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School biology notes: Evolved adaptations - examples described & explained

leopard animal adaptationsfish adaptationsEvolution 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

wolf adaptations through evolutionbird adaptations through evolutionYou 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.

      • Deep sea fish often have large mouths to collect scraps of food from the seabed and/or have large eyes to cope with dim light conditions to see prey and some deep sea creatures have long feelers to detect prey.

    • 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.

  • Know and understand that animals may be adapted for survival in dry and arctic environments by means of:

    • Changes to surface area - heat/water transfer surface factors

      • Increasing (in hot environments) or reducing heat (in cold environments) transfer from organisms is an important adaptation to help survival.

      • Desert animals eg in Africa, tend to have a large surface area/volume ratio to allow excess body heat to be readily lost. This helps overheating, particularly as they do not sweat much and produce smaller volumes of concentrated urine, both helping to reduce water loss.

      • Animals living in very cold climates eg the arctic regions and northern Europe and Russia, tend to have a smaller surface area/volume ratio to minimise heat loss. Their bodies need to compact with a minimum volume - 'roundish' to minimise the surface area through which heat is lost.

      • The arctic fox and wolves have short ears and a short snout to minimise surface area, hence minimise heat loss.

    • Thickness of insulating coat

      • Desert animals have thinner coats than animals in colder climates, which aids heat loss.

      • 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.

    • Amount of body fat

      • Desert animals have thin layers of body fat compared to animals in colder climates, which aids heat loss.

      • 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

    • Camouflage

      • Desert animals have sand coloured coats which give good camouflage to minimise being seen and attacked by predators, it also the enables animal to a predator itself, prey becomes the hunter!

      • 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!

      • Birds like the ptarmigan stand a better chance of survival from predators turning white in colour in winter, and brown in the summer, thereby blending into the landscape with the change in seasons

  • Some insects and other animals have very bright 'warning' colours to look 'fearful' to potential predators e.g. wasps.

    • Insects like bees and wasps have stings as a means of defence against predators.

 


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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.

The upper side of a leaf is smoother and greener - richer in chloroplasts to capture the sunlight The under side of a leaf is rougher - more 'porous' for efficient gas exchange and the veins more prominent

See photosynthesis page for details of leaf adaptations to favour efficient rates of photosynthesis

  • 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.

      • This adaptation means the water has only got to move a short distance to the xylem and transported up through the whole of the plant.

    • 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.

      • Plants like cacti have evolved systems of storing water in their tissues to conserve water.

    • 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

  • -

-

  • Water storage and water retention tissues

  • 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.

      • They are not parasites and do not extract nutrients from the host plant.

    • (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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