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Higher Biology

Higher Biology. Adaptation Part 4. Adaptation 4. By the end of this lesson you should be able to:. Know what a xerophyte is. Describe the problems that xerophytes face. Describe how xerophytes are adapted to survive in their environment. Know what a hydrophyte is.

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Higher Biology

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  1. Higher Biology Adaptation Part 4

  2. Adaptation 4 By the end of this lesson you should be able to: • Know what a xerophyte is. • Describe the problems that xerophytes face. • Describe how xerophytes are adapted to survive in • their environment. • Know what a hydrophyte is. • Describe the problems that hydrophytes face. • Describe how hydrophytes are adapted to survive in their environment.

  3. Xerophytes Moorlands- exposed and windy • Xerophytes are plants that have become adapted to survive in habitats where transpiration rates are very high. • Examples of habitats are: Deserts- hot and dry

  4. Xerophytes • There are 3 categories of xeromorphic adaptations: Structural adaptations- reduce transpiration rate Structural adaptations- resisting drought Physiological adaptations

  5. Structural adaptations To reduce transpiration rate: • Leaves have a reduced number of stomata. • Leaves have a thick cuticle. • Leaves can be rolled and/or hairy. • Leaves have sunken stomata in pits. • Leaves can be small and circular. • Leaves are reduced to spines.

  6. Structural adaptations To reduce transpiration rate: Marram Grass (T.S.) Rolled leaf Hairs Thick cuticle

  7. Structural adaptations To reduce transpiration rate: Cactus surface Sunken stomata in pits Thick cuticle

  8. Structural adaptations To resist drought: • Long roots. • Extensive system of superficial roots. • Storing water in succulent tissues. • Folded stems.

  9. Physiological adaptations To reduce water loss: • Reversed stomatal rhythm- closed during the day and open at night. They take in CO2 during the night and store it for use in photosynthesis during the day. • Ceasing vegetative activity during dry times- e.g. existing in a desiccated state (seed) and only germinating when water becomes available. • Insert and complete the “Xerophytes” summary sheet .

  10. Hydrophytes Partially submerged e.g. water lily • Hydrophytes are plants that live either partially or completely submerged in water. Completely submerged e.g. water milfoil

  11. Hydrophytes • These have evolved adaptations to help them survive in an aquatic environment.

  12. Hydrophytes- adaptations Specialised leaves • Submerged leaves have no stomata. • Floating leaves have all their stomata on the upper surface. • Floating leaves have long leaf stalks (petioles) to enable the leaves to move up and down in response to changes in water level. • Submerged leaves are narrow or finely divided.

  13. Hydrophytes Floating leaves- stomata on top surface e.g. water lily Narrow, finely divided leaves e.g. water milfoil

  14. Hydrophytes adaptations Reduced Xylem: • Not required since water provides the support for submerged plants. • Any xylem is found at the centre of the stem- to allow flexibility in response to water movements.

  15. Hydrophytes adaptations Extensive air spaces: • Store O2produced during photosynthesis for use in respiration. • Provide buoyancy for leaves- keeps them near the surface for maximum exposure to light. • Insert and complete the “Hydrophytes” summary sheet.

  16. Practice Questions • Torrance • TYK page 183 Q1-5 • AYK page 184 Q4-6

  17. Adaptation 4 Can you do it? • Know what a xerophyte is. • Describe the problems that xerophytes face. • Describe how xerophytes are adapted to survive in • their environment. • Know what a hydrophyte is. • Describe the problems that hydrophytes face. • Describe how hydrophytes are adapted to survive in their environment.

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