5.5 - B - Plant And Animal Responses Flashcards
Why do plants need to respond to their environment?
To avoid abiotic stress
To maximise photosynthesis or to obtain more light/water/minerals
To ensure germination occurs in suitable conditions
Herbivory
How do plants respond to their environment?
Higher temps - more waxy later - reduce evaporation
Very windy - more lignification - reduce water loss
Drought - root growth slows - save energy, stomata close - reduce water loss
Herbivory - release chemicals
List the 3 chemical defences to herbivory
Tannins
Alkaloids
Pheromones
What are tannins?
They are toxic to microorganisms and larger herbivores. In leaves, they are found in the upper epidermis and make the lead taste bad. In roots, they prevent infiltration by pathogenic microorganisms.
What are alkaloids?
They are derived from amino acids. In plants, scientists think they are a feeding deterrent to animals, tasting bitter, they are located in growing tips and flowers, and peripheral cell layers of stems and roots.
What are pheromones?
Chemicals released by one individual and which can affect the behaviour or physiology of another
What are tropisms?
Directional growth responses or plants to a stimulus in which the response is determined by the direction of the external stimulus
List the 4 types of tropisms
Phototropism
Geotropism
Chemotropism
Thigmotropism
Define phototropism
Shoots grow towards sunlight, which enables them to photosynthesise
Define geotropism
Roots grow towards the pull of gravity. This anchors them in the soil and helps them to take up water, which is needed for support (to keep cells turgid), as a raw material for photosynthesis and to help cook the plant. There will also be minerals, such as nitrate in the water, needed for the synthesis of amino acids.
Define chemotropism
On a flower, pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation can take place.
Define thigmotropism
Shoots of climbing platen, such as ivy, wind around other plants or solid structures to gain support.
What is the difference between a positive tropic response and a negative tropic response
Positive - when a plant moves towards the stimulus
Negative - when a plant moves away from the stimulus
Define thigmonasy
The nastic response of a plant or fungus to touch or vibration
List the 5 plant hormones
Cytokinins Abscisic acid Auxins Gibberellins Ethene
What do cytokinins do?
Promote cell division
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
Inhibit growth of side-shoots
Inhibit leaf abscission
Define leaf abscission
Leaf fall
What do gibberellins do?
Promote seed germination and internodal growth of stems
What does ethene do?
Promotes fruit ripening
List the 3 ways hormones move around the plant
Active transport
Diffusion
Mass flow in the in phloem sap or in the xylem vessels
What are auxins?
Plant hormones which are responsible for regulating plant growth
Define apical dominance
Inhibition of lateral buds further down the shoot by chemicals produced by the apical bug at the tip of a plant shoot
Give 3 similarities of plant and mammalian hormones
Hormones bind to receptors causing a cascade of events/enzyme reactions. This may involve switching on / off genes only present/needed in small concentrations/quantities (to have an effect).
They may have effect on more than one location/target tissue.
There is an idea that hormone effect may involve interaction of more than one hormone.
Give 4 differences between plant and mammalian hormones
Mammalian hormones are made in endocrine glands versus plant hormones which are made in many plant tissues.
Mammalian hormones move in blood versus plant hormones which move in the xylem or phloem or from cell to cell.
Mammalian hormones act on a few specific target tissues versus plants which act on most tissues. They can also act in cells where produced.
Mammalian hormones act more rapidly.
Explain the commercial uses of auxins
Cuttings of plants are dipped in rooting powder containing low
concentrations of auxin (promotes root growth)
Weedkiller ‐ promotes rapid shoot growth ‐ plant can’t support itself and falls and dies
Can help make seedless fruits
How do levels of auxin affect cytokinins?
High levels of auxin inhibit cytokinins’ effects
Low levels of auxin allows cytokinins to promote lateral bud growth
What are the commercial uses of cytokinins?
Prevent yellowing of lettuce leaves (senescence)
In tissue culture (artificial cloning of plants) cytokinins added to promote many side shoots ‐ can be grown into new plants ‐ hgiher production of new plants
What are the commercial uses of gibberellins?
Elongate internodal cells in stalks of grapes ‐ grapes spread out and get bigger
Elongation of internodal cells in sugar cane ‐ more sugar
Beer production needs malt. Gibberellins added to encourage barley
seed to make amylase so starch ‐‐> maltose. Germination then
stopped by drying.
What are the commercial uses of ethene?
Spraying fruit with an ethene based compound can:
> speed up ripening in bananas and other fruits
> promote fruit abscission in cherries and other fruits
Cold conditions, little oxygen and high carbon dioxide prevents ethene
synthesis and can prevent fruit ripening during shipping
Define action potential
The change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.
What is the mammalian nervous system split into?
Central nervous system
Peripheral nervous system
What is the central nervous system split into?
Brain
Spinal chord
What is the peripheral nervous system split into?
Sensory system
Motor system
What is the motor system split into?
Somatic nervous system
Autonomic nervous system
What is the autonomic nervous system?
The part of the nervous system responsible for controlling the involuntary motor activities of the body
What is the CNS?
The central nervous system
The central part of the nervous system composed of the brain and spinal chord
What is the PNS?
The peripheral nervous system
The sensory and motor nerves connecting the sensory receptors and effectors to the CNS
What is the somatic nervous system?
The motor neurones under conscious control
What must a communication system enable?
Detection of changes in the environment
Cell signalling to occur between all parts of the body
Coordination of a range of effectors to carry out responses to the sensory input
Suitable responses
Describe the structure of the brain in respect to the CNS
It contains about 86 billion neurones. Much of the brain is composed of relay neurones, which have multiple connections enabling complex neural pathways. Most of these cells are non-myelinated cells and the tissue looks grey. It’s also known as grey matter.
Describe the structure of the spinal chord in respect to the CNS
It has many non-myelinated relay neurones making up the grey cell matter. It also contains large numbers of myelinated neurones making up an outer region of white matter. These myelinated neurones carry action potentials up and down the spinal cord for rapid communication over long distances.
It’s protected by the vertebral column.
What is the role of the PNS?
To ensure rapid communication between the sensory receptors, the CNS and the effectors.
Describe the structure of the PNS
It’s composed of sensory and motor neurones. These are usually bundled together in a connective tissue sheath to form nerves.
Explain the structure of the somatic nervous system
It consists of motor neurones that conduct action potentials from the CNS to the effectors that are under voluntary (conscious) control, such as the skeletal muscles. These neurones are mostly myelinated, so that responses can be rapid. There is always one motor neurone connecting the CNS to the effector.
Explain the structure of the autonomic nervous system
It consists of motor neurones that conduct action potentials from the CNS to effectors that are not voluntary control. There are at least 2 neurones involved in the connection between the CNS and the effector. These neurones are connected at small swellings called ganglia.
What does autonomic mean?
Self-governing
What can the autonomic system be divided into?
The sympathetic system
The parasympathetic system
What does the sympathetic system do?
Prepares the body for activity
Fight or flight
What does the parasympathetic system do?
Conserves energy
Rest and digest
What type of systems are the sympathetic and parasympathetic systems?
Antagonistic - the action of one system opposes the action of the other.
Explain the difference in the number of nerves between the sympathetic and parasympathetic systems
Sympathetic - consists of many nerves leading out of the CNS, each leading to a separate effector.
Parasympathetic - consists of a few nerves leading out of the CNS, which divide up and lead to different effectors.
Explain the difference in where the ganglia are located between the sympathetic and parasympathetic systems
Sympathetic - just outside the CNS
Parasympathetic - in the effector tissue
Explain the difference in the length of the ganglia between the sympathetic and parasympathetic systems
Sympathetic - short pre-ganglionic neurones. Long post-ganglionic neurones (variable in length, dependent upon the position of the effector)
Parasympathetic - long pre-ganglionic neurones (variable in length, dependent upon the position of the effector). Short post-ganglionic neurones.
Explain the difference in what is used as the neurotransmitter between the sympathetic and parasympathetic systems
Sympathetic - noradrenaline
Parasympathetic - acetylcholine
Explain the difference in the when the systems are most active between the sympathetic and parasympathetic systems
Sympathetic - most effective at times of stress
Parasympathetic - most effective during sleep or relaxation
Lost 5 effects of the sympathetic nervous system
Increase heart rate Dilated pupils Increases ventilation rate Reduces digestive activity Orgasm
List 5 effects of the parasympathetic nervous system
Decreases heart rate Constricts pupils Reduces ventilation rate Increases digestive activity Sexual arousal
What is a ganglion?
A structure containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fibre.
What are the 4 main parts of the human brain?
Cerebrum
Cerebellum
Hypothalamus and pituitary complex
Medulla oblongata
What is the cerebrum?
The learners part of the brain. It organises most of our higher thought processes, such as conscious thought and memory.
It is divided into 2 cerebral hemispheres.
What is the cerebellum?
A region of the brain which coordinates balance and fine control of movement.
What is the hypothalamus?
Part of the brain that coordinates homeostatic responses?
What is the pituitary gland?
An endocrine gland at the base of the brain, below but attached to the hypothalamus; the anterior lobe secretes many hormones; the posterior lobe stores and releases hormones made in the hypothalamus.
How are the 2 cerebral hemispheres connected?
Via major tracts of neurones called the corpus callosum
What does the outermost layer of the cerebrum consist of?
A thin layer of nerve cell bodies called the cerebral cortex
List 5 functions of the cerebrum
Conscious thought
Conscious actions (including the ability to override some reflexes)
Emotional responses
Intelligence, reasoning, judgement and decision making
Factual memory
What are the 3 subdivisions of the cerebral cortex and why is it subdivided?
Sensory area
Association areas
Motor areas
For specific activities and body regions
What do sensory areas in the cerebral cortex do?
Sensory areas receive action potentials indirectly from sensory receptors. The size of the region allocated to receive input from different receptors correlates to the sensitivity of the area that inputs are received from.
What do association areas in the cerebral cortex do?
Association areas compare sensory inputs with previous experience, interpret what the input means, and judge an appropriate response.
What do motor areas in the cerebral cortex do?
Motor areas send action potentials to various effectors (muscles and glands). The sizes of the regions allocated to deal with the different effectors correlates to the complexity of the movements needed in the parts of the body. Motor areas on the left side of the brain control the effectors on the right side of the body and vice versa.
How many neurones does the cerebellum contain?
Over half of all the neurones in the brain
How does the cerebellum carry out its functions?
It must receive information from many sensory receptors and process the information accurately. The sensory receptors that supply information to the cerebellum include the retina, the balance organs in the ear and spindle fibres in the muscles - these give information about muscle length and joints.
List 4 muscular movements that the cerebellum coordinates the fine control of
Maintaining body position and balance, such as when riding a bicycle.
Judging the position of objects and limbs while moving about or playing sport.
Tensioning muscles in order to use tools and play musical instruments effectively.
Coordinating contraction and relaxation of antagonistic skeletal muscles when walking and running.
What connects the cerebrum and the cerebellum?
The pons
Explain how the hypothalamus controls temperature regulation
It detects changes in core body temperature. However, it also receives sensory input from temperature receptors in the skin. It will initiate responses to temperature change that regulate body temperature within a narrow range. These responses may be mediated by the nervous system or by the hormonal system (via the pituitary gland)
