Adaptation & Mutation (College Board AP Biology)

• Adaptive features are the inherited functional features of an organism that increase its fitness
  • Fitness is the probability of an organism surviving and reproducing in the environment in which it is found
  • An adaptation, therefore, is favored by selection as it provides a selective advantage to an organism in a particular environment
    
• Mutations are random
  • They do not occur as a result of specific environmental pressures
  • However, whilst this is not always the case, mutations can provide a selective advantage which leads to an increase in the fitness of an organism
  • In this scenario, the mutation is also favoured by selection
• Both mutations and adaptations can affect whole ecosystems, not just the single species in which they first occur
• The effects occur because of the interdependency of all the species within an ecosystem; a slight change of balance in one species can have a dramatic set of consequences on many other species

• A species that has moved into an ecosystem where it was previously unknown is an invasive species
• An invasive species can occur naturally as a result of a species migrating or expanding their habitat but most recorded incidents of invasive species have been caused by humans
• In the past humans have:
  • Knowingly collected and traded species between countries via ships
  • Unknowingly provided transport for invasive species to a new ecosystem
  • Introduced alien species deliberately as a biological control for pests

Problems with Invasive Species

• The biological process of evolution often brings balance to an ecosystem
• Through evolution the environment a species lives in influences strongly the adaptations that the species evolves to live in that environment
• A non-native invasive species will have evolved adaptations for survival in different environmental conditions so when they are introduced into the new ecosystem this can upset the balance
• In a new ecosystem invasive species will have few or none of the natural population controls that existed in their previous ecosystem:
  • They will have no natural predators or competitors
• As a result they can increase in number at a rapid rate
• This can affect the processes within an ecosystem
  • Competition may occur between invasive species and native species that occupy a similar niche with the native species getting displaced or pushed to extinction. It could be competition for things such as prey, soil nutrients, light and space
  • Many invasive species can be overly successful predators causing a massive decline in their prey species
  • Invasive species can introduce new diseases, to which the native species have no natural immunity
  • The biodiversity of an ecosystem is negatively impacted which reduces its productivity
• Humans can also feel the consequent effects of an invasive species taking over an ecosystem
  • The spread of novel diseases and irritants of the skin / breathing system directly affect human health
  • The economy of a country can be impacted severely by the costs of trying to control invasive species and their negative effects
  • In the past, travel has been brought to a standstill by invasive species, with some plant species prone to blocking up waterways

Invasive Species - Cane Toads

Cane toad (Bufo marinus)

CC BY-SA 4.0, Charles J Sharp, via Wikimedia Commons

• In the early 1900s, there was a major problem with the sugarcane crop in Australia
• An insect pest was destroying the crop and causing major economic losses for many farmers
• It was decided that the non native cane toad (Bufo marinus, from Hawaii) should be introduced so that it could act as a biological control
• After a short period of time the numbers of cane toads increased rapidly due to a lack of natural predators and they spread into other habitats outside of the sugarcane plantations
• This had a consequent effect on other species:
  • The cane toad is toxic when eaten
  • The northern quoll, which is an endangered marsupial carnivore, declined steeply in numbers as they preyed on the cane toad
  • Other amphibian species face increased competition for food and resources
  • The eggs of ground nesting birds are often eaten by cane toads

Invasive Species - Kudzu

• Kudzu (Pueraria montana) was brought into the US from Japan and southern China as an ornamental plant
• It was also prized for its ability to bind soil and to halt soil erosion
• It is a semi woody vine plant that produces red or purple flowers every 3 years
• Kudzu grows at a phenomenally fast rate, sometimes up to 30cm (1 foot)  per day
• It deploys runners to spread quickly and will literally grow over everything in its path
• It has been known to create 'kudzu graveyards' where it grows over everything else in the area because of its lack of competition, predators and its adaptations to the new environment

A 'kudzu graveyard'

CC BY-SA 4.0, Rhododendrites, via Wikimedia Commons

Invasive species - Zebra mussels

• The zebra mussel (Dreissena polymorpha) is a native species of the Black Sea and Caspian Sea in western Asia
• It has become an invasive species in many European and North American countries
• They are thought to have been transferred inadvertently by ships traversing oceans
• Their reproductive success has caused varied problems, notably clogging of man made waterways and water treatment infrastructure

Zebra mussels

CC BY-SA 1.0, User Lamiot on fr.wikipedia, via Wikimedia Commons

Invasive Species - Japanese Knotweed

• Japanese knotweed (Reynoutria japonica) is the most invasive non native plant species in the United Kingdom
  • There are several natural population controls that exist for Japanese knotweed in its natural habitat in Japan
  • The irregular climate and the deposits of volcanic ash over the ground limit its growth
  • A German botanist brought the plant to the UK in the 19th century because he admired its beauty
  • As the UK does not possess the same environmental factors the plant was able to grow unchecked
  • Since the 1800s it has spread across the UK and become a major problem
  • It grows at a rapid rate, breaking up tarmac and blocking out all sunlight for native plant species in its  immediate surroundings

Japanese knotweed

CC BY-SA 3.0, Julia Kruse, via Wikimedia Commons