1
Q
What must all living organisms be able to do?
A
» Organise biological molecules on a higher level
» Access and use energy
» Grow
» Respond to their environment
» Make more of themselves
- In order to stay alive, plants and animals must be able to detect and respond to changes in their external environment
2
Q
Define behavior
A
» The way in which an organism responds to an external stimulus
» In general terms, animals respond with movement, plants with growth
3
Q
What are the effects that determine the way a plant grows
A
- All plants grow and move in response to environmental information
» Stem and leaves towards the sun
» Foraging roots towards nutrients in the ground
» Root elongation slows down and root hairs spread out in areas of high nutrients
» Slow, so we generally don’t see it
4
Q
How do plants behave?
A
- Plants can detect a variety of external stimuli, and respond appropriately
5
Q
How do plants detect light and environmental factors?
A
- Photoreceptors: » Light - Mechanical stimulation » Wind, herbivory » Physical environment (eg, support structures)
6
Q
How do plants detect nutrients and physical forces of nature like temperature?
A
- Physical environment
» Gravity, temperature, soil water, salt, CO2 - Chemical receptors:
» Nutrients
» Scents (eg, dodder vine can detect tomato smell)
» Chemical messages from other plants (eg, smell of freshly cut grass )
7
Q
Why is light an especially important environmental factor for plants
A
» Required for photosynthesis
» Triggers key events in plant development (“photomorphogenesis”)
» Allows plants to measure the passage of days and seasons
8
Q
What about light can plants detect?
A
» Presence/absence of light, but also
» Direction
» Intensity
» Wavelength (especially blue and red)
9
Q
How is blue light received in plants and what is it used for?
A
- Blue light receptors (cryptochromes)
- Blue light initiates a range of responses in plants:
» Phototropism (growth towards light)
» Light-induced opening of stomata
» Light-induced slowing of elongation of the juvenile shoot (hypocotyl) after it breaks ground
10
Q
How is red light received in plants and what is it used for?
A
- Red light receptors (phytochromes)
- Plants use red light as a measure of light quality (and competition)
» Measure ratio of far red (730 nm, NOT absorbed by overhanging leaves) to red (660 nm, absorbed by overhanging leaves)
» This occurs because phytochromes change shape depending on the presence of red, far red, or no light
11
Q
What are the responses t red light?
A
- Seed germination » Seeds have limited food reserves, so many seeds germinate only when light environment (and other conditions) are optimal (eg, death of a shading tree) - Shade avoidance » Stimulates branching » Inhibits vertical growth - Setting of internal clock - Flowering
12
Q
What are biological clocks?
A
- Biological systems (plants and animals) exhibit cyclic activity patterns (“circadian rhythms”)
» circa- = approximately, -dies = day
» Opening and closing of stomata, sleep (orientation of leaves in legumes)
13
Q
How does light effect biological clocks?
A
- Biological clocks are internal
» Still being researched, but appear controlled by alternating feedback loops of transcription of “clock genes” - But those internal clocks are not perfectly aligned to 24h (vary between 21-27h) … to avoid desynchronisation, they are constantly re-set by light cues (both red and blue)
14
Q
How does photoperiod effect plants?
A
- Plants also use the changing of the length of day (“photoperiod”) over a year to adapt to different seasons
» Eg, to avoid producing leaves in winter (for deciduous trees) - The photoperiod is a critical determinant of flowering → ensure flowers are produced when the right pollinators are present
15
Q
What are long-day plants?
A
- “Long-day plants” (spinach, lettuce, irises …) flower only when the photoperiod is more than 14h, ie in spring/summer
» Measure is very accurate (just a minute can make the difference!)
» Actually controlled by length of darkness rather than day length )
16
Q
What are short-day plants?
A
- “Short-day plants” (chrysanthenums, soybeans …) flower only when the photoperiod is less than a specific number of hours, ie in autumn/winter
» Measure is very accurate (just a minute can make the difference!)
» Actually controlled by length of darkness rather than day length)
17
Q
How does gravity effect plants?
A
- Shoots grow upwards, roots grow downwards even in the absence of light because plants can detect gravity
18
Q
What are Statoliths?
A
- Statoliths: dense components within the cytoplasm of sensor cells that settle at the bottom of the cell, with gravity (≈ balance in animals)
19
Q
What are the types of Environmental stresses plants face?
A
- Environmental stresses can be biotic (living, eg herbivores) and abiotic (non living, eg water, temperature) - plants respond to both
20
Q
What are the types of water stress?
A
- Drought
- Flooding
21
Q
What are the effects of a drought?
A
» Water is needed for photosynthesis …
» Water deficit causes stomata to close → greatly reduces transpiration
» Other responses within different species
• Grass roll into tubelike shape to reduce exposure to dry air
• Other shed leaves in response to seasonal drought
» All reduce photosynthesis, but at least the plant survives
22
Q
What are the effects of flooding?
A
» Flooded soils have no air space (thus less oxygen for cellular respiration)
» Some have adapted specialized aerial roots (eg mangroves)
» Others produce ethylene in response to flooding, which kills some cells in the root cortex, creating an air tube (≈ snorkel)
23
Q
What are the effects of salt on plants?
A
- Salt stress affects plants for two reasons:
» Excess soil sodium decreases water potential of the soil, thus causing a deficit in net movement of water to the plant
» Sodium is toxic to plants at high concentrations - Some plants can produce organic compounds to counter-act these negative effects (to a certain extent …)
24
Q
What are the types of temperature stress
A
- heat
- cold
25
What are the effects of the heat temperature stress?
» Heat denatures proteins
» Transpiration helps plants cool down (by evaporative cooling)
» But if it is also dry, plants close their stomata, which stops this cooling, so plants also synthesize heat-shock proteins (HSPs; ≈ animals), which acts as scaffolds around proteins to help maintain their shape
26
What are the effects of the cold temperature stress?
» Cold decreases membrane fluidity, altering transport across the cell membrane → plants increase proportion of unsaturated fat in membrane when exposed to low temps (which helps maintain fluidity)
» Plants in cold climates also secrete extra sugar to protect against frost
27
How do plants respond to mechanical stimulation?
- Plants respond to touch » Plants that are touched grow more slowly
» Vines coil rapidly around support, to climb upwards towards a forest canopy
- Most plant responses are mediated by hormones (chemical messengers of the endocrine system), but a few are similar to an action potential in the nervous system
28
How do animal and plant communication systems differ?
- Plants do not have a nervous system, but they use chemical communication to coordinate their multicellular activity
- Endocrine communication in plants
29
How does the endocrine system in plants work?
- Plant hormones regulate virtually all aspects of growth and development
» Plant hormones can have different effects in different tissues and the developmental stage of the plant
» Multiple hormones often interact to control growth and development
30
What are signal transduction pathways
- The chains of molecules that relay signals inside a cell
31
What are the steps of signal trasnduction?
1) Reception
2) Transduction
3) Response
32
Draw and label the diagram of signal transduction
Google Doc
https://docs.google.com/document/d/1BpabtfqIj5MGsWdBTMRokVNMhJZjMkFjHpc7UqK5cCk/edit?usp=sharing
33
Provide examples for four types of plants hormones
- Auxin
- Cytokinins
- Giberellins
- Ethylene
34
What is Auxin and what is it used for?
```
- Chemical messenger produced mainly by shoot, involved in
» Cell elongation (increases cell size)
» Stem elongation
» Enhances apical dominance
» Formation of lateral and adventitious roots
» Regulates development of fruit
» Phototropism (response to light)
» Gravitropism (response to gravity)
```
35
Where is synthetic Auxin used?
- Uses of synthetic auxins
» Useful in vegetative propagation of plants by cuttings (stimulates formation of adventitious roots)
» Monocots can rapidly degrade auxins, but eudicots cannot … application of synthetic auxins (eg, herbicide 2,4-D) kills eudicots by hormonaloverdose
36
What is Cytokinins?
- Chemical messenger produced mainly in roots, involved in
» Cell division (thus works in concert with auxin for elongation)
» Antagonises the apical dominance action of auxin
37
What is Giberellins?
- Chemical messenger
- Also involved in stem elongation
- With auxin, involved in fruit development
» Use of synthetic giberellin sprays to make fruit bigger
- When combined with water, triggers seed germination
38
What is Ethylene?
- When tip of growing seedling meets obstacle, ethylene is produced → “triple response” (enables the shoot to avoid the obstacle):
» Slowing of stem elongation
» Thickening of the stem (makes it stronger)
» Curvature (causes the stem to grow horizontally)
39
What are some function that Ethylene is used for?
» Senescence (programmed cell death)
» Leaf abscission (loss of leaves from deciduous trees)
» Fruit ripening: initiates enzymatic breakdown of cell wall and conversion of acids and starches to sugars to make the fruit sweet and attract animals
• Commonly used in commercial fruit production
40
What is the first piece of evidence that proves plants have intelligence?
- Plants communicate with other lifeforms
» Other plants
» Animals (eg, plants attacked by herbivorous insects release “help” chemicals that attract carnivorous insects)
41
What is the second piece of evidence that proves plants have intelligence?
- Just like animals, plants interact and compete with each other to capture sunlight and nutrients
» “Pushing and shoving” towards the sun
» Some even release of toxins and conduct chemical warfare underground
42
What is the 3rd piece of evidence that proves plants have intelligence?
- Plants also collaborate …
» Can recognise relatives (by chemical signatures), and reduce root growth when near siblings to reduce competition
» In forests, trees are connected underground by huge mycorrhizal network through this network, trees share carbon with fungi and with each other!
• Expose one tree to 14CO2, and a few days later you’ll find that 14C in seedlings around it → seedling are being nurtured by larger plants
• Dying trees can send food (and alarm signals) to neighbours from a different species
Biology
flashcards
Decks in class (27)
# Cards
-
Biology and the origin of life60
-
Cell Biology38
-
Cell division40
-
Metabolism32
-
Cellular Respiration28
-
Prokaryotes29
-
Fungi28
-
Protists26
-
Animal Diversity I47
-
Animal Diversity II39
-
Animal Form and Function31
-
Resource Acquisition and Transport in Animals74
-
Osmoregulation and Excretion47
-
Animal Reproduction32
-
Sensing and Reacting43
-
The Animal Immune System29
-
Animal Behaviour35
-
Plant Diversity I55
-
Plant Diversity II52
-
Plant Anatomy53
-
Plant Growth and Development52
-
Resource Acquisition and Transport in Vascular Plants36
-
Soils and Plant Nutrients46
-
Plant Behaviour42
-
Plant Defenses20
-
Plant-Animal Interactions20
-
Principles of Ecology20
