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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. - PowerPoint PPT Presentation
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Higher Biology
AdaptationPart 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.
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Xerophytes 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
Moorlands- exposed and windy
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Xerophytes
There are 3 categories of xeromorphic adaptations:
Structural adaptations-reduce transpiration rate
Structural adaptations-resisting drought
Physiological adaptations
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Structural adaptations
To reduce transpiration rate:1. Leaves have a reduced number of
stomata.2. Leaves have a thick cuticle.3. Leaves can be rolled and/or hairy.4. Leaves have sunken stomata in pits.5. Leaves can be small and circular.6. Leaves are reduced to spines.
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Structural adaptations
To reduce transpiration rate:
Marram Grass (T.S.)
Rolled leaf
Hairs
Thick cuticle
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Structural adaptations
To reduce transpiration rate:
Cactus surface
Sunken stomata in pits
Thick cuticle
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Structural adaptations
To resist drought:1. Long roots.2. Extensive system
of superficial roots.
3. Storing water in succulent tissues.
4. Folded stems.
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Physiological adaptations
To reduce water loss:1. 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.
2. 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 .
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Hydrophytes Hydrophytes are
plants that live either partially or completely submerged in water.
Completely submergede.g. water milfoil
Partially submergede.g. water lily
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Hydrophytes
These have evolved adaptations to help them survive in an aquatic environment.
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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.
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Hydrophytes
Narrow, finely divided leavese.g. water milfoil
Floating leaves- stomata on top surfacee.g. water lily
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Hydrophytes adaptations
Reduced Xylem:1. Not required since water provides the
support for submerged plants.2. Any xylem is found at the centre of
the stem- to allow flexibility in response to water movements.
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Hydrophytes adaptations
Extensive air spaces:1. Store O2 produced during
photosynthesis for use in respiration.2. Provide buoyancy for leaves- keeps
them near the surface for maximum exposure to light.
Insert and complete the “Hydrophytes” summary sheet.
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Practice Questions
Torrance1. TYK page 183 Q1-52. AYK page 184 Q4-6
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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.
