Adaptive Features

• 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
• You should be able to interpret images or other information about a species in order to describe its adaptive features

  • A typical question might be to explain how the leaf area and distribution and density of stomata help different species of plant survive in their different habitats
• Hydrophytes - plants adapted to live in extremely wet conditions
• Common adaptations of hydrophytes include:

  • Large air spaces in their leaves for flotation, to keep the leaves close to the surface of the water where there is more light for photosynthesis
  • Small roots as they can also extract nutrients from the surrounding water through their tissues
  • Stomata usually open all the time and mainly found on the upper epidermis of the leaf where they can exchange gases much more easily with the air
• Common adaptations of hydrophytes include:

  A) hydrophyte

  B) stomata concentrated

  C) upper epidermis

  D) large air spaces

  E) flat

  F) small roots

  
• Xerophytes - plant adapted to live in extremely dry conditions
• Common adaptations of xerophytes include (1):

  • Thick waxy cuticle - the cuticle cuts down water loss in two ways: it acts as a barrier to evaporation and also the shiny surface reflects heat and so lowers the temperature
  • Sunken stomata: stomata may be sunk in pits in the epidermis; moist air trapped here lengthens the diffusion pathway and reduces the evaporation rate
  • Leaf rolled with stomata inside and an inner surface covered in hairs - traps moist air and prevents air movement across stomata which reduces transpiration
• Common adaptations of xerophytes include (2):

  • Small leaves: many xerophytic plants have small, needle-shaped leaves which reduce the surface area and therefore the evaporating surface
  • Extensive shallow roots allow for the quick absorption of large quantities of water when it rains
  • Thickened leaves or stems which contain cells that store water
• Common adaptations of xerophytes

  A) xerophyte

  B) thick waxy

  C) small leaves

  D) needle-shaped

  E) shallow, extensive

  F) thickened stem

  G) reservoir

  H) store water

  
• Feature - an inherited (structural) feature that helps an organism to survive and reproduce in its environment
• Xerophytes live in deserts where water is scarce, and evaporation is rapid or in windy habitats

  • Deep roots reach the water far underground
  • Leaves have reduced spines with minimum surface area for transpiration
  • Shallow spreading roots to collect occasional rain
  • Rolled leaves, leaf hairs, and stomata sunk in pits to trap moist air
  • Waxy leaf cuticle, impermeable to water
  • Stomata open at night and close at midday when evaporation is highest
  • E.g. cactus and marram grass
• • Hydrophytes - live wholly or partly submerged in water. Their features are:
  • Leaves are highly divided to create a large surface area for absorption and photosynthesis
  • Minimal cuticle formation
  • Lack of xylem tubes, no stomata underside of leaves
  • Stomata are on the upper surface and have a thick waxy layer to repel water and to keep the stomata open and clear
  • Roots are often reduced, and root hairs are often absent
• A change in base sequence → variation
• Different amino acids, different shape of protein
• Cancer is caused by mutations from chemicals or ionising radiation

  • e.g. UV radiation, X-rays, cigarettes, HPV, nitrate, barbecuing
• Mutation is the only source of new alleles and variation
• New combinations of alleles is a type of variation
• Sexual reproduction does everything it can to try maximise variation by creating new combos

  • independent assortment of chromosomes in meiosis
  • random mating
  • random fusion of gametes in fertilisation
• All organisms have adaptations that allows them to survive

  • e.g. humans have opposite thumbs to grab things
• Adaptive features - inherited functional features of an organism that increases its fitness
• Fitness - probability of survival and reproduction in the environment it is found
• Xerophyte adaptations:

  • thick cuticle - stops uncontrolled evaporation through leaf cells
  • small surface area - less area for evaporation
  • low stomata density - smaller area for diffusion
  • sunken stomata - maintains humid air around stomata
  • stomatal hairs - maintains humid air around stomata
  • extensive roots - maximise water uptake
• Xerophyte adaptations:

  A) stomata hairs

  B) sunken stomata

  C) rolled leaf

  D) extensive roots

  E) leaves with small surface area

  F) few stomata

  G) thick waxy cuticle

  H) top root

  I) water table

  
• Hydrophyte adaptations:

  • chloroplasts are found in epidermal layer - stomata found only on the side exposed to air
  • thin leaves lacking in stomata - have thin layers for faster diffusion of dissolved gases
  • often extensive air channels - allows plant to float in the water
• Hydrophyte adaptations:

  A) stomata up here

  B) very thin

  C) air channels

  D) oxygen

  E) roots

  F) air channel

  
• Adaptive features of a species can be recognised from its physical features
• What are the adaptations of a hydrophyte?


  Reduced roots and xylems, large air spaces in tissues, leaves with stomata on the upper surface
• Define adaptive features


  Adaptive features are features that increase the chance of an organism surviving and reproducing in its environment.