral hemispheres?

Corpus Callosum and Cerebral Cortex.


What are the different areas in the cerebrum? And what do they do?

Sensory areas - action potentials from sensory neurones. Association areas - compares sensory input with previous experiences. Motor areas - action potential to effectors.


What is the cerebellum?

Coordinates movement and balance


What does the cerebellum contain?

Over half of all neurones


Where does the cerebellum receive information from?

Sensory receptors in the the retina, balance organs in the inner ear and spindle fibres.


What does the cerebellum do?

Decision to tcontract voluntary muscles made here - but does not provide the signals. Maintains body position and balance. Tensioning muscles to manipulate tools. Judging position of objects and limbs (sports).


Why is the cerebellum strengthened by practise?

Requires learning but once learnt some activities involve unconscious control - muscle memory.


What are the cerebrum and the cerebellum connected by?



What is the medulla oblongata?

Coordinates autonomic responses


How does the medulla oblongata control non-skeletal muscles?

Sends action potentials out through the autonomic nervous system


What can the medulla oblongata control?

Smooth muscle in the the gut. Breathing movements. Heart rate.


What does the medulla oblongata regulate?

The cardiac center. The vasomotor center. Respiratory center.


What is the hypothalamus and pituary complex?

Homeostatic responses


What does the hypothalamus and pituary complex control?

Temperature regulation. Osmorgeulation


How are the pituary and hypothalamus linked?

By neurosectretory cells (the posterior lobe) - hormones manufactured by the hypothalamus and release into the blood by the pituary gland.


What does the anterior lobe do?

Produces own hormones. Releases into the blood following releasing factors form the hypothalamus. Controls some physiological processes eg response to stress.


What system does the heart pump blood around?

The circulatory system


What does the circulatory system transport?

Oxygen. Nutrients. Removes waste products eg CO2. Transports urea.


What does myogenic mean?

The heart initiates its own heartbeat - own pacemake the SAN


How does the SAN work?

Initiates a wave of excitation. Causes an action potential causing the walls of the atria to contract.


What is the electrical impulse from the SAN picked up by? And what happens next?

Picked up the AVN and travels along Purkyne fibres. The ventricles then contract upwards pushing the blood upwards.


Where is the frequency of the excitation waves altered from?

The cardiovascular centre in the medulla oblongata. Nerves from here supply the SAN


What is the accelerans (sympathetic) nerve? And what does it do?

Action potentials sent down here causing the release of noradrenaline. Speeds up.


What is the vagus (parasympathetic) nerve? And what does it do?

Action potentials sent down here causing the release of acetylcholine. Inhibit.


What is the role of stretch receptors?

Detect movement of the limbs and send messages that more oxygen is needed - this increases heart rate. Also monitor blood pressure in the walls of cartoid sinus.


What is the role of chemoreceptors?

Monitor pH. Detect a drop in pH caused by an increase in CO2 concetration.


What does a high concentration of CO2 indicate? What is the response to this?

Indicates high rate of aerobic respiration. Increase heart rate - increase removal of CO2 and supply of oxygen.


How is blood pressure maintained?

By varying heart rate.


What factors causes the heart rate to be adjusted?

Blood CO2 levels and blood pressure.


How does the medulla oblongata affect the heart rate?

Increases the frequency of signals. Sends an action potential to the SAN along the sympathetic nerve - increases heart rate. The frequencies of the signals will then stop as CO2 is removed and the pH rises.


What are the 3 types of muscle?

Smooth. Cardiac. Skeletal.


Where is cardiac muscle found?

In the ventricle and atrium walls.


What is the function of cardiac muscle?

Contracts rhythmically and doesn't fatigue. It is myogenic.


What is the structure of cardiac muscle?

- Striated
- Small long fibres with a single nucleus.
- Cross bridges, ensure electrical stimulation spreads evenly
- Cells joined by intercalated discs (produce gap junctions allowing diffusion of ions)


Where is smooth muscle found?

Lining of internal organs


What is the function of smooth muscle?

Digestive system - moves food along. Slow to fatigue. Controlled by the autonomic nervous system. Involuntary muscle.


What is the structure of smooth muscle?

- Longitudinal layers
- Cells are spindle shaped, short and thing
- Each cell has a single nucleus
- Unstriated
- Contains bundles of actin and myosin


Where is skeletal muscle found?

Attached by tendons. Arranged in antagonistic pairs - when contracts the other relaxes.


What is the function of skeletal muscle?

Contract quickly and powerfully - fatigue quickly. Voluntary muscle.


What is the structure of skeletal muscle?

- Cells elongated
- Contain multiple nuclei
- Striated, light and dark bands
- Muscle cytoplasm called sarcoplasm
- Membrane is the sarclemma
- Fibres arranged into myofibrils which are divided into sacromeres containing actin and myosin


How is energy provided for the muscle contraction?

Hydrolysis of ATP


Why do muscle fibres store creatine phosphate?

Can phosphorylate ADP to ATP


What are fast twitch fibres?

Used for short bursts of activity. Quick and powerful. Respire anaerobically. Lots of creatine phosphate. They fatigue easily.


What are slow twitch fibres?

Used during endurance activities. Work slowly and for a long period of time. Large number of mitochondria. High concentration of myoglobin. excellent blood supply. Slow to fatigue.


Why are fast twitch fibres known as white fibres?

Poor blood supply


Explain with an example how must joints work in pairs to generate movement.

1. Triceps are stimulated pulls on the tendon and extends the arm (extendor). The biceps relax.
2. Biceps are stimulated it shortens pulling on the tendon and bending the arm (flexor)


What is a neuromuscular junction?

Specialised synapse between a neurone and a muscle fibre


What are T-tubules?

Infoldings of the membrane which help direct the membrane depolarization.


What is the Sarcoplasmic Reticulum?

Type of endoplasmic reticulum found in the cell cytoplasm close to myofibrils


What triggers a muscle contraction?

Action potential.


Why does muscle fibre surround the end of the neurone?

To increase the surface area of over which signals are received.


Describe the stages of an action potential triggering a muscle contraction.

1. AP arrives at motor neurone, causes Ca channels to open and ions flood in
2. Ca ions stimulate vesicle containing acetylcholine to fuse with the presynatpic membrane
3. Acetylcholine diffuses across the synaptic cleft and binds with receptors on the postsynaptic membrane
4. Na channels open and Na ions flood in - the membrane depolarizes
5. Reach threshold value and an action potential is generated travels to T-tubules
6. T-tubules channel the action potential to the sarcoplasmic reticulum
7. Releases stored Ca ions
8. This increases causes the muscle to contract


What is the pattern of banding on a myofibril called?

Sacromere - smallest contractile unit arranged end to end, formed from protein filaments


What do the thin filaments form?

The light band


What is the dark band formed from?

Thick filaments - myosin filaments


What are the filaments held together by?

The z line


What is the H zone?

No overlap. Contains only myosin. Ends where myosin and actin begin to interlock.


What is the I Band?

Region which only contains actin filaments. Light.


What is the A Band?

Contains H zone and is the same length as myosin filamnets. Actin and myosin interlock.


What are the thin filaments?

Actin. 2 chains of actin sub units twisted together wound round the actin is a molecule of tropomyosin.


What are the thick filaments?

Bundles of myosin. Has two heads which stick out of each end of the molecule - can bind to actin.


What happens to the filaments during contraction?

I Band shrinks. H zones shrink. Z lines move closer together.


What is the sliding filament hypothesis?

The thin and thick filaments slide past each other


Describe the sliding filament hypothesis

1. filaments become interlocked
2. heads of myosin form cross bridges with actin - bind
3. myosin heads change shape pulling the actin towards the centre of the sacromere - called a powerstroke
4. myosin heads uses energy from ATP to detach and return to their original position


What happens when the muscles relaxes?

The myosin heads are prevent from binding to the actin by tropomyosin which is on the actin filament.


How are actin filaments formed?

Helix of actin subunits each containing a binding site for myosin heads. Two other proteins attached - typomyosin and troponin.


How is contraction of muscles controlled?

1. AP stimulates release of Ca ions in sarcoplasmic reticulum
2. Ca ions bind to the troponin altering its shape and exposes actin binding sites
3. Myosin heads move pulling the actin filament past the myosin filament - ADP released from myosin head.
4. ATP can now bind to the myosin head - broken down to release energy
5. The energy allows myosin to release actin
6. Ca is actively removed from the sarcoplasm when the muscle is no longer stimulated by a nerve


What are some differences between the CNS and the PNS?

CNS: Brain and Spinal Cord. Intermediate neurones. Coordination.
PNS: Nerves from sense organs to muscles. Sensory and Motor neurones. Sensing stimuli. Control effectors.