Sensory concepts

Question 2

Why do organisms need sensory inputs/conceptS?

Answer 2

organisms need information about thier food sources, risk of predation and prescence of competition and location of mates in order to survive and propogate
this can be provided through sensory signals and cues

Question 3

how are sensory cues conveyed, general?

Answer 3

conveyed by different sensory modalities. It is important that they only convey information if it is reliable and detectible. These signals often have innate responses

Question 4

abiotic changes

Answer 4

temperature
humidity
sunlight

Question 5

biotic changes

Answer 5

abundance of food
competition
predators/pathogens/parasites
reproductive partners

Question 6

what are cues?

Answer 6

readily and reliably discernible from background noise
has to always mean the same thing
has to be different from other background information in order to be meaningful

Question 7

sensory modalities?

Answer 7

the channels through which animals receive and perceive sensory information from their environment

types include
- chemical
-electrical
- mechanical
-photo
-magnetic
-auditory

each organism has a range within each of its sensory modelities that it can perceive cues from its surroundings (hearing ranges or the visible light spectrum)

Question 8

signals

Answer 8

are acts of structures, generally created by an organism that influences the behaviours of other organisms or receivers

they evolved specifically because of the effect they have on their intended receivers

can initially evolve for one purpose and be co-opted for another

Question 9

sensory receptors

Answer 9

the different cues and signals an organism is capable of sending depends on the sensory receptors it possesses

they all function via changes in action potentials across cellular membranes

they are specialised protein molecules

there are 4 basic ones primary sensory receptors are:
- chemo receptors
- thermo receptors
- mechano receptors
- photo receptors

they enable organisms to detect chemical compounds, temperatures, motion and light

Question 10

chemical receptors

Answer 10

chemical sensitive protein receptors that are activated through physical interaction with specific types of molecules through lock and key mechanism

they can be activated through direct or indirect activation

Question 11

direct activation

Answer 11

when interaction directly opens a channel in the cell membrane

Question 12

indirect activation

Answer 12

activation of another protein inside the cell that then carries the signal along, opening a different protein chennal through which ions pass

Question 13

temperature sensors

Answer 13

modified versions of chemical receptors

they change shape in response to changes in temperature, enabling the passage of ions across the cell membrane

can be both chemical and temperature receptors

Question 14

motion sensitive proteins

Answer 14

mechanical movement signals through movement, stretch or vibration
channels that extend through the cell membrane, where stimuli causes the channels to open, allowing ions through

Question 15

photo receptors

Answer 15

respond to specific wavelengths of light
proteins absorbs energy of the photons and temporarily changes shape, using this energy to cause ions to move in channels

Question 16

photoreceptors in plants

Answer 16

plants have a wide variety of photoreceptors
they often contain photopigments

photochromes are a class of photoreceptor in plants that can sense red and far-red light allowing plants to respond to the intensity and duration of colour of the environmental light

Question 17

photopigments

Answer 17

protein compound bound to a non-protein light absorbing pigment called the chromophore
can possess more than one type
when it absorbs light they change shape, triggering a signalling cascade which can even trigger gene expression

Question 18

Growth through photoreceptors

Answer 18

For example, bright direct sunlight contains more red light than far-red light

plants use phytochromes to adapt their growth in response to levels of direct sunlight or shade.

Exposure to far-red light in shaded regions triggers the elongation of stems and petioles in search of light.

On the other hand, exposure to red wavelengths from unfiltered sunlight enhances lateral growth and branching.

Question 19

what are circadian rhythms

Answer 19

24 hour behavioural cycle
intrinsic, timekeeping, molecular mechanism
allows plants to coordinate physiological activities over a 24-hour cycle called circadian rhythms

Question 20

What is the phytochrome system

Answer 20

light sensitive receptors that allow plants to respond to seasonal changes
they do this by measuring day length (photoperiod) and enables plants to compare the duration of dark periods over several days
they regulate photoperiodism

Question 21

photoperiodism what is it and how does it work?

Answer 21

collective term for the biological responses of plants to variations in teh relative lengths of dark and light periods

it depends on the cycling between inactive Pr and active Pfr

phytochromes are synthesised in the dark in their inactive form in the cytoplasm, they absorb red light in the day and turn into the active form

Pfr can activate cytoplasmic molecules or translocate to the nucleus and regulate gene exprerssion
at light Pfr reverts back to Pr through darkness reversion or destruction by enzymes

Due to the changing in day/night ratios in seasons, this changes the Pfr/Pr ratio in plants, changing plant activity

for example: higher Pfr (active) may cause flowering in some plants that flower in longer days (summer), and vice versa

Question 22

How to plants know which way to grow/which way is up and down (especially for roots)

Answer 22

they adjust their position by changing the rate of growth/elongation in different tissues in asymmetrical ways

this can be done through gravitropism

Question 23

what is gravitropism?

Answer 23

growth in response to gravity

this is how plants know which way is up down

positive gravitropism
- growth in the opposite direction to gravity/with gravity

negative gravitropism
- growth in the direction of gravity/against gravity

Question 24

what are statocytes, how do they work?

Answer 24

specialised cells on root caps that can sense gravity

amyloplasts/statolyths are dense starch filled organelles
they settle downward in the statocyte in response to gravity

the direction in which they settle shows gravity, and allows the plants to either undergo:

• assymetrical elongation of roots (horizontal root plants)
  growth is stimulated on the top of the root, and supressed on the underside, working to curve roots down
• symmetrical elongation of roots (for verticle plants)

Question 25

What else influences plant direction growth other than gravity and light?

Answer 25

touch

plant grow and wrap around things

plants also grow around obstacles

Question 26

what is thogmotropism and how does it work?

Answer 26

directional plant growth in response to touch

negative:
when plants encounter an obstacle they grow around it to avoid it

positive:
when plants encounter an obstacle they grow towards them, rapidly coiling

Question 27

What are sensory organs? What do they do?

Answer 27

sensory receptors are bundled together into sensory organs

they receive information initially and process it, then send it on to the brain depending on the sensory modality of the species in general

Question 28

How does a signal pass to the brain

Answer 28

pass from peripheral sensory receptors along the nervous system to the brain for processing, perception and response. Using action potentials generated by sensory receptors.

Question 29

How does the strength of stimuli occur?

Answer 29

range of the specific receptor which is activated, if it is inside the range, you will perceive it

the number of sensory receptors that are being stimulated

the rate of actions potentials produced by the sensory receptor

Question 30

Smell, how does it work? Example

Answer 30

chemoreceptors embedded in a layer of epithelial tissue in the uppermost tissue in the uppermost region of the nasal cavity

specific oderant molecules bind to the cavity and send informationto other nerves within the olfactory bulb and onto the brain for processing

oderant molecules can be complex and multiple parts of the molecule can bind to multiple different receptors, therefore they can activate a unique sense of nerve clusters within the olfactory bulb called the glomeruli

Question 31

what are pheromones

Answer 31

chemical signals used for communication among conspecifics (individuals of the same species)

individuals secrete pheromones into the environment and trigger a specific behavioural response

can attract mates, cause alarm signals etc.

Question 32

Light detection in animals

Answer 32

Eyes and eye-like structures determine light

The suprachiasmatic nucleus (SCN) sits within the hypothalamus deep in the centre of the brain, right above the optic chiasm where the nerve of the eyes cross over via the retinohypothalamic nerve tract

The retinohypothalamic nerve tract stimulates the release of specific neurotransmitters and other peptides that interact with other regions of the brain and control many physiological processes, like sleep, digestion and thermoregulation

Question 33

what is the somatosensory system? what does it do?

Answer 33

central and peripheral nervous ststem component that senses and processes touch, pressure, pain, temperature, body position or proprioception

Question 34

what are the 3 levels the process of sensation takes place at/

Answer 34

receptor
circuit
perceptual

Question 35

How does the somatosensory perception work?

Answer 35

incoming stimulus excites a sensory receptor

converted to electrical signal, generating a graded potential

graded potential reaches a threshold, and a nerve impulse is generated

At the circuit level, the impulse is received and reaches the CNS throgh several ascending pathways

majority of the impulses reach teh somatosensory area of teh cerebral cortex, but some proprioceptive impulses are processes in the cerebellum

sensory information is processes by the CNS at the perceptual level

Question 36

what is homeostasis

Answer 36

maintenance of relatively constant internal environments

Question 37

How to thermoreceptors work?

Answer 37

Thermoreceptors detect the change in temperature, the message goes through the CNS and reaches the brain, or the control centre, then the brain compares the stimulus with a set point.

If it is outside this set point/range, then the effectors will cause physiological change in order to counteract the change and regain homeostasis.

One of the physiological changes in this case would be sweat glands producing sweat to cool you down

Question 38

Thermal response curves and maths

Answer 38

Q10=Rt/(Rt-10)

where Q10 denotes the rate of change of a reaction over a 10 degree change in temperature

the rate of reaction at a given temp/rate of reaction at 10 degrees less

if Q10=1 then the OROR doubles with each increase in temperature of 10 degrees

therefore is Q10=3 a tripling

Question 39

What is acclimitisation

Answer 39

organisms can eventually adapt to their surroundings, shifting the optimal ROR into the range of temperature to which they are exposed

Question 40

How do sedentary plants acclimate

Answer 40

they have limited means for controlling their internal temperature, these strategies are effective

Question 41

How do large mobile plants acclimate

Answer 41

the maintenance of an optimal internal temperature (thermoregulation) occurs via physiological and behavioural means which enable individuals to balance the heat they gain from their environment with the heat they lose

Question 42

What are ectotherms and endotherms?

Answer 42

Ectotherms
Primarily rely on heat generated from external sources (cold blooded)

Endotherms
produce heat internally (warm blooded)

Question 43

what are heterotherms and homotherms

Answer 43

body temperature fluctuates=heterotherm

body temp remains the same=homotherm

Question 44

Physiological thermoregulation for endo and ectotherms

Answer 44

can all regulate physiologically to some degree

endotherms have greater capacity because they can adjust metabolic rate and heat internally

Question 45

how to organisms gain or lose heat?

Answer 45

radiation from the sun or sky

lose heat produce via metabolism through conduction, convection or evaporation

Question 46

exampels of physiological responses to thermoregulation

Answer 46

vasoconstriction
vasodilation
shutting off blood to specific regions of the body

Question 47

thermoregulation curve explained wiht ecto and endo

Answer 47

CTmin and CTmax are at the 2 points of zero on performance, they indicate the thermal tolerance breadth

Topt is the top of the curve

For ectotherms, they will be linearly dependent on heat, whereas for endotherms, they may increase slightly with heat, but too much will ultimately result in a decrease

Question 48

what is a therone neutral zone

Answer 48

endotherms have a therone neutral zone, a temp range where the cost of maintaining optimal body temperature is minimised,

when it is below, you increase metabolic heat production to compensate for heat loss

when it is above you increase metabolic rate because it costs energy to dump heat from the body when it is already hot

Question 49

what is thermal conductance

Answer 49

the rate at which an animal exchanges heat wiht its environment