Transcript Lesson 4 Flowering in plants - MrHay

Animal Behaviour and
Plant Responses.
Year 13 Biology
Environmental Cycles
• The astronomical cycles
– The motions of the Earth, moon and
sun result in complex and
interdependent cycles.
– These create environmental changes
that range from short term to long term.
Biological Rhythms
• Environmental cues such as daylength,
timing and the height of tides, and phase
of the moon are often used by plants and
animals to establish and maintain a
pattern of activity.
• They synchronize important events in the
life cycle of an organism.
Biological Rhythms
• Biological rhythms in direct response to
environmental stimuli are said to be
exogenous – the rhythm is controlled by
an environmental stimulus that is external
to the organism
• Those rhythms that continue in the
absence of external cues are said to be
endogenous
The Biological Clock
• Biological clock – an internal timing system
which continues without external time clues, and
controls the timing of activities of plants and
animals.
• Uses of biological clocks
– Control of the daily rhythms of the body e.g. sleep,
pulse, metabolic rate, sex drive
– Reproductive timing
– Preparing for migration by eating a lot of food
– Preparing for winter by storing a lot of food
– Navigating by the sun or the stars.
Some Biological Rhythms
• Circadian – daily activity period, approximately
24 hours (circa=about, dies=day)
• Circatidal – tidal activity period, approximately
12.4 hours
• Circasemilunar – spring/neap tidal period,
approximately 14.7 days (semilunar=half moon)
• Circalunar – monthly activity period, 29 days
(circa=about, lunar=moon)
• Circannual – yearly activity period,
approximately 360 days (circa=about,
annual=year)
Daily Cycles in Animals
(circadian rhythms)
• Animals are active at different times of the
day:
– Diurnal – active during the day, inactive at
night
– Nocturnal – active at night, inactive during
the day
– Crepuscular – active at dawn and dusk
– Arrhythmic – no regular pattern
Other Important Terms
• Free running period – when the biological clock
is running without any cues for the environment,
so is ‘running free’
• Entrainment – the resetting of the biological
clock on a regular basis, forcing it to take up the
period of the environment. This is done with a
Zeitgeber.
• Zeitgeber – (‘time giver’ – the German word is
the most commonly used) – the environmental
agent that resets the biological clock. This could
be light, temperature etc.
Plant Rhythms
• Plants are capable of responding to
environmental variables in a variety of
ways.
• Some activities follow daily rhythms, while
others are seasonal.
Photoperiodism in Plants
• Photoperiodism is the response to the
relative length of daylight and darkness.
• Photoperiodic activities are controlled by a
pigment called phytochrome. It acts as a
signal for some biological clocks in plants
and is also involved in other light initiated
responses such as germination, shoot
growth and chlorophyll synthesis.
The flowering of Plants
• A photoperiodic response of plants
depends on the critical night length
• Plants can be divided into 3 types:
– Short-day plants
– Long-day plants
– Day-neutral plants
The flowering of plants
• Short-day plants
– Require a short day and long night
– Will flower if the photoperiod is less than a
certain critical length
– See page 69 workbook
– Long-day plants
– Require a long day and short night
– Will flower if the photoperiod is greater than a
certain critical length
The flowering of plants
• Day-neutral plants
– Flowering is unaffected by the amount of
daylight per day.
The Phytochrome System
• Photoperiod of plants controlled by
pigment phytochrome
• There are two forms of this pigment
– P665 (Pr) – inactive form that absorbs red
light
– P725 (Pfr) – active form that absorbs far-red
light
The Phytochrome System
• So how does it all work?
– During the day P665 absorbs red light
(present during the day) and as a result is
quickly converted to the active form, P725.
– This P725 then accumulates.
– During the night P725 absorbs far-red light
(present during the night) and slowly converts
back to the inactive form, P665.
The Phytochrome System
• What is the link between this system and
flowering?
– If the day is long enough P725 accumulates
and long-day plants flower
– If the night is long enough P665 accumulates
and short-day plants flower (it is thought that
this may be due to the low concentration of
P725 rather than high concentrations of P665)
– See page 68 workbook
Plant Pigments
• Bailey p:28
• Review Bailey Chapter 2.
• Try the questions at the end.
Plant Responses to the
Biotic Environment
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Plant-plant relationships
Plant-fungi relationships
Plant-animal relationships
Plant defences (aggressive)
Co-operative relationships
Plant-plant relationships
• Relationships between plants are more
complex than you might think.
• Examples
– Allelopathy – this is when a plant may
secrete a toxic substance from their roots or
leaves that inhibits plants growing near them.
• E.g. Chaparral bush, black walnut
– Seed dispersal mechanisms – ensures
spread of offspring over a wide area
Plant-plant relationships
– Growing larger leaves to capture available
light when it is reduced
– Plants arranging in layers (stratification) in
response to differing environmental conditions
(will have adaptations enabling them to
survive in certain layers)
– Epiphytes – grow on other trees to gain
access to better conditions
– Lianas – plant climbs up trees
– These are just some examples –
Plant-fungi relationships
• Many plants will form relationships with Fungi
– Mycorrhizal fungi form mutualistic relations with
many plant roots. The fungi help the plant roots
absorb water and minerals and in return get organic
molecules (nutrients) made by the plant by
photosynthesis
– Obligate mutualistic relationships – lichen (made
up of algae and fungi) that are obliged to live
together. Fungi absorbs water and nutrients and
keeps the algae wet and the algae carries out
photosynthesis and provides sugars and food for the
fungus.
Plant-animal relationships
• Herbivores eat plants by
– Grazing
– Browsing
– Suck sap
– Feed on nectar, pollen, fruit and seeds
– Chew roots
– Eat gum
Plant defences
• Plants must have strategies to defend
themselves against herbivory.
– Examples
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Thorns
Divarication
Chemicals
Low growing point
Seed masting
Hiding etc
Co-operation in plants
• Co-operative interactions between plants
and other plants, and plant and animals
can include
– Pollination – animal pollinators (insects/birds)
are attracted by rewards or advertisements
– Guarding plants by animals
– Animals gaining protection from thorns
– Eating fruits and seeds pass through digestive
track and are dispersed
• Self check page 208 C.B
Animal Responses to the
Biotic Environment
• Intraspecific responses – aggressive and
co-operative
• Interspecific responses – aggressive and
co-operative
Intraspecific aggressive
responses
• Agonistic behaviour
– Is aggressive
– Towards members of the same species
– Involves threats or fighting
– Determines which competitor gains access to
resources.
– Especially strong between members of the
same sex e.g. males fighting over females.
Intraspecific aggressive
responses
• Territories
– Are established areas for feeding, mating or
rearing young, that are defended.
– Held by aggressive behaviours
– Usually consist of a lair or nest in the centre of
the territory, surrounded by a large home
range that animals cover regularly in search
of food and mates.
– Only the territory is defended
Intraspecific aggressive
responses
• Advantages of territoriality
– Ensures space for each animal
– Reduces disease
– Harder for predators to find animals if they are
spread out
– Reduces fighting
– Ensures there is enough food for everyone
– Safe breeding sights that are defended
– Best genes are handed on to offspring
Intraspecific aggressive
responses
• Disadvantages of territoriality
– Males without territories fail to breed as not
seen as attractive
– Losers must spread out to find food rather
than fight
Intraspecific aggressive
responses
• Marking and defending
– Singing
– Mark with urine
– Using scent glands
– Using signals
– Calling
• See page 234 C.B. for examples
Intraspecific aggressive
responses
• Hierarchies
– when every animal is either above or below
another (linear hierarchy).
– There are no equals
– Forms “Pecking Orders” (see pg 234 C.B.)
– Usually established competitively
– “top dog” will usually make decisions for the
group
– Maintained by posture and display
Intraspecific co-operative
behaviour
• Includes
– Group formation
– Courtship and pair-bond formation
– Parental care
Group Formation
• When animals join together to cooperatively undertake tasks
– E.g. Hunting, defence, protection etc
Advantages of forming
groups
• Team work while hunting leads to increased
success rate.
• Less predation as can have members of the
group on “look out”
• Older members protect young or weak
individuals
• Large numbers can cause confusion for
predators
• Breeding sites are located within a boundary
that is protected by members of a group
Disadvantages of group
formation
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Competition is increased
Disease can spread faster
Parasites (e.g. fleas) spread faster
Increases conflict between members
Courtship/pair-bond
formation
• Requires co-operation, suppression of
aggressive behaviours and
communication.
• Usually females make the choice who they
mate with, but both partners need to make
sure;
– They are the same species
– Both fertile
– Both fully prepared to mate.
Courtship
• Males usually will compete for the
attention of females by;
– Competing with other males by fighting or
ritualised combat
– Compete indirectly by attracting females by
displays and adornments
• E.g. antlers in deer, brightly coloured feathers in
peacocks, singing and dancing of many bird
species, producing pheromones.
Pair-bond relationship
• A stable relationship between animals of
the opposite sex that ensures co-operative
behaviour on mating and rearing of the
young
– E.g. turns, albatross
Parental Care
• Survival depends on successfully breeding
adequate numbers of offspring.
• Can be achieved by two possible
strategies
– R-strategy – produce large numbers of
unprepared offspring with a low chance of
survival
– K-strategy – produce few, well prepared
offspring which have a high chance of survival
Parental Care
• Degree of parental care depends on the
species
– E.g. eggs buried and then abandoned (many
fish species), nest constructed and defended,
offspring themselves defended
– Often those species that have a high degree
of parental care will teach their offspring how
to find food, where to find water, how to make
a home etc.
Reproductive Strategies
• Monogamy – each mating with only one
member of the opposite sex (often for life)
• Polygyny – males mate with many females thus
fathering many offspring
• Polygamy – dominant males mates with a
harem of females
• Polyandry – females mate with more than one
male
• Polygynadry (promiscuity) – both male and
female mate with more than one member of the
opposite sex.
• http://www.youtube.com/watch?list=PLFD
68901F35A20FF2&v=YmVZ8zXJO48&fea
ture=player_detailpage
• Hammer Orchid and Wasp
• http://www.youtube.com/watch?v=Hv4n85
SqxQ&list=PL0CC0E52BC7BCC6D1&feat
ure=player_detailpage
Death with Lily
• http://www.youtube.com/watch?v=4HkvW
8xgcPY&list=PL0CC0E52BC7BCC6D1&fe
ature=player_detailpage
Stench Flower
• http://www.youtube.com/watch?v=4P8YhP
5_oig&list=PL0CC0E52BC7BCC6D1&feat
ure=player_detailpage
Water Plant Reproduction
• http://www.youtube.com/watch?list=PL0C
C0E52BC7BCC6D1&v=77QqpmaOSY&feature=player_detailpage
Lock and Key
• http://www.youtube.com/watch?v=CP1A6
TLDQLQ&list=PL0CC0E52BC7BCC6D1&f
eature=player_detailpage
Pollination, Plants and
Insects
• http://www.youtube.com/watch?feature=pl
ayer_detailpage&v=FiwkJui2mh0&list=PL0
CC0E52BC7BCC6D1