adaptations Flashcards
what are adaptations
Adaptations are characteristics that increase an organism’s chance of survival and reproduction in its environment. Adaptations can be divided into three groups:
-anatomical adaptations - physical features (internal and external)
• behavioural adaptations - the way an organism acts. These can be inherited or learnt from their parents.
• physiological adaptations - processes that take place inside an organism.
Many adaptations fall into more than one category. For example, the courtship behaviour of a peacock requires it to lift its huge, colourful tail to attract the peahen. This is an example of both a behavioural and anatomical adaptation.
anatomical adaptations
Some examples of anatomical adaptations:
• Body covering - animals have a number of different body coverings such as hair, scales, spines, feathers, and shells. These can: help the organism to fly, such as feathers on birds - help it to stay warm, such as the thick hair on polar bears - provide protection, such as a snail’s shell. Thick waxy layers on plants prevent water loss and spikes can deter herbivores and protect the tissues from sun damage.
• Camouflage - the outer colour of an animal allows it to blend into its environment, making it harder for predators to spot it.
For example, the snowshoe hare is white in winter to match the snow, and turns brown in summer to blend in with the soil and rock environment in which it lives.
• Teeth - the shape and type of teeth present in an animal’s jaw are related to its diet. Herbivores, such as sheep, have continuously growing molars for chewing tough grass and plants. Carnivores, such as tigers, have sharp large canines to kill prey and tear meat.
• Mimicry - copying another animal’s appearance or sounds allows a harmless organism to fool predators into thinking it is poisonous or dangerous. For example, the harmless hoverfly mimics the markings of a wasp to deter predators.
marram grass
Marram grass (Ammophila spp.) is commonly found on sand dunes around the UK. It is a xerophyte, a plant that has adapted to live in an environment with little water. Its adaptations reduce the rate of transpiration and include:
-curled (or rolled) leaves to minimise the surface area of moist tissue exposed to the air, and protect the leaves from the wind
• hairs on the inside surface of the leaves to trap moist air close to the leaf, reducing the diffusion gradient
• stomata sunk into pits, which make them less likely to open and lose water
• a thick waxy cuticle on the leaves and stems, reducing water loss through evaporation.
behavioural adaptations
Some examples of behavioural adaptations:
-Survival behaviours - for example, an opossum plays dead and a rabbit freezes when they think they have been seen.
-Courtship - many animals exhibit elaborate courtship behaviours to attract a mate. For example, scorpions perform a dance to attract a partner. This increases the organism’s chance of reproducing.
• Seasonal behaviours - these adaptations enable organisms to cope with changes in their environment.
They include:
-migration - animals move from one region to another, and then back again when environmental conditions are more favourable. This may be for a better climate or a source of food
-hibernation - a period of inactivity in which an animal’s body temperature, heart rate and breathing rate slow down to conserve energy, reducing the animal’s requirement for food. For example, brown bears hibernate during the winter.
Generally, behavioural adaptations fall into two main categories:
• Innate (or instinctive) behaviour - the ability to do this is inherited through genes. For example, the behaviour of spiders to build webs and woodlice to avoid light is innate. This allows the organism to survive in the habitat in which it lives.
• Learned behaviour - these adaptations are learnt from experience or from observing other animals. An example of learned behaviour is the use of tools. For example, sea otters use stones to hammer shells off rocks, and then to crack the hard shells open.
However, many behavioural adaptations are a combination of both innate and learned behaviours.
physiological adaptations
Some examples of physiological adaptations:
• Poison production - many reptiles produce venom to kill their prey and many plants produce poisons in their leaves to protect themselves from being eaten.
• Antibiotic production - some bacteria produce antibiotics to kill other species of bacteria in the surrounding area.
-Water holding - the water-holding frog (Cyclorana platycephala) can store water in its body. This allows it to survive in the desert for more than a year without access to water. Many cacti and other desert plants can hold large amounts of water in their tissues.
Many other examples are less unusual, and include reflexes, blinking and temperature regulation.
anatomical adaptations provide evidence for convergent evolution
Analogous structures-
Although the tail fins of a whale and a fish perform the same role, when you look at them in detail their structures are very different.
These are known
as analogous structures - they have adapted to
pertorm the sam
le function but have a different genetic origin.
Convergent evolution takes place when unrelated species begin to share similar traits. These similarities evolve because the organisms adapt to similar environments or other selection pressures (for an explanation of the term ‘selection pressure’, Topic 10.8, Changing population characteristics). The organisms live in a similar way to each other. Using our example of whales and fish, their similar characteristics have evolved over time to allow the organisms to move efficiently through water.
Marsupials in Australia and placental mammals in the Americas are an example of convergent evolution. Species in each continent resemble each other because they have adapted to fill similar niches.
In placental mammals, a placenta connects the embryo to its mother’s circulatory system in the uterus. This nourishes the embryo, allowing it to reach a high level of maturity before birth. Marsupials also start life in the uterus, but then leave and enter the marsupium (pouch) while they are still embryos. They complete their development here by suckling milk.
These two subclasses of mammals separated from a common ancestor more than 100 million years ago. Each lineage then evolved independently. Despite this large temporal and geographical separation, marsupials in Australia and placental mammals in North America have produced varieties of species that bear a strong resemblance in overall shape, type of locomotion and feeding techniques. This is because they have adapted to similar climates and food supplies. However, these organisms have very different methods of reproduction. This is the feature that accurately reflects their distinct evolutionary relationships.
Examples include:
-marsupial and placental mice - both are small, agile climbers that live in dense ground cover and forage at night for small food item.
The two mice are very similar in size and body shape
• flying phalangers and flying squirrels (Figure 7) - both are gliders that eat insects and plants. Their skin is stretched between their forelimbs and hind limbs to provide a large surface area for gliding from one tree to the next
• marsupial and placental moles (Figure 8) - both burrow through soft soil to find worms and grubs. They have a streamlined body shape and modified forelimbs for digging. They also have velvety fur, which allows smooth movement through the soil. However, they differ in fur colour - the marsupial mole ranges in colour from white to orange whereas the placental mole is grey.
Convergent evolution can also been seen in some plant species.
For example, aloe and agave appear very similar as they have both adapted to survive in the desert. However, these species developed entirely separately from each other. Aloe are sometimes referred to as ‘old world’, having evolved in sub-Saharan Africa. Agave, by comparison, are ‘new world’, having evolved in Mexico and the southern United States.
