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Biology > Tropisms and plant hormones > Flashcards

Tropisms and plant hormones Flashcards

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1
Q

What is a tropism

A

Growth/ movement of part of a plant in response to directional stimulus

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2
Q

What’s a positive response

A

When the plant grows towards the stimulus

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3
Q

What’s a negative response

A

When a plant grows away from the stimulus

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4
Q

How do plants detect and respond to stimuli

A

Sense light and grow and grow towards it to maximise amount they receive
sense and respond to gravity, ensuring roots and shoots grow in right direction

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5
Q

What is the response for light and how does a plant show its response

A

Phototropism
positive in shoots grows towards light
negative in roots as they grow towards the ground

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6
Q

What is the response for gravity and how does a plant show its respnse

A

Geotropism
positive in roots to seek anchorage in soil
negative in shoots allowing it to grow in right direction without any light

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7
Q

What is the response to water and how does a plant show its response

A

Hydrotropism
positive in roots to seek water
negative in shoots

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8
Q

What is auxin

A

Plant hormone that controls growth near tips of roots and shoots in response to different stimuli

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9
Q

Which direction does auxin diffuse

A

Backwards to stimulate cell elongation which happens in cells just behind the tips

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10
Q

What happens if the tip of the shoot is removed

A

No auxin is available so the plant stops growing

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11
Q

What does auxin in the shoots do

A

Stimulates cell elongation

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12
Q

What does auxin in the roots do

A

It inhibits growth (in high concentrations)

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13
Q

What does unequal distribution of auxin cause

A

Unequal growth rates in plant shoots and roots

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14
Q

Auxin and gravity process

A

At start equal distribution of auxin in roots and shoots
auxin diffuses downwards behind tip of roots and shoots
cells in roots where no auxin is grow faster than other side where auxin is as it inhibits growth in roots and grows down
auxin on lower side in shoot stimulate elongation so shoot grows away from direction of gravity

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15
Q

Auxin and light process

A

If light from above: auxin diffuses behind shoot evenly so equal growth upwards
If light from side: auxin accumulates on shaded side so greater cell elongated on shaded side causing it to grow towards the light

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16
Q

What happens if tips of plant are capped

A

no stimulation from sun so no auxin production, no growth, auxin diffuses downwards so plant grows straight

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17
Q

Definition and example of population

A

All the organisms of one species living in a habitat e.g. cat tails

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18
Q

Definition and example of community

A

Populations of different species living in a habitat e.g. all organisms in a pond

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19
Q

Definition and example of ecostystem

A

The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment e.g. rainforest, arctic, barier reef

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20
Q

Definition and example of habitat

A

Where an organism lives e.g. woodland, grassland, ice cap

21
Q

What is interdependence

A

Organisms are dependent on their organisms within their community to survive and reproduce

22
Q

What other organisms may organisms depend on

A

Food
Shelter
Pollination
Seed dispersal

23
Q

What is a stable community

A

One where all the species and environmental factors are in balance so the population remains fairly constant

24
Q

What is an abiotic factor

A 
Non-living factors which can affect a community e.g.
Light intensity
Temperature
Moisture levels
Soil pH
Soil mineral content
Wind intensity and direction
Carbon dioxide levels for plants
Oxygen levels for aquatic animals
25
Q

What is a biotic factor

A 
Living factor that affects a community therefore distribution of organisms e.g.
Availability of food
New predators
New pathogens
Competition
26
Q

What do field studies enable us to do

A

Look at the distribution of organisms and the effects of environmental factors on this

27
Q

Examples of field studies

A

Daisies may be more common in open field than under trees

some types of mayfly more common in colder parts of stream as can’t tolerate colder temps

28
Q

How does the level of mineral ions available affect the distribution of venus fly traps

A

They thrive in areas where nitrate ion levels are very low as there are nitrate ions in the flys protein

29
Q

What is random sampling

A

Using quadrats in areas in which distribution is quite uniform

30
Q

What is systematic sampling

A

Using transects to observe changes in distribution across areas of the habitat

31
Q

What is quantitative sampling

A

Take a number of random readings then find the mean number of organisms per m^2

32
Q

How can you study distribution

A

Measure how common an organism is in 2 or more sample areas using quadrats and compare
study how distribution changes across an area placing quadrats along a transect

33
Q

Why is random sampling a good idea when counting the number of daisies in a field

A

Too difficult to count them all so must estimate in logical way, avoiding bias and still getting accurate, representative reading

34
Q

What else can you measure using a transect

A

abitoic factors such as light levels, soil pH that might affect the growth of plants along transect

35
Q

What do plants compete for

A

Light
Space
Minerals from soil

36
Q

What do animals compete for

A

Food
Mates
Territory

37
Q

Structural adaptation

A

Features of an organism’s body structure e.g. fur colour, blubber

38
Q

Behavioural adaptation

A

The way they behave e.g. huddling, migration, display, avoiding the sun

39
Q

Functional adaptation

A

Process within organism e.g. hibernating lowers metabolism which conserves energy or conserving water my producing very little sweat

40
Q

What are extremophiles

A

Mostly microorganisms that have adapted to live in extreme conditions

41
Q

Conditions include extreme:

A 
Temperatures
Salinity
pH
Pressure
Nutrients
Oxygen levels etc.
42
Q

Thermophiles

A

produce some of the bright colours in hot springs e.g. Yellow stone national park. They have thermostable enzymes that don’t denature at high temps

43
Q

Ice fish found in Antarctica

A

Have no haemoglobin but enlarged hearts and very large blood vessels

44
Q

Water bear

A

Many species of tardigrades live in water but on land you find them almost everywhere there’s moss or lichen. can survive long periods of desication and have survived being taken to space

45
Q

How do rooting powders increase the chances of a plant growing

A

Contains auxin so when cutting dipped in powder, chances of success greatly increased as stimulates growth

46
Q

How is auxin used as weed killer

A

If sprayed on weed, excessive auxin sends plant to uncontrolled growth, killing them.
Most weeds are broad leaved so large SA meaning more successful at killing but narrow leaved plants are unaffected as small SA

47
Q

How is Auxin used in modern plant tissue cultures as part of plant cloning

A

They stimulate growth and cell division in the tissue culture, helping to produce many identical plants to help farmers

48
Q

How are Gibberellins used

A

brewing industry to end seed dormancy, speeding up germination of barley seeds to make malt
promote flowering throughput year e.g chrysanthums
increase size of fruit e.g. seedless grapes would be small as seed contain gibberellins to make fruit grow

49
Q

How is ethene used

A

growers harvest unripe fruit, transported and chilled so won’t get damaged and not over-ripe if any delays
stored until needed
warmers temps then ethene added to atmosphere meaning fruit can be rapidly ripened and sold when needed

Biology (16 decks)

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