Embedded Files
Koala's are adapted to climb trees
Adaptations
Adaptations
Organisms do not intentionally change to suit their environments, nor can they intentionally produce offspring that have these changes. An adaptation is a result of a change or variation that arises, at random, when cells divide and replicate during the process of reproduction. The new organisms produced possess a changed feature and this random difference may happen to benefit the organisms by making them more suited to the environment they live in. This is then passed on to its offspring in turn through gametes.
Australian environments are varied and diverse with some harsh conditions for organisms to survive in. the three main abiotic factors that affect survival in Australia are water, temperature and sunlight.
There are three types of adaptations which are often intertwined and can be difficult to separate.
Structural adaptations
Structural adaptations
Structural adaptations are those that form part of the physical features of an organism.
There are many examples of structural adaptations, as it basically just refers to any part of an organism that isn't chemical. Structural adaptations are physical features, on both the inside and outside of an organism.
Structural adaptations in plants:
The main problems faces desert plants are to balance photosynthesis with water loss via transpiration. The continuous transpiration that occurs in plants is a form of evaporative cooling for temperature regulation. Xerophytes (such as cactus) live in hot dry habitats where they are exposed to high temperatures and bright sunlight. Structural adaptations maximise the absorption and storage of water to minimise water loss.
Succulents such as Pigface have adaptations such as fleshy stems or leaves. These swell up and retain moisture when it is available so that they can survive dry periods.
Eucalypts and banksias have coarse, leathery leaves with a thick cuticle are insulated and are reflective, reducing the effects of sunlight.
Leaf shape is important in retaining water. Leaves with a high surface area to volume ratio have reduced water loss.
Epidermal hairs on the surface of the leaf trap moist air. This results in a small difference in concentration gradient from the inside and outside of the leaf tissue, preventing osmosis from causing water loss.
Structural adaptations in animals:
The main survival issues for animals are nutrition, hydration, temperature regulation, shelter, reproduction and survival from predators.
The Thorny Devil is a small lizard that lives in Australian deserts. It lives off of black ants and termites. The body of the lizard is covered with large prickly spikes, making it dangerous to eat, deterring predators. Water from rain and dew is captured by a complicated set of layered scales all over the lizards body. Each scale is attached by a hinge joint that enables the lizard to collect water and funnel it to the back of its mouth where it uses its tongue to drink it.
The wombat is a nocturnal animal that lives in an extensive burrow. The burrow can be up to 11m in depth and 30m long. Because wombats are frequent diggers they have large muscular shoulders and long claws on their front feet. Wombats give birth to underdeveloped young which spend the next five months maturing in the pouch. The pouch is rear facing and this is a structural adaptation in response to digging. The pouch orientation ensures that the joey will be protected from the dirt that would otherwise fill the pouch, this increases the joey's survival chance.
Wombats have 24 rootless teeth which continuously grow. This is an advantageous adaptation, as wombats live in an environment full of tough fibrous grasses. Their continuously growing teeth means they can grind these difficult to consume plants, and obtain nutrients from them, and not worry about the wear on their teeth, as they will regrow. This enables the wombat to best exploit their environment.
Echidnas are Australian monotremes which burrow for shelter. This enables them to effectively hide from predators, as well as keep cool in the warmer climate. To facilitate rapid burrowing, echidnas have evolved hind legs which face backwards so that they can burrow with more speed. In addition, these hind legs are equipped with long claws for effective excavation.
Xerophyte
Pigface succulent
Eucalyptus leaves
Epidermal hairs
Thorny devil
Wombat pouch
Wombat skull
Echidna claws
Physiological adaptations
Physiological adaptations
Physical adaptations are those which result in a chemical change to the body of an organism.
Physiology consists of all the processes involved in an organism carrying out its function. Physiological adaptations relate to how an organisms function can increase its chance of survival. They involve variations in the metabolism or physiology or organisms at a cellular, tissue, organ or system level, giving them environmental advantages.
Physiological adaptations in plants:
Abiotic factors influence the vegetation present in an environment. This also affects the animal life that is present in the environment as this affects herbivore population which in turn affects predator population.
Plants that grow in very cold areas reduce the risk of ice forming within and between their cells. ice crystals pierce cell membranes. Some alpine plants produce organic 'anti-freeze' compounds which reduces the temperature needed for ice to form.
Some deciduous plants lose their leaves in winter and go into a period of dormancy. This allows them to survive low temperatures, water shortages and lower light availability.
The deciduous beech tree is one of the few native deciduous trees. Leaves fall off the tree in response to shorted days where the unavailability of sunlight causes the formation of a waterproof layer at the base of the leaf. Without access to water, photosynthesis in the leaf stops and the pigment anthocyanin is exposed as chlorophyll degrades, giving the leaves their yellow autumn colour.
Tulip bulbs will only flower when exposed to a period of intense cold. This is called vernalisation and is an adaptation to the seasons in central Asia.
Salt, even in small concentrations is damaging to cell structure and metabolism. Plants adapted to saline environments are called halophytes. The plants use salt tolerance or salt avoidance to survive these environments.
Salt tolerant plants accumulate salt in their cells. They minimise toxicity by increasing their water content in large vacuoles. Succulents minimise the salt toxicity through increasing water content in large vacuoles, where the salt is balanced out.
Saltbush is a salt excluder, it actively removes salt into bladder cells on the tips of leaf hairs. When the bladder cell is full it bursts, releasing the salt.
Mangroves are extremely well adapted to salt by using both salt-avoidance and salt-tolerance strategies. Salt accumulates in bark and leaves and is lost when the bark or leaf leaves the tree. Salt can also be actively excreted through glands on the leaf surface. Furthermore their roots exclude salt from the roots, reducing its uptake into the plant.
In response to food availability, locusts will undergo physiological changes that cause them to form swarms, this also has a colour change
Physiological adaptations in animals:
Animals have physiological adaptations which allow them to survive in harsh environments. Animals are able to move between environments and so can be exposed to a range of conditions.
The intertidal marsh crab has gills and kidneys that function to concentrate and excrete excess salt.
Flamingos can tolerate the alkaline waters of soda lakes which kill other birds.
The spinifex hopping mouse is able to reduce water loss by having highly concentrated urine. This is due to their ability reabsorb most of the water back into their bloodstream. The 'waste' waster produced by cellular respiration is reused as well.
Freshwater fish have a higher concentration of ions in their cells so water diffuses in. to counter this, they rarely drink water, have a high kidney filtration rate and produce heavily diluted urine.
Penguins are aquatic birds, relying on fish as a food source, yet requiring air to breathe. Therefore, to effectively hunt fish they have adapted to be able to regulate their heart rates, controlling the amount of oxygen they use during deep diving. An emperor penguin can drop their heart rate from a resting bpm of 72 to 6 bpm during an 18 minute dive. Once they re-surface, they raise this rate to about 200bpm, allowing them to rid of CO2, and flow oxygen back to their tissue.
Animals that live in very cold environments convert their food into a layer of blubber that insulates them from the cold. In Polar bears this layer can be up to 12cm thick. They are so well insulated that they cannot run long distances otherwise they will overheat.
Land snails will move into the shade, seal the opening to their shell with a mucus material and reduce its metabolic rate so that its temperature is lowered to that of the environment. Cane toads will burrow underground and seal themselves in a water-tight mucus cocoon.
Koalas live in eucalyptus trees, and consume a diet composed entirely of eucalyptus leaves. Eucalyptus leaves are very low in nutrition, extremely fibrous, and poisonous to most animals. In order to eat these leaves, Koalas have adapted to have a very slow rate of metabolism. This means that the leaves remain in their stomachs for a long period of time, enabling for energy to be extracted from them. They also have digestive systems adapted to detoxify the toxins in the eucalypts leaves. Additionally, they have a long caecum, enabling the tough leaves to be broken down completely.
Anti-freeze plant
Deciduous plant
Tulip bulbs
Mangrove leaves
Penguin circulation
Polar bear skin layers
Snail mucous
Burrowed Cane toad
Digestive system length in various animals
Behavioural adaptations
Behavioural adaptations
Behavioural adaptations are changes to an organism's behaviour in order for them to better live in their environments.
Behavioral adaptations refer to those actions performed by an organism in response to a stimulus that improves its chances of survival.
Behavioural adaptations in plants:
Plants generally do not move much. Plant behaviours are more subtle than behaviours shown by animals.
Mimosa pudica is a houseplant originally from tropical America that responds to touch stimulus. When a leaf is touched it folds inwards, defending itself from harm.
The Venus flytrap is a plant that is adapted to live in nitrogen-poor soil by 'eating' insects. Part of the plant is able to snap shut when the insect touches delicate sensory hairs. The insect becomes trapped and the plant secretes digestive enzymes and then the nutrients are absorbed by the plant.
In the two plants, touch stimulus causes cell vacuoles to lose turgor pressure and the cells collapse. This is an example of a physiological adaptation that leads to a behavioural adaptation.
Venus fly trap trigger hairs
Some plants react to a touch stimulus
Behavioural adaptations in animals:
Animals display a much greater range of behavioural adaptations than plants. These behaviours can be shown by individuals or by groups. The result of the behaviour is to increase the chances of survival.
As snakes are ectotherms, they rely upon external temperatures to regulate their internal body temperature. Therefore, to ensure that they survive in the Australian desert environments, King Brown Snakes will move to regulate their body temperature. They will move into the sun to warm themselves during the day. At night when the temperature drops they will curl up underneath rocks or into burrows, where temperatures remain warmer.
Kangaroos are very well adapted to their hot Australian environment. Their behaviour are dependent on the climate, so during warmer days they will move into the shade of trees, and during cooler days they will sunbake. Additionally, kangaroos are known to lick their forearms in hot weather. As the saliva evaporates, heat from blood vessels close to the skin dissipates, cooling the kangaroo.
The central netted dragon is a desert-adapted lizard that inhabits central Australia's plains and open scrub. It is able to withstand variations in body temperature from 13 to 44 degrees Celsius. In low temperatures the dragon will bask in the sun and it shelters from cold weather. If the temperature is high the dragon will retreat into the shade and reduce its activity to reduce overheating. It then hunts at night in the cooler temperature.
Burrowing animals will take shelter during the hottest or coldest parts of the day.
Some species exhibit social behaviour that increases the survival chance of the group. Sugar Gliders produce a pungent aroma from scent glands located on the head, on their chest or about the genitals. Members of a group are permeated by the scent of the dominant male and therefore are able to locate each other successfully in fading light.
Meerkats live in large social communities. They are burrowing carnivores that spend a large amount of the day digging for food. This makes them vulnerable to attack. One meerkat will be posted as a sentry at a high vantage point to watch for danger and it will warn the other members of the group with distinctive calls. The rest of the colony will then also scan the area for predators.
Kangaroo licking
Central Netted Dragon
Sugar Glider
Meerkat sentry
A Giraffe's long neck evolved to help them access their food in the tops of trees
Darwin's observations of Natural Selection
Darwin's observations of Natural Selection
In 1831, Charles Darwin left England on the HMS Beagle, beginning a world trip whose discoveries would revolutionize the scientific community, and have lasting impacts throughout society. The journey, lasting 5 years, was an opportunity for Darwin to collection geological and natural history samples, and make observations about the diversity of life across the globe.
The voyage of the HMS Beagle
Charles Darwin
Charles Darwin
The belief at the time was that all species on Earth had been independently created. During his travels he found that fossilized invertebrates were similar to the shells of present-day organisms in the Canary Islands. Furthermore he found that the outer shell of an armadillo was similar to the fossil shell of a glyptodont that he found between Argentina and Bahia Blanca. He began to consider if there was a relationship between extinct species and present-day organisms.
The Armadillo is likely to have evolved from the Glyptodont based on their similar physical features
The Galapagos finches have diversified their beak shapes to better suit their food sources
Darwin's finches
Darwin's finches
The Galapagos Islands, an archipelago composed of 13 major islands, were a treasure trove of wildlife and geological phenomena for Darwin to explore. One of Darwin's major observations in this region were the variety of birdlife on each island, native finches whose appearance and behaviour have quickly adapted to their changing environments.
Darwin collected 14 different finch specimens across the Galapagos. They each had variations in their beak form and function, distinct to each island.
Ornithologist John Gould verified the samples as 14 distinct species, 12 of which had never before been documented
The smallest inch, the warbler-finch was about 10cm in size and weighed 8 grams, whereas the largest finch, the vegetarian finch, was about 20cm and weighed 38 grams.
This provided evidence for evolution from a common ancestor of mainland finch. It showed that beak-traits were selected for over many generations, until eventually the populations had branched into separate, distinct species. They had adapted to fill ecological niches on the islands, where different foods were available compared to the mainland.
Some of the earliest drawings of the Platypus
Australia's flora and fauna
Australia's flora and fauna
Darwin landed in Australia on January 12th 1836, having the opportunity to travel to multiple regions of Australia and observe the varied flora and fauna.
Around Sydney, Darwin collected at least 110 animal samples and 97 insect samples (42 of which had never been documented).
In Hobart, Darwin discovered a new species of skink (Tiliqua casuarinae), a new species of flatworm (Planaria tasmaniana), and 119 species of insects (63 of which had never before been described).
During a trip to the Blue mountains, Darwin observed the rat kangaroo and the platypus. He noted that they occupied similar ecological niches to different animals in the Northern Hemisphere. Of this difference, he remarked: 'Surely two distinct creators must have been [at] work'.
This particular observation added weight to his argument of evolution, as it showed how the variety of species isolated on different continents at different points in history may adapt to become similar when exposed to similar selection pressures. This underlies the theory of convergent evolution.
The Rat Kangaroo
Darwin went on to propose the 'Survival of the fittest' which has five main tenets:
Variation exists within populations.
More offspring are produced than can survive.
Those offspring that are better adapted to their environment will survive and reproduce.
The favourable adaptations are passed on to the next generation.
Over time, the favourable adaptations will increase in the population (as long as the environment does not change).
The Banksia has a unique flower shape with numerous, small, thin petals
The Eucalyptus tree is adapted to the hot, dry conditions in Australia
The implications of Darwin's observations for Natural Selection
Adaptations
Inquiry question: How do adaptations increase the organism's ability to survive?
Conduct practical investigations, individually or in teams, or use secondary sources to examine the adaptations of organisms that increase their ability to survive in their environment, including:
Structural adaptations
Physiological adaptations
Behavioural adaptations
Investigate, through secondary sources, the observations and collection of data that were obtained by Charles Darwin to support the Theory of Evolution by Natural Selection, for example:
Finches of the Galapagos Islands
Australian flora and fauna
Page updated
Report abuse