5.5 Plant & Animal Responses Flashcards
what are examples of abiotic factors?
- light
- soil moisture/minerals
- temperature
- pH
- gravity
- toxins
what are examples of biotic factors?
- herbivory
- touch
- chemical signals
what are the types of plant responses?
- responses to abiotic/biotic factors
- responses to herbivory
- tropisms
- nastic
what are examples of tropisms?
- phototropism
- geotropism
- hydrotropism
- thigmotropism
- chemotropism
what is a phototropism in response to?
light
what is a geotropism in response to?
gravity
what is a hydrotropism in response to?
water
what is a thigmotropism in response to?
touch
what is a chemotropism in response to?
chemicals
what is a tropism?
a directional growth in response to a stimulus
what are plant responses to herbivory?
producing:
- alkaloids
- pheromones
- tannins
how do alkaloids defend plants against herbivores?
they are bitter tasting or toxic which deters or kills herbivores
how do pheromones defend plants against herbivores?
they affect the behaviour of other organisms
what are examples of plant responses to abiotic stress?
- closing stomata
- dropping leaves
- antifreeze chemicals
- forming a thick waxy cuticle
- rolling leaves
What are nastic responses?
Non directional growth or movements in response to an external stimulus.
What is an example of a nastic response?
thigmonasty
- a response to touch e.g. mimosa or venus flytrap
What do plants use to respond?
Hormones.
How are plant hormones different to animal hormones?
Plants don’t have endocrine glands. and one hormones can have different effects in different parts of the plant.
What effects could plant hormones have?
- cell division
- cell differentiation
- cell elongation.
What are five examples of major plant hormones?
- auxin
- cytokinins
- gibberellins
- ethylene
- abscisic acid
Where is auxin produced or found?
Apical shoot. and meristem
What is the function of auxin?
- suppresses growth of lateral buds
- stem elongation
What is the function of cytokinins?
- stimulate cell division and differentiation alongside auxin
Where are cytokinins found or produced?
They are produced in the roots and transported from there.
What is the function of Gibberellins?
- Trigger seed germination
- stem an internode elongation.
Where are gibberellins produced or found?
The apical portions of roots and shoots.
Where is ethylene produced or found?
- leaves
- stems
- young fruits
What is the function of ethylene?
- hastens fruit ripening
- controls the removal of leaves/flowers/fruit
What is abscisic acid found or produced?
- root caps
- mature leaves
- fruits
What is the function of abscisic acid?
- suppresses bud growth
- involves in stomatal opening
- promotes leaf senescence
Where are the lateral buds of a plant?
On the sides of the stem.
What is apical dominance?
the apical bud grows so it can become closer to the sun.
What would happen when the apical bud is cut?
The lateral buds would grow because the auxin is no longer being produced so their growth is not being inhibited.
How do gibberellins trigger seed germination?
- water enters cell triggering the embryo to release gibberellins
- gibberellins cause aleurone layer to produce amylase
- amylase catalyses the breakdown of starch into maltose
- maltose is converted to glucose
- glucose is used for growth of the embryo so seed germinates
what is the role of control variables?
- repeatability
what was the experiment to prove apical dominance in plants?
When the apical bud was decapitated, auxin no longer diffused down the shoot, allowing the lateral buds to grow.
what is a positive phototropism and where does it occur?
- when the shoot grows towards the light
why do plants grow towards light?
to increase their surface area exposed to sunlight for photosynthesis
what is the effect of a high concentration of auxin in the shoots?
the cells elongate and grow on the shaded side with more auxin
what is the effect of a high concentration of auxin in the roots?
the growth on the shaded side is inhibited, so growth occurs downwards on the light side
what is a negative phototropism?
- when roots grow away from light
Outline what the investigations by Darwin, Boysen and Jensen proved about phototropism and auxin.
Auxin is produced at the tip of the shoot and must move down the stem to have an effect on growth. When light is evenly distributed at the tip auxin will also be evenly distributed so the plant has no directional growth. If light is unevenly distributed, auxin will accumulate on the shaded side causing the cells to elongate and the plant to grow towards the light.
what is a positive geotropism?
when roots grow downwards due to gravity
what is a negative geotropism?
when shoots grow upwards away from gravity
what is the investigation for the effect of geotropism?
A plant is slowly rotated in a clinostat which keeps it at a constant angle. This would cause the plant to grow outwards instead of upwards because the effect of gravity is removed as it is equal on all sides.
what does reproducibility mean?
someone can reproduce similar results from the same experiment
what are meristems?
Regions of the plant where growth occurs by mitosis, differentiation and elongation.
Outline the mechanism of auxin
- Auxin binds to the hydrogen pump
- H+ ions pumped into the cell wall
- The cell wall weakens due to an increase in H+ ions as they disrupt hydrogen bonds and decrease pH
- water can move in, causing the cell to elongate
Outline the mechanism of action for abscisic acid in guard cells.
- abscisic acid bind to ABA receptors on guard cell surface membrane
- Ca2+ enter and K- leave
- water potential increases so water leaves the guard cell
- guard cells are flaccid, stoma close
What are the commercial uses of gibberelins?
- increase fruit size
- brewing
- sugar production
- prevent lodging
What is lodging and how can Gibberellins be used to prevent it?
- bending of stems due to weight above
Removing gibberellins stops elongation so the plant is shorter.
How do gibberellins increase fruit size?
- cause stalks to elongate so fruit has more space to grow
How are gibberellins used in brewing?
They are added to barley to trigger sugar production from starch which is then used in anaerobic respiration for fermentation.
How are gibberellins used in sugar production?
They elongate the stem of the sugar cane plant, increasing sugar yields
What are the commercial uses of auxin?
- herbicide
- seedless fruit
- plant cuttings
How are auxins used as herbicides?
They promote rapid shoot growth, so the stem can’t support itself, buckles then dies.
How are auxins used to produce seedless fruit
It promotes ovule growth, which triggers the production of auxin in developing fruit. This means that fruit can be produced without seeds, as there is no need for fertilisation.
How are auxins used for plant cuttings?
Dipping the end of a plant cutting into auxins before planting encourages root growth.
What is the commercial use of ethene/ethylene?
induced fruit ripening
What are the commercial uses of cytokinins?
- delay leaf senescence
- encourage cell division for mass-produced plants
What is leaf senescence?
where the leaf is growing old
what are the 5 parts of the brain?
- cerebrum
- cerebellum
- hypothalamus
- pituitary gland
- medulla oblongata
what is the function of the cerebrum?
involved in conscious activities such as vision, speech, thinking, memory etc.
what happens if the cerebrum goes wrong?
- personality disorders
- problems with cognitive skills
how is the cerebrum divided?
- into 2 cerebral hemispheres joined by a band of nerve fibers
- highly folded ‘grey matter’
- myelinated neurons in the ‘white matter’
what is the function of the hypothalamus?
- links the endocrine and nervous systems
- monitors the blood and releases hormones itself or stimulates the pituitary gland in response.
what is the function of the pituitary gland?
to produce and release a range of hormones
what is the function of the anterior pituitary gland?
produces and releases certain hormones
what is the function of the posterior pituitary gland?
stores and releases hormones produced by the hypothalamus
what is the function of the cerebellum?
controls fine motor skills such as balance, speech and walking
what is the function of the medulla oblongata?
- controls non-skeletal muscles
what does the medulla oblongata consist of?
- cardiac centre
- respiratory centre
- vasomotor centre
what happens if the medulla oblongata is damaged?
- respiratory failure
- paralysis
- death
what is the function of the respiratory centre?
controls breathing rate
what is the function of the cardiac centre?
controls heart rate
what is the function of the vasomotor centre?
controls blood pressure
How is the nervous system organised?
- CNS –> brain + spinal cord
- PNS
–> sensory neurons
–> motor neurons
what is the CNS
central nervous system
what is the PNS
peripheral nervous system
how is the motor neurons divided into systems?
- somatic nervous system
- autonomic nervous system
what is the somatic nervous system?
- controls voluntary movements
what is the autonomic nervous system?
controls involuntary responses
How is the autonomic nervous system divided?
- sympathetic
- parasympathetic
what is the sympathetic nervous system?
- fight or flight
what is the parasympathetic nervous system?
- rest or digest
what is a neuron?
a nerve cell
what is a nerve?
a tissue made up of nerve cells (neurons)
what are reflexes?
- actions that don’t require processing
why do we have reflexes?
for survival
why can you override the corneal/blinking reflex?
There is a relay neuron which allows you to inhibit an action potential reaching the motor neuron, preventing a response.
why cant you override the knee-jerk reflex?
there is no relay neuron
What are the three types of muscle?
- cardiac
- smooth
- skeletal
What types of muscle are involuntary?
- cardiac
- smooth
What are the characteristics of smooth muscle?
- uninucleate
- slow contraction so don’t fatigue
- tapered shape
- controlled by the autonomic nervous system
What are the characteristics of cardiac muscle?
- uninucleate
- myogenic
- faint striations
- intercalated discs
- cross bridges
- dont get tired
Why does cardiac muscle have intercalated discs?
It allows for the faster diffusion of ions because there are smaller gaps. This leads to faster action potentials.
Why the cardiac muscle have crossed bridges?
Allows action potentials to spread quickly and causes a squeezing action when fibres contract.
Why the characteristics of skeletal muscle?
- multiculeate
- multiple fibres
- sarcoplasm
- sarcolemma
What is the sarcoplasm?
The cytoplasm in skeletal muscle.
What is the sarcolemma?
The cell membrane in the skeletal muscle.
What are features of the sarcolemma?
- folded inwards to form T-tubules to allow action potentials to spread quickly
What are the features of the sarcoplasm?
- many mitochondria
- myofibrils
- sarcoplasmic reticulum
Where is the function of the sarcoplasmic reticulum?
To store and release calcium ions for muscle contraction.
What two proteins make up skeletal muscle fibre?
- myosin
- actin
How do you muscle fibres contract?
The actin slides over myosin causing the muscle fibre to contract.
What controls heart rate?
The cardioregulatory centre in the medulla.
What does the Parasympathetic nerve do to heart rate?
Decrease heart rate.
What does the sympathetic nerve do to heart rate?
Increase heart rate.
How can heart rate be controlled?
Synapse connected to the Parasympathetic or sympathetic nerve releases a neurotransmitter which causes an effect to the sino atrial node (SAN).
What does acetylcholine do to heart rate?
slows down heart rate
What does noradrenaline do to heart rate?
speeds up heart rate
What two neurotransmitters affect heart rate?
- acetylcholine
- noradrenaline
How is the fight or flight response coordinated?
The hypothalamus receives an impulse from the sense organs. It then triggers a response in both the nervous and endocrine systems.
How is the fight or flight response coordinated by the nervous system?
- sympathetic neurons receive an impulse from the hypothalamus.
- The adrenal medulla receives an impulse, adrenaline hormone is released.
- adrenaline targets organs and tissues to increase sensory awareness.
How is the fight or flight response coordinated by the endocrine system?
- Hypothalamus releases peptide hormone.
- Anterior pituitary gland releases ACTH.
- Adrenal cortex releases cortisol hormone, Blood pressure and glucose concentration increases.
What does ACTH stand for?
Adreno cortico tropic hormone.
What sensory input does the cardiovascular centre receive?
- Stretch receptors in muscles.
- Baroreceptors in carotid sinus.
- Chemoreceptors in the aorta and carotid arteries.
What do stretch receptors recept?
The shape of the sensory endings changes during muscle contraction, causing an action potential. This stimulates the acceleratory center, so heart rate is increased.
What do baroreceptors recept?
The stretch receptors in the carotid sinus monitor blood pressure at. During exercise, blood pressure drops. Acceleratory centre stimulated, causing heart rate to increase.
What do chemoreceptors recept?
A decrease in the PH of blood due to. the conversion of carbon dioxide into hydrogen ions in the red blood cell. The acceleratory centre is stimulated so heart rate increases.
