Survival And Response Flashcards
What is the advantage of being able to respond to a stimuli?
- increase chance of survival
- detect and move away from harmful stimuli
- more likely to survive, thrive and reproduce advantageous alleles to offspring
- selection pressures favour those with favourable responses
What is the order of the reflex arc
- Stimulus
- Receptor
- Coordinator
- Effector
- Response
What is a stimulus?
- a detectable change or alteration in the internal or external environment of an organism that produces a response in the organism
What is a receptor?
- cells or organs that detect stimuli, transforming the energy from the given stimulus to a form that the organism is able to process, producing a response
- receptors are specific to one stimulus
What is a coordinator?
- an inbuilt system that connects with each receptor with an appropriate effector
What is an effector?
- cells, tissues or organs that respond to simulation by a nerve impulse, resulting in a change/response
What do plant receptors produce in response to stimuli?
- chemicals like hormones to respond to stimuli by growing
How do animal receptors respond to stimuli?
- use nerve impulses to communicate, along with chemicals to coordinate muscle contraction
What are the 3 innate behaviours?
- Reflexes
- Kinesis
- Taxis
What are reflexes?
- involuntary responses which follow a specific pattern in response to given stimulus
- may invertebrates have an escape reflex to avoid predators
What is kinesis?
- involves random movements by the hole organism leading to non directional response
- if organism is in unfavourable conditions, it moves fast and turns little, if organism is in favourable conditions, it moves slowly and turns a lot
What is taxis?
- directional response where a whole organism moves either towards (positive taxis) or away from (negative taxis) the stimulus
State an example of kinesis
-woodlice and maggots do not seek out dark and damp areas, they avoid dry and bright conditions to avoid predators and prevent drying out
What is tropism?
- directional response that involves an organism (plant) either growing towards (positive tropism) or away from (negative tropism) a stimulus such as light and gravity
Responses that plants carry out for survival
- Moving towards light
- Moving in response to gravity
- Responding to predators eg. Producing toxins
- Responding to abiotic stress eg. Drought
What is controlled by plant growth factors (hormones) in plants?
- bud formation
- growth of roots and shoots
- fruit formation
- seed germination
- leaf fall
- ripening of fruit
- flowering time
- disease resistance
Why are auxins referred to as growth factors rather than hormones?
- exert their influence by directly affecting growth
- unlike animal hormones, they’re made by cells all over the plants rather than in particular organs
- unlike animal hormones, some growth factors affect the tissues that released them as opposed to a distant target organ
Phototropism
- response in which parts of plant grow towards or away from the direction from the high light is coming
Geotropism/gravitropism
- response in which parts of a plant grow towards or away from gravity
Where is indoleacetic acid (IAA) (the main auxin) made in plants?
- produced by mitosis in the tips of roots and shoots
What is the diffusion of IAA affected by?
- light and gravity
What is IAA action in response to light?
- diffuses to the side of the shoot in shade
What is IAA response to gravity?
- downwards
What is IAA effect in shoots?
- stimulates cell elongation and growth
What is IAA effect in roots?
- inhibits cell elongation and growth
What is the response of a sideways shoot to sunlight ?
- IAA accumulates on shaded side (lower side) causing cell elongation
- with only lower part growing the shoot bends upwards towards the light (positive phototropism)
What is the response of a sideways shoot to gravity?
- gravity pulls auxin to the lower side of the shoot causing cell elongation
- with the lower part growing the shoot bends upwards towards the light (negative geotropism)
What is the response to a sideways root to sunlight?
- when exposed to small amount of sunlight IAA accumulates in the shaded side of the root but growth is inhibited
- upper surface grows causing root to bend downwards (negative phototropism)
What is the response of a sideways root to gravity?
- gravity pulls IAA to the lower side of the root where growth is inhibited
- upper surface grows causing the root to bend downwards (Positive geotropism)
Benefits to a plant of having shoots growing towards light
- leaves exposed to more sunlight and carry out more photosynthesis
- flowers can be seen by insects for pollination
- plants get higher for better seed dispersal
Benefits to a plant having roots growing down in response to gravity
- by growing deeply into the soil, the root fixes the plant into the ground firmly
- roots are able to reach more water
- roots have larger surface area for more diffusion and osmosis
Effect of plant B having a black cap placed on top of shoots
- IAA produced but cap means no stimulus for IAA to redistribute to one side so diffuses equally down whole shoot causing growth upwards
Effect of plant A having their shoots cut off
- no IAA produced so no growth seen
Effect of plant c being closest to light
- positive phototropism as AII diffuses down shade side causing cell elongation on that side causing shoot to bend towards light source
Give one similarity and one difference between taxis and tropism
- similarity: both directional response to a stimulus
- difference: taxis occurs in animals and tropism occurs in plants, in taxis whole organism moves and tropism is growth response
Why does IAA increase plasticity of the plant cell wall?
- by actively transporting H+ ions from cytoplasm into spaces in the cell wall allowing cell to elongate by expansion (acid growth hypothesis)
Why is the acid growth hypothesis easier in younger cell walls?
- rigidity develops with maturity so roots and shoots become less responsive
What practical can show the effect on an environmental variable on the movement of an animal using either a choice chamber or maze?
- maggot/woodlice practical
What abiotic factors could you investigate?
- dark and damp, dark and dry, light and damp, light and dry
How might the environmental conditions affect the behaviour of maggots?
- maggots avoid light areas as it makes them more visible to predators
- avoid dry areas as it leads to excessive water loss
How should we ethically treat the maggots?
- do no harm to the maggots like using excessive force to get them into the chamber
Which stats test would be useful to analyse the results and why?
- chi squared as we are looking at the difference between observed data and expected data to see if results are due to chance or are significant
What are the choice chambers useful for?
- used in experiments to study taxis and kinesis responses of model organisms to stimuli and determine their preferred conditions
- they allow for controlled variables like humidity, temperature, light and the presence of certain materials and we can easily observe their responses
What are the three key neurones?
- sensory
- motor
- relay
What are the two types of nervous systems?
- peripheral nervous system
- central nervous system
What is the central nervous system composed of?
- brain and spinal cord
What is the peripheral nervous system composed of?
- sensory nervous system and motor nervous system
What is the motor nervous system composed of?
- voluntary nervous system and autonomic nervous system system
What are the structures of a motor neurone?
- dendrites
- Dendrons
- axon
- myelin sheath
- branched axon terminals
- cell body
- nucleus
- cytoplasm
- nodes of ranvier
What is the adaptation of dendrites?
- fine extensions of dendrons which are larger extensions of the cytoplasm of the neurone
What is the function of dendrites?
- carry electrical impulses towards cell body
What is the adaptation of axon?
- long thread like extension of the cell membrane and cytoplasm
What is the function of axon?
- transmits the nerve impulse from the cell body down to an effector
What is the adaptation of the myelin sheath?
- sheath of lipid wrapped around the axon with gaps
What is the function of the myelin sheath?
- insulates the neurone preventing short circuits with other axons and speeds up conduction of impulses
What is the adaptation of branched axon terminals?
- branched extensions of the axon at the end of the neurone
What is the function of branched axon terminals?
- carries impulse to an effector such as a gland or muscle forming a neuromuscular junction
What surrounds the axon?
- Schwann cells
What do schwann cells do?
- protect the axon, provide electrical insulation, carry out phagocytosis and play a role in nerve regeneration
What do the membranes of the Schwann cells form?
- sheath that is rich in lipid called myelin
What are neurones with myelin called?
- myelinated neurones
What is the structure of a sensory neurone?
- junctions with sensory receptors
- dendron
- cell body
- axon
- junctions with neurone in CNS
What is a sensory neurone also called?
- afferent neurone
What is a relay neurone?
- short neurone that connects a sensory neurone with a motor neurone in the CNS
What is a relay neurone also called?
- association neurone
What is a motor neurone?
- transmits nerve impulses from the CNS to an effector organ (muscle or gland)
What is a motor neurone also called?
- efferent neurone
What are reflexes?
- involuntary actions that: are automatic, faster than voluntary actions, synapse in the spinal cord or in unconscious areas of the brain, require no processing, involve short neural pathways
Why are reflexes important for survival?
- reduce damage to tissues eg. from burning, allow organism to escape from predators, form part of homeostasis
What are the steps of the reflex arc?
- Stimulus
- Receptor
- Sensory neurone
- Relay neurone
- Motor neurone
- Effector
- Response
What is a stimulus?
- detectable change in the surroundings
What is a receptor?
- cells or organs that detect the stimulus
What is a sensory neurone?
- neurone that transmits electrical impulses from the receptor to the CNS
What is a relay neurone?
- neurone carrying electrical impulses from sensory neurone to motor neurone by diffusion of neurotransmitter across synapses
What is a motor neurone?
- neurone that transmits electrical impulses from the CNS to an effector (muscle or gland)
What is an effector?
- muscles or glands that bring about a response
What is a response?
- reaction to the change
Describe how the reflex arc works in response to pain
- Receptor in skin surface detect stimulus
- Electrical impulses sent from the receptor along a sensory neurone to a relay neurone in the CNS by diffusion or neurotransmitter across a synapse
- Information passed from relay neurone to the effector
- Effector muscle contracts pulling hand away from pin
Relay neurone in spinal cord is in the darker region called grey matter, what is it?
- where lots of neurone cell bodies are
What is the white matter?
- mainly axons and fatty myelin sheaths
What is a dorsal root?
- large spinal nerve that sensory neurone travels down
What is the ventral root?
- large spinal nerve that the motor neurone travels down
Why do the pupils contract?
- prevents too much light entering eye, damaging cells of retina
How does blinking protect you?
- removes dust, debris and other foreign bodies from eyes
If someone were to shine a light in a persons left eye, what might you observe in their right eye?
- as optic nerves connect, right eye responds same as left eye
- pupil should constrict
What does it mean if pupils don’t constrict when light is shined into eyes?
- head injury or optic nerve damage
Comparisons of hormonal and nervous system
- in hormonal, communication is by hormones that travel in blood, in nervous, communication is by electrical impulses down neurones
- in hormonal, response is slow, in nervous, response is instant
- in hormonal, response is long lasting, in nervous, response is short lasting
- in hormonal, hormones can have widespread effect on many cells and organs, in nervous impulse acts on one or a few cells only
- in hormonal, effect may be permanent and long lasting, in nervous, effect is not permanent and is short lasting
