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  Evolution
and ADAPTATIONS in plants and animals
including extremophiles
Doc Brown's
school biology revision notes: GCSE biology, IGCSE biology, O level
biology, ~US grades 8, 9 and 10 school science courses or equivalent for ~14-16 year old
students of biology
  You should appreciate that organisms are well adapted to survive in their normal,
but often very different environments.
Adaptations are features of an organism
that make it better suited to live and prosper in its environment. From your knowledge and understanding you
should be able to suggest how organisms are adapted to the
conditions in which they live.
Organisms that are better adapted to their
environment are more able to compete for food resources. Know examples of adaptations, e.g. body shape,
colour and other structural features of a range
of organisms (plant or animal) from different habitats, and understand the ways in which
adaptations enable organisms to survive in different habitats and produce
fertile offspring, thus enabling the species to continue to exist
and further reproduce
to pass on their adaptations.
Sub-index for
adaptations
Adaptations - introduction
(1) Animals - Structural adaptations - lots of examples
explained
(2) Animals - Behavioural adaptations - lots of
examples explained
(3) Animals - Functional adaptations - lots of examples
explained
(4) More on thoughts on animal adaptations including
extremophiles
(5) Adaptations in plants - emphasis on extreme
environments
Adaptations
- introduction
You should be able to explain how organisms are
adapted to their environment and describe and explain their characteristics that enable them to survive,
even in extreme environments,
including deep-sea hydrothermal vents and polar regions.
In studying these examples you should know and understand that organisms, including
microorganisms have features (adaptations) that enable them to survive in
the conditions in which they normally live and some cases understand that some organisms
have adapted to live in
environments that are very extreme.
Adaptations can be classified into
groups e.g. structural, behavioural and functional - but there is often overlap
in adaptive traits.
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(1)
Animals
- Structural
physical
adaptations described and explained
This applies to features of organism's
body structure, anatomical adaptations e.g. colour, shape, nature of outer
body layers etc.
Arctic animals like the arctic fox and
polar bears have white fur for camouflage against the background of snow and
offer some 'avoidance protection' against predators, but also allows the fox to sneak up
on prey!
One of my 'favourite' set of
adaptive traits is shown by the snowshoe hare!
This animal is well adapted for their
life in the cold northern regions of the Earth. This hare has large,
furry feet that act as snowshoes for travelling on top of the snow
(wonderful !!!). Their fur is thick to protect them from freezing
temperatures - traps insulating warm air. They are brown in the summer,
blending in with the tundra, but the snowshoe hare also turns white in
winter so that they are almost invisible in a snowy background and helps
them hide from predators. These physical adaptations make it possible to
survive in their harsh, northern climate.
 Another
favourite adaptation of mine is the ironclad beetle.
The ironclad beetle is an insect that
has lost the ability to escape by flying but evolved an extraordinary
tough body armour. It can survive being stamped on and even withstand
the pressure of a car tyre. It lives under the bark of trees or rocks.
To survive being pecked to death by hungry birds, the ironclad beetle,
having lost the ability to fly away from danger, has evolved
crush-resistant forewings (known as elytra) - these have a series of
interlocked jigsaw-shaped joints within the exoskeleton.
Material scientists are interested in
the potential of this type of structure as a way of joining together
different materials, such as plastics and metal. Scientists have
designed and made a series of joints from metal and composites based on
those seen in the beetle to enhance the strength and toughness of the
materials. So, it isn't just new medicines we can get from natural
world, new structural designs too!
Thermal insulation: Animals living in cold climates like
polar bears have thick layers of fur to trap a good insulating layer of warm
air next to the skin - air is a poor conductor of heat.
As well as a thick hairy coat the fur is 'greased'
from glands in the skin and this greasy fur lets water run off easily so
there is less water to evaporate giving a cooling effect.
It is the same for
seabirds and penguins who must keep their wing feathers oily - often seen
pruning their feathers.
Note on bear and fur adaptations -
camouflage as well as
insulation:
Polar bears have white fur to
blend in with ice and snow enhancing their camouflage and ability to
hunt prey in arctic conditions - a brown bear would rather
conspicuous!
The fur colour of brown bears
helps them blend in with their forest environment - a white bear
would rather conspicuous!
The arctic fox has a white coat
in the winter but this turns brown along the back with light grey
around the abdomen in summer. This ensures the fox is camouflage
throughout the seasons and better able to sneak up on its prey!
Many desert animals have sand coloured
fur to give good camouflage protection from predators or to act as predators
themselves!
Animals in very cold aquatic climates, like
whales (mammals), seals and penguins in polar oceans, have a thick layer of
blubber (fat) and a low surface area to volume ratio (from nearly the most
compact shape) to help reduce heat loss through the skin.
The blubber acts
as an insulator to retain body heat - applies to the
bodies of seals, penguins and polar bears.
The greater the surface area the
greater the rate of heat transfer.
The most compact shape to give the
lowest surface area/volume ratio is a
sphere, but that's
no good for swimming efficiently through oceans, so a rounded
streamlined whale (mammal) shape
is a good compromise!
The polar bear is large but reasonably compact
bearing it mind it needs arms and legs to walk, swim and hunt!
Compared to similar animals in warm
climates, some animals in cold climates have smaller ears to minimise
surface area contact with cold air - so minimising heat loss.
A bit of surface area/volume maths...
(need to add diagrams or
photographs?)
... to
illustrate this adaptation I'm starting with cubes of various sizes (6 faces/sides):
(Ex. 1) A 1 cm cube has a volume
of 1 cm3 (1 x 1 x 1), a surface are of 6 x 1 x 1 = 6 cm2
So the surface area / volume
ratio = 6 / 1 = 6 cm-1
(6 : 1 ratio)
(Ex. 2) A 2 cm cube has a volume
of 8 cm3 (2 x 2 x 2), a surface are of 6 x 2 x 2 =
24 cm2
So the surface area / volume
ratio = 24 / 8 = 3 cm-1
(3 : 1 ratio)
(Ex. 3) A 3 cm cube has a volume
of 27 cm3 (3 x 3 x 3), a surface are of 6 x 3 x 3 =
54 cm2
So the surface area / volume
ratio = 54 / 27 = 2 cm-1
(2 : 1 ratio)
I've worked out the surface area
: volume ratio for other shapes.
(Ex. 4) Take a 1 cm x 2 cm x 4 cm
rectangular block.
The volume = 1 x 2 x 4 = 8
cm3 (this volume matches Ex. 2 above)
The surface area = 28 cm2
(from 2 + 2 + 4 + 4 + 8 + 8)
Surface area / volume = 28 /
8 = 3.5 cm-1
(3.5 : 1, note this is higher than Ex. 2)
(Ex. 5) Take a 1 cm x 3 cm x 9 cm
rectangular block.
The volume = 1 x 3 x 9 =
27 cm3 (this volume matches Ex. 3 above)
The surface area = 78 cm2
(from 3 + 3 + 9 + 9 + 27 + 27)
Surface area / volume = 78 /
8 = 2.9
cm-1 (2.9 : 1, note this is much higher
than Ex. 3)
It turns out the cube or a sphere
have the smallest surface area : volume ratio.
In fact, for a given volume, the
sphere has the smallest surface area : volume ratio.
(Ex. 6) In this example I'm
matching the volume of 8 cm3 for Ex. 2 and Ex. 4)
Take a sphere of radius
1.24 cm (I worked backwards using the formula below to get
this!)
Volume of sphere = 4/3 x π x
r3 = (4 x 3.142 x 1.243) / 3 = 7.99 cm3
Surface area of sphere = 4 x
π x r2 = 4 x 3.142 x 1.242 = 19.325 cm2
Surface area / volume ratio =
19.325 / 7.99 = 2.4
cm-1 (2 s.f., ratio
2.4 : 1)
This value is lower than the
cube (3.0) and rectangular volume (3.5) computed for the same
volume.
Note that the smaller the sphere,
the greater the surface area : volume ratio
For a given radius: surface
area / volume = 4 x π x r2 / 4/3 x π x r3
= 3 / r
So, the smaller the radius r,
the greater the surface area : volume ratio is.
You can see clearly that the smaller
(thinner etc.) of the animal the greater the surface to volume ratio and
the greater the rate of heat loss.
So, you can clearly see the advantage
of a compact shape minimising the surface area for larger animals i.e.
to minimise heat loss in large animals like polar bears, but the fat
layer and fur help too!
You might have noticed that many
animals try to adopt a spherical shape, though often a rugby ball shape.
e.g. warm bloodied mammals like
rabbits, hedgehogs or mice.
Note that cats/kittens and
dogs/puppies instinctively curl up into the minimum volume before
going to sleep - this minimises surface area : volume ratio and so
minimises heat loss.
You completely reverse the argument
when dealing with the transport of substances in multi-cellular
organisms, when you want the most efficient transfer system possible for
one or more functions of the organisms.
This is best achieved with a
high surface area to volume ratio.
A good example is the fine and
numerous villi in the intestine where their large surface
area is very efficient for absorbing nutrients from absorbed food.
The villi can be envisaged
as tall thin rectangular blocks in shape.
See also
Diffusion, osmosis and active transport and
Examples of exchange surfaces
The blubber in whales and seals is also a
great store of energy for the whale and other species like seals.
Animals that live in very hot climates eg
desert camels, only have a thin layer of fat and a large surface area to
volume ratio to lose excess body heat efficiently.
Animals in hot dry climates have the
minimum of fat and body hair to prevent overheating.
Most a camel's fat
(energy store) is in the hump which means the rest of the body doesn't need
a layer of insulating fat that would reduce heat loss through the skin.
A
camel's fur layer is also thinner so too much heat is not retained.
Animals like camels do no sweat to
minimise water and need the minimum of water to drink to help cope with
the scarcity of water in desert regions.
Birds have wings to fly and fish and
penguins have flippers/fins to propel themselves by swimming.
Some fish tail
fins are large in surface area to increase traction, but other fins are
smaller and adapted to help stability when moving fast through water.
Large heavy animals like polar bears have
large flattish feet to spread their weight more evenly and reducing their
sinking into snow and falling through ice.
A physics note in biology!:
pressure = force (weight) / surface area, increase area, pressure
reduced
Seals, penguins and many fish have
streamlined bodies adapted for swimming.
The streamlining reduces water
resistance, friction, (just like an aircraft's shape reduces air resistance)
and enables the creature to escape from predators OR catch some prey!
Giraffes have long tall necks to eat
leaves that other animals can't reach.
Fish have gills, which have a large
surface area, to extract oxygen (at low concentration) from water for
respiration.
Fish have an organ called a swim bladder
containing gas, and the volume can be adjusted to enable the fish to change
its depth in the water without having to use valuable energy.
Animals like penguins standing on cold
ice, have blood vessels through which the flow is in opposite directions and
these vessels pass close to each other and allow heat transfer between them.
Warm blood flows in the arteries to heat up the feet and cold blood returns
to the heart in the veins.
The feet are still relatively cold but it stops
cold blood from cooling down the body.
Many animals in hot environments, by
being small, have a large surface area to volume ratio which helps them keep
cool by losing more heat through the skin.
Also, large thin ears with a
large surface area and lots of blood vessels have the same effect increase
heat loss by conduction and radiation.
Hedgehogs have needle like spikes/spines
over the upper side of their body and can curl up to give all round
protection - predators from biting and trying to eat them!
Some insects display prominent warning
colours to deter predators.
The work of Wallace (with Darwin, joint
founder of
evolution theory)
showed that many
species of butterflies had a (i) peculiar odour and
taste or (ii) warning colours - all adaptations to deter
potential predators from eating them - these beneficial
characteristics had come about by natural selection - the
fittest traits to help the species survive -
beneficial characteristic passed on in the alleles of their
offspring.
Mimicry, looking like something
they are not, is used by both plants and animals to help them survive e.g.
The hoverfly has warning colours like
a wasp - so is observed-perceived to be potentially harmful.
Some butterfly markings mimic another
unpleasant tasting species, but orchid plants are tops at mimicry!
A group of orchids with very apt
names such as fly orchid, bee orchid, and spider orchid actually mimic
the insects themselves to attract them. These orchid flower species look
and act as a dummy female of the insect species. The resemblance is so
good that males visit the flower in an attempt to copulate with the
dummy female! In trying to copulate, the visiting male insect acquires
the pollen sacs of the orchid and so transfers them to other orchid
flowers - nice one!
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(2)
Animals - Behavioural adaptations
described and explained
These describe how an organism
behaves
to adapt to its environment e.g.
Many animals migrate from colder
to warmer climates to find food and breed, and return at the end of the season e.g.
birds like ducks and swallows.
By migration many species avoid the harshness
and dangers of a cold climate.
In e.g. low temperature arctic
regions where food resources are low in winter, other animals that do
not migrate can hibernate - they 'fatten up' in the summer and 'sleep'
through the winter months.
Penguins huddle together to keep each
other warm in the frozen wastes or the Arctic and Antarctic.
On average
there is less body surface area exposed to the cold air and winds.
 Many desert animals
in hot climates live for much of
their time in burrows underground where there is more moisture and cooler
out of direct sunlight.
Such animals tend to be more active
in the cooler mornings as well as moving to more shaded areas to keep
cool and other animals rest in the shade particularly in the
middle hottest parts of the day to minimise the absorption of heat.
Minimising excessive heat gain can be helped by being more active
(hunting-feeding) in the cooler nighttime.
In hot countries animals can increase
their heat loss and cool down by bathing in water. Not only does the water
absorb heat, but evaporation from the skin absorbs heat energy (just like in
sweating) - latent heat of evaporation absorbed from the animals body.
Unlike mammals, reptiles find very high
and very low temperature conditions difficult to deal with because they have
no internal mechanism to control their body temperature.
Therefore reptiles either (i) bask in
the sun to warm up or (ii) rest in the shade to keep cool in the hottest
part of the day.
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(3)
Animals - Functional adaptations
e.g. organs and metabolism
described & explained
These are features of an organisms
body that relate to the fundamental processes such as
reproduction and
metabolism (some of the most important chemical reactions in the body).
In very dry arid conditions e.g. desert
animals may conserve water by having a specialised kidney that produces very
small amounts of concentrated urine.
So very little water is used in the
excretion process.
Such animals may not have sweat
glands so there is no water loss from sweating evaporation.
Organisms eg animals like penguins (with
feet on ice!), are helped to survive in extreme cold conditions (<0oC)
by producing antifreeze proteins in their tissue fluids.
Its rather like putting
salt on roads, these proteins lower the freezing point of water, and so reduce the chance of ice crystals forming that would
otherwise damage cell structure.
Many animals have adapted to hibernate over
winter to conserve energy and not have to go hunting for prey in harsh
conditions with little prey around.
In these very cold climates, animals
like bears, can lower their rate of metabolism to a point where very little food
(energy) is needed to keep alive and they go into a deep sleep and wake in
the spring when life supporting conditions are much better. A very sleepy
way to save energy!
Bees and insects have the means to sting potential predators.
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(4)
More on animal adaptations including extremophiles
described and explained
Don't forget that microorganisms, like
bacteria, live in a huge variety of environments, some of them in quite extreme
conditions and not surprisingly they are called extremophiles!
Some
microorganisms live on very hot rocks/water eg by hot volcanic vents and some exist
under very pressure and temperature in the deep ocean volcanic vents.
Some
bacteria can live in water containing very high concentration of dissolved
salts.
The above examples plus others are further
discussed below along with the sort of learning objectives you need to cope
with.
-
Know and understand that to survive and reproduce,
organisms require a supply of materials from their surroundings and from the
other living organisms there.
-
Know and understand that plants often compete with
each other for light and space, and for water and nutrients from the soil.
-
Know and understand that animals often compete with
each other for food, water, mates and territory.
-
In the wild territorial
disputes between species or members of a species are common - an example of
competition.
-
Those animals who are best adapted will nudge out of other
species from a particular habitat.
-
In most UK woodlands, the grey
squirrel from North America, has displaced the native red squirrel,
principally because it out-competes for food. The grey squirrel can feed
more at ground level and can digest acorns and red squirrels can't).
-
Know and understand that organisms, including
microorganisms have features (adaptations) that enable them to survive in
the conditions in which they normally live.
-
Know and understand that some organisms live in
environments that are very extreme.
-
Know that so-called
extremophiles
may be tolerant to high levels of salt, high temperatures, high pressures or
adapted to extremes of pH.
-
Flamingos filter-feed on brine
shrimp and blue-green algae and their pink or reddish colour comes from
carotenoid proteins in their diet of animal and plant plankton which can
survive in the very salty lakes the flamingos fly to for feeding.
-
Some microorganisms can survive in very
acid water (low pH <<7) or very alkaline water (high pH >>7)
-
There are certain microorganisms, eg
bacteria colonies, that live by hot volcanic vents of water on land
(eg
geysers) or on the seabed (where the vents are called 'black smokers').
-
The
bacteria cannot rely on photosynthesis so they make there own food by using
chemical energy derived from the minerals on and around the vent.
-
These
processes are called chemosynthesis, powered by chemical energy, as opposed
to photosynthesis in plants powered by sunlight.
-
The bacteria then become
the producers for a food chain that can support several animal species - so
we still have food chains and food webs in these extreme conditions.
-
These
bacteria must be adapted to cope with both high temperatures and high
pressures in extreme depths of the ocean in volcanically active regions.
-
Biochemical points and conditions:
-
Extremophile bacteria
living in very hot water have enzymes whose optimum operating temperature is
much higher than 'normal' for most organisms e.g. ours is ~37oC.
-
The high temperatures encountered eg by deep oceanic volcanic vents
would normally denature the protein structure of enzymes, but the enzymes
have evolved and adapted to function efficiently at higher ambient temperatures
of over 100oC.
-
Some organisms can withstand pressures
1000 x normal atmospheric pressure deep in the oceans.
-
Other organisms are found deeper than 6
km in the Earth's crust and have adapted to sparse resources - they can even
exist deep in oil wells.
-
There are creatures that happily
live on the deep ocean beds where the pressure from the water above is
enormous.
-
It should be pointed out that deep in
seas and oceans there is virtually no light, the depth being such that
sunlight doesn't penetrate to the sea or ocean bed. This means no plants
because of no light for photosynthesis. Therefore deep sea organisms often have to
rely on scraps of food that sink down from richer regions of life. This hard
life has produced some interesting adaptations e.g.
-
Some deep sea fish can give out
light from organs on their body's surface like the angler fish which has
rod-shaped spine sticking out from its face which emits light to attract
prey.
-
The Pacific black dragon is one of the
blackest fish in the deep sea because its ultra-black skin makes it as
invisible as possible to predators. The pigment particles in the skin are in
dense layers that scatter the light so much that virtually non is reflected.
This is an 'extremophile' that is 'extremely' invisible' that helps such a
fish survive at these great depths in the ocean!
Know and understand animals and plants may be adapted for survival in
the conditions where they normally live, eg deserts,
the Arctic.
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(5)
Adaptations in plants
- emphasis plants living in extreme environments
Cacti galore!
(pictures
of cacti from the Leicester University Botanic Garden)
Know and understand that plants may be adapted to survive in dry environments
by means of structural adaptations ...
Examples of plant adaptations are
described below, many are to do with controlling water uptake and retention.
-
Plants are adapted to live in a variety of environments including extreme environments that are very hot
and/or very dry like deserts. need more photographs to
illustrate this section
-
These adaptations affect, in
particular, the size and shape of a plant's leaves, cuticle and the
number and position of the stomata.
-
Plants grow well in warmer climates,
particularly summer, as conditions favour photosynthesis to build up
food stores for the colder winter.
-
See
factors affecting rate of photosynthesis.
-
Changes to surface area, particularly
roots, and the leaves
- through which water is naturally lost by transpiration
-
Even narrow roots are further covered
in tiny root hairs that greatly increase the surface area even more and
hence increase the efficiency (rate) of water absorption.
-
In contrast, in hot climates, to reduce the surface area,
to
reduce water loss by evaporation, plants like cacti have a rounded shape with thin spines instead of broader
leaves.
-
Spines also deter animals from
feeding on the plants like cacti.
-
See
Plant diseases and defences against pathogens
and pests
-
Pine trees grow up in a cone shape
to expose the most thin pine needles to the sun - increase in
surface area, increases the rate of photosynthesis.
-
Marram grass grows on sand dunes and
has adaptations to reduce water loss by transpiration in dry windy
conditions.
-
The leaves are compacted and rolled
with the stomata sunk into pits in the thick waxy cuticle.
-
Also, interlocking leaf hairs retain
water vapour, so all these features reduce water loss.
-
need diagram
-
-
-
-
Plants are well adapted to live in
extreme environments e.g.
very hot and very dry environments.
-
Adaptations are often to do with the
size and shape of leaves, cuticle structure and the number and position
of stomata.
-
Many adaptations are about reducing
the rate of evaporation of water and retaining or storing water.
-
Illustrates many of the adaptations described here.
-
Plants in hot and very dry environments tend to
have thick waxy cuticle to reduce water loss by evaporation.
-
Plants like cacti, living in deserts,
tend to have adaptations which help them to conserve water - retain as
much water as they have access too.
-
Plants like cacti have
relatively thick fleshy stems which contain groups of specialised cells that
store water.
-
Some giant cacti like the saguaro cactus in the deserts of
Arizona (USA) can be 20m high and hold in storage several tonnes of water -
more than enough to see it through the driest of dry seasons and survive
long periods of drought.
-
Cacti also have a water repellent
thick waxy layer (the cuticle) which further reduces water loss by
evaporation.
-
Leaves can be curled or have hairs on
their surface.
-
This reduces air flow over the leaf keeping more water
vapour near the surface and so reducing the diffusion of water vapour
from the leaf surface to the surrounding air.
-
Needle-like spines or very small
leaves, reducing surface area, also have a similar
effect in reducing loss of water by evaporation - spines also deter
animals from eating them and reduce air flow.
-
A lot of water is lost by
evaporation from the stomata.
-
Most stomata are on the underside of
leaves and so evaporation of water is less affected by environmental
conditions such as sunlight or wind.
-
See
Plant cells
- transport, gas exchange,
transpiration, absorption of nutrients, leaf & root structure
-
Plants with fewer stomata on their
leaves or have stomata that only open at night are adaptations that
reduce water loss by evaporation.
-
Stomata can be sunk in pits below the
leaf surface, this reduces flow of air across
the stomata and so less water vapour carried away - helping water
retention.
-
-
-
Extensive root systems
-
Cacti generally have one of
two kinds of root system. (i) Some have relatively few roots, but roots
that can burrow deep into the ground to seek out underground water. (ii)
Most other cacti have many shallow spread out roots that can rapidly absorb
water quickly over a large area eg if it rains, which may be very infrequent in desert regions.
-
Other 'defences':
 Know and understand that plants may be adapted to cope with
specific features of their environment, these specialised features to deter
predators include thorns and
poisons to deter 'predators' e.g.
-
Roses have thorns, cacti have sharp spines to deter
animals (herbivores) eating them, turtles, armadillos and tortoises have
hard protective shells. These are examples of organisms having a sort of
'armour' for protection!
-
Plants like ivy contain poisons that
deter animals from eating them.
-
Some desert shrubs secrete toxic
compounds into the soil to prevent other plants growing nearby.
-
Some species of epiphytes grow in
rainforests and exhibit several adaptations to survive by growing above
ground level e.g.
-
(i) They can grow on other plants,
preferentially capturing sunlight through the trees for photosynthesis.
-
(ii) These epiphyte type of plants have
roots that rely on nutrients from the air, falling rain, and the compost
(leaf litter) that lies on tree branches.
-
(iii) They can have upturned leaves that
capture and store rainwater or dew.
-
-
See also
Plant diseases and defences against pathogens
and pests gcse biology revision notes
Photosynthesis,
importance
explained, limiting factors affecting rate, leaf adaptations
gcse biology revision notes
Plant cells, transport and gas exchange in plants,
transpiration, absorption of nutrients, leaf and root structure
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Animals
living very cold climates have thick hairy coats to minimise heat loss, but
the fur must be in good condition to trap insulating air and keep cold water
away from the skin. The fur of animals like the arctic fox is an extremely
good insulator and can survive at temperatures as low as -50oC.
It has a long winter coat with thick dense under fur. Bears, similarly, have
thick fur coats.
Animals
in arctic regions have thick layers of insulating fat or blubber AND these
also act as an important energy store - fat/blubber has a very high
calorific value, useful in lean times and scarcity of food. eg seals,
penguins, polar bears, whales
Arctic
animals like polar bears have white fair to blend in with the icy/snowy
background to increase the chances of a kill. Smaller white coated animals
are less likely to seen and caught. The white arctic fox is a mean hunter!
Some insects and other animals
have very 
Enter specific biology words or courses e.g. topic, module, exam board,
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of biological interest!