(4) More on examples of adaptations and extremophiles

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 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.

• (a) Know and understand that to survive and reproduce, organisms require a supply of materials from their surroundings and from the other living organisms there.

• (b) Know and understand that plants often compete with each other for light and space, and for water and nutrients from the soil.

• (c) 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).

• (d) Know and understand that organisms, including microorganisms have features (adaptations) that enable them to survive in the conditions in which they normally live.

• (e) 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. These 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 point: 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 ~37^oC. 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 higher ambient temperatures.

  • 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 have to rely on scraps of food that sink down from richer regions of life. This hard life has produced some interesting adaptations eg

    • 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.

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 factor

    • 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 -50^oC. It has a long winter coat with thick dense underfur. 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 s a means of defence against predators.

(5) Adaptations in plants

Know and understand that plants may be adapted to survive in dry environments by means of eg examples of structural adaptations ...

• Plants are adapted to live in a variety of environments including extreme environments that are very hot and/or very dry like deserts.

  •  These adaptations affect, in particular, the size and shape of a plant's leaves, cuticle and the number and position of the stomata.

• Changes to surface area, particularly of the leaves - through which water is naturally lost by transpiration

  • 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.

  • Other plants have smaller leaves.

  • Spines also deter animals from feeding on the plants like cacti.

• Water storage and water retention tissues

• 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. Spines also have a similar effect in reducing air flow.

• Plants with fewer stomata on their leaves or have stomata that only open at night are adaptations that reduce water loss.

• Stomata can be sunk in pits, so being below the leaf surface, they do not experience the same flow of air as the surface 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.

• Know and understand that plants may be adapted to cope with specific features of their environment, these specialised features to deter predators include thorns, poisons and warning colours to deter predators eg

  • Roses have thorns, hedgehogs have needle like spikes/spines over the upper side of their body and can curl up to give all round protection, 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, insects like bees and wasps have stings, some desert shrubs secrete toxic compounds into the soil to prevent other plants growing nearby.