DIR Return Create A Forum - Home
---------------------------------------------------------
social facebook
HTML https://socialfacebook.createaforum.com
---------------------------------------------------------
*****************************************************
DIR Return to: Images
*****************************************************
#Post#: 46--------------------------------------------------
Animal groups:
By: eyeconic Date: April 5, 2018, 9:07 am
---------------------------------------------------------
Animal groups:
HTML https://www.youtube.com/watch?v=IPNXcytsslY
<script>
(function() {
var cx = '017846004531943245215:ntog6z4xfuc';
var gcse = document.createElement('script');
gcse.type = 'text/javascript';
gcse.async = true;
gcse.src = '
HTML https://cse.google.com/cse.js?cx='
+ cx;
var s = document.getElementsByTagName('script')[0];
s.parentNode.insertBefore(gcse, s);
})();
</script>
<gcse:search></gcse:search>
#Post#: 54--------------------------------------------------
Snakes
By: eyeconic Date: April 5, 2018, 9:15 am
---------------------------------------------------------
[quote author=eyeconic link=topic=46.msg46#msg46
date=1522937229]
Animal groups:
[/quote]Popular snake species
The king cobra is the longest venomous snake in the world and
can grow to over five metres in length.
Although it doesn't have the most toxic venom among snake
species, a single bite still could kill up to 30 humans, or a
fully grown Asian elephant. However, the king cobra is generally
a non-aggressive species which feeds almost entirely on other
snakes.
#Post#: 55--------------------------------------------------
British seagulls
By: eyeconic Date: April 5, 2018, 9:17 am
---------------------------------------------------------
[quote author=eyeconic link=topic=46.msg46#msg46
date=1522937229]
Animal groups:
[/quote]
The everyday term 'seagull' doesn’t refer to any one species of
bird but is used to broadly cover the gull family
Although often classed as 'sea' gulls, many gulls head inland
for some, or even most, of their life
Worldwide there are around 50 species of gull, but only 11
species are found in the UK
The UK is home to both the world's largest gull - the great
black-backed gull, and the world's smallest – the little gull
What makes a gull a gull?
Black-headed gull
Black-legged kittiwake
Common gull
Glaucous gull
Great black-backed gull
Herring gull
Iceland gull
Lesser black-backed gull
Little gull
Mediterranean gull
Yellow-legged gull
What makes a gull a gull?
Common gull (Larus canus) perched on rock,
Seagulls can be quite tricky to tell apart. Although we have 11
different species of gull that live in the UK, they all have a
similar body shape and markings. These markings can change with
the season and also vary with the age of the bird making it
difficult to tell a herring gull from a common gull, although
species can be determined by those with a well-trained eye. The
length of a gull's body is highly variable depending on the
species, and little gulls (the world's smallest gull) usually
measure up to 30 centimetres, whereas great black-backed gulls
can be a staggering 75 centimetres long. The wings of gulls are
long and narrow when in flight and all species have strong
webbed feet to help them to grip rocks and swim on the water's
surface. Although mostly white with grey, black or brown
markings, gulls can have colourful bills and legs, and these
features can often be used to help identify them.
To download all of the colour ID guides from this page for your
next gull-spotting trip, click here
Here's a guide to the gulls of the UK and colour ID guides to
help you tell them apart:
Black-headed gull
Black-headed gull summer plumage
The common name of the black-headed gull is misleading as an
adult black-headed gull actually has a chocolate-brown head -
and only in summer. In winter, the brown hood retreats and the
birds have a largely white head with a dark spot behind the eye.
This relatively small gull is widespread in Britain and
particularly common at inland sites in north England, Scotland
and Wales, therefore it is not really a true ‘sea’ gull at all.
Black-headed gulls are known to be fairly long-lived, with the
oldest recorded individuals reaching ages of up to 32-years-old.
Resident in the UK all year round, the black-headed gull is a
sociable bird that is often found in groups and has large
colonies along the south and east coasts of England. In these
colonies, pairs avidly defend their small territories from other
birds using unusual ritualised displays.
View more images and information on the black-headed gull
Life history
Black-headed gull chick hatching
Black-headed gull feeding chicks
Juvenile black-headed gull
Black-headed gull in winter
Black-headed gull, winter plumage
Black-headed gull moulting into summer plumage
Courtship
Black-legged kittiwake
Black-legged kittiwake
The black-legged kittiwake is a small, graceful, cliff-nesting
gull, named for its loud, nasal ‘kitti-wake’ call. As its common
name gives away, its legs are usually black. However, a few
individuals may have orange or reddish legs.
This seagull is a true ‘sea’ gull as it is only found around the
UK’s coast and not inland. It can be found nesting on cliffs in
the spring and summer (February - August) and spends the winter
in the Atlantic Ocean.
The tips of the wings are black, giving the appearance of having
been dipped in ink, and the tail is slightly forked. Outside of
the breeding season, the adult black-legged kittiwake has darker
grey marks around the crown and the back of the neck, and a dark
mark behind the eye. The scientific name of the black-legged
kittiwake - tridactyla - means 'three-toed', as the fourth toe
of each foot has reduced over time to a mere stump, meaning it
only has three functional toes instead of the usual four seen in
other gull species.
View more images and information on the black-legged kittiwake
Life history
Black-legged kittiwake eggs in nests
Black-legged kittiwake chick and eggshell
Black-legged kittiwake adult and fledglings
Black-legged kittiwake juvenile
Black-legged kittiwake rolling over in freshwater to bathe
Black-legged kittiwake taking off
Black-legged kittiwake courtship
Common gull
Common gull (Larus canus) perched on rock,
The common gull, also known as the mew gull, is actually not all
that common even though it can be locally abundant in some
areas. It is generally similar in appearance to the herring gull
but is smaller and has a more delicate appearance.
This gull is generally found throughout the UK all year round,
but is more often found in more northern areas in summer and
more southern areas in winter. There are four subspecies of
common gull which occupy different ranges throughout the
Northern Hemisphere including Russia and North America.
The common gull’s white head develops grey streaks in winter,
when it can be seen on more inland areas such as farmland,
lakes, playing fields and rubbish tips.
View more images and information on the common gull
Life history
Common gull eggs
Common gull chick
Juvenile common gull
Common gull adult in winter plumage
Common gull in flight
Common gull aggression
Common gull courtship
Glaucous gull
Glaucous Gull (Larus hyperboreus)
The glaucous gull is a winter visitor to the UK - mostly seen
between November and March. It is not a common bird but can
occasionally be seen around the coast or with large groups of
other seagulls in inland areas, such as at rubbish tips.
It has mottled brown markings on its head when in winter plumage
- which is when it can be seen in the UK.
This large pale gull is bigger and bulkier than a herring gull.
It is also very similar to the Iceland gull, but it is
significantly larger.
View more images and information on the glaucous gull
Life history
Glaucous gull at nest with chicks
Immature glaucous gull
Group of glaucous gulls
Glaucous gull in flight
Glaucous gulls fighting near polar bear kill
Glaucous gull with prey
Glaucous gull being eaten by polar bear
Great black-backed gull
Great black-backed gull standing
The great black-backed gull is the largest gull species in the
world, with a wingspan of up to 160 centimetres and weight of up
to 2 kilograms. Its wings are blacker than the smaller lesser
black-backed gull and the herring gull and it has a heavier
build than both of these other species.
During the breeding season in the summer it can most often be
found all round the UK coast, while in winter it is more often
found inland.
Young great black-backed gulls undergo several plumage changes
before taking on that of the breeding adult. Juveniles are pale
brown with heavy white mottling, while immature birds are also
mottled, but have a whitish head and breast, with a dark-tipped,
pale bill.
A voracious predator, the great black-backed gull has been known
to hunt puffins and grebes and regularly bullies other birds to
steal their food. This species has been described as a
'merciless tyrant' when it comes to food!
View more images and information on the great black-backed gull
Life history
Great black-backed gull chicks in the nest
Great black-backed gull turning eggs during incubation
Young great black-backed gulls
Young great black-backed gulls
Immature great black-backed gull
Great black-backed gull taking off in flight
Great black-backed gull swallowing a large fish
Great black-backed gull pair 'trumpet calling'
Herring gull
Herring Gull on rock facing R
Probably the most familiar gull on this page, the herring gull
is found in high densities at UK seaside towns during the summer
months, where it can be seen as a pest due to its highly
opportunistic nature exploiting almost any available food
source. During winter months this gull spends its time inland,
often foraging around rubbish tips or reservoirs.
Herring gulls are able to excrete the salt from seawater through
special glands above their eyes, helping them when they
accidentally ingest seawater along with their food or have to
drink saltwater when there is no freshwater available. The
secreted salt then passes through the nostrils and drips from
the end of their bill. A very long-lived species, herring gulls
have been recorded at up to 32 years old.
View more images and information on the herring gull
Life history
Herring gull eggs
Herring gull chick and egg hatching
Herring gull chick
First year herring gull
Herring gull in flight
Herring gulls fighting over a fish
Herring gull courtship
Iceland gull
Iceland gull (Larus glaucoides) on the shore
The Iceland gull is quite rare in the UK, with only a small
number of birds visiting during the winter months when it has
mottled brown markings on its head.
This gull is smaller than both the gulls to which it is most
similar – the glaucous gull and the herring gull. There are two
subspecies of Iceland gull, one of which is found in Canada and
another which overwinters in Europe, but breeds in Greenland. A
relatively short-lived species, Iceland gulls only live for a
maximum of four years.
Iceland gulls are usually seen on their own rather than in
groups and stay near to their feeding grounds – either near to
the coast or inland at reservoirs or rubbish tips with other
species of gull.
View more images and information on the Iceland gull
Life history
Iceland gull eggs
Adult Iceland gull
Iceland gull in flight
Iceland gull in flight over water
Iceland gulls feeding
Lesser black-backed gull
Lesser black-backed gull
A middle-of-the-road species in relation to its size and weight,
the lesser black-backed gull is widespread in the UK, and
becoming increasingly common in urban areas. However, the
species is at risk as more than half of the UK population is
found at fewer than ten sites, and is therefore vulnerable to
local extinctions due to extreme weather or conversion.
Found in the UK all year round, this gull breeds on the coast of
Scotland in the summer and moves south and inland during the
winter months.
There are several subspecies of the lesser black-backed gull
which differ in the colouration of their back, with some being
much darker than others. The subspecies that breeds in the UK
can be differentiated from others due to it having the lightest
coloured wings.
During the breeding season, individuals who are not partaking
will form groups closeby to the breeders and spend the time
relaxing as if on holiday. Lesser black-backed gulls are
monogamous, forming breeding pairs that are retained for life.
To attract a female, males call, perform courtship displays and
may occasionally regurgitate food, all in the hope of securing a
lifelong mate.
View more images and information on the lesser black-backed gull
Life history
Lesser black-backed gull hatching
Young lesser black-backed gull
Juvenile lesser black-backed gull
Lesser black-backed gull in flight, first winter plumage
Lesser black-backed gull catching a fish
Lesser black-backed gull in flight
Lesser black-backed gull in flight
Lesser black-backed gull pair
Little gull
Little gull taking off from water
The little gull has an entirely black head in the summer
breeding season, which becomes completely white during the
winter aside from a dark cap and spot behind the eye. Aptly
named, this species is the smallest gull in the world, with a
wingspan measuring a maximum of 78 centimetres and weighing up
to a diminutive 162 grams.
The wings are rounded and in adults, the underneath of the wings
are darker than the tops. Young birds have a very distinctive
bold, black zig-zag pattern on their back and wings and they
don’t gain their full adult plumage until their third year.
The little gull does not breed in the UK, but it can be found
around the coast between July and April. This species is known
to mostly breed in northern Scandinavia, the Baltic republics
and western Russia.
View more images and information on the little gull
Life history
Little gull eggs on nest
Juvenile little gull
Immature little gull standing in water
Little gull in non-breeding plumage
Little gull stretching wings
Little gull skim-feeding surface of lake for flies
Mediterranean gull
Mediterranean gull pair interacting
The Mediterranean gull is a particularly attractive bird with a
blood-red beak and black head during the summer breeding season.
It was once rare in the UK, but can now be found along the coast
in the south and east of the UK, where it can often be found
with black-headed gulls. In winter Mediterranean gulls can be
found further along the south coast in Cornwall and further
north along the east coast, where they can be found in large
numbers on some beaches in Norfolk and Kent.
It is thought that the warming climate of the UK may have made
it more suitable for this species, explaining increased numbers
in the area.
View more images and information on the Mediterranean gull
Life history
Mediterranean gull adult with chick
Juvenile Mediterranean gull
Mediterranean gull in transitional summer phase
Mediterranean gull in winter plumage
Mediterranean gull taking off
Mediterranean gull pair calling in breeding colony
Mediterranean gulls displaying courtship behaviour
Yellow-legged gull
Yellow-legged gull (Larus cachinnans michahellis) standing on
city wall high above the sea
The yellow-legged gull has only recently been recognised as its
own species - having previously been thought to be a race of
herring gull (which have pink legs).
It can be found in southern and eastern Britain, often with
lesser black-backed gulls. The lesser black-backed gull is
similar in appearance, but the yellow-legged gull has a paler
back and wings than the lesser black-backed gull. This species
also has a very distinctive bright red ring around its eye.
The yellow-legged gull is found in Britain throughout the year,
but in greater numbers in late summer and autumn when adults and
juveniles disperse after breeding.
View more images and information on the yellow-legged gull
#Post#: 56--------------------------------------------------
Predator-prey relationships in the African savannah
By: eyeconic Date: April 5, 2018, 9:18 am
---------------------------------------------------------
[quote author=eyeconic link=topic=46.msg46#msg46
date=1522937229]
Animal groups:
[/quote]African savannah facts
Complex predator-prey relationships maintain the delicate
balance of the ever-changing African savannah ecosystem.
The rolling grasslands of the African savannah are subject to a
year-round warm climate that fluctuates between wet and dry
seasons.
The African savannah is home to the greatest diversity of hoofed
mammals in the world.
#Post#: 57--------------------------------------------------
Camouflage
By: eyeconic Date: April 5, 2018, 9:19 am
---------------------------------------------------------
[quote author=eyeconic link=topic=46.msg46#msg46
date=1522937229]
Animal groups:
[/quote]
Camouflage describes the variety of tricks that animals use to
disguise their appearance. Camouflage is a very useful defence
mechanism and allows an animal to hide from predators, but it
can also be used to approach prey without being noticed.
Camouflage doesn't just refer to patterns that make it difficult
to see an individual, but also refers to adaptations that can
disguise how fast an animal is moving. Read on to explore the
different types of camouflage and see if you can spot the hidden
animals.
Background matching
Tonkin bug-eyed frog camouflaged on moss
The tonkin bug-eyed frog matches its mossy habitat very well
Most people associate camouflage with colouration and patterning
that resembles the environment in which an animal is found. This
means that prey or predators may often overlook an individual
unless searching very thoroughly. Animals that lie on the sea
bed often have a sand-like colouration and pattern, for example
the eastern angel shark, while forest species such as the kakapo
often have mottled and green or brown colouration to match the
lighting and colours of the habitat.
Many species in cool or seasonal habitats have different summer
and winter colouration to reflect the changing environment. For
example, the snowshoe hare has a white coat in winter to
camouflage itself against the snow, but has a brown coat in
spring and summer when white would make it very obvious.
Some animals take this form of camouflage to the extreme and may
be transparent or semi-transparent which allows them to blend
into the background in different habitats or from many
perspectives.
Examples of background matching
Peppered moth
Crab spider
Snowshoe hare
Kakapo
Egyptian nightjar
Disruptive camouflage
Bengal tiger resting in grass
The tiger’s striped pattern makes seeing its outline more
difficult
A different way in which an animal’s pattern and colouring can
conceal it from predators, or allow it to trick prey, is
disruptive camouflage. This form of camouflage involves a
pattern of light and dark patches, stripes or spots, which often
appear to make the individual more obvious, not less. However,
these patterns can help to disrupt the outline or shape of the
animal, which can prevent an observer from recognising it as a
threat or potential prey item. For example, the stripes of a
tiger or the pattern of a camouflage grouper can make it harder
to see the animal's outline.
Examples of disruptive camouflage
Camouflage grouper
Jaguar
Pickerel frog
Giraffe
Mimicry
Leaf-tailed gecko on forest floor
The satanic leaf-tailed gecko closely resembles a dead leaf
Another way for an animal to avoid being recognised is to mimic
the appearance of another object or species. For instance, many
animals mimic the appearance of background material such as dead
leaves. An excellent example of this type of mimicry is the
satanic leaf-tailed gecko. Other animals mimic dangerous
species, for example the wasp hoverfly looks similar in
appearance to a wasp and the cuckoo may mimic the Eurasian
sparrowhawk. Some species even mimic behaviour as well as
appearance. For example, some stick insects and mantises sway to
look like sticks moving in the wind, although this motion may
also help them to see prey.
Examples of mimicry
Pygmy seahorse
Ghost pipefish
African giant toad
Leafy seadragon
Adaptive camouflage
camouflaged Common octopus resting
The common octopus can change colour and shape to blend into its
environment
Background matching camouflage can sometime be quite
restrictive. For instance, if an individual moves from one
habitat to another it may no longer blend into the background.
Some species get around this problem with active or adaptive
camouflage, changing their colour, pattern, shape and texture in
response to their environment and needs.
Chameleons are well known for being able to change their colour
and pattern within minutes using pigments in their skin.
However, cuttlefish, squid, octopuses, and flounders probably
have some of the best active camouflage. Changing colours and
patterns almost instantly, they can even create moving flashing
displays on their skin. This ability is not only used to
camouflage the individual, but is also used in communication.
Octopuses are so flexible that they can combine mimicry with
this active camouflage, allowing them to take both the shape and
colour of objects around them.
Examples of adaptive camouflage
Peacock flounder
Namaqua chameleon
Lemur leaf frog
Flamboyant cuttlefish
Common seahorse
Other types of camouflage
Plains zebra herd running away from the Mara River
One theory is that a zebra’s stripes may disrupt the observer’s
estimation of speed, direction, or size
Motion dazzle
One problem with many of the other camouflage mechanisms is that
once an individual moves it becomes easy to see. However, motion
dazzle camouflage, which uses light and dark patterns and
stripes, may be able to disguise the direction, speed, or size
of a moving animal and help to prevent its capture. One group of
animals often said to use motion dazzle camouflage is zebras,
although there are also many other suggestions for the reasons
behind the zebra’s striped pattern. Another species that may use
motion dazzle camouflage is the adder, whose zig-zag pattern and
quick movements may make it harder to catch.
Countershading
A number of species use countershading as a form of camouflage,
which typically involves the animal being darker on top and
paler underneath. This helps an animal to blend in with a darker
background such as the ground or sea floor when viewed from
above, or to blend in with the paler, brighter sky when viewed
from below.
#Post#: 58--------------------------------------------------
Pollination
By: eyeconic Date: April 5, 2018, 9:21 am
---------------------------------------------------------
[quote author=eyeconic link=topic=46.msg46#msg46
date=1522937229]
Animal groups:
[/quote]
The techniques used by the plant kingdom to achieve pollination
are extremely varied and can be very odd.
Some plants can only be pollinated by certain animals, which
will usually have evolved unique physical adaptations that allow
them to feed on the plant’s hard-to-reach nectar.
Pollination provided by bees is responsible for one of every
three bites of food eaten by humans.
Pollinator decline in some areas has been so drastic that
farmers now have to pollinate their crops by hand.
The black and white ruffed lemur is the largest pollinator in
the world.
Two of the world’s most unpopular animals, mosquitoes and wasps,
are known to pollinate certain plants.
What is pollination?
Types of pollination
Cross-pollination
Pollinator
Wind
Water
Self-pollination
Why is pollination important?
What threats do pollinators face?
What conservation measures can we take to help pollinators?
How you can help pollinators
Find out more about pollinators and their conservation
What is pollination?
Close-up of Poppy flower stamens and stigma
Pollination is the fertilisation process that is required by
plants to reproduce. Only when a plant has been pollinated can
it produce seeds and fruit.
Pollination occurs when pollen, a plant’s male gamete, is
transferred from the male part of the flower (anther) to the
female parts (stigma) of another plant of the same species. The
pollen begins to grow and forms a pollen tube on the surface of
the stigma, which navigates its way through the tissue of the
flower until it reaches an ovule inside the ovary. The nucleus
of the pollen grain then passes through the pollen tube and
fuses with the nucleus of the ovule. After this process has
occurred the female parts of the plant are fertilised and the
ovules develop into seeds. The seeds contain all of the genetic
information that is required to create a new plant.
A small amount of plants are self-pollinating and therefore do
not require any assistance from external sources, although most
are cross-pollinators and rely on other organisms or natural
processes to reproduce. The majority of plants are wholly
reliant on the mutualistic symbiotic relationship they have with
pollinators to be able to reproduce, and its pollinators are
reliant on the plants as a food source. A much smaller
percentage of plants rely on the Earth’s physical processes to
transport their pollen and have evolved many weird and wonderful
ways to ensure that their pollen reaches the right destination.
Plant reproductive organs
Johnsongrass anthers
Flame tree stamen
Mistletoe pollen
Capparis stigma
Lecythis ovary
Types of pollination
All plant species have a main method of reproduction, relying on
a specific evolutionary adaptation that helps pollination.
Despite this, a large number of plants will also have the
capacity to reproduce using another pollination method, using it
as an ‘insurance policy’.
Cross-pollination
Cross-pollinating plants are self-incompatible, so they need to
spread their pollen to a different plant of the same species to
reproduce. There are three external factors which allow plants
to spread their own pollen away from themselves – pollinators,
wind and water.
Pollinator
Bee
Pollinators are responsible for reproduction in the majority of
plant species, both naturally occurring and cultivated, and play
a critical role in maintaining plant communities around the
world. Plants produce nectar to attract and feed pollinators and
this generosity is returned by the visitor spreading the pollen
that it has unknowingly acquired while in contact with the
plant. This mutualistic symbiotic relationship is the
reproduction strategy for over 80 percent of the world’s plant
species.
Pollinators come in all shapes and sizes, from insects so small
that they are invisible to the naked eye to large primates and
bats. Some pollinators are generalists and will visit numerous
different plant species for nectar, whereas others are wholly
reliant on a specific species and may have developed adaptations
that allow them to feed on plants that others cannot, such as
the thin, elongated bill of the sunbirds which enables them to
feed from the long, tubular flowers of aloes.
The pollen of these plants is usually sticky and has barbs
attached to its surface to allow easy attachment to the body of
a visiting organism to ensure that it will remain there until it
reaches the next plant. Many pollinators have morphological
adaptations which make them better at collecting pollen from
plants, such as the fine hair around the mouths of nectar-eating
bats.
Protein-rich pollen and energy-rich nectar are an attractive
prospect for most pollinators, although some plants use flowers
to entice more passers-by, producing elaborate inflorescences of
all colours and shapes and countless different scents. Some
plant species even use mimicry to attract attention from
pollinators.
Bees are the best-known and most significant pollinators in the
world and are responsible for the majority of pollination in
both natural and cultivated plant communities. Perfectly
designed for pollination, bees have an electrostatic body which
attracts pollen grains, stiff hairs on their legs which allow
them to groom the pollen into pockets on their body to be
carried back to their nest and a lifestyle that is seemingly
solely dedicated to collecting pollen. Bee species usually focus
on one flower type, improving the chance that the pollen from
one plant will be transferred to another of the same species.
Despite bees being the world’s number one pollinator, birds,
bats, primates and other insects play very important roles in
generalist and specialist pollination, and even the wildly
unpopular wasps and mosquitoes assist in the pollination of
certain species.
Animal-pollinated plants
Cape buttercup with bee
Foxglove and rufous hummingbird
Bramble and bumble bee
Agave and Mexican long-tongued bat
Liparia parva and Cape spiny mouse
Grey tree pincushion and Cape sugarbird
Ragwort and six-spot burnet moth
Wind
Grass flowers with pollen blowing in the wind
Around 12 percent of the world’s flowering plants are
wind-pollinated. Naturally occurring species such as conifers
and grasses, as well as cultivated crop plants such as rice and
wheat, are reliant on the wind’s currents to disperse and
deliver their pollen. Most of these plants do not have the
impressive flowers produced by insect-pollinated plants and
usually have exposed stigmas and stamens to ensure that contact
with floating pollen grains occurs as often as possible. The
stamen of many of these species is arranged in a catkin, a long
structure with many small, grouped inflorescences, which produce
large amounts of pollen.
As wind-pollinated plants do not need to attract pollinators,
they do not need to produce nectar or showy flowers and can
invest more of their energy into producing pollen, which they
produce in vast quantities. The pollen of these species is
extremely small and lightweight so that can be easily dispersed
within wind currents. These types of plants are responsible for
producing most of the pollen that causes hay fever in humans.
Wind-pollinated plants
Pinus taeda
Japanese cedar
Scots pine
Bulrush
Canary grass
Water
#Post#: 59--------------------------------------------------
Bioluminescence
By: eyeconic Date: April 5, 2018, 9:22 am
---------------------------------------------------------
[quote author=eyeconic link=topic=46.msg46#msg46
date=1522937229]
Animal groups:
[/quote]
Bioluminescence has mystified scientists throughout history, and
many aspects of this biological phenomenon are still unknown
Most bioluminescent species are found in the deep sea, although
a small amount of terrestrial organisms also possess the ability
to produce light
Nine out of ten marine species that live at depths below 1,000
metres are able to produce light
There are thought to be many reasons that organisms produce
light such as defence, offense or attracting a mate
Definition
Big fin reef squid in deep water {Sepioteuthis lessonians}
Bioluminescence is light that is produced when a chemical
reaction occurs within a living organism. Unlike other sources
of light, bioluminescence is considered to be a ‘cold’ reaction
as it does not give off any heat. Bioluminescence has mystified
humankind throughout history and initial reports of sightings
were discarded as myths. Modern day scientists continue to be
eluded by the function and mechanisms of the process. A high
percentage of bioluminescent species are found in the oceans,
although a small amount are found in terrestrial ecosystems. It
is thought that ocean-living organisms evolved the ability to
produce light around 150 million years ago.
A diverse array of organisms have evolved the ability to
bioluminesce, and it is thought that this adaptation has evolved
between 40 and 50 times. Despite a small amount of terrestrial
species possessing this quality, it is thought that four out of
five bioluminescent species are found in the ocean. Nine out of
ten species that live in the ocean at depths below 1,000 metres
can produce light.
Biofluorescence is often confused with bioluminescence, although
this process is very different and involves an organism
absorbing light, before transforming it and re-emitting the
light at a lower-energy wavelength, rather than producing its
own.
Chemical processes
Bioluminescence is the product of a chemical reaction that
occurs between a substrate (luciferin) and an enzyme
(luciferase) which are solely found in organisms capable of this
process. When luciferin reacts with oxygen and is in the
presence of luciferase, light and oxyluciferin are produced.
Fireflies are known to convert the byproduct from this reaction,
oxyluciferin, back into luciferin to be used again. This
recycling process has only been documented in fireflies but is
likely to exist in other bioluminescent species.
Other bioluminescent species have different photoprotein
substrates (coelenterazine in the reaction below) and rely on a
charged ion to trigger the reaction, rather than an enzyme.
Organisms who use this second process can control the brightness
of their lights by releasing more or less photoproteins. The
exact formula for this reaction, and the chemicals used, vary
depending on the species.
Bioluminescent organisms carefully control their ability to
produce light by regulating the chemical processes in their
body. Luminescence is a response triggered by the central
nervous system in response to an external factor. Some animals
can produce their own luciferin, such as dinoflagellates,
whereas others capture bioluminescent bacteria, retaining them
within their internal organs and forming a symbiotic
relationship, such as the bacteria in the lure of an anglerfish.
Physical processes
Bioluminescent deep-sea Ophiuroid Brittle Star (Ophiochiton
ternispinus)
The wavelength, and therefore the colour, of the light produced
by an organism is dependent on the arrangement of the luciferin
molecules, and these vary greatly between species and habitats.
Long wavelengths (red light) cannot travel very far into deep
water, so most bioluminescence in the ocean is either blue or
green as these colours have shorter wavelengths. Light from the
sun is able to penetrate through the euphotic and disphotic
zones of the ocean, also known as the sunlight and twilight
zones respectively, but does not reach the aphotic zone, also
known as the midnight zone, which occurs below depths of 1,000
metres and is where most light-producing organisms live.
Red light has the longest wavelength and is therefore unable to
reach the deep sea from the surface. Many organisms in the deep
sea therefore have red colouration, making them completely
invisible to predators. A large amount of deep-sea animals have
lost their ability to see red light, although some species use
this evolutionary adaptation to their advantage, such as
dragonfishes. Dragonfishes are able to produce red light, which
not only serves as a method of communication between individuals
but also allows them to easily see their prey. As most other
deep sea animals are unable to see the red light that dragonfish
produce, they will not see the predator before it attacks. This
deep sea fish occasionally uses its red light to expose prey
items to other dragonfish.
On land, bioluminescent organisms are not restricted to
producing only green or blue light although many do, and
fireflies and Quantula striata, the only land snail known to
bioluminesce, can produce yellow light.
Occurrence
Deep sea Anglerfish female with lure {Himantolophus sp} Atlantic
ocean
Bioluminescent organisms are mostly found in the deep sea below
depths of 1,000 metres, although a smaller amount are found in
shallower water and at the water’s surface, as well as on land.
On land, bioluminescence is rare and is only found in a few
insects, including fireflies and certain species of click
beetle, annelids (worms) and centipedes, as well as over 80
fungi species belonging to the order Agaricales. Bioluminescence
is even rarer in freshwater environments, with very few species
known to possess this quality, such as Latia neritoides, a
freshwater snail species.
The colour and patterns of bioluminescent light vary greatly
between species and are often a reflection of the habitat in
which an individual is found. Albeit relatively rare, some
organisms emit light continuously, such as foxfire fungi and
glow worms. Bioluminescence occurs in many patterns and
sequences and can vary between a light that glows continuously,
such as that seen in the ghost fungus, or flashing, as with
fireflies, or can form mesmerising light displays across the
entire body of the individual, as seen in squids and
dinoflagellates. Most frequently, light is usually produced in
flashes that last between 0.1 and 10 seconds and occurs in
specific areas on the body.
Function
The function of bioluminescence in many species continues to
elude scientists who can only take a knowledgeable guess as to
why most organisms produce light. The function of light
production in certain species; however, is more obvious and it
has been observed being used for hunting prey, defence, finding
a mate and communication, and many species use light for more
than one of these purposes.
Reproductive
Light production is an important factor in finding a mate both
for marine and terrestrial bioluminescent species. Males can use
light to advertise their interest in a female, while the female
can use it to let the male know that she is receptive to mating.
Some species even judge the virility of a potential partner by
the brightness of their light, and will ignore the advances of
any less impressive individuals. Certain species also use their
bioluminescence to publicise their gender to the opposite sex.
Defensive
One of the most common uses of bioluminescence is as a defence
mechanism, with light often being produced to startle or confuse
a predator.
Many marine species use counterillumination to protect
themselves from predators. Similar in function to
countershading, counterillumination is a method of camouflage
but relies on light rather than colouration. Light is produced
by photophores on the underside of the body, which from
underneath, make the outline of the individual disappear against
the lighter, shallower water. This prevents many predators who
hunt from below, such as sharks, from seeing their prey and
therefore being unable to attack.
Flashes of light can be an extremely effective way of deterring
predators from attacking, as not only can it startle an
individual and make it confused about the location of its prey,
but it can also alert bigger predators to the location of the
original predator and initiate an attack on them. This type of
defence bioluminescence is often referred to as a ‘burglar
alarm’. When predators are present, they create a disturbance in
the water which makes the plankton at the surface of the water
glow. The light alerts larger predators, such as whales and
sharks, to their location, making them an easy target. The
plankton then stops glowing when the water is calm.
Some deep water species are able to detach bioluminescent parts
of their body as a distraction technique, so that the predator
chases after the limb rather than attacking the main body. Some
species even detach limbs onto other animals so that the
predator attacks them rather than its original target. If a
bioluminescent animal is successfully attacked by a predator, or
its detached limb is consumed, often the light will continue
being produced within its stomach, which can alert larger
animals to its location and trigger an attack.
Offensive
As well as being used as a defence mechanism, bioluminescence is
also used as a way of luring prey, as many deep sea creatures
are attracted to light and will pursue it. Many species have
lures containing bioluminescent bacteria, which are usually
located around their mouthparts. Once the attracted prey comes
close enough, the predator can easily consume it, preventing it
from having to expel energy searching for food. Bioluminescence
is also used by predators to improve their sight, and therefore
locate their next meal more easily.
*****************************************************