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Biology Scholarship > B3.3 > Flashcards

B3.3 Flashcards

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1
Q

Abiotic

A

Physical factors of the environment eg. light, humidity

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2
Q

Biotic

A

Factors in the environment due to other living things eg. parasitism

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3
Q

Habitat

A

The place where an organism lives

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4
Q

Ecological Niche

A

The sum total of an organisms requirements and its interrelationship with the other organisms in the community

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5
Q

Daily Rhythm

A

A rhythm with a period of 24 hours

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6
Q

Circadian Rhythm

A

A rhythm with a period of approximately 24 hours under constant environmental conditions

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7
Q

Circalunar Rhythm

A

A rhythm with a period of approximately 29 days under constant environmental conditions

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8
Q

Circatidal Rhythm

A

A rhythm with a period of approximately 12 hours under constant environmental conditions

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9
Q

Circannual Rhythm

A

A rhythm with a period of approximately 1 year under constant environmental conditions

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10
Q

Exogenous Rhythm

A

A rhythm that is controlled by an external environmental stimulus detected by an organism

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11
Q

Endogenous rhythm

A

A rhythm that is controlled by an internal biological clock

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12
Q

Period

A

the time it takes to complete one cycle of activity

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13
Q

Phase shift

A

When the onset of the period of the rhythm is changed (either earlier or later)

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14
Q

Free running period

A

The time when the clock is running without any cues from the environment

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15
Q

Entrainment

A

Th resetting of the clock on a regular basis, forcing it to take up the period of the environment

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16
Q

Zeitgeber

A

Time keeper

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17
Q

Diurnal

A

Active during the day and inactive at night

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18
Q

Nocturnal

A

Active during the night and inactive during the day

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19
Q

Crepuscular

A

Active at dawn and dusk

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20
Q

Arrhythmic

A

No regular pattern of activity

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21
Q

Photoperiodic Response

A

The response of an organism to the change in day or night length

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22
Q

Long Day Plants

A

Plants that flower when the photoperiod exceeds a certain critical day length

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23
Q

Short Day Plants

A

Plants that flower when the photoperiod is less than a certain critical day length

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24
Q

Vernalisation

A

The induction of flowering or seed germination by a period of chilling

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25
Q

Dormancy

A

Metabolic inactivity in plants

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26
Q

Abscission

A

Leaf or fruit fall

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27
Q

Hibernation

A

A period of suspended activity during winter

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28
Q

Aestivation

A

A period of suspended activity during summer (avoiding dry conditions)

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29
Q

Diapause

A

A period of arrested development at an immature stage of growth (and can only be broken by a definite environmental stimulus such as a period of exposure to cold)

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30
Q

Tropism

A

The growth response of a plant towards or away from a stimulus coming from one direction

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31
Q

Nastic Response

A

The movement of a plant in response to a non directional stimulus

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32
Q

Kinesis

A

The change in rate of movement of the whole organism in response to the change in intensity of a non directional stimulus

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33
Q

Taxes (plural taxis)

A

The movement of the whole organism in response towards or away from a stimulus coming from one direction

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34
Q

Photo

A

Light

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35
Q

Geo

A

Gravity

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36
Q

Helio

A

Sun

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37
Q

Thigmo

A

Touch

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38
Q

Chemo

A

Chemical

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39
Q

Thermo

A

Temperature

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40
Q

Hydro

A

Water

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41
Q

Migration

A

Regular, annual mass movement of animals from an area where they breed to an area where they do not breed

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42
Q

Territory

A

The area an animal will defend

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43
Q

Home range

A

The area an animal will search for food, mates, and will make its home

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44
Q

Homing

A

The ability of an organism to find its way home over unfamiliar territory

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45
Q

Intraspecific competition

A

Competition between individuals of the same species

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46
Q

Interspecific competition

A

Competition between individuals of different species

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47
Q

Agonistic

A

Any social behaviour related to fighting, such as aggressive or submissive behaviours

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48
Q

Parasitoid

A

An insect, usually a wasp, which lays its eggs in a living host

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49
Q

Pathogen

A

A disease causing organism

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50
Q

Mutualism

A

A relationship where both species benefit (+, +)

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51
Q

Exploitation

A

(Parasitism, predation) A relationship where one species is harmed and the other benefits (+, -)

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52
Q

Competition

A

A relationship where both species are harmed (-, -)

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53
Q

Batesian Mimicry

A

The resemblance of a harmless or palatable species to one that is dangerous or poisonous

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54
Q

Mullerian Mimicry

A

Several poisonous or dangerous special that all have similar warning coloration patterns

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55
Q

Linear Hierarchy

A

A linear order of animals from the most dominant to the least dominant

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56
Q

Species

A

A group of organisms that can interbreed and produce fertile offspring

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57
Q

Population

A

A group of organisms of the same species living together in a defined area at the same tome

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58
Q

Innate behaviour

A

Genetically determined behaviour (instinctive)

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59
Q

Endemic Species

A

A species that can only be found in one place (e.g. New Zealand)

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60
Q

Liane

A

Climbing Plant

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61
Q

Epiphyte

A

Perching Plant

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62
Q

Pair Bond

A

A prolonged relationship between male and female associated with joint parental care

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63
Q

Adaptation

A

The special features an organism possesses that enable it to survive

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64
Q

Structural Adaptation

A

A physical feature of an organism that enables it to survive

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65
Q

Physiological Adaptation

A

A chemical feature of an organism that enables it to survive

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66
Q

Behavioural Adaptation

A

How an organism acts which enables it to survive

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67
Q

What is involved in an organism’s niche?

A
  1. Opportunities provided by its environment

2. The adaptations that enable the organism to survive in its environment

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68
Q

Gause’s Principle

A

No two species with identical ecological niches can co-exist for very long

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69
Q

What happens when two species have the same ecological niche?

A

One is out-competed and either dies out, moves away, or alters its requirements.

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70
Q

Fundamental Niche

A

The full range of conditions an organism could exist in

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71
Q

Realized Niche

A

The niche the organism actually occupies. This is normally narrower as competition forces them out of parts of their niche

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72
Q

What are the two different animal behaviors?

A

Innate (instinctive)

learned

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73
Q

What is a ‘group’

A

Formed when members of a species GATHER together, REMAIN together, and RESPOND to one another’s presence.

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74
Q

What are the disadvantages of living in a group?

A
  • Increased competition for resources- eg. food, mates, shelter. Individuals are less likely to survive or less likely to have offspring.
  • Increased chance of spread of disease and parasites. Less likely to survive.
  • Interference with reproduction eg. infanticide.
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75
Q

What are the advantages of living in a group?

A
  • Easier to find a mate
  • Increased chance of finding food (predators) or spotting predators (prey). This is because there are more eyes to work as a team.
  • Increased chance of taking down larger/more difficult prey due to teamwork (predators)
  • Able to form defensive circles to protect young/weak members (prey)
  • Statistically less likely to be taken (prey)
  • Confusion can be created when being hunted eg. shoals of fish flashing colors and bright scales can confuse predators.
  • Protection from physical factors eg. penguins clump together to keep warm. This creates a MICROCLIMATE.
  • Greater learning opportunities
  • Division of labour (eg. bees, ants)
  • can navigate as a group when migrating and therefore less likely to get lost (birds)
  • Hydro/aerodynamic effects- V shape conserves energy when migrating long distances (less wind resistence on members behind) and therefore individuals more likely to survive, more energy for reproduction.
76
Q

Why must aggression be suppressed in groups?

A
  • Allow for mating
  • Protect young
  • Reduce conflict between siblings (same genes)
  • Maintain hierarchy
77
Q

How is aggressiveness suppressed?

A
  • Smell marking a large group
  • Social grooming
  • Baby characteristics
  • Appeasement/ submissive gestures
78
Q

What are some features of a group?

A
  • Altruistic behavior:helping less advantaged members of a group (most members are kin so it’s helping the genes to survive)
  • Overpopulation- avoided by reduced fertility in crowded conditions.
  • Stress occurs which alters behavior and lowers population numbers.
79
Q

What is required for mating to occur?

A
  • Co-operation
  • Suppression of aggressive behavior
  • Systems of communication and species recognition
80
Q

What does courtship behavior do?

A
  • Ensures pair is the same species
  • Attract a mate
  • Trigger ovulation (some cases)
  • Synchronize gamete release (some cases)
  • Suppress aggression
  • Select best mate
  • Initiate nest building (some cases)
81
Q

What is a pair bond?

A

A stable relationship between opposite sexes. Ensures co-operative behavior during mating and rearing young.
(NB some species mate for life, some find new mates each breeding season)

82
Q

What are the advantages of mating for life?

A
  • Do not have to expend energy finding a mate
  • After the first set of offspring, both members are experienced parents and so likely to raise the next sets more successfully in future.
83
Q

What are the advantages of finding a new mate each breeding season?

A
  • Increased genetic diversity- can survive changes in environmental conditions
  • If one mate dies, the other can acquire a new one.
84
Q

What is an r-strategist

A

An organism which produces large numbers of offspring but provides no parental care. This relies on a few of the young surviving to adulthood (statistically high chance).

85
Q

What is the advantage and traits of being an r- strategist?

A

Good for unstable environments as reproduction is quick. Traits include high fecundity, small body size, early maturity onset, short generation time, ability to disperse offspring widely.

86
Q

What is a K-strategist?

A

An organism which produces few offspring but provide lots of parental care. This relies on the young being raised to adulthood and equipped with the skills to survive on its own.

87
Q

What are the advantages and disadvantages of being a K-strategist?

A

A:
Offspring is well fed/protected.
- Only one offspring needs to be provided for at a time
- offspring not produced every year so energy conserved
D:
- Offspring is dependent on parents- vulnerable if one/both dies.
- Parenting is energy expensive.

88
Q

What are the traits of K-strategists?

A

Large body size, long life, production of few offspring.

89
Q

What are the reasons for aggressive behavior?

A
  • Protection of young
  • Fighting for access to mates
  • Fighting for some crucial resource in limited supply (space, food)
  • Self defense and property protection
  • Pain
  • Motivational conflict (eg. animal is trapped)
90
Q

What is a threat display?

A

A symbolic behavior (a ritual they all recognize) which allow the animals to avoid an actual fight which could result in injury or death. This often leads to submission or appeasement from one of the animals.

91
Q

How do animals mark territory with scent?

A

Animals use urine and faeces to mark the boundary of their territory. Some animals have scent glands not heir wrists or rumps which they rub against surfaces.

92
Q

How do animals mark their territory with vocalisation?

A

Birds mark their territories (and signal their willingness to mate) by singing on the boundaries of their territory at dawn and dusk.
- Howler monkeys are most vocal in the morning.

93
Q

How do animals mark their territories with visual signals?

A

Crabs wave their claws, birds swoop and dive, pukekos flash their white tail feathers to indicate danger to the rest of the group.

94
Q

What are the advantages of maintaining a territory?

A
  • Only the fittest animals can hold a territory so the best genes more likely to be passed on.
  • Ensures enough food and water for animals
  • Reduces aggression (once boundaries established)
  • Safe, protected home for young
  • Reduces spread of disease and parasites
  • Ensures enough space (if space is limited this will keep population down)
95
Q

What are the disadvantages of maintaining a territory?

A
  • Energy cost to organism of the species : defending the territory
  • Energy cost to individual: not as much time to find food for itself.
96
Q

What is a linear hierarchy?

A

Where animals of a species have a rank order from the most dominant animal to the most submissive animal (always assume linear unless otherwise stated)

97
Q

What are features of a complex hierarchy?

A
  • Separate male/female hierarchies, status depends on fertility, possibility of forming alliances.
98
Q

What do hierarchies depend on?

A

Individuals recognizing each other and one organism giving way to one another.

99
Q

What are dominance displays?

A

Behavior to make an animal submit to it.

e. g.. making the individual appear bigger (fluffing feathers, standing hair on end, standing on hind legs, tail erect)
- Vocalizations (eg. snarling)
- Threat displays (yawning to display teeth, wide eyed glare)
- Physical aggression

100
Q

What are appeasement gestures?

A

Behavior to decrease the chance of the dominant animal harming it

eg. Making the animal look smaller (eg. lowering head, cringing, tucking tail
- Exposing vulnerable parts of the body

101
Q

What is play fighting good for?

A

Allows young animals to test their relative strength and sort their position in the hierarchy early on. Also allows young to develop stalking/hunting skills.

102
Q

What does an individual’s status in the hierarchy depend on?

A
  • Sex (males bigger than females so more dominant)
  • Age (older animals have more experience/strength)
  • Size (larger animals stronger so more dominant)
  • Strength (stronger animals more dominant)
  • Experience (may have skills)
  • Intelligence (in some cases) (may have alternate strategies for dominance)
103
Q

What are the advantages of living in a hierarchy?

A
  • Decrease in aggression once the hierarchy is established (everyone knows their place)
  • More dominant animals have the ‘best genes’ which are more likely to be passed on as they have the most mates
  • Most dominant animals get most food (more likely best genes will survive)
  • Subordinate animals may get more food than if not in a hierarchy (large game they could not kill on their own)
  • Subordinate animals protected by the dominant animals from external threats
  • Subordinate more likely to mate than if it lived alone (though less likely than dominant animals)
104
Q

Define Mutualism

A

When both species benefit from the relationship.

105
Q

Give some examples of mutualism

A
  • Small fish clean larger fish and eat the parasite
    -Alarm calls of some prey species are heeded by other species
  • Micro-organisms break down cellulose in cows’ guts. Bacteria get living space and cellulose while cow obtains nutrients
    NB. This can be either desired (not necessary) or required (necessary)
106
Q

Define Commensallism

A

Occurs when one species benefits and one is unaffected

107
Q

Give some examples of commensalism

A
  • Sucker fish attaches to sharks and scavenges leftovers

- Pea crabs live in some mussel shells getting shelter and maybe leftovers

108
Q

Give the three categories of exploitation:

A
  • Herbivory
  • Predation
  • Parasitism
109
Q

Define Herbivory

A

Where an animal eats a plant or plant like organism (seaweed)

110
Q

Define Predator

A

An organism that catches and kills prey for food

111
Q

What are some predator strategies?

A
  • Belonging to a group to locate and catch food
  • Using snares (eg. webs)
  • Rapid speed (eg. cheetah)
  • Using poison to stun/kill (e.g. snakes, sea anemones)
  • Camouflage and waiting (eg. chameleons)
  • Using tools (humans)
  • Using mimicry (e.g. predatory fish mimic cleaner fish)
  • Stealth
112
Q

What are some prey defenses?

A
  • Living in groups for protection (can post sentries) (eg. meerkats)
  • Disruptive coloration to hide the outline of the body (eg. zebras)
  • Cryptic coloration that matches the background
  • Retreating into a shell (eg. snails)
  • Startling the predator (eg. butterflies with false eyes)
  • Chemical defense (e.g. skunks)
  • Mimicry (Batesian and Mullerian)
  • Confusion by numbers (eg. schools of fish)
  • Pretending to be inedible (eg. stick insect)
  • Structural defenses (eg. pufferfish)
113
Q

Define Mullerian Mimicry

A

Occurs when several poisonous/dangerous species have similar markings- makes it easier for predator to recognize and avoid all harmful species.

114
Q

Define Batesian Mimicry

A

Occurs when palatable animal resembles unpalatable or dangerous animal so that it will hide behind the learned behavior of the predator. NB this only works if there are more of the unpalatable species than palatable.

115
Q

How do you tell which is the predator from a predator/prey graph?

A

The predator always peaks and drops after the prey

116
Q

What are the defining features of parasites

A
  • They exist at the expense of the host without killing it

- Invasions are mainly density dependent- crowded conditions makes it easier to transfer

117
Q

What are the 4 types of parasite?

A
  • Ectoparasites (live outside the body)
  • Endoparasites (live inside the body)
  • Social parasites (eg. cuckoos)
  • Plant parasites
118
Q

Define interspecific competiton

A

Occurs between different species when the demand for a resource exceed supply

119
Q

Define Allelopathy

A

Reduces competition in plants by one plant producing a chemical which inhibits the growth of other species

120
Q

Define Antibiosis

A

Fungus produce chemicals that kill/inhibit growth of other species

121
Q

What happens when interspecific competition occurs?

A

There is selection for any differences in the niche to avoid competition. If this does not happen, one is driven away or dies out.

122
Q

How do similar species avoid competition?

A
  • Having different rhythms
  • Feeding in different areas
  • Utilizing different light intensities
  • Living in different parts of the tidal zone
  • Giving rise to different patterns in the community
123
Q

Define Lianas

A

Long stemmed, woody vines which are rooted in the ground and use trees and other vertical supports to climb up the canopy and get access to well lit areas of the forest. They can protect weaker trees from strong wind. They compete with forest trees for sunlight, water and nutrients.

124
Q

Define Epiphyte (perching plant)

A

A plant that grows non parasitically upon another plant and derives its moisture and nutrients from the air, rain, and debris around it, rather than the structure it is fastened to.

125
Q

What promotes cell elongation in stems and inhibits it in roots?

A

Auxin (IAA)

126
Q

What is the process of a shoot bending towards the light?

A
  1. Auxin is produced in the apical meristem.
  2. From here, it moves to the dark side of the apical meristem.
  3. The auxin then flows down the dark side of the zone of elongation. (NB: Auxin is soluble though agar or gelatin, but will not mass through silver or mica.
  4. The cells with auxin grow more than those without, causing the plant to bend towards the light.
127
Q

What does auxin have to do with making plants bushy/non bushy?

A

Auxin inhibits laterally growing buds- auxin from the meristem diffuses down to these buds to stop them growing. This causes more energy to be put into growing upwards. Once the plant as reached its required height, the auxin is produced less and lateral buds can grow.

128
Q

What is etoliation?

A

Desperate growth upwards in order to find a light source. This results in long stems, white/yellow color and tiny leaves.

129
Q

How does auxin cause a root to grow downwards and a stem to grow upwards?

A
  1. Statoliths are starch holding organelles which are very dense. When the root and stem are horizontally planted, the statoliths sink to the bottom of the cells.
  2. This is thought to trigger some kind of auxin production.
  3. In stems, this causes the lower sides of the cells to elongate more, resulting in a curve upward. In roots, this causes the lower sides of the cells to elongate less, resulting in a downward curve.
130
Q

What does the root cap do?

A
  1. The root cap secretes slime to ease the root’s passage through soil
  2. It protects the growing part of the root
  3. It is thought to produce abscisic acid, which also inhibits root growth.
131
Q

What are rapid leaf movements?

A

When the leaves of a plant are touched and quickly drop down and leaflets fold together. This is called a thigmonasty, and is presumably a response to animal herbivory, or to prevent water loss in windy conditions.
Also seen in venus fly traps to catch prey

132
Q

What are sleep movements?

A

Leguminous plants lower leaves in evening and raise them in the morning. Flowers opening and closing is another example of this.

133
Q

How do plants’ nastic responses work?

A

A change in turgor pressure (pressure of water against cell walls).
1. When disturbed by touch, cells at the base of leaflets release K+ ions which reduce water concentration outside the cells.
2. This causes water molecules to move from inside the cell to outside the cell as there is now a higher concentration inside the cell.
3. As a result, the cells become flaccid and collapse.
This makes the plant less attractive to herbivores, and exposes thorns.

134
Q

Define Klino-taxis

A

An animal that moves away or towards a stimulus by moving its body side to side to detect source of a stimulus. (e.g. large exhibit negative phototaxis avoiding light source)

135
Q

Define Tropo-taxis

A

An animal moves towards or away from a stimulus without moving the body side to side as stimulus is detected simultaneously on both sides of the body. (e.g. snails move up walls to find food, escape predators, and when the ground is too hot or wet.)

136
Q

Define telo-taxis

A

Orientation directly towards or away from a stimulus which occurs whether or not both symmetrical organs are functional.

137
Q

Define rheo-taxis

A

Movement against a current

138
Q

Define orthokinesis

A

The speed of movement is related to the intensity of the stimulation (eg. slaters move faster in bright light than dim light.)

139
Q

Define klinokinesis

A

The amount of random turning is related to the intensity of the stimulation eg. flatworm turns more frequently in response to light (find a way out)

140
Q

Give the advantages of homing

A

Can find food and mates with a stable environment to return to which provides shelter and protection, warmth and a place to rear young.

141
Q

What are some triggers to migration?

A
  • Drop in temperature
  • Days becoming shorter
  • Inbuilt genetic drive
142
Q

What are some advantages of migration?

A
  • Animals remain in a favorable temperature. Are more likely to survive as they don’t have to spend as much energy thermoregulating.
  • Have a constant food supply, therefore better breeding conditions and higher survival rate
  • Reduction in parastitism, predation and spread of disease
  • Better genes passed on (those who survive the migration)
  • More genetic mixing
143
Q

What are some disadvantages to migration?

A
  • Animals could get caught in a storm and get lost (blown off course) or killed
  • Could be eaten by unfamiliar predators en route
  • Huge investment in energy- may run out of energy/starve en route and die
144
Q

What are the 6 ways animals navigate?

A
  • Visual cues
  • Magnetism
  • Sun compasses
  • Star compasses
  • Chemical navigation
  • Sonar
145
Q

How do animals use visual cues to migrate?

A
  • Learn their surroundings and use landmarks.
146
Q

How do animals use magnetism to navigate?

A

Many animals are sensitive to magnetism and can follow the earth’s magnetic field lines. This is due to the magnetized particles in their brains. NOTE if magnets are placed on their heads they will likely get lost

147
Q

How do organisms use sun compasses to navigate?

A

They compensate with an inbuilt clock for the changing direction of the suns movement. eg. if bird flies 45 degrees left of sun at 9am, it will fly 45 degrees right of sun at 3pm.

148
Q

How do bees show where food sources are?

A

Round dance: Used if nectar is 50m or less from hive. Be runs of comb in a circle clockwise and anti clockwise. Does not indicate direction of food.
Waggle dance: Used when nectar is 50m or more from hive. Bee traces figure 8 pattern. Speed and number of waggles it does on straight run indicates distance. Direction is given by way the bee faces on straight run.

149
Q

How do animals use star compasses to navigate?

A

Some organisms follow a star or group of stars. When night is overcast they may get lost

150
Q

How do animals use chemical navigation

A
  • Involves taste or smell
    eg. salmon detect the exact river they were born in by chemical odor of the river.
  • Fire ants leave trail of volatile chemicals for other to follow. This lasts 80 secs. but other ants add to it. Ants can tell the difference between trail with food and trail without food.
151
Q

How do animals use sonar to navigate?

A
  • bats use high pitched squeaks which bounce off objects in their path
  • Whales migrate to antarctic and arctic oceans each year, orientating themselves with sonar.
152
Q

What are biological rhythms and why are they important?

A
  • Environmental cues affected by abiotic factors which are used by plants and animals to establish and maintain a pattern of activity
  • Important for synchronizing events in their life cycles- e.g. pollination, mating, birth, germination, parental care and food storage
153
Q

What is a daily rhythm

A

Linked to the day/night cycle. Animals can be:

  • Nocturnal
  • Diurnal
  • Crepuscular

Plants also exhibit this by only photosynthesizing at day and some flowers showing sleep responses

154
Q

What is a tidal rhythm?

A

Every 12.4 hours
Caused by the rise and fall of tides.
In most organisms: When the tide is in they are active, feeding and mating, and when it goes out they must hide.
Some organisms (eg. brown must snail) feed when tide is out and bury themselves in mud when tide is in.

155
Q

What is a lunar rhythm?

A

Every 29 days
Linked to moon phases: e.g.. salmon migrate downstream where they wait until the new moon, causing a surge in hormone thyroxine, allowing them to regulate their internal salt conc. They then mass migrate to the sea.

156
Q

What is a semilunar rhythm?

A

Once every 15 days
Caused by new/full moons and lowest low and highest high tides as a result. Eg. Inunga lay eggs at the very top of the shore during the king tide. They bury these in the sand and leave them. At the next king tide, the eggs hatch nd the fish swim out to sea. This protects them against predators.

157
Q

What is an annual rhythm?

A

Once every 365 days.

Result of temp change or change in day/night length. Eg. flowering, hibernation, germination, aestivation and mating.

158
Q

What is an exogenous rhythm?

A

A direct response to environmental cues, not internally controlled.

159
Q

What is an endogenous rhythm?

A

A rhythm controlled by internal biological clocks, which continue in the absence of biological cues, though the period may change slightly.

160
Q

What is a Zeitgeber?

A

The environmental cue that resets the biological clock to sychronise with the environment.

161
Q

What is entrainment?

A

When the internal clock is reset to take up the period (follows a cue)

162
Q

What is a period?

A

The length of one complete cycle of a rhythm.

163
Q

What is a free running period?

A

When all environmental cues are removed.

164
Q

What is LL?

A

Constant light intensity

165
Q

What is DD?

A

Constant darkness

166
Q

What is LD?

A

Natural light cycles

167
Q

What is LD 12:12?

A

12 hours of light and 12 hours of dark

168
Q

What is a phase advance?

A

When the rhythm is 12/24 hours or less- eg. start of rhythm is advanced

169
Q

What is phase delay?

A

When the rhythm is 12/24 hours or more- eg. start of rhythm is delayed.

170
Q

How can you tell if a rhythm is endogenous?

A
  • Continues under a constant environment

- When free running, period does not correspond exactly to natural rhythm- i.e. becomes a ‘circa’ rhythm.

171
Q

How can you tell if a rhythm is exogenous?

A

Rhythm stops or disappears under constant condition.

172
Q

What is photoperiodism?

A

The regulation of seasonal activity by daylength.

173
Q

How does a plant know when to flower?

A

The photoperiod is detected by the leaves- the site of flower production is insensitive to this. The leaves produce a chemical signal which flows around the whole plant to the stem apices.

174
Q

What affects if plants will flower?

A

The length of uninterrupted darkness is the main feature. Short Day Plants will flower when there is a long period of darkness, Long Day plants will flower when there is a short period of darkness. This is when the plant’s environment exceeds a certain CRITICAL DAY LENGTH.

175
Q

What are the 3 types of plant?

A

Day neutral
Short Day Plant
Long Day Plant

176
Q

What are day neutral plants?

A

They are insensitive to the photoperiod as they have a life cycle too short for seasonal factors to be important (eg. tomatoes, dandelions)

177
Q

What are Long Day Plants?

A

They only flower when: Photoperiod exceeds a certain critical day length
Days are getting longer
Nights are getting shorter.
Eg. lettuce, petunias, radishes

178
Q

What are Short Day Plants?

A

Only flower when: Photoperiod is less than a certain critical day length
Days are shortening
Nights lengthening

179
Q

Why can’t LDP and SDP flower at the same time?

A

LDP flower when days are getting longer, SDP when days are getting shorter.

180
Q

Which is more important- uninterrupted dark or light for flowering?

A

Uninterrupted dark as this is when the Pfr is converted into Pr.

181
Q

What are the two phytochromes?

A

Pr

Pfr

182
Q

What do the two different phytochrome do?

A
  • Pr absorbs red light and when it does so it is quickly converted into Pfr
  • Pfr can absorb red light and when it does so is quickly converted to Pr
  • Daylight contains most red light, so Pfr is highest at day’s end. During the night Pfr is slowly converted to Pr
  • Pfr has evolved to affect short and long day plants differently.
183
Q

How does Pfr affect long day plants?

A

High levels promote flowering. Low levels are not high enough to promote flowering.

184
Q

How does Pfr affect short day plants?

A

High levels inhibit flowering. Low levels are not high enough to inhibit flowering.

185
Q

What happens with flowering in long days/short nights?

A
  1. Not enough dark time to convert all of Pfr back to Pr, so high levels of Pfr
  2. In LDP, this promotes flowering.
  3. In SDP, this inhibits flowering.
186
Q

What happens with flowering in short days/long nights

A
  1. Plenty of time to convert Pfr back to Pr, so low levels of Pfr.
  2. In LDP this cannot promote flowering
  3. In SDP this cannot inhibit flowering.
187
Q

What is a photonasty and what is its advantage?

A

The opening and closing of flowers. This prevents flowers from being robbed of nectar during the nighttime when their pollinators are inactive.

Biology Scholarship (4 decks)

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